BIOL300: Chapter 13 & 14

Exam #1

Why do cells break down food step-by-step?

To release energy slowly and store it as ATP instead of losing it as heat.

Overall equation of cellular respiration?

Glucose + O₂ → CO₂ + H₂O + ATP

Where does glycolysis occur?

Cytoplasm

Does glycolysis require oxygen?

No (anaerobic)

Starting molecule of glycolysis?

Glucose

End products of glycolysis?

2 pyruvate, 2 ATP, 2 NADH

What happens to pyruvate without oxygen?

Converted to lactate

Why are enzymes in glycolysis important?

They are regulation points

Where does pyruvate oxidation occur?

Mitochondrial matrix

Enzyme complex for pyruvate → acetyl-CoA?

Pyruvate dehydrogenase complex

What is released during this step?

CO₂ and NADH

Why is this step important?

Links glycolysis to the Krebs cycle

Where does the Krebs cycle occur?

Mitochondrial matrix

Starting molecule of Krebs cycle?

Acetyl-CoA

Does the Krebs cycle require oxygen?

No (but depends on oxygen indirectly)

Products per turn of the cycle?

3 NADH, 1 FADH₂, 1 GTP, 2 CO₂

Main purpose of the Krebs cycle?

Produce electron carriers (NADH, FADH₂)

Where does oxidative phosphorylation occur?

Inner mitochondrial membrane

Does oxidative phosphorylation require oxygen?

Yes

What is oxygen’s role?

Final electron acceptor → forms H₂O

How much ATP is produced here?

~ 30 ATP

Where is most ATP made?

Oxidative phosphorylation

What molecules donate electrons to the ETC?

NADH and FADH₂

What builds the proton gradient?

Proton pumps in the ETC

What enzyme makes ATP?

ATP synthase

What drives ATP synthase?

Protons moving down their gradient

Can fats be used for energy?

Yes, converted to acetyl-CoA

How does fat energy compare to sugar?

Produces ~6× more energy per weight

What is gluconeogenesis?

Making glucose when energy is low

When does gluconeogenesis occur?

Low blood glucose

What organ depends almost entirely on glucose?

Brain

Does gluconeogenesis require energy?

Yes, a lot

Storage form of glucose in animals?

Glycogen

Enzyme that builds glycogen?

Glycogen synthase

Enzyme that breaks glycogen?

Glycogen phosphorylase

Hormones that regulate glycogen?

Insulin, glucagon, adrenaline

How is fat stored?

As triacylglycerols in adipose tissue

Where is the Krebs cycle located?

Matrix

Where is the ETC located?

Inner mitochondrial membrane

Why is the inner membrane folded?

Increases surface area for ATP production

Storage carbohydrate in plants?

Starch

Do plants use mitochondria?

Yes

Cellular Respiration

Process by which cells break down food molecules to produce ATP.

ATP (Adenosine Triphosphate)

Main energy currency of the cell.

Oxidation

Loss of electrons (often loss of hydrogen).

Reduction

Gain of electrons (often gain of hydrogen).

Electron Carrier

Molecule (NADH, FADH₂) that carries high-energy electrons.

Glycolysis

First stage of cellular respiration where glucose is broken down into pyruvate.

Cytoplasm

Location where glycolysis occurs.

Anaerobic

Process that does not require oxygen.

Pyruvate

3-carbon molecule produced from glycolysis.

Lactate

Product formed from pyruvate when oxygen is absent.

Enzyme

Protein that speeds up chemical reactions.

Acetyl-CoA

2-carbon molecule that enters the citric acid cycle.

Pyruvate Dehydrogenase Complex

Multi-enzyme complex that converts pyruvate to acetyl-CoA.

Mitochondrial Matrix

Inner space of mitochondria where acetyl-CoA formation and Krebs cycle occur.

Citric Acid Cycle (Krebs Cycle)

Second stage of respiration that oxidizes acetyl-CoA to CO₂ and produces electron carriers.

NADH

Electron carrier that delivers electrons to the electron transport chain.

FADH₂

Electron carrier that delivers electrons to the electron transport chain.

GTP

ATP-equivalent molecule produced in the Krebs cycle.

Carbon Dioxide (CO₂)

Waste product released during the Krebs cycle.

Oxidative Phosphorylation

Stage of respiration where ATP is made using electrons and oxygen.

Electron Transport Chain (ETC)

Series of proteins that transfer electrons and pump protons.

Inner Mitochondrial Membrane

Location of the electron transport chain and ATP synthase.

Oxygen (O₂)

Final electron acceptor in the ETC.

Water (H₂O)

Formed when oxygen accepts electrons and protons.

Chemiosmosis

Process where ATP is produced using a proton gradient.

Proton (H⁺)

Hydrogen ion pumped across the membrane during electron transport.

Proton Gradient

Difference in proton concentration across a membrane.

ATP Synthase

Enzyme that makes ATP as protons flow through it.

Glycogen

Storage form of glucose in animals.

Glycogen Synthase

Enzyme that builds glycogen.

Glycogen Phosphorylase

Enzyme that breaks down glycogen.

Triacylglycerol

Storage form of fat in animals.

Adipose Tissue

Tissue specialized for fat storage.

Gluconeogenesis

Process of making glucose when energy levels are low.

Lactate

Common starting material for gluconeogenesis.

Mitochondria

Organelle that produces most cellular ATP.

Cristae

Folds of the inner mitochondrial membrane that increase surface area.

Intermembrane Space

Space where protons accumulate during electron transport.

Starch

Storage form of glucose in plants.

Chloroplast

Organelle where photosynthesis occurs.

Thylakoid

Membrane structure inside chloroplasts.