AP Biology 2007 (Period 1&2)

Science Debate 2008

kim@ExploreBiology.com (KB Foglia) — Fri, 22 Feb 2008 18:13:00 +0000

Have you seen this:
http://sciencedebate2008.com

Would be great if you students got to see this.
==========================================

Universities, corporations and a host of individuals are calling for a debate with all four of the remaining presidential candidates discussing critical scientific issues that impact everything from the environment to the economy.

Sciencedebate2008.com, formed by two Hollywood screenwriters who had time to mull science recently while on strike, is an effort aimed at thrusting technology into the limelight.

One of the initiative's founders, Shawn Otto, said yesterday more than 17,000 American universities and the editors of nearly every major science publication in the nation have added their names to the Web site, encouraging the presidential hopefuls to debate key scientific issues.

"This is a nonprofit organization we set up to raise the profile of science and technology in our national political diaglogue," Otto said, adding that his initiative is now being co-sponsored by the National Academy of Sciences, the Institute of Medicine, the National Academy of Engineering, the Council on Competitiveness and the American Association for the Advancement of Science.

Yesterday, John Podesta, chief of staff for former President Bill Clinton, posted a video statement on YouTube echoing that science remains one of the nation's primary areas of focus. He called for a presidential debate "in charting a path forward on national security, on energy and climate change policy, really on the core fundamentals of our economic policy."

Otto said it would be "really fabulous" to see Democrats and Republicans on the same stage debating issues in science.

"All of us believe that almost every major policy challenge that the next president will face revolves around questions of science and technology," Otto said, referring to signers of his initiative.

"Ever since World War II, America has been leading in science and technology, and science and engineering have driven half of our economic growth."

But in the not-too-distant future, he added, 90 percent of all scientists will be living in Asia, causing a major "shift in intellectual capital."

James McCarthy on Science Debate 2008

John Porter on Science Debate 2008

Francesca Grifo on Science Debate 2008

Immune system

noreply@blogger.com (mike m) — Wed, 13 Feb 2008 02:44:00 +0000

3rd line of defense in your immune system

the last say in the immune systems defense is lymphocytes.

B cells and T cells recognize the foreign antigens. B cells get their name because they're matured in the bonemarrow.
T cells get their name because....

So moving away from that...
B cells floating in blood and lymph check out antigens(the protein coat to identify cells) at random.
should they happen to find some one they dont recognize, or better yet DO recognize as a hazard, they release
the antibodies.
Antibodies stick to the foreign cell to slow it down acting as shackles.... but more acurately like...

thats right...net guns

Once officially "netted" T cells call in the macrophages, and from there... its good game pathogen

B cells keep memeory of every antigen, so when it comes around again they know just how to fight back.

HORMONES

noreply@blogger.com (Jackie) — Wed, 13 Feb 2008 01:29:00 +0000

Action Of Protein Hormones

on a signal-transduction pathway

First, the protein hormone is reconized by the receptor and binds to it (signal). Then a secondary messenger system, and transduction (to transfer a message from one form to another) occurs. And finally a response from a cell is produced.

This all takes place on a signal transduction pathway. This requires the use of energy and different messengers.

Action Of Epinephrine

(adrenalin)

First the epinephrine binds to receptor than a message is sent to second receptor. It goes through a secondary messenger system and eventually sends a response to release glucose to blood.

2° Messenger System

has benefits
A 2° messenger system is a chain reaction, allowing for amplication and a very fast response.

Maintaing Homeostasis
negative feedback

When a specific body condition gets to high, a glad is signaled to produce a hormone, which lowers body condition. When condition gets too low, gland is signaled to produce a different hormone to raise body coondidtion.

An example of this is the Nervous System controlling Body temperature. When body temperature gets too high, brain sends nerve signals which make body sweat and dilate survace blood vessels, lowering temperature. When body temperature gets too low, brain sends nerve signals to make body shiver and constrict surface blood vessels bringing temperature back up.

Better to breathe like a camel than look like one...

noreply@blogger.com (Dan) — Thu, 07 Feb 2008 22:32:00 +0000

Dear Journal,

Today, at like, 6 o'clock or something, I was too lazy to get up, but I did anyway. So when I was up, I took a shower and got ready. Then I think I went to school. In Bio we learned some stuff I think, but I mostly just dazed off and thought about things. Like why peanutbutter is sticky, and how awesome it sounds when you rub two pickle slices together, 'cos you get that tiny little squeeky noise...

Anyway.

If I had paid attention (or stayed awake for that matter) in Bio, I probably would've learned about antibodies and stuff. But I was too lazy. So let's see, what do I know about antibodies.....

They're Greeeeeat!

Why you ask?
READ ON!

Without our immune system we would be.....

Why?
Our B-Cells, which produce antibodies, test every cell they come in contact with. They check its antigens, which are really like name tags. Antigens are present on EVERY SINGLE CELL....even our own! But, luckily for us, our antigens are recognized by our B-cells as our own, and they do not trigger a response.

However, when a B-cell comes in contact with a foreign invader, such as a virus, B-cells speed into action! Now there are two things that can happen:

1) If the virus has been in the body at an earlier time, the B-cells would already have made antibodies. If this is so, then the B-cells recognize the virus as an intruder, clone 1000's of B-cells with antibodies, and plasma cells release antibodies. Antibodies are "handcuffs" and they slow down the intruder for an easier destruction! How exciting!

2) If this virus is a new intruder, B-cells make antibodies for that specific virus or invader. At this rate, it takes a long time (about 10-17 days) to dispose of the virus, but antibodies have now been made, and are ready to leap like a crouching tiger!

YIKES! I feel bad for the virus the next time it tries to get in your blood!

Then of course, after these antibodies are made, the next time the virus enters, our immune system is able to recognize it so much quicker, and therefore destroy it uber quickly.

This graph shows the concentration of antibodies before and during the first exposure to the virus, and before, during, and after the second exposure. As you can clearly see, after the first attack, antibodies are at the ready, and can recognize, locate, and destroy the unwanted invader quickly and efficiently. This truly was an amazing adaptation.

Now comes the ever popular question: How can we produce millions of antibody proteins if we only have a few thousand genes?

AHA! The answer seems difficult. But behold! It is not!

If we had four decks of cards, and we picked 1 card from each at random, we could end up with a total of 7,311,616 possible combinations. That's alot of combos!

But seriously...

There are more than 52 selections to pick from in humans. We are only able to make these millions of combinations by picking different parts of DNA and putting them together. This process allows for an enormous amount of options.

And now......

For the moment you've all been waiting for.......

It's finally time......

Don't hold your breath......

Here it comes.....

OH NO!!!!

It's..................

Vaccinations???? Oh well.

Vaccinations are really weakened or even dead forms of viruses. They cant harm us as much as the actual virus because, well, they're weak! These weak viruses allow our immune system to make antibodies specifically for the virus, without making us feel the full effects of the disease.
Vaccines are most successful against viral diseases.

Does this school look familiar? It should! This is Jonas E. Salk Middle School, and it was named after the man who invented the vaccination.

Here he is.

That's right. Jonas E. Salk.

Although Salk did not win a nobel prize for medicine, he was a brilliant man, and should be acknowleged for his findings, and specifically for his ending of the polio epidemic.

So if that is Active Immunity, then what is Passive Immunity??

The best example of passive immunity is when infants obtain antibodies from their mothers breast milk. This is specifically referred to as Maternal Immunity. Antibodies pass from the mother to the infant, and because the two are exposed to the same virus's and invaders, these antibodies are especially helpful.

Another way to obtain passive immunity is through injection. In these cases, antibodies are injected into the bloodstream. However, this type of immunity only lasts for a very short time. Hence the term, "Passive Immunity."

And what about the virus's that sneak into the body cells?
Well now, thats a different story for another journal entry.
Until next time.

Sean

Immune System

noreply@blogger.com (Melissa C.) — Wed, 06 Feb 2008 02:24:00 +0000

Immune/Lymphatic System

Avenues of Attacks

- Any opening in the body is a point of entry:

- digestive system

- respitory system

- urogenital tract

- breaks in skin

- Routes of attack: how foreginers move around the body once in
- circulatory system

- lymph system

- Why an immune system?

- Attack from outside

- organiams like to feed upon us due to our containement of fats,

lipids, and proteins

- we must protect our cells because cell wall protection has

been traded for mobility

- animals must defend themselves against invaders

- Viruses: HIV, flu, colds etc.

- Bacteria: Pneumonia, meningitis, etc.

- Protistis: amoeba

- Attack from the inside

- when own cells let go of the restrictions of their genitically programed jobs

- ex: cancer cells

- Animals evolved a lymph system

- The production and transprt of leukcytes traps foreign invaders

- Development of Red and White blood cells
- 3 Lines of Defense

- 1st line: barriers

- external defense

- skin and mucus membranes

- 2nd line: non- specific patrol
- broad internal innate defense; attempts to keep everything out

- attacks anything not recognized

- leukocytes = phagocytic WBC

- 3rd line: immune system

- specific aquired immunity

- inherit the ability but aquire defense

- lymphocytes (trained cells) and antibodies

- B cells

- make antibodies

- T Cells

- 1st line: External Defense

- Physical and Chemical Defenses

- non-specific defenders

- External Barrier

- epithelial cells and mucus membranes

- skin

- respiratory system

- digestive system

- uro-genital tract
-Chemical Barriers on epithelium

- Skin and mucous membrane secretions

- acidity in sweat

- tears act as a washing action

- mucus traps microbes

- saliva contains an anti-bacterial

- acidity in the stomach

- anti-microbial proteins

- lysozyme enzyme

- digests bacterial cell walls
- 2nd line: Internal, broad range patrol

- Innate, general defense

- Rapid response

- Patrolling cells and proteins

- they attack invaders that penetrate body's outer barriers

- leukocytes

- phagocytic (engulfing) white blood cells

- Complement system

-Anti-microbial proteins- in blood & plasma

- Inflammatory response

- Leukcoytes: Phagocytic WBC's

- attracted by chemical

- signals released by damaged cells

- enter infected tissue, engulf and ingest microves

- lysosomes

- Neutrophils

- most abundant WBC's

- Macrophages

- "big eater"- long lived

- take pieces of digested invaded and they destroy their cell with it as an alarm

- Natural Killer Cells

- destroy virus-infected cells and cancer cells

- Destroying cells gone bad

- Natural Killer Cells perforate cells
- release perforin protein

- insert into membrane of target cells

- forms pore allowing fluid to flow into cell

- no longer selectively permeable

- cell ruptures

- in flow of liquids into cell causing cell the rupture- apoptosis

- Anti- microbial protein

- 20 proteins circulating in blood plasma

- attacks bacterial and fungal cells

- form a membrane attack complexstamines and prostaglandins

- perforate target cell

- apoptosis

- cell lysis

- Inflammatory Response

- damage to tissue triggers local non-specific inflammatory response `

- release histamines and prostaglandins

- cappilaries dilate - more permeable - all in an attempt to "plug the leak"

- increase blood supply

- delivers WBC, RBC, platelets clotting factors

- fight pathogens

- clot formation

- Fever
-When a local response is not enough

-systemic response to infection

- activated macrophages release interleukin-1

- triggers hypothalamus in brian to readjust body thermostat to raise body temperature (fever)

- higher temperature helps defense

- inhibits bacterial growth

- stimulates phagocytosis

- speeds up repair of tissues

- causes liver and spleen to store iron, reducing blood iron levels

- bacteria need large amounts of iron to grow

Circulation in Animals

noreply@blogger.com (Sean Perez) — Tue, 15 Jan 2008 05:50:00 +0000

What truly is the point of Circulation? Why build such a complex system stretching through out the entire body? Below these questions shall be answered.

Exchange of Materials

The true point of the Circulatory system is to exchange, and transport materials from cells, and to cell, and to other parts of the body. This includes:
Needs

Oxygen
nutrients
Sugars, proteins, etc.
Water
Protective Agents(White blood cells, antibodies, platelet's, etc.)
Hormones

Wastes

Carbon Dioxide
Urea
Water

Multicellular Animals need these essential materials, and to get ride of waste, but unlike unicellular organisms cant obtain it through diffusion alone, for this reason they need the Circulatory system, this network or highway for transport.

Types of Circulatory Systems

All Animals have some characteristics in common for their mode of circulation. The all contain blood vessels, a heart, and some type of fluid to transport materials in (blood for humans).
Open

Invertebrates( insects, mollusk, anthropods) contain an open circulatory system which means they have no separation between blood, and interstitial fluid, instead they have hemolymph. This is a fluid that runs through their entire body touching the organs, and giving them nutrients.

Closed

Invertebrates( Octopie, earthworms, squid ) have separate blood from interstitial fluid. They have at least one heart, complex blood vessels, exchanging of materials between the blood, and the outside interstitial fluid.
Vertebrates( humans, clownfish , macaques ) also have a closed circulatory system. They have seperate blood from interstitial fluid, and complex blood vessels. The characteristics of vertebrates differ greatly through different evolutionary stages.

Evolution of heart chambers

The number of heart chambers differs greatly ranging from 2-4 in vertebrates. Having more chambers was a selective value because it is more efficient system, separating oxygen rich, and oxygen poor blood giving cells a fresh supply of concentrated oxygen. Having only 2 chambers, like a fish mixes the oxygen rich, and oxygen poor blood giving less overall oxygen to the cells. Since mammals, and birds are endothermic they also had a selective force to heave 4 chambered hearts so they could supply they needs of making heat by getting the supplies around faster, and with what is truely needed.

Blood Vessels

There are 3 main types of Blood Vessels found in the circulatory system of vertebrates.
Arteries

Arteries are the blood vessels that carry blood away from the heart.
They are thicker than veins so that they can be able to make high pressure pumping of blood. Since it is pumping blood to the body it ne eds pressure to force the blood to move to the different parts of the body.
Has a narrow diameter to help keep high pressure within the vessels.

Veins

Veins are the blood vessels that carry blood towards, or back to the heart.
Low pressure so that skeletal muscle contractions are able to move the blood flow more easily towards the heart.
Wider diameter so there is less pressure.
Thinner walls for less pressure.
Valves in some of the larger veins help to direct blood flow by opening and closing leading blood to the heart.

Capillaries

Very small blood vessels that branch from the larger veins, and arteries but connected to the arterioles, and venules.
Very thin, only one layer of cells, endothelium.
Very permeable from thinness allowing the diffusions of molecules such as oxygen, and urea, and making for the connection for the transp ort of materials between cells, and the circulatory system.

The blood flow in capillaries can be controlled through the pre-capillary sphincters. They can retrict or allow blood flow through capillaries by either closing, or opening up. This is useful for when certain body parts are in need of blood, open, an d to close them when the part is in no need of blood.
The capillaries also exchange fluids, and solutes into the interstitial fluid through "bulk flow" or having a high pressure gradient. The interstitial fluid also flows into the capillaries through osmosis.

Lymphatic System

The Lymph system very much like the circulatory system and is parallel with it. The Lymph system is an open system, and helps collect, and return interstitial fluid to the blood. It also helps the bodies immune system greatly. It aids in the production of lymphocytes, and anti-bodies, also transporting these throughout the whole body as well as white blood cells to aid wherever they are needed. The system drops its load into the circulatory system near the vena cava, and right atrium.

Mammalian heart

The heart of your typical mammal is very similar, as we saw in the cow heart dissection. It consists of Pulmonary arteries, and veins which pump blood to and out the capillaries of the lungs, and the Aorta which is an artery that pumps blood throughout the body. The Coronary arteries give a supply of blood to the heart giving fresh supplies of oxygen. Many times this is blocked by buildup of cholesterol, and can cause a heart attack which can lead to needing bypass surgery, in which a alternate pathway from the aorta is made to the heart so it can get its supply of blood and not fail to pump.
The heart is made of up 4 chambers, the left and right Ventricle, and the left and right Atrium. These chambers are separated by four valves, made up of connective tissue that prevent back flow keeping the blood pumping in the direction it is needed. The sounds "Lub" and "dub" are produced from these valves closing, and opening. The Atrioventricular valves (AV) are between the atrium, and ventricle, and prevents blood from flowing in the atria when the ventricles contract. The Semi lunar valves are between the ventricles, and arteries and prevent blood from flowing into the ventricles from the arteries when the heart is relaxing.
A Cardiac cycle is one complete cycle of the hear pumping. This is when the heart contracts, and pumps, then relaxes and refills with blood. The contraction phase is called systole, and the relaxation phase is called diastole. This is the way someones blood pressure is measured to check if they have hypertension. The top number is systolic pumping(a higher number), and the bottom number is the diastolic pumping(lower number).

Jan. 10

noreply@blogger.com (Ryan) — Tue, 15 Jan 2008 03:05:00 +0000

Here are some key points we should have absorbed today

Animals get thier food by
-Filter (suspension) feeding
-Substrate feeding
-Fluid feeding
-Bulk feeding

-Animals cannot make: elements; N, P, K, Fe, Na, Ca and NAD, FAD so they must take it in through food

peristalsis-push food along by rhythmic waves of smooth muscle contraction in walls of the digestive system.

Sphincters-muscular ring-like valves, regulate the passage of material between sections of digestive system.

Accessory glands- salivary glands, pancreas, liver, and gall bladder secrete digestive juices such as enzymes and fluid.

Stomach-stores foos, disinfects food, performs chemical digestion

Ulcers-caused by a bacteria overload in your stomach called helicobacter pylori cured with antibiotics.

Small intestine-chemical digestion, absorption through lining
-duodenum=most digestion
-jejunum=absorption of nutrients and water
-ileum=absorption of nutrients and water

-the small intestine is lined with villi and microvilli
the villi increase the surface area to absorb materials into the blood

large iontestine-re-absorb water
the large intestine is inhabited by countless bacteria including E. coli
the bacteria produce necessary vitamins for survival and help with digestion

Rectum-eliminate feces (extracellular waste) this waste has never been absorbed into the bloodstream.

Digestion continued...

noreply@blogger.com (Alex E) — Wed, 09 Jan 2008 05:11:00 +0000

The liver is responsible for the production of bile. Bile is a chemical made from dead red blood cells. Bile breaks down the fats that we eat.
After bile is produced it is stored in the gall bladder, it is released in the presence of fats

in order to break them down.

THIS IS ONLY ONE OF MANY FUNCTIONS THAT THE LIVER IS RESPONSIBLE FOR SUCH AS THE POISON CONTROL OF THE BODY

The pancreas breaks down carbohydrates and further breaks down proteins. The peptidases that are made by the pancreas are called

Trypsin, Chymotrypsin, and carboxypeptidase.these are then changes to their inactive form which are trypsinogen,chimotrypsin, and procarboxypeptidase. This change occurs in order to protect the pancreas from getting digested. When needed tripsinogen is changed back into tripsen by the small intestine then tripsen activates the other enzymes to change.

The small intestine is the major organ of digestion and absorption.

The small intestine is over 6m and has a alot of surface area for absorption due to the thousands of villi against its lining.

The small intestine is made of 3 parts the Duodenum where most digestion occurs.

Jejunam and Ileum where absorption of nutrients and water occur.

The nutrients from the food are absorbed through the capillary walls which are only one cell thick

What ever the body cannot put to use gets sent to the large intestine. Products such as cellulose which or body cannot digest is sent here. The large intestine has a bunch of good bacteria

that prduce vitimans and help digest cellulose.

The liver also re-absorbs water back into the blood stream so we dont dehydrate.

The last section of the large intestine is the rectum which eliminates the pheces and undigested materials from the body

and lastly you end up with...

Digestion

noreply@blogger.com (Alex E) — Wed, 09 Jan 2008 02:48:00 +0000

Chemical digestion occurs once food has

entered the stomach from the esophagus.

Most people believe that the stomach's function is digestion. The true function of the stomach is to store food, the stomach makes it possible for us to eat meals through out the day. The stomach also disinfect anything that is not suppose to come down with the food. HCl make the disinfection possible, with a ph of 2 it kills bacteria and begins to break apart food.

The enzyme that digests protein is called pepsin

Luckily we have mucus that is secreted to protect

our stomach lining. If we didn't then the pepsin would digest our stomachs since the stomach is made out of protein.

A Gastric ulcer is when ones stomach begins to digest itself. Gastric Ulcers are caused by a bacterial infection known as Helicobacter Pylori. Gastric Ulcers are cured with weeks of antibiotics.

While all of this is occuring the food

stays put in the stomach due to 2

sphincters. One is called the cardiac sphincter

which keeps the food from going up.

The 2nd is called the pyloric sphincter which keeps the food from going down.

The liver is responsible for the production of bile.

Bile is a chemical made from dead red blood cells.

Bile breaks down the fats that we eat.

After bile is produced it is stored in the gall bladder, it is released in the presence of fats in order to break them down.

PPPPP

Nutrition

noreply@blogger.com (nross) — Tue, 08 Jan 2008 00:02:00 +0000

All animals need to consume food to live. Oxygen and some sort of food source are needed for animals to grow. The raw materials are gained through eating and the oxygen is used in respiration which makes the energy needed for the synthesis of those raw materials into larger molecules.

Animals get their food in four different ways-

~Bulk Feeding~

Bulk Feeding is cosuming large concentrated portions of your food source.

~Fluid Feeding~

This is when organisms get theier nutrients from a liquid like blood or sap.

~Substrate Feeding~

Substrate feeding is when the organism spends part of its' life living in its food source.

~Filter Feeding~

This mode envloves the intake of huge amounts of your food source straight out of the environment.

Your digestive system is basically a really long tube where food products are broken down and the needed parts are absorbed the rest excreted as extracellular waste because it never actually entered your cells.

Food is pushed through the digestive track by involuntary muscle contractions known as peristalsis. According to Paige this is like an utter.

Digestion starts with Ingestion

Swallowing starts off the process the epiglottis (cartilage flap) closes securing itslef over your trachea preventing food from "going down the wrong pipe". Waves of muscle push the food towards the stomach which is where we finished our lesson.

noreply@blogger.com (Jess) — Fri, 21 Dec 2007 04:24:00 +0000

Stage One: Glycolysis

Whats the point? To make ATP!!

Glycolysis literally means splitting two sugars. This name is appropriate because this is exactly what happens during the first stage of cellular respiration; glucose is digested.

Glycolysis is an ancient process. Bacteria where the first to do this.
Glycolysis is where energy transfer first evolved. It is a transfer of energy from organic molecules to inorganic molecules.

But its inefficient!
A working muscle use millions of molecules of ATP a second. Glycolysis only makes 2 ATP's.

Who were the first to do glucolysis?
Prokaryotes!
Billions of years ago there was no free oxygen in the atmosphere.Oxygen had to be captured by organic molecules such as glucose.

All cells undergo glycolysis!

The Reaction:
1. Begins with one glucose molecule (six carbons)
2.Fructose-16bP takes off Phosphate from 2 ATP and place a phosphate on either side of the glucose.
3. The carbons pull apart due to oxygen's high electronegativity. This forms 2 pyruvates or two 3 carbon molecules.
4. 4 ATP's and 2NADH's (piggy bank) are formed. However 2ATP's were used to start the process (the match).
5. Net: 2ATP's and 2NADH's

What is the point? TO MAKE ATP

noreply@blogger.com (Muskan) — Tue, 18 Dec 2007 21:25:00 +0000

Guys today we learned how our body makes energy. Well what is the point? POINT IS TO MAKE ATP.

Energy is really important because we need it to reproduce, synthesis, to move, to grow, and to regulate our temperature.

The work of life is done by energy coupling, which is using exergonic reactions to fuel the endergonic reactions.

Whatever we eat, we have to digest or break it down to simpler molecules that can enter our cells and they can eventually use them. We need something in our body which helps to pass this energy around. And the best answer is ATP!!!.

ATP stands for Adenosine Triphospate. Where do we see Adenine before? In RNA and DNA.

ATP has three phosphate group attaches to an adenine and ribose.

First we start out with adenosine, and ribose, and when we attach one phosphate to this, this is named AMP or adenosine monophosphate, which means one phospate.

Then when we add another phosphate group to the adenine, ribose, and previous phosphate group, we make adenosine diphosphate, meaning two phosphates.

Third, we make ATP by adding another phosphate group, thus making adenine triphosphate.

Adding all these phosphates requires A LOT of energy and I mean A LOT.

BUT, the question is why does it require so much energy? Well lets see an example, remember when we hold magnets together towards the same poles, WHAT DO THEY DO? THEY REPEL EACH OTHER. This is the same reason for the phosphates. The phosphates are highly negative and do not want to be with another molecule which is also highly negative. This is due to the oxygen. AND WHAT IS OXYGEN? HIGHLY ELECTRONEGATIVE.

The phosphate bonds make ATP an excellent energy donor.

HOW DOES ATP TRANSFER ENERGY?

The word is PHOSPHORYLATION. This is when phosphate is taken off of ATP. This released phosphate can be transferred to other molecules. And enzyme that helps in this is kinase.

Building polymers from monomer is a perfect example of phosphorylation. The bonds holding the monomer have to be destabilized in order to make it a polymer.

The first step of cellular respiration is glycolysis. This is the breaking of glucose to make ATP. First the bonds of glucose have to be destabilized in order for it to be broken down. And whenever a carbon to carbon bond is broken, energy is released!!

Activators and Inhibitors

noreply@blogger.com (Navneet) — Tue, 18 Dec 2007 21:11:00 +0000

Hey guys, yesterday we finished our lecture on enzymes by talking about how activators and inhibitors affect enzyme activity. We also talked about allosteric regulation, cooperativity, metabolic pathways and how these pathways are efficient for the cell.

Enzyme activity is sensitive to the presence of specific substances that bind to the enzyme and cause conformational change in the enzyme (conformational change is the change in the shape of the molecule, in this case the active site of the enzyme). Through these substances, a cell is able to regulate which of its enzymes are active and which are inactive at a particular time. This allows the cell to increase its efficiency and to control changes in its characteristic during development.

The first type of substance that we will talk about is an activator which binds to the active site of the enzyme and increases the activity of the enzyme. Enzyme function is often assisted by additional chemical components known as cofactors and coenzymes.

Cofactors are non-protein, small inorganic compounds and ions. Inorganic compounds are compounds that do not have carbon to carbon bonds. These small molecules are usually metals and bind within the enzyme molecule. For example zinc is used by some enzymes to draw electrons away form their position in covalent bonds in the substrate, making the bonds less stable and easier to break the bonds between the substrate. *Remember glucose, it is stable and needs something to disrupt the bond well here the metals in the enzyme draw the electrons away from the substrate molecules, disrupting the bonds between the substrate.*

Coenzymes are nonprotein, organic molecules which are molecules that have carbon to carbon bonds. These molecules bind temporarily or permanently to the enzyme near its active site. Many vitamins are parts of coenzymes. In numerous ozidation reduction reactions that are catalyzed by enzymes, the electrons pass in pairs from the active site of the enzyme ot a coenzyme that serves as the electron acceptor. The coenzyme then trasfers the electrons to a different enzyme, which releases them to the substrates in another reaction. These electrons have energy with them. One of the most important coenzymes is the hydrogen acceptor nicotinamide adenine dinucleotide (NAD+).

Those were activators but there are also substances that bind to he an enzyme and decreases the activity of the enzyme and these substances are called inhibitors. There are four types of inhibition: competitive inhibition, noncompetitive inhibition, irreversible inhibition, and feedback inhibition.

competitive inhibitor

Competitive inhibitors compete with the substrate for the same active site, displacing a percentage of substrate molecules from the enzymes. One example of this type of inhibitors is the medicine penicillin. Penicillin blocks the enzyme bacteria use to build their cell wall. To overcome competitive inhibition is to increase the substrate concentration because if there is higher concentration of substrates than the inhibitor, then there would be more collisions between the enzyme and the substrate; the enzyme will more frequently collide with the substrate.

noncompetitive inhibitor

Noncompetitive inhibitors bind to the enzyme in a location other than the active site, changing the shape of the active site of the enzyme making the enzyme unable to bind to the substrate. Most noncompetitive inhibitors bind to a specific portion fo the enzyme called an allosteric site. A substance that binds ot an allosteric site and reduces enzyme activity si called an allosteric inhibitor. When this substance binds to this site, it causes a conformational change in the active site which is no longer a functional binding site.

Irreversible inhibitors are the same thing as competive and noncompetitive inhibitors, however irreversible inhibitors are inhibitors that permanently bind to the enzyme. So competitor would bind permanently to the active site while the allosteric (noncompetive) will permanently bind to the allosteric site of the enzyme.

Before we can talk about the last inhibitor, it is important if we get the understanding about metabolic pathways. Organisms contain thousands fo different kinds of enzymes that catalyze a wide variety fo reactions. Many of these reactions in a cell occur in sequences called metabolic or biochemical pathways. In such pathways, the product of one reaction becomes the substrate for the next reaction. Metabolic pathways creates organization and efficiency amongst the cell.

Now we can talk about feedback inhibition. Feedback inhibition is a process where the end production of a biochemical pathway acts as an inhibitor of an early reaction. Not only is it unnecessary to synthesize a compound when plenty is already present, but doing so would waste energy and raw materials. It is therefore advantageous for a cell to temporarily shut down biochemical pathways when their products are not needed and this is when feedback inhibition comes in. The end product of the pathway binds to an allosteric site on the enzyme that catalyzes the first reaction in the pathway, causing conformational change and preventing the enzyme from functioning properly.

For a better understanding of the biochemical pathway and the feedback inhibition please go to http://www.explorebiology.com/apbiology/resources/ and go under enzymes and metabolism and click on the second biochemical pathway animations.

Allosteric regulation is conformational changes by regulatory molecules like inhibitors that keep enzyme in an inactive form and activators that keep the enzyme in an active form. Cooperativity is when a substrate acts as an activator because it causes a conformational change in the enzyme and this makes it easier for other substrates to bind to the enzyme.

Well I hope I had helped you out.

Metabolism and Enzymes

noreply@blogger.com (Jackie) — Wed, 12 Dec 2007 02:21:00 +0000

Metabolism and Enzymes!

Chemical Reactions:

Metabolism is a chemical reaction of life. Bonds forming and breaking between molecules are both involved.

Forming bonds are known as dehydration synthesis, and anabolic reactions. This synthesis requires an enzyme and the release of H2O, while bringing two molecules together.

This diagram shows the dehydration synthesis of sucrose. An enzyme combines Glucose and Frustose, while releasing H2O, to form the compound Sucrose.

Breaking bonds is known as hydrolysis, digestion and catabolic reastions. Breaking of bonds requires a different enzyme, and H2O, to breakdown a compound into two molecules.

This diagram shows Hydrolysis. An enzyme, as well as H2O, is used breakdown the compound into two seperate molecules.

Energy is present is both breaking and forming of bonds. Some reactions release energy, for example hydrolysis, the digesting of polymers. When reactions release energy, it is known as Exergonic.

While some reactions release energy, others require energy. Dehydration Synthesis, the building of polymers, is an example of a chemical reaction requiring energy. These chemical reactions are known as Endergonic.

Activation Energy:

Since reactions don't just happen spontaneously, since covalent bonds are stable, energy is needed to initiate a chemical reaction. This energy is known as Activation Energy. Sometimes the amount of energy needed to destabilize a bond is too much for life. An example of this is lighting a match to burn a piece of paper, like Ms. Foglia did in class.

When there is too much activaton energy in a reaction, a catalyst can be added to reduce the amount of activation energy used to start a reaction. For a cell to reduce energy, an enzyme is added. The enzyme acts as a catalyst for the cell. As Philmore said "Call in the ENZYMES!"

The Nervous System

noreply@blogger.com (deeba) — Thu, 06 Dec 2007 03:29:00 +0000

Today in class we continued to learn about the NERVOUS SYSTEM.

Voltage-Gated Channels

Changes in charge across the membrane causes ion channels to open and close.

In response to depolarization, Na+ channels open quickly and close slowly. While K+ channels open slowly and close slowly in response to depolarization.A neuron has to re-set itself after every reaction for the next reaction. Na+ is moved back out while K+ is moved back in. One protein pumps both potassium and sodium out with the use of energy because both are moving against the concentration gradients.
The nerve re-sets itself by pumping 3 Na+ out and 2 K+ in, which is not an equal exchange. Active transport proteins in the membrane are responsible for pumping Na+ out and K+ in. These proteins require a great deal of energy, or ATP.
Action Potential Graph

1. Resting potential- voltage-gated ion channels are closed but some K+ pass through 2. Threshold Potential- an action potential is produced
3. Depolarization- voltage-gated sodium channels open and allow Na+ to diffuse
4. Na+ channels close and K+ channels open
5. Repolarization- diffusion of K+ out of the axon; resets charge gradient
6. Undershoot- K+ channels start to close

Myelin Sheath

Axons are lined with Schwann cells which act as insulators to ensure that signals go far. Signals travel from node to node to reach their destination. A loss of signal can cause Multiple Sclerosis, when the immune system attacks myelin sheath.

Due to the gaps between neurons, impulses have to jump the synapse as quickly as possible to get to other cells. A chemical charge is needed to jump the gaps, so chemicals stored in the vesicles release neurotransmitters. The diffusion of chemicals across the synpases carry the chemcial signal across the synapse.

Neurotransmitters:

-Acetylcholine: help in the contraction of muscles, transmit signals to skeletal muscle

-Epinephrine & Norepinephrine: fight or flight response

-Dopamine: help in getting people out of comas but too much of it can cause schizophrenia

-Serotonin: affects sleep, learning and attention

Our next sherpa will be Ashley Scavo.

Regulating The Internal Environment Part 2

noreply@blogger.com (nross) — Tue, 04 Dec 2007 22:13:00 +0000

~Maintaining Homeostasis~

Homesostasis in the body is maintained through a series of different actions trigured by different internal and external stimuli.

The Negative Feedback Loop is one of the most essential actions. It starts with a stimulis, sensors within the body monitor these changes and immdeiately send information to the corresponding intergrating sensor such as an organ or a gland. From there chemicals are released to return the condition to its normal state. Once the response is complete sensors stop sending information and the chemical is stopped, thus allowing the system to enter a state of rest until it must perform its' function again.

An example of this is the action your body goes through when you are threatened or excited. The pituitary gland releases a hormone that causes your adrenal glands to release adrenaline which allows your body to perform basic functions at a heightened level. Adrenaline effects your heartrate and general awareness, giving you abilities that you don't normally have.

The endocrine system also plays a large role in regulating homeostasis. Blood pressure and osmolarity are regulalted by the endocrine system, specifically the brain and kidneys. The pituitary gland monitors these conditions and when something happens to the levels of either osmolarity or BP then action is immediately taken.

-If blood osmolarity rises to high meaning it becomes hypertonic the pituitary gland trigures the release of an anti-diuretic hormone a.k.a. ADH. This increases the permeability of the collecting ducks in the kidneys allowing for increased water absorption. This dilutes the blood bringing it back down to a more stable level.

-If blood pressure drops too low renin is released which removes part of the protein angiotensinogen already found in the blood exposing its' reaction site allowing it to cause the kidneys to release aldosterone. This causes increased water and salt absorption replacing missing components of the blood so pressure is restored.

The other key system to maintaining homeostasis is the

Nervous System.

The most important cell of the nervous system is the neuron. The neurons in the body work very similar to a line of dominoes. A signal starts the reaction like knocking over the first one. A wave is then sent through each single cell until it reaches its predetermined destination. The only way it can occur again is if you reset the axons in a neuron or the lines of dominoes.

Nerve cell live in a sea of charged ions. Ions with negative charges (anions) are found more within the cell, and ions with positive charges (cations) are more common outside the cell. When a nerve is stimulated Sodium channels in the cell membrane open allowing the diffusion of positively charged ions into the cell. At this point the charge on the cell is reversed. Following the first wave another wave of channels is opened this time allowing cations to move out of the cell causing the repolarization of the nerve cell. This is the way messages are sent from anywhere in your body to your brain within milliseconds. After all channels have been closed again and the cell is stabalized it is ready to fire again.

Monday Dec. 3

noreply@blogger.com (Ryan) — Tue, 04 Dec 2007 03:37:00 +0000

Mammalian Kidney

-The 2 kidneys have 1,000,000 nephrons each inside them.
-The Nephron filter out urea and other solutes
-the blood leading to the kidneys is from the inferior vena cava
-an animals blood pressure forces the blood into the glomerulus forcing out the liquid and small solutes in the blood.
-too high of blood pressure in this region is hypertension which causes kidney damage
-the glomerulus is a ball of capilaries surrounded by the bowmans capsule which collects the liquid from the blood
-the bowmans capsule then leads to the loop of henle.
-the descending loop of henle reabsorbs h2o
-the ascending loop reabsorbs salts and pumps cl- that it followed by na+ due to unlike charge attraction.
-the collecting duct reabsorbs h2o and urea is passed through the bladder

-diffusion is used in the nephron whenever possible, water is never moved by active transport because it is unnecessary energy use

Whats left in the blood if all the liquid is squeezed out in the glomerulus?
-cells and proteins are too big to fit diffuse through the capillaries

Whats excreted?
-highly concentrated urea, excess h2o, excess solutes (salts and glucose)

Regulating The Internal enviorment

noreply@blogger.com (Alex E) — Mon, 03 Dec 2007 06:30:00 +0000

Homeostasis is the tendency of the body to seek and maintain a condition of balance within its internal environment, even when faced with external changes. this includes cell growth ion balance temperature blood sugar levels energy production cell growth water balance and nutrients.

There are conformers and Regulators. Conformors change their internal conditions to what ever the external enviorment is. An example of a conformors are snakes.

Regulators maintain their interal conditions constant. Such as as body temperature, in humans the normal body temperatur is 98.6

Osmoregulation is the balance of fluids in order to maintain homeostasis.

Their are three conditions that are involved. For each of these conditions the kidney works in different ways.

Hypertonic is a solution with higher solute concentration (higher osmotic pressure) than another so water wants to move in.

Hypotonic is a solution with lower solute concentration (lower osmotic pressure) than another so water wants to move out of

Isotonic is solution with the same solute concentration (same osmotic pressure) as another no net movement of water.

fish that live in fresh water take up salt from the enviorment. Water will flow into the fish and the fish will excrete a low concentration urine to get rid of all of the extra water.

As for fish that live in salt water they tend to lose water and gain salt. They excrete salt from their gills. Water organisms excreteamonia they do not transform it.

Land animals need to conserve water and may need to conserve salt since they live in a dry enviormnent. When we digest foods we create waste products . when we consume nucleic acids we create amonia. Amonia is toxic an carcinogenic it is easily put into cells(soluble). Land animals change amonia into urea to make it less toxic and terrestrial. Uric acid is Eliminated in a pastelike form through the cloaca (mixed with feces) in birds and reptiles. Land animals must excrete it quickly, the longer that amonia is in our body the more problems we can encounter

Egg animals conserve as much water as possible. They create uric acid which is less soluble. it is not a liquid waste. To make something less soluble you make it bigger.

The kidney maintains homeostasis in the body by

removing waste products from the body
removing drugs form the body
balance the body's fluids
releases hormones that regulate blood pressure
produce an active form of vitamin D that promotes strong, healthy bones
control the production of red blood cells.

The kidney works in 4 steps

Filtration- body fluids are collected (blood).

Water and soluble material are removed.

Reabsorption- reabsorb needed substances back in the blood

Secretion- pump out unwanted substances to urine.

Excretion-remove excess substances and toxins from body.

Movement Across the cell membrane

noreply@blogger.com (Chad B.) — Fri, 30 Nov 2007 01:35:00 +0000

So in class we learned about diffusion, and the channels within the cell membrane. The definition of Diffusion is the movement of high to low concentration.

CELL MEMBRANE
The cell membrane is a buffer zone between the internal cell, and the outside of the cell. Cells need to get material in, and wastes out. The cell membrane allows for things such as food, carbohydrates, sugars, proteins, amino acids, lipids, salts, oxygen, and water. The cells need to get wastes such as ammonia, salts, carbon dioxide, water, extra sugar, and other products out of the cell. They are stern. Stern but fair. They must be tough.

As you can see the membrane surrounds the cell, and makes sure only necessary materials get in and out.
DIFFUSION THROUGH A PHOSPHOLIPID BILAYER
Since the middle of the phospholipid bilayer is non polar, only other non-polar molecules can get through, such as Fats and other lipids. Water, other polar molecules, ions, and large molecules cant get though. It's like a hip Hollywood party. Only the coolest celebrities get access, Fats, and other lipids. Polar molecules, ions, and large molecules aren't "cool" enough to get into this party.
CHANNELS THROUGH CELL MEMBRANE
Protein Channels make a membrane semi-permeable. Certain channels allow certain membranes across into the cell.

FACILITATED DIFFUSION
This is just simple diffusion through a membrane channel. When a channel and a molecule are right for each other, the channel moves a specific molecule across the channel into the cell. This doesn't require any energy.
ACTIVE TRANSPORT
Sometimes high to low concentration just isn't the cool thing to do. Therefore molecules must succumb to peer pressure and go against the concentration gradient. The protein pump, changes its shape to transport the molecules from one side to another. What does this cost you may ask? ATP. Energy. you know.LARGE MOLECULES
Large molecules need loving to. You know what I'm saying. They can move in through vesicles, and vacuoles. There is endocytosis, and exocytosis.

Endocytosis has two parts.
-Phagocytosis is "cellular eating". I mean cells get hungry too. It is a process where cells absorb material ( molecules such as proteins) from the outside by engulfing it with the cell membrane. -pinocytosis is "cellular drinking". is a form of endocytosis in which small particles are brought into the cell suspended within small vesicles which subsequently fuse with lysosomes to hydrolyze, or to break down, the particles.
Exocytosis is the process in which a cell directs secretory vesicles to the cell membrane.
that should be sufficient

REGULATING THE INTERNAL ENVIORNMENT

noreply@blogger.com (Melissa C.) — Thu, 29 Nov 2007 22:19:00 +0000

Regulating the Internal Environment

Conforemers vs. Regulators
There are two evolutionary paths for organisms, they can either regulate their internal enviornment or conform to their external environment. When organisms regulate thier internal enviornment they are able to maintain a relatively constant internal condition, when they conform they allow their internal conditions to fluctuate along with
any external changes.

Water Balance and Nitrogenous Waster Removal
As there was a change from unicellular to mutlicellular organisms the syestems within animal had to evolve in order to support all multicellular life.One can see this through the respitory system, digestive system and circulatroy system all working together. Through entry ways foods and other materials are entered into the body but at the same time both extra cellular waste and intrecellular waste are being removed. Another example is systems built inside larger cells. Becasue the cells have divided and therefor created a larger surface area the cells inside are not exposed to water and there for are not able to diffuse items into them, but becasue
these cells have systems that creates entry ways into them they are able to gain materials no matter what their location maybe.

Solving Exchange Problems
In order to over come the limitations of diffusion certain systems much have evolved.Exchange systemes are of use in distributing nutrients by the circulatory system and removing of wastes through the excrectory system.

Osmoregulation
We were also introduced to the beginnings of osmoregulation or the balancing of water.Osomoregulation is determined by where you live and the amount of water in your surronding areas.Organims found in fresh water will regulate their water systems differently then let say those found on land due to the amount and the type of water that is availible to them.

pardon the lack of pictures, but the system doesn't seem to be working in my favor today
and our next report will be delivered by Alex.
Enjoy! =)

Diffusion 101

noreply@blogger.com (Jess) — Wed, 28 Nov 2007 18:12:00 +0000

For the past few days we have learning the basics of diffusion.

But what is diffusion?

Diffusion refers to the process by which molecules intermingle as a result of their kinetc energy of random motion.

We having been trying to figure out why cells can not get infinetly large. This is because the rate of diffusion will always remain the same; therefore if the cell gets too big the middle out the cell with die because it will not get nutrients fast enough or waste out fast enough. In order words the surface area to violume ratio will work against the cell.

In the cell races lab, six teams compete to make the cell with the most mass and the smallest diffusion time. Congrats to Muskan's group for winning in our class!

In our labs we also tested to see what elements would diffuse across the cell membrane. We set up an experiment with one beakers. In the beaker we placed water and a tester and in the diffusion tube we placed water starch and glucose.

In conclusion we found that the tester, water, and glucose diffused in and out of the cell; however starch did not because the molecule was to big.

Starch looks like this:

or like this:

Theme 8: SCIENCE, TECHNOLOGY & SOCIETY

kim@ExploreBiology.com (KB Foglia) — Wed, 21 Nov 2007 17:38:00 +0000

Theme 8: SCIENCE, TECHNOLOGY & SOCIETY
Explanation: Scientific research often leads to technological advances that can have positive and/or negative impacts upon society as a whole.
Clarification: You would post here examples of how technological innovations have helped advance science whil ethose technolical accomplishments may have also had either beneficial or deleterious impacts on human society.

Theme 7: INTERDEPENDENCE IN NATURE

kim@ExploreBiology.com (KB Foglia) — Wed, 21 Nov 2007 17:34:00 +0000

Theme 7: INTERDEPENDENCE IN NATURE
Explanation: Living organisms rarely exist alone in nature.
Clarification: You would post here examples of how organisms must interact together to live successfully.

Theme 6: REGULATION

kim@ExploreBiology.com (KB Foglia) — Wed, 21 Nov 2007 17:27:00 +0000

Theme 6: REGULATION
Explanation: Everything from cells to organisms to ecosystems is in a state of dynamic balance that must be controlled by positive or negative feedback mechanisms.
Clarification: You would post here examples of how a dynamic equilibrium is maintained at different levels of life, from homesostatic control of cellular and body conditions to maintenance of population levels in ecosystems.

Theme 5: RELATIONSHIP OF STRUCTURE & FUNCTION

kim@ExploreBiology.com (KB Foglia) — Wed, 21 Nov 2007 17:13:00 +0000

Theme 5: RELATIONSHIP OF STRUCTURE & FUNCTION
Explanation: The structural levels from molecules to organisms ensure successful functioning in all living organisms and living systems.
Clarification: You would post here examples of structure-function relationships in living organisms. How specific molecules, organelles, cells, tissues, organs, and body structures are structured to support the functions that they perform. (Don't forget plants!)