AP Bio Thread

[BioBeaver]

What are you guys studying now? We have a test Friday over Metabolism, Cellular Respiration, and Photosynthesis

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[JPodel]

Got an A on our Metabolism/Enzyme test we took the last day before break! Great way to end 1st quarter!

 

[futuredoc44]

Got an A on our Metabolism/Enzyme test we took the last day before break! Great way to end 1st quarter!

Congrats! We're working through organic chemistry and we're going in a different order than you guys for sure.

 

[JPodel]

What book are you guys using? We have Campbell 8th Edition Biology (AP Edition) and we go through the units from there.

Also, have you guys ordered any AP study books? Which one should I get? I heard Barrons is nice but wanted to know what you guys are doing...

 

[futuredoc44]

What book are you guys using? We have Campbell 8th Edition Biology (AP Edition) and we go through the units from there.

Also, have you guys ordered any AP study books? Which one should I get? I heard Barrons is nice but wanted to know what you guys are doing...

Well since ours is all virtual, we're using a McGraw-hill. And for test prep, we have the 5 steps to a 5 app. So far. Haha

 

[Hisaam]

Test on Friday over chapters 6,7,11,12 from Campbell Reece. I'm a little nervous for this one. I had no issues with the chem unit and got an A on that test, but there is quite a bit of material on this one so it should be interesting!

 

[BioBeaver]

Anyone want to tutor me on Glycolysis, Citric Acid Cycle, and the Electron Transport Chain?

 

[BioBeaver]

For reference to my above post, I found some great videos from "crashcourse" on YouTube covering Cell Respiration and Photosynthesis. They don't go as in-depth as we may need, but they do a great job on explaining the concepts.

 

[Arayh]

What do you need help with in glycolysis, krebs and electron transport chain?

 

[BioBeaver]

What do you need help with in glycolysis, krebs and electron transport chain?

The inputs and outputs of each process, what the roles of NAD, FAD, and NADH are, and which processes use oxygen/which produce CO2.

 

[Arayh]

The inputs and outputs of each process, what the roles of NAD, FAD, and NADH are, and which processes use oxygen/which produce CO2.

How detailed is AP Biology nowadays anyways? Here's a general summary:

Glycolysis (aerobic) is

[Glucose] + 2 [Pi] + 2[NAD+] + 2[ADP] -> 2 [Pyruvate] + 2[ATP] + 2[NADH] + 2[H+] + [H2O]

and Anaerobic is:

[Glucose] + 2 [Pi] + 2 [ADP] -> 2 [Lactate] + 2 [ATP] + 2 [H2O]

Neither reaction uses oxygen, and the net gain is 2 ATP per molecule of glucose (where by 2 ATP are used to catalyze reactions, and 4 ATP are produced so NET Gain = 2 ATP). Two molecules of NADH produced in aerobic glycolysis are going to be transported into the mitochondria for the electron transport chain (which gives each NADH a loss of about 1 ATP per molecule, so rather than ~3 ATP for each NADH, you only get ~2ATP for each of these 2 NADH). Though there is some controversy about this.

The main purpose of anaerobic glycolysis is to generate energy but to also remove the 2 NADH produced. The 2 NADH are used by lactate dehydrogenase to turn pyruvate into lactate, which in turn recycles the NADH into NAD+ (which are necessary for another round of glycolysis).

So Overall Energy Gain for Aerobic Glycolysis turns to 2 ATP, and 2 NADH for each Glucose.

Glycolysis occurs in the cytoplasm.

PDC:

Before the Kreb's cycle, the 2 Pyruvate are turned into 2 Acetyl-CoA via Pyruvate Dehydrogenase Complex (PDC). With this process, 1 NADH and 1 CO2 is formed for each Pyruvate. Totaling 2 NADH and 2 CO2 produced.

Kreb's Cycle:

The Kreb's Cycle provides numerous functions in metabolism, feeding various other cycles and processes with its byproducts or catalysts, and its entire function is exceedingly complex, probably something you don't need for this level in education. Its main role is to oxidize Acetyl-CoA into CO2 and H2O.

The overall reaction simplifies to:
1 [Acetyl-CoA] + 3 [NAD+] + [FAD] + [GDP] + [Pi] + 2[H2O] -> 2 [CO2] + 3 [NADH] + 1 [FADH2] + 1 [GTP] + 3 [H+] + CoA.

Two carbon atoms enter the cycle as acetyl Co-A and leave as 2x CO2. So for 2 Acetyl-Co-As -> 4 CO2 produced.

Since there's 2 Acetyl-CoA Molecules, you get double that reaction, so overall energy gain is 6 NADH, 2 FADH2, and 2 GTP.

Kreb's Cycle occurs in the Mitochrondrion Matrix.
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So far you have produced 2 FADH2, 6 NADH inside Mitochrondria, 2 NADH via PDC in Mitochrondria, 2 NADH in Cytoplasm (needs transport into Mitochondria), 2 ATP from Glycolysis and 2 GTP from Krebs which converts to ATP.

ETC:

Finally everything goes to the Electron Transport Chain for final energy metabolism. Glycolysis and Kreb's Cycle's oxidation pathways ultimately turn Glucose into CO2, and the metabolic intermediates of these reactions donate electrons to specialized coenzymes NAD+ and FAD (Nicotinamide adenine dinucleotide and Flavin adenine dinucleotide) to form the energy rich reduced coenzymes NADH and FADH2. These reduced coenzymes can then donate these electrons down a specialized set of carriers collectively called the Electron Transport Chain. As electrons are passed down this chain, they lose their free/potential energy and part of this energy is captured to produce ATP via oxidative phosphorylation.

The inner mitochrondrial membrane can be separated into 5 different enzyme complexes (I, II, III, IV and V). Complex V catalyzes ATP synthesis. Each complex accepts or donates electrons to relatively mobile carriers which can then further donate electrons, ultimately to combine with oxygen and protons to form water. This requirement for Oxygen as the final electron acceptor makes it ultimately aerobic, and accounts for the body's greatest utilization of oxygen.

You should understand that electron transport chain via these complexes is coupled to a proton pump, which pumps H+ across the inner mitochrondrial membrane, from the matrix into the intermembrane space, each time electrons are passed down the transport chain (from NADH/FADH2) and energy is liberated from the electrons. This process creates an electrochemical gradient which is then used to drive ATP synthesis.

The complex V (ATP Synthetase or ATPase) acts as a channel for this gradient of protons. The chemiosmotic hypothesis proposes that the re-entering of protons through this channel down their gradient results in the synthesis of ATP from ADP + Pi.

For calculatory purposes, each NADH molecule generates approximately 3 ATP (except for the 2 NADH from the cytoplasm via Glycolysis -> where there's debate that they only generate 2 ATP because 1 ATP is necessary to transport them into the matrix). Each FADH2 generates 2 ATP approximately via the ETC.

Though in reality each NADH generates actually only close to 2.6 ATP, and Cytosolic NADH is around 1.5-1.6 ATP, while FADH2 generate around 1.5 ATP each due to leakiness of membranes and other energy inefficiencies.

So in total calculation wise, with aerobic respiration:

[1 Glucose] generates [2 Cytosolic NADH = 4 ATP] + [2 ATP] + [2 PDC-NADH = 6 ATP] + [2 GTP/ATP] + [6 Mitochrondrial NADH = 18 ATP] + [2 FADH2 = 4 ATP] -> 36 ATP Total.

If you need more detailed information about ETC complexes like NADH Dehydrogenase, CoQ..etc, various reactions, enzyme differences like Hexokinase vs Glucokinase, I recommend Lippincott's Illustrated Biochemistry Review for fast review with most essentials, and a copy of Lehninger's Principles of Biochemistry for more detailed aspects. Feel free to reply here for more help, or PM me.

 

[BioBeaver]

EXACTLY what I'm looking for! Thank you so much!

 

[Arayh]

EXACTLY what I'm looking for! Thank you so much!

You're welcome, let me know if there's anything else unclear and I'll try my best to explain.