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Flashcards in Cellular Respiration Deck (27):
1

Substrate-level phosphorylation

Substrate (organic molecule) gives phosphate to ATP

2

3 steps of cellular respiration

Glycolysis
Citric acid cycle
Oxidative phosphorylation

3

Glycolysis

"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

4

Cell's energy

ATP (GTP)
Reduced electron carriers (NADH, FADH, NADPH)

5

Chemotrophy

Use of organic material for energy (source of electrons)

6

Fructose 1,6-bisphosphate

Non-reversible intermediate generated in glycolysis

7

Oxidation of glucose

6O2 + C6H12O6 -(burning)> 6CO2 + 6H2O
G=-686 kcal/mol

8

Fate of pyruvate

Depends on O2 availability and availability of electron transport chain

9

Obligate aerobes

Require O2 as electron receptor
Cannot ferment

10

Facultative aerobes

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

11

Fermentation

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)

12

Comparison of cellular respiration and fermentation

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

13

Conversion of pyruvate to acetyl-CoA

Occurs in mitochondria
Products of sugar and fats converted

14

Citric acid cycle

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

15

Biosynthetic intermediates

Glycolysis and the citric acid cycle supply them
Cell doesn't use all of its glucose to make energy

16

Gluconeogenesis

Transformation of lactic acid into glucose
Used when glucose is unavailable

17

Glycogen

Storage form of glucose

18

Beta-oxidation of fatty acids

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

19

Mitochondrial matrix

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

20

Inner mitochondrial membrane

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

21

Outer mitochondrial membrane

Contains porins- permeable

22

Mitochondrial intermembrane space

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

23

Chemiosmotic hypothesis

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

24

Electron transport chain

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

25

Proton motive force

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

26

ATP synthase

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

27

Total ATP yield

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