Chapter 9 (cellular respiration)

Question 1

Glycolysis (10 steps)

Answer 1

1) Phosphorylation of glucose (1 ATP invested) [Hexokinase]
2) Ring change 6 to 5 [Phosphoglucoisomerase]
3) Phosphorylation of 5 member ring (1 Atp invested; total 2 invested) [Phosphofructokinase]
4) Cleavage of 6 carbons into 2 (3 carbon) molecules [Aldolase]
5) Isomerization of DHAP into g3p [isomerase]
6) Oxidation of 2 equivalents of g3p and addition of phosphate group to make 2 equivalents 1,3-bisphosphoglycerate (2 NAD+ picks up the electrons and the protons) [Glyceraldehyde-3-phosphate dehydrogenase]
7) Loss of 1 phosphate group from 1 position (ADP picks up the lost phosphate group; net 2 ATP produced so far) [phosphoglycerokinase]
8) Swap of phosphate group
9) Dehydration reactyion
10) Loss of the phosphate group (ADP picks up phosphate; net 4 ATP so far) and makes pyruvate

Question 2

Pyruvate Oxidation

Answer 2

1) Pyruvate undergoes decarboxylation (decarboxylated pyruvate results in an acetyl group)
2) Electrons from pyruvate are transferred to NAD+ (NADH produced)
3) Acetyl group gets attached to sulfur and coenzyme A

Net: 1 NADH and acetyl coA produced

Question 3

Citric acid cycle

Answer 3

1) acetylCoA (2 carbon) + oxoloacetate (4 carbon) makes citrate (CoA is leaving group)
2) two decarboxylation events, each producing NADH by having NAD+ pick up electron and proton
3) ATP generated when ADP takes phosphate from GTP
4) succinate (4 carbon) gets oxidized (1 FADH2 and 1 NADH produced)
5)Oxoloacetate is regenerated

Net: 3 NADH and 1 FADH2

Question 4

Electron Transport Chain

Answer 4

-Coenzyme Q is not a protein and is mobile through the membrane
-Cyt C is a peripheral membrane protein meaning that it is loosely associated with the outer surface (towards the intermembrane space side). It can also rapidly diffuse between 3 and 4 facilitating movement of electrons.

Complex 1 (proton pump)
1) NADH transfers electrons to complex 1
2) Complex 1 transfers electrons to coenzyme Q

Complex 2 (not a proton pump)
-Integral but not transmembrane protein (associated on matrix side)
1) FADH2 transfers electrons to complex II then to coenzyme Q

Complex 3 (proton pump)
1) Takes electrons from coenzyme Q and passes them to cyt C

Complex 4
1) Passes electrons to oxygen

Question 5

Chemiosmosis (what drives chemiosmosis and how does ATP synthase function)

Answer 5

-Simple diffusion of H+ down electrochemical gradient is not possible. Inner mitochondrial membrane is not as permeable so ATP synthase is required

Driven by protein motive force:
1)Membrane potential (intermembrane space is more positive because of protons being pumped out)
2)pH gradient (intermembrane space is lower in pH)

How ATP synthase functions:
1)Protons move through channel into the membrane bound portion which provides the mechanical energy to rotate the catalytic knob
2)Rotation puts ADP and inorganic phosphate back together. No organic substrate is required

Question 6

Alcohol Fermentation

Answer 6

-Happens in yeast

1) 2 pyruvates get decarboxylated into acetaldehyde
2) acetaldehyde gets reduced by NADH

net: 2 NAD+ form and 2 ethanol

Question 7

Lactate Fermentation

Answer 7

-Happens in animals

1) Pyruvate gets reduced by NADH

net: 2 NAD+ and 2 lactate

Question 8

regulators of PFK

Answer 8

-work allosterically
1) Citrate (negative)
2) ATP (negative)
3) AMP (positive)