Semester 1 Final: Cellular Respiration

Question 1

Glycolysis

Answer 1

Occurs regardless of oxygen availability
– steps 1-5: uses energy (2 ATP) & creates G3P molecules
– 6-10: produces energy (4 ATP & 2 NADH) & creates two pyruvate molecules
• WHERE: the cytoplasm (substrate level phosphorylation)
• WHAT: 2 ATP & 2 NADH
• WHY: to create 2 pyruvate molecules to enter the Krebs cycle

Question 2

The Fate of Pyruvate

Answer 2

If oxygen is present:
– Enters mitochondria
– Aerobic respiration occurs
– Pyruvate is decarboxylated & attached to coenzyme A to create acetyl CoA
• If oxygen is not present:
– Anaerobic respiration occurs in cytoplasm

Question 3

The Prep Phase (link reaction)

Answer 3

Pyruvate enters mitochondria through active transport
• 3 steps to prepare pyruvate
1. Pyruvate’s carboxyl group (COO-) is removed & released as CO2
2. The 2 carbon compound (acetate) is oxidized which reduces NAD+ into NADH
3. Coenzyme A is attached to the acetate with an unstable bond making acetyl coenzyme A (acetyl CoA)
- Remember, this happens twice because 2 pyruvates per glucose molecule
• WHERE: in the mitochondria
• WHAT: 2 CO2
, 2 NADH, 2 acetyl CoA
• WHY: to make a product that can enter the Krebs cycle

Question 4

Krebs Cycle/Citric Acid Cycle

Answer 4

Acetate is released from acetyl CoA into the Krebs cycle
• Numerous steps occur to release energy
• WHERE: mitochondrial matrix
• WHAT: 2 ATP, 6 NADH, 2 FADH2, 4 CO2
– This represents both
pyruvate molecules (aka: 2 turns of the cycle)
• WHY: to create electron carriers to enter the ETC

Question 5

Electron Transport Chain (ETC)

Answer 5

NADH & FADH2 donate electrons to the ETC
• NADH enters at a higher energy level & produces more ATP
• Oxygen pulls electrons down the ETC & is the final electron acceptor
– H+ ions follow to create water
• WHERE: the inner mitochondrial membrane
• WHAT: water molecules
• WHY: transporting electrons to create proton concentration gradient
• HOW: electrons passed between cytochromes provide the energy to move H+ against their concentration gradient into the intermembrane space

Question 6

Chemiosmosis

Answer 6

WHERE: inner membrane of the mitochondrial matrix
• WHY: to produce LOTS of ATP
• WHAT: 32 ATP
• HOW: Done as H+ diffuse through ATP synthase to the matrix

Question 7

Fermentation

Answer 7

– Substrate level phosphorylation
– Two types:
• Alcohol: Pyruvate is converted to ethanol (ethyl alcohol)
– Release CO2
– Used for brewing, winemaking, and baking
• Lactic Acid: Pyruvate is reduced to form lactate
– Used to make cheese and yogurt
– Happens to humans during strenuous exercise and results in fatigue and pain in muscles