Topic 3: Cellular Respiration

Question 1

• Oxidative exergonic process that breaks down glucose to derive energy in the form of ATP
• High energy H atoms are removed from organic molecules
• Aerobic process (occurs in presence of oxygen)

Answer 1

Cellular Respiration

Question 2

• Entry of air into lungs and gas exchange between alveoli and blood

Answer 2

External Respiration

Question 3

• Exchange of gas between blood and cells

Answer 3

Internal Respiration

Question 4

• Decomposition of glucose into pyruvate in the cytosol
  1. 2 ATP added; 2 NADH, 4 ATP, and 2 pyruvates formed
  2. ATP is produced via substrate level phosphorylation, which involves the direct enzymatic transfer of a phosphate to ADP
  3. Hexokinase phosphorylates glucose, which is irreversible, and glucose can’t diffuse out of the cell
  4. Phosphofructokinase (PFK) adds 2nd phosphate, forming fructose 1,6-biphosphate, which is irreversible and commits glucose to glycolysis

Answer 4

Step 1: Glycolysis

Question 5

1. We are now in the mitochondrial matrix
2. Pyruvate becomes acetyl CoA while producing 1 NADH and 1 CO2
3. Reaction is catalyzed by PDC enzyme

Answer 5

Step 2: Pyruvate Decarboxylation

Question 6

1. In Krebs Cycle, acetyl CoA merges with oxaloacetate to form citrate, and the cycle continues with 7 intermediates
2. 3 NADH, 1 FADH2, 1 ATP, and 2 CO2 are produced per pyruvate molecule. Each glucose molecule forms two pyruvate in glycolysis, so the cycle turns two times, created a net of 6 NADH, 2 FADH2, 2 ATP, and 4 CO2
3. This occurs in the mitochondrial

Answer 6

Step 3: Krebs Cycle/Citric Acid Cycle/Tricarboxylic Acid Cycle

Question 7

• Takes place in inner membrane
  1. Oxidative phosphorylation occurs here, which is the process of ADP -> ATP from NADH and FADH2 via passing of electrons through carrier proteins. Energy does not accompany the phosphate group but comes from the electrons in the ETC establishing an H+ gradient that supplies energy to ATP synthase
  2. NADH makes more energy than FADH2, and more H+ is pumped across per NADH
  3. The final electron acceptor is oxygen, which combines with H+ to form water
  4. Electron carriers extract energy from NADH and FADH2 while pumping protons into the intermembrane space – ATP synthase uses this gradient to make ATP as it shuttles H+ back into the inner matrix
  5. Coenzyme Q is a soluble carrier dissolved in the membrane that can be fully reduced/oxidized as it passes electrons
  6. Cytochrome C is a protein carrier in the ETC and is used for genetic relations. Cytochromes have nonprotein parts like iron that donate or accept electrons.
  7. ETC couples flow of electrons with endergonic pumping of H+ across the cristae membrane
  8. There is a difference between ATP totals in eukaryotes and prokaryotes because pro have no mitochondria, so they do not need to transfer the two NADH into the matrix (which is done via active transport costing 1 ATP each). Pyruvate is actively transported into the mitochondrial matrix (in euk) but its transport is secondary active (symport with protons) and does not directly use ATP

Answer 7

Step 4: Electron Transport Chain