Glucose Metabolism and Energy Production

These flashcards cover key concepts and processes involved in glucose metabolism, including oxidation, glycolysis, the Krebs cycle, and ATP production.

What is oxidation?

Loss of electrons.

What does losing electrons mean in biology?

Releasing energy.

What happens to the released energy?

Used to make ATP.

What carries electrons after oxidation?

NAD⁺ → NADH and FAD → FADH₂.

What is glucose?

A main source of chemical energy in the body.

Why is glucose good for energy?

It is highly reduced (has lots of electrons to lose).

What happens to glucose in metabolism?

It gets oxidised to release energy.

Is breaking down glucose catabolic or anabolic?

Catabolic.

What is catabolism?

Breaking molecules → releases energy.

What is anabolism?

Building molecules → requires energy.

Are catabolic pathways oxidative or reductive?

Oxidative (lose electrons).

What enzymes digest carbohydrates?

Salivary amylase and pancreatic amylase.

What do these enzymes break down?

Starch → sugars → glucose.

What is glycolysis?

Breakdown of glucose into 2 pyruvate.

Where does glycolysis occur?

Cytosol.

How many carbons does glucose have?

6 carbons.

How many carbons in pyruvate?

3 carbons each (2 molecules).

What is the energy investment phase of glycolysis?

Uses 2 ATP.

What is the energy payoff phase of glycolysis?

Produces 4 ATP + 2 NADH.

What is the net ATP from glycolysis?

2 ATP.

What is the net NADH from glycolysis?

2 NADH.

What must you always track in metabolism?

Carbons (6 → 2 × 3).

What happens if oxygen is present after glycolysis?

Aerobic respiration.

Is aerobic respiration efficient?

Yes — lots of ATP.

What happens if no oxygen is present after glycolysis?

Anaerobic respiration.

Is anaerobic respiration efficient?

No — very little ATP.

What is produced in humans during anaerobic respiration?

Lactate.

Why do we need NAD⁺ in glycolysis?

To accept electrons.

What happens if NAD⁺ runs out?

Glycolysis stops.

How is NAD⁺ regenerated without oxygen?

Pyruvate → lactate.

What happens to pyruvate in aerobic respiration?

Converted to acetyl-CoA.

What is released during the conversion of pyruvate to acetyl-CoA?

CO₂ and NADH.

Where does the Krebs cycle occur?

Mitochondria.

What does the Krebs cycle produce per glucose?

2 ATP, 8 NADH, 2 FADH₂, CO₂.

What is the Electron Transport Chain (ETC)?

Final stage that produces most ATP.

What molecules feed into the ETC?

NADH and FADH₂.

What do NADH and FADH₂ donate in the ETC?

Electrons.

What does the ETC create?

Proton (H⁺) gradient.

What is the proton gradient like?

A dam storing energy.

What uses the proton gradient?

ATP synthase.

What does ATP synthase do?

Makes ATP.

How much ATP is produced from NADH?

~3 ATP.

How much ATP is produced from FADH₂?

~2 ATP.

What is the total ATP yield from glucose?

~38 ATP.

What happens to pyruvate in humans?

→ lactate.

What happens to pyruvate in yeast?

→ ethanol + CO₂.

What is the process by which yeast convert pyruvate?

Fermentation.

What are the 3 key enzymes in glycolysis?

Hexokinase, Phosphofructokinase-1 (PFK-1), Pyruvate kinase.

What does insulin do in glycolysis?

Activates glycolysis.

What does glucagon do in glycolysis?

Inhibits glycolysis.

What does AMP signal in glycolysis?

Low energy → increase glycolysis.

What does ATP signal in glycolysis?

High energy → decrease glycolysis.

What does citrate signal in glycolysis?

High energy → inhibit glycolysis.

What is the full pathway of glucose metabolism?

Glucose → Glycolysis → Pyruvate → (with O₂) Krebs + ETC → lots of ATP → (no O₂) Lactate → little ATP.