Chapter 7

Question 1

Autotrophs

Answer 1

Produce their own organic molecules through photosynthesis

Question 2

Heterotrophs

Answer 2

Eat organic compounds produced by other organisms

Question 3

Cellular (Aerobic) Respiration 666 Equation

Answer 3

C6 H12 O6 +6 O2 = 6 CO2 + 6 H2O + Energy
Glucose. Oxygen = Carbon deioxide. Water Heat and ATP.
Change in G = -686 kcal/mol of glucose

Question 4

Cellular respiration (definition)

Answer 4

Cellular respiration is a series of redox reactions (Many small steps, slow release of energy)

Question 4

Dehydrogenation

Answer 4

Lost electrons are accompanied by protons (Hydrogen). Hydrogen atom is lost (1 electron, 1 proton)

Question 5

Electron Carriers in cell respiration

Answer 5

NAD+. Oxidized form NAD+ (ready to accept electron)
NADH. Reduced form (accepted an electron)

FAD+ Oxidized form (ready to accept electron)
FADH2 . Reduced form (accepted an electron)

Question 6

Final acceptor of electron in cell respiration

Answer 6

Oxygen. When O2 accepts electron it produces H2O

Question 7

Final electron acceptor in other forms of energy creation

Answer 7

Aerobic respiration = Oxygen
Anaerobic respiration = Final electron acceptor is an inorganic molecule (not O2)
Fermentation = Final e- acceptor is an organic molecule, converted into lactic acid or ethanol+CO2

Question 8

2 mechanisms for synthesis of ATP

Answer 8

1 Substrate-level phosphorylation. Transfer phosphate group directly to ADP. Uses an enzyme directly to transfer P group to ADP. During glycolysis and Krebs cycle.
2. Oxidative phosphorylation. ATP synthase uses energy from a proton gradient. During Electron Transport Chain and Chemiosmosis

Question 9

Glycolysis and oxygen availability

Answer 9

Step 1) Occurs in cytoplasm. Converts 1 Glucose (6 carbons) to 2 Pyruvate (3 carbons). 10 step biochemical pathway. End products: 2 pyruvates, 4 total ATP (net of 2 ATP), 2 NADH.

For glycolysis to continue NADH must be recycled to NAD+ by either
1. Aerobic respiration- O2 is available and final electron acceptor (Produces significant amount of ATP)
2. Fermentation- O2 unavailable. Organic molecule final e- acceptor

Question 10

Pyruvate Oxidation

Answer 10

Step 2) Occurs in the mitochondria in eukaryotes. Plasma membrane in prokaryotes. Start with 2 pyruvates. Each pyruvate is oxidized, looses e- collected by NAD+. Pyruvate oxidize to Acetyl CoA. NAD+ reduced to NADH
End products: 2 Acetyl-CoA. 2 NADH. 2 CO2

Question 11

Krebs Cycle (Citric Acid Cycle)

Answer 11

Step 3) Occurs in matrix of mitochondria. Oxidizes acetyl group from pyruvate. Biochemical pathway in 9 steps and 3 segments. 1 acetyl-CoA + oxaloacetate= citrate. 2. citrate rearrangement and decarboxylation. 3. regeneration of oxaloacetate.

For each Acetyl-CoA entering: Release of 2 molecules of CO2, reduce 3 NAD+ to 3 NADH, Reduce 1 FAD to FADH2, Produce 1 ATP regenerate oxaloacetate.
Multiply by 2 since there are 2 Acetyl-CoA

At this point 6 CO2, 4 ATP, 10 NADH, 2 FADH2

Question 12

Electron Transport Chain (ETC) and Chemiosmosis

Answer 12

Step 4) Located in mitochondrial membrane (cristae) in eukaryotes, plasma membrane of prokaryotes. Electron carriers from previous step “drop-off” electrons (NADH, FADH2). Used to pump H+ out of cell, creates gradient for next step, chemiosmosis. Driven by oxygen.
ETC is a series of membrane-bound electron carriers embedded in the inner mitochondrial membrane (Cristae). Electrons from NADH and FADH2 are transferred to complexes of the ETC.
Each complex has a proton pump creating proton gradient, transfers electrons to the next carrier, Electrons end up at oxygen (reduced to H2O).
Chemiosmosis- accumulation of protons in the intermembrane space drives protons into the matrix via diffusion (membrane relatively impermeable to ions) most protons can only reenter matrix through ATP synthase [rotor] (uses energy of gradient to make ATP from ATP +P i)

End products: 32 ATPs, H2O, NAD+, FAD+

Question 13

Energy yield of respiration

Answer 13

Theoretical energy yield - 36-38 ATP per glucose
Actual yield: 30 ATP per glucose in eukaryotes
32 ATP per glucose in prokaryotes
(reduced yield due to leaky membrane use of proton gradient for purposes other than ATP synthesis)

Question 14

Fermentation

Answer 14

Reduces organic molecules in order to regenerate NAD+ for glycolysis.
1 Ethanol fermentation occurs in yeast. CO2, ethanol and NAD+ are produced
2 Lactic acid fermentation occurs is animal cells (especially muscles) electrons are transferred to NADH to pyruvate to produce lactic acid

Question 15

Alcohol fermentation in yeast

Answer 15

No O2 present for NADH produced in glycolysis has no ETC to drop-off e- and become NAD+ again. NADH drop e- off at acetaldehyde and becomes NAD+ again.
End Product : CO2 (waste), Ethanol (waste), NAD+ (purpose)

Question 16

Catabolism of protein

Answer 16

Amino acid undergo deamination to remove the amino group. Remainder of the amino acid is converted to a molecule that enters glycolysis or the Krebs cycle

Question 16

Catabolism of Fat

Answer 16

Fats are broken down to fatty acids and glycerol (use hydrolysis to break glycerol from fatty acids)
Fatty acids are converted to acetyl groups by beta-oxidation.Acetyl group joins with CoA to make Acetyl-CoA which can enter Krebs cycle
The respiration of a 6-carbon fatty acid yields 20% more energy than 6-carbon glucose.

Question 16

Alcohol fermentation in Muscle cells

Answer 16

No O2 present for NADH produced in glycolysis has no ETC to drop-off e- and become NAD+ again. NADH drop e- off at pyruvate and becomes NAD+ again.
End Product : CO2 (waste), lactate (waste), NAD+ (purpose)

Question 17

Glycolysis start and end product

Answer 17

Glucose and NAD+

2 Pyruvate, net 2 ATP, 2 NADH

Question 18

Pyruvate oxidation start and end product

Answer 18

2 pyruvate

2 Acetyl-CoA, 2 NADH, 2 CO2

Question 19

Krebs Cycle start and end product

Answer 19

2 Acetyl- CoA

6NADH, 2 FADH2, 2 ATP, 4 CO2

Question 20

ETC and chemiosmosis start and end product

Answer 20

NADH, FADH2, O2, ATP synthase

32 ATP, H20, NAD+, FAD+