Glucose Metabolism Flashcards
Where does glycolysis occurs?
Occurs in the Cytoplasm
What is ATP synthase and what is it used for?
- the pH and membrane potential across the inner mitochondrial memberane is sensed by this enezyme
- it can
- sense the proton gradient
- pumps protons back into the mitochondrial matrix
- uses the free energy associated with pumping the protons to make ATP
- ATP synthase makes the majority of ATP
Where does the citric acid cycle and oxidative phosphorylation occur?
In the Mitochondria
- Citric Acid Cycle
- occurs in the mitochondrial matrix
- Oxidative phosphorylation
- performed by membrane proteins in the inner mitrochondrial membrane
Details about the Proton Gradient
- proton pumping produces an unequal distribution of protons called proton motive force that contains:
- a pH gradient (chemical gradient)
- a strong membrane potential (charge gradient)
What is the first step of the Citric Acid Cycle?
- Pyruvate from glycolysis undergoes
- a decarboxylation
- an oxidation
- electrons are relayed to NAD+
- a transfer to CoA to make acetyl CoA
- all steps performed here are done by a large enzyme complex named Pyruvate dehydrogenase
- size ranges from 4-10 megadaltons
What is the Electron Transport Chain and how does it work?
- the enzymes in the inner membrane that make energy from electrons
- electrons are relayed through a decreasing free energy with the final electron acceptor being molecular oxygen
What is the main regulatory enzyme in glycolysis?
Phosphofructokinase
It catalyzes the first irreversible step of the patheay
Turns Fructose 6-phosphate into Fructose 1,6-bisphosphate using ATP
What is Alcoholic Fermentation?
- ethanol can be formed from pyruvate by yeast and other microorganisms and is done by
- decarboxylation of pyruvate to form acetaldehyde
- reduction of acetaldehyde by NADH to form ethanol
- this regenerates NAD+ which is recycled back to glycolysis
Define Glycolysis
- an anaerobic pathway
- no oxygen is required for this pathway to proceed
- this pathway evolved before there were sufficient oxygen levels in the atmosphere
- no oxygen is required for this pathway to proceed
- a metabolic pathway where one glucose molecule is converted to:
- 2 molecules of pyruvate
- 2 moleules of ATP
- 2 molecules of NAD+ are reduced to NADH via the oxidation of glucose
What are the three reactions that pyruvate may go through depending on the organism and oxygen supply?
Alcoholic Fermentation
Lactic Acid Fermentation
Aerobic Respiration
What are the two parts of the overall glycolysis reaction?
Hint: Input and Output
Input
Glucose + 2 Pi + 4 ADP + 2 ATP + 2 NAD+
Output
2 pyruvates + 4 ATP + 2 NADH + 2H+ + 2 H2O
What is Lactic Acid Fermentation?
- lactic acid is produced anaerobically from pyruvate in a variety or organisms, including higher organisms
- occurs in higher organims when oxygen is limiting
- pyruvate is reduced to lactate by the enzyme lactate dehydrogenase
- converts NADH to NAD+
What are the stages of Glycolysis?
- Two Stages
- 1st Stage
- trapping and prep phase (no ATP produced)
- 2nd Stage
- 3 carbon fragments are oxidized
- 1st Stage
What happends after glycolysis?
- the pyruvate generated in glycolysis can have three different fates that depend on the organism and the oxygen supply
What is the next step after the Citric Acid Cycle?
- next step is to take all of the electrons harvested in the citric acid cycle and make energy
- done by a series of enzymes that are embedded in the inner mitochondrial membrane
- electron transport chain
What is Cellular Respiration?
- the combined citric acid cycle and oxidative phosphorylation pathways that lead to ATP production
Describe this picture
As electrons are relayed through the electron transport chain, the free energy released is used to pump protons (H+) into the mitochondrial intermembrane space (against the concentration gradient
What process is this?
Glycolysis
Depending on the organism and oxygen availability, pyruvate generated from glucose has multiple potential fates.
True or False
The pumping of protons by complexes I, II, III, and IV in the electron transport chain is what leads to ATP synthesis
False
Only pumping of protons from complexes I, III, and IV leads to ATP synthesis
What is Pyruvate Dehydrogenase and what is it use for?
- an enzyme found in the citric acid cycle
- it decarboxylizes pyruvate
- oxidizes
- transfer to CoA to make acetyl CoA
True or False
One molecule of glucose can yield approximately 30 ATP molecules
True
True or False
Phosphofructokinase is allosterically regulated and is the most important checkpoint in glycolysis
True
- high levels of ATP allosterically inhibit the enzyme
- AMP stimulates activit
binding curve shifts from hyperbolic (green) to sigmoidal (red)
What is the main function of the citric acid cycle?
- to provide electrons (via NADH and FADH2) that will be used by the electron transport chain to make ATP
for picture
- purple = electrons that will be used to make ATP
- blue = small amount of energy produced
