Cellular Respiration

Question 1

glycolysis overall equation

Answer 1

C6H12O6 + 2ADP + 2Pi + 2NAD+ –> 2 pyruvate + 2 ATP + 2 NADH + 2H20 + 2H+

Question 2

3 irreversible steps of glycolysis (enzymes)

Answer 2

glucose –> glucose-6-phosphate (hexokinase)
fructose-6-phosphate –> fructose-1,6-bisphosphate (phosphofructokinase)
phosphoenolpyruvate –> pyruvate (pyruvate kinase)

Question 3

energy investment phase of glycolysis

Answer 3

ATP required first step with hexokinase and third step with PFK-1

Question 4

what does hexokinase do that’s important to start glycolysis?

Answer 4

it traps glucose in the cell

Question 5

how many times does energy payoff phase of glycolysis occur?

Answer 5

twice
once per molecule of glyceraldehyde 3-phosphate
produce two pyruvate at the end

Question 6

what enzyme is rate-limiting enzyme?

Answer 6

PFK-1

catalyzes formation of fructose-1,6-bisphosphate from fructose-6-phosphate

Question 7

how many carbons is pyruvate?

Answer 7

three carbons

Question 8

total glycolysis energy

Answer 8

makes 4 ATP, uses 2 ATP –> NET 2 ATP

2 NADH

Question 9

overview pyruvate oxidation

Answer 9

2 pyruvate are converted to 2 acetyl CoA
2 carbons are released as CO2
2 NADH are generated

Question 10

where does pyruvate oxidation occur in eukaryotes and prokaryotes?

Answer 10

eukaryotes: matrix
prokaryotes: cytoplasm

Question 11

how many steps of the CAC?

Answer 11

8

Question 12

what are products of one turn of the CAC?

Answer 12

2 CO2
3 NADH
1 FADH2
1 ATP or GTP

Question 13

how many cycles does a molecule of glucose go through CAC?

Answer 13

twice

1 glucose –> 2 pyruvate –> 2 acetyl-CoA –> 2 turns

Question 14

what two enzymes of CAC are important to regulate speed of cycle?

Answer 14

isocitrate dehydrogenase and α-ketoglutarate dehydrogenase

*NAD+ –> NADH during both of these steps and a molecule of CO2 is released

Question 15

is FAD or NAD+ a better electron acceptor?

Answer 15

FAD so it will pull electrons from succinate in the CAC

Question 16

what is the function of the ETC?

Answer 16

electrons are transferred through the membrane proteins

ENERGY released generates electrochemical gradient

Question 17

what is the function of chemiosmosis?

Answer 17

energy stored in the gradient is used to make ATP

Question 18

why is oxygen important in the ETC?

Answer 18

it sits at the end of the ETC and accepts electrons and picks up protons from water

without it, ETC will stop and ATP will not be produced by chemiosmosis

Question 19

where does ETC gets electrons?

Answer 19

electron carriers (FADH2 and NADH)

Question 20

how to electrons travel in ETC?

Answer 20

they travel from higher to lower energy levels

release energy

Question 21

functions of oxidative phosphorylation

Answer 21

1. regenerate electron carriers (NAD+ and FAD) that are important for glycolysis and CAC
2. proton gradient generated across the inner mitochondrial membrane
   high [H+] in intermembrane space
   low [H+] in matrix

Question 22

NADH role in ETC

Answer 22

good at donating electrons (high energy) so energy released at complex I can pump protons from matrix into intermembrane space

Question 23

FADH2 role in ETC

Answer 23

not as good at donating electrons (low energy) so feeds into ETC through complex II (which does not pump protons across the membrane)

Question 24

order of complexes of ETC

Answer 24

I –> Q –> III –> cytochrome C –> complex IV

Question 25

chemiosmosis

Answer 25

any process in which energy stored in a proton gradient is used to do work

Question 26

ATP synthase role

Answer 26

the flow of H+ protons causes it to turn which catalyzes addition of phosphate to ADP to capture energy as ATP

(protons flow from intermembrane space to matrix)

Question 27

what happens if ATP synthase not used to synthesize ATP?

Answer 27

energy can be released as heat

uncoupling proteins are channels that allow proteins to pass to matrix –> dissipated as heat

Question 28

where do parts of cellular respiration occur?

Answer 28

glycolysis: cytosol
pyruvate oxidation: matrix
CAC: matrix
oxidative phosphorylation: intermitochondrial membrane

Question 29

NAD+ and FAD reduction equations

Answer 29

NAD+ + 2e- + 2H+ –> NADH + H+

FAD + 2e- +2H+ –> FADH2

Question 30

overall ATP yield

Answer 30

30-32 ATP
glycolysis: 2 ATP, 3-5 ATP (NADH) = 5-7 ATP
pyruvate oxidation: 5 ATP (NADH)
CAC: 2 ATP, 15 ATP (NADH), 3 ATP (FADH2) = 20 ATP

Question 31

why is there variation of glycolysis NADH ==> ATP conversion?

Answer 31

NADH cannot cross the inner mitochondria membrane to enter ETC so it is converted via a shuttle system where some may be lost

Question 32

pH of mitochondria parts

Answer 32

intermembrane space (high [H+]) low pH
cytosol
matrix (low [H+]) high pH

Question 33

two types of fermentation (where)

Answer 33

alcohol in yeast

lactic acid in muscle

Question 34

what does anaerobic cellular respiration use as final electron acceptor?

Answer 34

sulfate or nitrate

Question 35

lactic acid fermentation

Answer 35

normal glycolysis
2 pyruvate –> 2 lactate (important for NAD+ regeneration)

lactate –> lactic acid –> back to pyruvate in liver

Question 36

alcohol fermentation

Answer 36

normal glycolysis

2 pyruvate –> 2 ethanol (important for NAD+ regeneration)

Question 37

what is gluconeogenesis?

Answer 37

formation of glucose

“almost” reverse of glycolysis

Question 38

regulation of glycolysis and gluconeogenesis

Answer 38

ATP is negative allosteric inhibitor of glycolysis

AMP is negative allosteric inhibitor of gluconeogenesis