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Flashcards in Stages of Glucose Oxidation Deck (36):

3 Stages of oxidation of glucose. Where do they take place.

1. Glycolysis, in the cytosol.
2. The krebs cycle, in the mitochondrial matrix
3. Oxidative phosphorylation, Across the inner mitochondrial membrane.


What does glycolysis mean

Splitting of sugar


What is glycolysis?

Metabolic pathway comprising of ten reactions.


What are the three major results of glycolysis?

1. By the end, each glucose has been split into two molecules of pyruvate.
2. During this process, 2 ATP are used but 4 are produced in substrate level phosphorylation. yielding 2 ATP.
3. Two molecules of NAD+ are reduced yielding two molecules of NADH for every molecule of glucose.


Is oxygen consumed and CO2 produced in glycolysis? This means it is ..

No. Anaerobic.


Why is glycolysis useful?

Produces some ATP and sets the stage for subsequent events that yield much more ATP.


What prevents pyruvate from proceeding through the further stages of glucose oxidation? If this is not avaible, what is pyruvate converted to?

A readily source of oxygen. Lactic acid(lactate) and not broken down further.


Aerobic respiration occurs where?



What is the end result of glycolysis?

2 Pyruvate


How many ATP required for glycolysis? What happens to them? What enzyme is active here?

2. converted to ADP and this results in a 6-carbon compound that has 2 phosphate groups. Hexokinase.


What happens to the 6-carbon compound during glycolysis?

The 6-carbon compound is split into two 3-carbon compounds. Each of these 3-carbon compounds has one phosphate group.


What occurs after the 6 carbon compound is split?

NAD+ pick up electrons and becomes NADH


What is the purpose of NADH?

NADH contains energy that can be used to produce ATP


After NADH is produced, what occurs?

Additional phosphorylation, creating three carbon groups that have two phosphate groups each.


What is hexokinase?

It is an enzyme that acts on 6 carbon atoms. It adds a phosphorus group thus phosphorylizing it.


What is happens to the NADH that is produced in glycolysis?

Eventually gives up its electrons.


What is the starting point of the krebs cycle?

There is none, because it is a cycle.


Glucose oxidation does not proceed beyond glycolysis until?

Pyruvate enters the mitochondrial matrix


When does fermentation occur?

If there is no oxygen present for the pyruvate.


What are the waste products of fermentation?

Lactate and alcohol.


Step 2 of cellular respiration

Formation of Acetyl CoA


What is pyruvate converted to, and how?

Acetyl CoA. converted to acetyl CoA by the removal of CO2 and the help of CoA. Pyruvate is a C3, acetyl CoA is a C2


During the linking step, what happens to NAD+. Why is it called linking step.

Reduces NAD+ to NADH+H+ links glycolysis to krebs cycle


How many acetyl CoA are produced from the initial one glucose molecule



The Acetyl portion become bonded to what in the krebs cycle?

C4 molecule, to produce a C6 molecule. CoA + C4  C6 + Coenzyme A


What occurs after it bonds to the c4 molecule. What else occurs at this step?

A Co2 is removed to produce C5 molecule. NADH is also produced from NAD+


After the C5 is produced, what happens? In the krebs cycle.

Another CO2 is released, Two more NADH are produced one FADH2 is produced and one ATP which is produced by subtrate level phosphorylation.


List the step of the krebs Cycle.

1.Pyruvate (3C) is stripped of carbon, producing acetate (2C) and releasing CO2
2.NAD+ is reduced to NADH
3.Acetate is coupled with coenzyme A to form Acetyl-CoA
4.Acetyl-CoA (2C) combines with oxaloacetate (4C) to form citrate (citric acid) (6C)
5.Citrate is cycled back to oxaloacetate
6.CO2 is released
7.Hydrogen (H+ and e-) is released to carriers NAD+ and FAD to form NADH and FADH2
8. 2 ATP formed


Which two molecules from the krebs cycle can be used to form ATP. Production of ATP from these uses what?

NADH and FADH2. The electron transport chain.


Electron transport chain occurs where

Inner mitochondrial membrane.


Go through electron transport chain. 8.

1. NADH and FADH2 from cellular respiration bring electrons to the electron transport system.
2.When a carrier is reduced, some of the energy that is gained as a result of that reduction is used to pump hydrogen ions across the membrane into the intermembrane space.
3.The electron is then passed to another carrier.
4.As before, some of the energy gained by the next carrier as a result of reduction is used to pump hydrogen ions into the intermembrane space.
5.Eventually, a concentration gradient of hydrogen ions is established in the intermembrane space (green on the diagram).
6.The last carrier must get rid of the electron. It passes it to oxygen to form water (next slide).
7.Two electrons are required to form one molecule of water. The process therefore happens twice for each water molecule.
8.ATP synthase produces ATP by phosphorylating ADP. The energy comes from hydrogen ions forcing their way into the matrix as they pass through the ATP synthase (due to osmotic pressure).


Fermentation involves what, plus additional steps?



Because glycolysis needs NAD+, The NADH that is produced must?

Regenerate to NAD+, otherwise glycolysis will stop.


What happens in when lactic acid is produced

NADH gives electrons to pyruvate which is reduced to lactate.


How does NAD+ function in cellular respiration?

by carrying two electrons. With two electrons, it becomes NADH


What does NAD+ do ?

NAD+ oxidizes its substrate by removing two hydrogen atoms. One of the hydrogen atoms bonds to the NAD+. The electron from the other hydrogen atom remains with the NADH molecule but the proton (H+) is released.
NAD+ + 2H ® NADH + H+
NADH then donate the two electrons (one of them is a hydrogen atom) to another molecule