biochem portage unit 7

What is bioenergetics?

The study of how nutrients provide energy for organisms, including energy-producing molecules, metabolic reactions, and energy exchange.

What is metabolism?

The sum of all chemical reactions occurring in a cell that sustain life.

What are anabolic reactions?

Metabolic reactions that build complex molecules from simpler ones; require energy.

What are catabolic reactions?

Metabolic reactions that break down molecules to release energy.

What is the primary energy currency of the cell?

ATP (adenosine triphosphate).

What molecule is the common intermediate for carbohydrate and lipid metabolism?

Acetyl-CoA.

Why is acetyl-CoA important?

It is the common molecule produced from carbohydrates and fats before entering the citric acid cycle.

What are the major stages of cellular respiration?

1. Glycolysis 2. Pyruvate oxidation (PDH) 3. Citric Acid Cycle (CAC/Krebs) 4. Electron Transport Chain (ETC)/Oxidative Phosphorylation.

Where does glycolysis occur?

In the cytosol.

Where do the Citric Acid Cycle and Electron Transport Chain occur?

In the mitochondria.

What does NADH do?

Carries high-energy electrons to the electron transport chain to make ATP.

What does FADH2 do?

Carries high-energy electrons to the electron transport chain to make ATP.

Approximately how much ATP does each NADH produce?

About 2.5 ATP.

Approximately how much ATP does each FADH2 produce?

About 1.5 ATP.

What happens during ATP hydrolysis?

ATP is broken into ADP + Pi, releasing energy.

Is ATP hydrolysis spontaneous?

Yes; ΔG°' is negative (about -30.5 kJ/mol).

What is energy coupling?

Using energy released from ATP hydrolysis to drive unfavorable cellular reactions.

What is glycolysis?

A 10-step pathway that converts glucose into two pyruvate molecules while producing ATP and NADH.

How many phases does glycolysis have?

Two: Preparatory phase and Payoff phase.

What happens during the preparatory phase?

2 ATP are invested to prepare glucose for splitting.

What happens during the payoff phase?

ATP and NADH are produced, yielding pyruvate.

How many ATP are used during glycolysis?

2 ATP.

How many ATP are produced during glycolysis?

4 ATP.

What is the net ATP gain from glycolysis?

2 ATP.

How many NADH are produced during glycolysis?

2 NADH.

How many pyruvate molecules are produced from one glucose?

2 pyruvate.

Which enzyme catalyzes glycolysis step 1?

Hexokinase.

What is the purpose of phosphorylating glucose?

To trap glucose inside the cell and commit it to metabolism.

Which enzyme converts glucose-6-phosphate to fructose-6-phosphate?

Phosphohexose isomerase.

Which enzyme splits fructose-1,6-bisphosphate?

Aldolase.

What are the two products of aldolase?

Glyceraldehyde-3-phosphate (GAP) and dihydroxyacetone phosphate (DHAP).

What happens to DHAP?

It is converted into GAP.

Which step produces NADH in glycolysis?

Step 6.

What is substrate-level phosphorylation?

Direct formation of ATP by transferring a phosphate from a metabolic intermediate to ADP.

Which glycolysis steps produce ATP?

Steps 7 and 10.

Which enzyme catalyzes the final step of glycolysis?

Pyruvate kinase.

What is the final product of glycolysis?

Pyruvate.

What happens to pyruvate under aerobic conditions?

It enters the mitochondria and is converted to acetyl-CoA.

What happens to pyruvate under anaerobic conditions in humans?

It is converted to lactate.

What happens to pyruvate under anaerobic conditions in yeast?

It is converted to ethanol.

Why is fermentation important?

It regenerates NAD+ so glycolysis can continue without oxygen.

Does fermentation require oxygen?

No.

What enzyme complex converts pyruvate into acetyl-CoA?

Pyruvate dehydrogenase (PDH).

Where does pyruvate oxidation occur?

In the mitochondria.

What are the products of pyruvate oxidation?

Acetyl-CoA, NADH, and CO2.

Why is pyruvate oxidation essentially irreversible?

It has a large negative ΔG°' and releases CO2.

How many NADH are produced when two pyruvate become two acetyl-CoA?

2 NADH.

What are other names for the Citric Acid Cycle?

Krebs Cycle and Tricarboxylic Acid (TCA) Cycle.

What is the purpose of the Citric Acid Cycle?

To oxidize acetyl-CoA and produce NADH, FADH2, GTP, and CO2.

How many reactions are in the Citric Acid Cycle?

8.

What molecule combines with acetyl-CoA to begin the Citric Acid Cycle?

Oxaloacetate.

What is formed when acetyl-CoA combines with oxaloacetate?

Citrate.

Which enzyme forms citrate?

Citrate synthase.

Which enzyme converts citrate to isocitrate?

Aconitase.

Which Citric Acid Cycle step produces the first NADH?

Isocitrate → α-ketoglutarate.

Which Citric Acid Cycle step releases the first CO2?

Isocitrate → α-ketoglutarate.

Which step releases the second CO2?

α-Ketoglutarate → succinyl-CoA.

Which Citric Acid Cycle step produces GTP?

Succinyl-CoA → succinate.

Which step produces FADH2?

Succinate → fumarate.

Which step regenerates oxaloacetate?

Malate → oxaloacetate.

What are the products of one turn of the Citric Acid Cycle?

3 NADH, 1 FADH2, 1 GTP, and 2 CO2.

How many turns of the Citric Acid Cycle occur per glucose?

2.

How many NADH are produced per glucose in the Citric Acid Cycle?

6 NADH.

How many FADH2 are produced per glucose in the Citric Acid Cycle?

2 FADH2.

How many GTP are produced per glucose in the Citric Acid Cycle?

2 GTP.

How much ATP/GTP is produced directly from complete glucose oxidation?

4 ATP/GTP.

How many total NADH are produced from one glucose?

10 NADH.

How many total FADH2 are produced from one glucose?

2 FADH2.

What is the approximate total ATP yield from one glucose?

32 ATP.

How many ATP come from 10 NADH?

25 ATP.

How many ATP come from 2 FADH2?

3 ATP.

What is beta-oxidation?

The process of breaking fatty acids into acetyl-CoA units.

Where does beta-oxidation occur?

In the mitochondria.

What must happen before beta-oxidation begins?

Fatty acid is activated to fatty acyl-CoA.

Where does fatty acid activation occur?

In the cytosol.

What transporter carries fatty acids into mitochondria?

Carnitine transporter.

How many steps are in one round of beta-oxidation?

4.

What does one round of beta-oxidation produce?

1 acetyl-CoA, 1 NADH, 1 FADH2, and a fatty acid shortened by 2 carbons.

Which carbon is oxidized during beta-oxidation?

The beta (β) carbon.

How many carbons are removed during each beta-oxidation cycle?

2 carbons.

Why is beta-oxidation called a spiral?

The same four reactions repeat until the fatty acid is completely degraded.

What happens to acetyl-CoA produced during beta-oxidation?

It enters the Citric Acid Cycle.

How many ATP are produced from a 14-carbon fatty acid?

Approximately 94 ATP.

How many rounds of beta-oxidation occur for a 14-carbon fatty acid?

6 rounds.

How many acetyl-CoA molecules are produced from a 14-carbon fatty acid?

7 acetyl-CoA.

How many NADH are produced during beta-oxidation of a 14-carbon fatty acid?

6 NADH.

How many FADH2 are produced during beta-oxidation of a 14-carbon fatty acid?

6 FADH2.

What molecule links glycolysis, beta-oxidation, and the Citric Acid Cycle?

Acetyl-CoA.

Which pathways produce NADH?

Glycolysis, pyruvate oxidation, Citric Acid Cycle, and beta-oxidation.

Which pathways produce FADH2?

Citric Acid Cycle and beta-oxidation.

Which pathway directly produces ATP through substrate-level phosphorylation?

Glycolysis and the Citric Acid Cycle (GTP).

Which pathway produces the majority of ATP?

Electron Transport Chain (oxidative phosphorylation).

Which metabolic pathway occurs entirely in the cytosol?

Glycolysis.

Which metabolic pathways occur in the mitochondria?

PDH, Citric Acid Cycle, beta-oxidation, and Electron Transport Chain.

Why is oxygen required for maximum ATP production?

It serves as the final electron acceptor in the Electron Transport Chain.

What is MCAD deficiency?

A mutation in medium-chain acyl-CoA dehydrogenase that impairs fatty acid oxidation.

What symptoms are associated with MCAD deficiency?

Hypoglycemia, vomiting, lethargy, seizures, coma, and possible sudden death.

How is MCAD deficiency managed?

Early diagnosis and dietary management.