Carbohydrate Metabolism
The Citric Acid Cycle
Electron Transport, Oxidative Phosphorylation, and Oxygen Metabolism
1
How many ATP are used and produced in glycolysis?
2 ATP are used in the energy investment phase, and 4 ATP are produced in the energy generation phase, for a net gain of 2 ATP.
1
What molecule enters the CAC?
Acetyl-CoA, a 2-carbon molecule.
1
Where is most ATP generated in cellular respiration?
Oxidative phosphorylation.
2
Which glycolysis step splits a 6-carbon sugar into two 3-carbon sugars?
The 4th step: Fructose-1,6-bisphosphate (F1,6-BP) is cleaved by aldolase into two 3-carbon molecules.
2
Where does the CAC take place?
In the mitochondrial matrix.
2
What is the mitochondrial matrix and what is its purpose?
The innermost compartment of the mitochondrion where the CAC and parts of oxidative phosphorylation occur.
3
What does hexokinase do in glycolysis?
Hexokinase catalyzes the first step of glycolysis by phosphorylating glucose to form glucose-6-phosphate.
3
What is the enzyme that converts pyruvate to acetyl-CoA?
Pyruvate dehydrogenase (PDH).
3
How do you identify the strongest reducing agent using reduction potentials?
The substance with the most negative standard reduction potential (E°) is the strongest reducing agent.
4
What are common substrates and products of glycolysis?
Substrate: glucose; Products: 2 pyruvate, 2 ATP (net), 2 NADH.
4
What do oxidoreductase enzymes do?
Catalyze oxidation reactions involving loss of hydrogen atoms.
4
What are the parts of the respiratory (electron transport) chain?
Complexes I, II, III, IV, and ATP synthase.
5
How do glycolysis and gluconeogenesis differ?
They are nearly reverse processes but use different enzymes and occur in different cellular compartments.
5
What are four types of biochemical reactions to recognize?
Hydration (add water), Dehydrogenation (lose H), Substrate-level phosphorylation (add phosphate), Oxidative decarboxylation (lose CO₂ with NAD⁺).
5
Which complexes pump protons (H⁺) across the membrane (against the gradient)?
Complexes I, III, and IV.
6
What molecules activate glycolysis?
F2,6BP, AMP, ADP, F1,6BP, and insulin.
6
What is the overall yield from one molecule of glucose through glycolysis and CAC?
6 CO₂, 10 NADH, 2 FADH₂, and 4 ATP.
6
What is the final electron acceptor in cellular respiration?
Oxygen (O₂).
7
Name three precursors that enter the glycolytic pathway.
Glycogen, glycerol, and lactose.
7
What is the yield from one turn of the CAC?
1 ATP, 3 NADH, 1 FADH₂.
7
How many ATP are produced from complete oxidation of one glucose molecule?
About 32 ATP.
8
What does glycogen release to enter glycolysis?
Glucose-1-phosphate, which is converted to glucose-6-phosphate.
8
What inhibits the PDH complex?
NADH and acetyl-CoA.
8
Name three reactive oxygen species that must be controlled.
Superoxide (O₂⁻), hydrogen peroxide (H₂O₂), and hydroxyl radical (•OH).
9
What is the role of glycogen in muscle and liver?
In muscle: energy for contraction. In liver: regulates blood glucose.
9
What is an anaplerotic pathway?
A pathway that replenishes intermediates of the CAC.
9
What is the order of glucose metabolism pathways?
Glycolysis → CAC → Electron Transport Chain → ATP Synthase.
10
When and how is glycogen made?
When blood glucose is high, glucose is activated to UDP-glucose and stored as glycogen.
10
What amino acid can be converted into α-ketoglutarate?
Glutamate.
10
How can ATP synthase be recognized in an image?
It’s the large protein complex embedded in the inner mitochondrial membrane, often shown as a turbine-like structure using the proton gradient to produce ATP.
