Chapter 13/14

Question 1

Describe the general idea behind biological oxidations. What is removed or gained? What are they usually catalyzed by?

Answer 1

Biological Oxidations remove protons, remove electrons, and are usually catalyzed by dehydrogenases

Oxidations in general add oxygen, remove hydrogen, and remove electrons

Question 2

Describe the ability of bacteria to perform oxidative respiration

Answer 2

Bacteria can perform oxidative respiration even though they do not have mitochondria. They use a plasma membrane instead of the mitochondrial membranes.

Question 3

Give the general equation behind cellular respiration

Answer 3

Sugar (C6H12O6) + O2 –> Oxidation -»»» CO2 + H2O

Question 4

Describe the general equation for Glycolysis (i.e. the starting materials and products). Where does Glycolysis occur? What can enter and where?

Answer 4

Glucose + 2 ATP → 2 Pyruvate + 2 NADH + 4 ATP

Series of 10 reactions catalyzed by 10 enzymes
Occurs in cytosol

Other sugars can enter as glucose or as intermediates, amino acids enter as pyruvate and fatty acids enter as acetyl CoA

Question 5

Describe NAD+. What is it classified as? What special thing is it made out of?

Answer 5

A coenzyme (non-protein compound required for enzymatic reaction) that serves as an electron acceptor in biological oxidations.
Reduced during aerobic respiration to NADH
B-vitamin

Question 6

What are the three main stages of Glycolysis? Describe them

Answer 6

1. ) Investment of 2 ATP for 2 phosphorylations by kinases (enzymes that - P from ATP and → substrate)
2. ) Cleavage of 6-carbon sugar to 2 3-carbon sugars

3.) Energy generation through
oxidation to generate NADH and ATP (substrate level phosphorylation)
In steps 6-7 (stage 3) High-energy thioester bond becomes high-energy phosphate bond

Question 7

What occurs in Glycogenesis? Where does it occur and why?

Answer 7

Occurs in skeletal muscles during intense exercise, due to lack of glucose (low blood sugar)

Pyruvate produced by glycolysis is fermented to lactate -> Cells in liver turn lactate back to pyruvate -> Pyruvate back to glucose using 6 ATP

Includes 3 bypass reactions to avoid irreversible steps

Feedback allows cells to switch between glucose catabolism (lysis) and synthesis (genesis)

Question 8

What molecules activate glycolysis? What molecules inactivate glycolysis?

Answer 8

Glycolysis is activated by ADP, AMP, and P and inactivated by ATP

Question 9

What molecules activate glycogenesis? What molecules inactivate glycogenesis?

Answer 9

Glycogenesis is activated by ATP and inactivated by ADP, AMP, and P

Question 10

Describe where animals store their energy. How much energy is stored in fat relatively speaking? What are fat cells called?

Answer 10

Animal cells store energy in glycogen (branched polysaccharide of glucose monomers)

Also store energy in fat droplets (triacylglycerols)
(1 gram of fat has 2x the energy of glycogen) fat cells are called adipocytes

Question 11

Where do plants store energy

Answer 11

Plant cells store starch and fat in chloroplasts

Question 12

Describe the fate of pyruvate in the presence of O2 (general, short)

Answer 12

Converted to acetyl CoA and enters the citric acid cycle

Question 13

Describe the fate of pyruvate in the absence of O2 (general, short)

Answer 13

Undergoes fermentation to regenerate NAD+

Question 14

Describe the process of Fermentation, including where it occurs and the two possible sets of products

Answer 14

Process of regenerating NAD+

Occurs in cytosol, no additional ATP generated

It can produce lactate during intense exercise

Or it can produce ethanol and CO2 (yeast)

Question 15

Differentiate between the inner membrane and the outer membrane of the mitochondria

Answer 15

The inner membrane is the site of ATP synthsis and the electron transport chain due to its high density of proteins (intermembrane space), and that it is impermeable to ions (such as H+)

The outer membrane is more permeable (due to porins/beta barrels, other proteins)

Question 16

Describe the general reaction/process of the pyruvate oxidation. Where does it occur? Give the general equation.

Answer 16

Pyruvate is oxidized in mitochondrial matrix by pyruvate dehydrogenase complex

3-C pyruvate + NAD+ + O2 → 2-C acetyl CoA + CO2 + NADH

Question 17

Describe the general reaction/process of the Citric Acid Cycle. Where does it occur? Give the general equation, and describe produced molecules.

Answer 17

Acetyl CoA (2C) + Oxaloacetate (4C) → Citrate (6C)

Each turn of the cycle produces CO2, FADH2, GTP (substrate level, converted to ATP), and NADH

Most of the energy is now in FADH2 and NADH (high-energy electron carriers)

Occurs in mitochondrial matrix

Oxaloacetate is regenerated in the final step

Question 18

Describe the Electron Transport chain. Where does it occur? What is it used for? What are the reactants and what are they converted into?

Answer 18

NADH and FADH2 are generated by glycolysis, pyruvate oxidation, and citric acid cycle and enter the electron transport chain

O2 is final electron acceptor (converts to H2O)

Energy of electron transport is used to pump protons across the membrane (From matrix through inner membrane to intermembrane space)

Question 19

Define Respiratory Complexes. Describe the different ones (3)

Answer 19

NADH Dehydrogenase Complex
NADH electrons enter here (H- → Proton and 2 Electrons)

Cytochrome C Reductase Complex
FADH2 electrons enter here

Cytochrome C Oxidase Complex
Produce H2O from ½ O2 and 2 H+

Question 20

Describe the two mobile carriers. What are their functions?

Answer 20

Ubiquinone: Small, hydrophobic, motile electron carrier molecule that picks up electrons from the NADH dehydrogenase complex and delivers them to the cytochrome c reductase complex

Cytochrome C: A cytochrome is a membrane-bound, colored, heme-containing protein that transfers electrons during cellular respiration

Question 21

What is delta E? What is the equation for the delta E naught of a reaction consisting of an electron acceptor and an electron donor? What is the relationship between delta E naught and delta G naught? Where do electrons move spontaneously? (higher Eo or lower)

Bonus: How does this relate to FADH2 and NADH?

Answer 21

Redox potential

ΔE0 = E0 Electron Acceptor - E0 Electron Donor’
(will go from a low E0 to a high E0)
When ΔE0 is positive, ΔG0 will be negative

Electrons will move spontaneously to molecules with greater redox potential

FADH2 cannot donate to the same respiratory complex as NADH due to different redox potentials

Question 22

Describe the function of ATP synthase. Where does it move things? What does it need?

Answer 22

Harnesses energy from proton gradient to make ATP by oxidative phosphorylation.

Reversible→ will follow H+ flow

ATP needs to be high, or else the mitochondria will stop working and the cell will die.

Question 23

Describe the structure of ATP synthase.

Answer 23

F0 roter
Ring of c subunits that is powered by H+
Y/Gamma-subunit is a shaft (proton channel) that connects the rotor to the head, drives changes in b subunit

F1 head
Three a and three b catalytic subunits (b is the important one)

Question 24

Describe the binding change model of ATP synthase

Answer 24

B catalytic subunit rotates through three conformations

Open, (O) → subunit can bind to ADP + P, ATP can exit

Loose, (L) → loose binding to ADP + P

Tight (T) → tight binding to ATP + P

Conformational changes are not required for proton movement through the channel, the other way around

Question 25

Recognize the effect of cyanide and rotenone

Answer 25

Cyanide → Prevents production of final H2O product, causes buildup of NADH

Rotenone → Prevents movement past the first step of electron transport chain

Question 26

What are the three general stages of aerobic respiration?

Answer 26

Breakdown of large macromolecules into simple subunits, further breakdown into acetyl CoA and the production of ATP/NADH, and the complete oxidation of acetyl CoA to CO2 (paired with reduction of O2 to H2O)

Question 27

Glycolysis: 2 NADH and 2 ATP -> 5 ATP
Pyruvate Oxidation: 2 NADH -> 5 ATP
Acetyl CoA Oxidation: 6 NADH, 2 FADH2 and 2 GTP -> 20 ATP

How many ATP are made by oxidative phosphorylation? How many by substrate level phosphorylation

Answer 27

26

2