Cellular Respiration

Question 1

Substrate-level phosphorylation

Answer 1

Substrate (organic molecule) gives phosphate to ATP

Question 2

3 steps of cellular respiration

Answer 2

Glycolysis
Citric acid cycle
Oxidative phosphorylation

Question 3

Glycolysis

Answer 3

“Splitting of sugar”
Oxidation of 1 glucose molecule to 2 pyruvate molecules
Occurs in cytoplasm of cell
2 major phases: energy investment phase and energy payoff phase
Overall yield: 2 pyruvate, 2 ATP, 2 NADH

Question 4

Cell’s energy

Answer 4

ATP (GTP)

Reduced electron carriers (NADH, FADH, NADPH)

Question 5

Chemotrophy

Answer 5

Use of organic material for energy (source of electrons)

Question 6

Fructose 1,6-bisphosphate

Answer 6

Non-reversible intermediate generated in glycolysis

Question 7

Oxidation of glucose

Answer 7

6O2 + C6H12O6 -(burning)> 6CO2 + 6H2O

G=-686 kcal/mol

Question 8

Fate of pyruvate

Answer 8

Depends on O2 availability and availability of electron transport chain

Question 9

Obligate aerobes

Answer 9

Require O2 as electron receptor

Cannot ferment

Question 10

Facultative aerobes

Answer 10

Can switch between anaerobic respiration and fermentation (use NO2, CO2, or SO4 as electron receptor)

Question 11

Fermentation

Answer 11

Takes place in absence of oxygen
Use pyruvate as an electron receptor
Regenerates NAD+
Less ATP than respiration
Alcohol: glucose is transformed into ethanol (2 steps, one of which releases CO2)
Lactic acid fermentation: glucose is transformed into lactate (direct reduction)

Question 12

Comparison of cellular respiration and fermentation

Answer 12

Both use glycolysis to oxidize glucose and other organic fuels to pyruvate
Different final electron receptor: O2 (cellular respiration), NAD+ (fermentation)
Cellular respiration produces more ATP

Question 13

Conversion of pyruvate to acetyl-CoA

Answer 13

Occurs in mitochondria

Products of sugar and fats converted

Question 14

Citric acid cycle

Answer 14

Takes place in mitochondrial matrix
Step 1: addition of acetyl CoA
Step 2: oxidation- CO2 lost
Step 3: regeneration of oxaloacetate
Step 1: Acetyl CoA + oxaloacetate -> citrate
Steps 2-8: Citrate -> oxaloacetate
Net result: 3 NADH, 1 GTP, 1 FADH2, -2 CO2

Question 15

Biosynthetic intermediates

Answer 15

Glycolysis and the citric acid cycle supply them

Cell doesn’t use all of its glucose to make energy

Question 16

Gluconeogenesis

Answer 16

Transformation of lactic acid into glucose

Used when glucose is unavailable

Question 17

Glycogen

Answer 17

Storage form of glucose

Question 18

Beta-oxidation of fatty acids

Answer 18

Hydrocarbons from fat -> acetyl CoA + reduced electron carriers
Occurs in mitochondria
Fat is the main storage form of energy

Question 19

Mitochondrial matrix

Answer 19

Highly concentrated mixture of hundreds of enzymes, including those required for the oxidation of pyruvate and fatty acids and for the citric acid cycle

Question 20

Inner mitochondrial membrane

Answer 20

Folded into cristae
Contains proteins that carry out oxidation reactions of electron transport chain and ATP synthase
Electrochemical gradient forms across

Question 21

Outer mitochondrial membrane

Answer 21

Contains porins- permeable

Question 22

Mitochondrial intermembrane space

Answer 22

Contains enzymes that use ATP passing out of matrix to phosphorylate other nucleotides
Protons from electron transport chain accumulate here

Question 23

Chemiosmotic hypothesis

Answer 23

Peter Mitchell (1970s)
Proton gradient that is generated by electron transport chain drives ATP synthesis

Question 24

Electron transport chain

Answer 24

NADH dehydrogenase complex -> ubiquinone -> cytochrome b-c1 complex -> cytochrome c -> cytochrome oxidase complex -> O2
Proton pumps: NADH dehydrogenase complex, cytochrome b-c1 complex, cytochrome oxidase complex
Mobile electron carriers: ubiquinone, cytochrome c

Question 25

Proton motive force

Answer 25

H+ gradient

Used to drive ATP synthesis, energy source for transport (mitochondria), bacterial flagellar movement

Question 26

ATP synthase

Answer 26

Uses proton gradient to synthesize ATP
Inorganic phosphate in matrix joins to ADP: energy comes from protons turning motor
2 parts: transmembrane H+ carrier (F0), F1 ATPase
Reversible: ATP can be broken down to make H+ gradient

Question 27

Total ATP yield

Answer 27

Cell: 30 ATP/ glucose
121: 30-36 ATP/ glucose