Metabolism Problem Solving week 8

Where does glycolysis occur and what does it produce?

Location: Cytoplasm

Products: 2 pyruvate, 2 ATP (net), 2 NADH

What are the two phases of glycolysis?

Preparation phase: Uses 2 ATP to phosphorylate glucose

Payoff phase: Produces 4 ATP (net gain 2), 2 NADH

Name 3 key enzymes in glycolysis and their steps.

Hexokinase: Glucose → Glucose-6-phosphate

Phosphofructokinase-1: F6P → F-1,6-BP

Pyruvate kinase: PEP → Pyruvate

What is the purpose of NADH in glycolysis?

Transfers electrons to electron transport chain for more ATP

Why are ketone bodies important during starvation?

Provide energy to the brain

Spare muscle protein from being broken down

Where does the Citric Acid Cycle occur and what is its input?

Location: Mitochondrial matrix

Input: Acetyl-CoA

What are the outputs of one citric acid cycle turn?

3 NADH, 1 FADH₂, 1 GTP/ATP, and CO₂

Name 3 key regulatory enzymes of the citric acid

Citrate synthase

Isocitrate dehydrogenase

α-Ketoglutarate dehydrogenase

What regulates the citric acid cycle?

Inhibitors: NADH, ATP

Activators: ADP, Ca²⁺

Substrate availability: Acetyl-CoA, Oxaloacetate

What is the electron transport chain (ETC) and where is it?

Final stage of respiration

Location: Inner mitochondrial membrane

Produces ATP using proton gradient

What is the role of oxygen in the ETC?

Final electron acceptor

Reduced to water

What are the 5 ETC complexes and their roles?

I: NADH dehydrogenase

II: Succinate dehydrogenase

III: Cytochrome bc₁

IV: Cytochrome c oxidase

V: ATP synthase – uses gradient to make ATP

What is chemiosmosis?

The use of a proton gradient to drive ATP synthesis via ATP synthase

What is the metabolic response in the first 24 hours of starvation?

• Glycogenolysis: Breakdown of liver glycogen to maintain blood glucose

What happens during 1–2 days of starvation?

• Gluconeogenesis: Synthesis of glucose from amino acids and glycerol

What is ketogenesis and when does it occur?

Long-term fasting (3+ days)

Converts fatty acids into ketone bodies for brain energy