Metabolism

Question 1

Overall theme of metabolism

Answer 1

Simplicity: limited number of enzymes to perform many different functions

Question 2

Phototrophs

Answer 2

Organisms that derive energy from light

Question 3

Chemotrophs

Answer 3

Organisms that derive energy from breaking down chemicals

Question 4

Anabolism

Answer 4

Building complex molecules from simpler ones

Useful energy + simple precursors -> complex molecules

Question 5

Catabolism

Answer 5

Breaking down complex molecules to harness energy

Fuel (carbs, fats, proteins) -> CO2 + H2O + useful energy

Question 6

Coupling of reactions

Answer 6

Using a favorable reaction to power an unfavorable one

Only works if reactions take place near each other (in the same cellular compartment)

Question 7

Currency of metabolism

Answer 7

ATP (adenosine triphosphate)
Contains energy-rich phosphoanhydride bonds (not stable: many negative charges right next to each other)
Favorable hydrolysis of phosphates: get rid of some of negative charge

Question 8

Standard delta G value of hydrolysis of ATP to ADP

Answer 8

-30.5 kJ/mol

Question 9

Electron carriers that are derivatives of ATP

Answer 9

NAD+ and FAD

A in both carriers refers to adenine

Question 10

Reasons why hydrolysis of ATP is favorable

Answer 10

1. Phosphate liberated from ATP can be stabilized through resonance
2. Electron repulsion of 4 negative charges on ATP is relieved when hydrolyzed
3. More water can bind ADP and the free phosphate than ATP (more bonds, more stability)

Question 11

What phosphoenolpyruvate (PEP) is used for

Answer 11

Doesn’t make good carrier: too big and too hard to regenerate
Has higher energy than ATP, so it can be used to phosphorylate ADP to ATP

Question 12

Why body performs anaerobic metabolism before aerobic metabolism

Answer 12

There are more steps to complete in aerobic than anaerobic metabolism, so body does simplest things first

Question 13

Calculating change in equilibrium constant of reaction coupled to ATP hydrolysis

Answer 13

1. Calculate Keq (Keq= 10^(-delta G/2.303RT)
R=8.314*10^-3 kJ/(mol*K), T=temp in K
2. Subtract 30.5 kJ/mol from delta G
3. Recalculate Keq with new delta G
4. Subtract old value from new value

Question 14

Way that energy to derive ATP is generated

Answer 14

Energy is generated from oxidizing molecules, which is then used to create a phosphoryl-transfer compound or an ionic gradient

Question 15

Why CO2 acts as body’s waste

Answer 15

CO2 is completely oxidized- no more energy can be harnessed from it

Question 16

Do sugars or fatty acids generate more energy?

Answer 16

Fatty acids generate more energy than sugars: they are less oxidized, so they have greater oxidizing potential

Question 17

Oxidative phosphorylation

Answer 17

Process of using ion gradients to form ATP

90% of ATP is made through this process

Question 18

Common pathway for making ATP out of nutrients

Answer 18

Fats, polysaccharides, and proteins follow same breakdown pathway to form ATP

Question 19

Electron carriers

Answer 19

Molecules that are used to fuel oxidation or biosynthesis
Necessary when reactants can’t be reduced or oxidized directly
2 most common: NAD and FAD

Question 20

Nicotinamide adenine dinucleotide (NAD)

Answer 20

Mobile electron carrier

Receives one proton and two electrons from the substrate (H-)

Question 21

Flavin adenine dinucleotide (FAD)

Answer 21

More immobile electron carrier- often part of complex

Unlike NAD+, can take on both protons and electrons

Question 22

Acetyl-CoA

Answer 22

Activated carrier of 2 carbon groups

Transfers acetyl group: moves carbons

Question 23

Why enzymes are needed in the reactions of high energy carriers

Answer 23

The reactions of the high energy carriers are slow, so enzymes are needed to speed them up

Question 24

Oxidation-reduction

Answer 24

Reaction that involves electron transfer

Question 25

Ligation requiring ATP cleavage

Answer 25

Reaction that involves formation of covalent bonds coupled to hydrolysis of ATP

Question 26

Isomerization

Answer 26

Reaction that involves rearrangement of atoms to form isomers

Question 27

Group transfer

Answer 27

Reaction that involves the transfer of a functional group from one molecule to another

Question 28

Hydrolysis

Answer 28

Reaction that involves cleavage of bonds by the addition of water

Question 29

Addition or removal of functional groups

Answer 29

Reaction that involves addition of functional groups to double bonds or their removal to form double bonds