metabolism

Question 1

what are metabolites?

Answer 1

chemical intermediates in metabolic pathways

Question 2

True or False: all pathways share the same functional chemical and thermodynamic principles

Answer 2

TRUE

Question 3

what are the 2 major purposes of metabolism?

Answer 3

1) obtain usable chemcial energy from the environment

2) make molecules that cells need to survive

Question 4

what is an anabolic pathway? what characteristics does it have?

Answer 4

processes that USE energy to build larger molecules
-reductive
-bonds are made using electrons

Question 5

what is a catabolic pathway? what characteristics does it have?

Answer 5

processes that RELEASE energy in breaking down molecules
-oxidative
-electrons are removed as bonds are broken

Question 6

what is an amphibolic pathway?

Answer 6

a process that operates in catabolic and anabolic ways
-depends on the condition

Question 7

in what metabolic process are co-factors reduced?

Answer 7

catabolism

Question 8

in what metabolic process are cofactors oxidized?

Answer 8

anabolic

Question 9

how are excess carbs stored?

Answer 9

stored as glycogen in the liver and skeletal muscle

Question 10

how are excess FA stored?

Answer 10

stored as fat (triacylglycerols) in adipocytes (fat cells)

Question 11

what is typically the end product for oxidation of carbon molecules?

Answer 11

CO2

Question 12

what is the difference between standard free energy and actual free energy?

Answer 12

standard free energy is a thermodynamic term indicating the reaction is proceeding at standard conditions

Actual free energy change depends on the [substances] in the system

Question 13

if the change in free energy for a rxn is ~0, what does this indicate?

Answer 13

the reaction is reversible
-system is close to equilibrium

Question 14

if the change in free energy for a rxn is «<0, what does this indicate?

Answer 14

the rxn is irreversible

Question 15

how does changes in [product] vs [reactant] change the direction of the rxn?

Answer 15

increases in [product] will favour the reverse

increases in [reactant] will favour forward rxn

Question 16

are reversible or irreversible steps usually regulated?

Answer 16

irreversible

-E1/ E4 are regulated

Question 17

what is the rate-limiting step in a reaction?

Answer 17

the irreversible regulated reaction that determines the overall rate of the pathway

Question 18

what are 2 examples of inhibition in metabolic pathways?

Answer 18

1) product inhibition
-enzyme inhibited by the product formed from that rxn

2) feedback inhibition
-enzyme inhibited by a metabolite further down the pathway

Question 19

what is feed-forward activation?

Answer 19

activation of an enzyme upstream due to a metabolite being produced

Question 20

what is reciprocal regulation? why is it important?

Answer 20

regulation where opposing pathways catalyze the revers of another pathway
-pathways are regulated in order to ensure that both do not operate at the same time

Question 21

what is considered to be a high energy molecule?

Answer 21

compounds that have usable chemical energy
- rxn associated with a large delta G

Question 22

what are three maojor types of high energy intermediates?

Answer 22

1) electron carriers
-NADH, NADPH,FADH2

2) nucleoside triphosphate
-ATP,UTP,GTP

3) thioesters

Question 23

what are 3 characteristics of oxidative rxn’s?

Answer 23

1) metabolites oxidized

2) cofactors are reduced (typically NAD+ or FAD)

3) catabolic rxn

Question 24

what are 3 characteristics of reductive rxn’s?

Answer 24

1) metabolites reduced

2) cofactors are oxidized (typically NADPH)

3) anabolic rxn

Question 25

why do nucleotides play a central role in metabolism as electron carriers?

Answer 25

the nitrogen base portion enables them to undergo reversible reduction rxn’s

Question 26

what are 2 common types of nucleotides that are important in metabolism?

Answer 26

-Nicotinamide adenine dinucleotide (NAD+)

-Flavin adenine dinucleotide (FAD)

Question 27

What form is the higher energy form for NAD+/NADP+?

Answer 27

the reduced form is higher energy
-NADH/NADPH

Question 28

what is the higher energy form for flavin adenine dinucleotide?

Answer 28

FADH2 is the higher energy form of FAD

Question 29

what kind of group is FAD?

Answer 29

a prosthetic group

-FADH2 must be reoxidized back to FAD for the next enzyme cycle to occur

Question 30

what makes ATP a high energy molecule?

Answer 30

phosphoanhydride bonds

Question 31

what is the delta G for the hydrolysis of a phosphoanhydride bond? what is it for the formation?

Answer 31

-32kJ/mol

+32kJ/mol

Question 32

is this a high energy molecule?

Answer 32

no, there are no phosphoanhydride bonds

Question 33

what makes the phophoanhydride bonds in ATP high energy?

Answer 33

1) decreased electrostatic repulsions

2) resonance stabilization

3) solvation effects- the number od interactions with solvent increases which decreases delta G

Question 34

what are the characteristics of thioesters?

Answer 34

-high energy compounds
-similar to esters with no electron delocalization

Question 35

what kind of process generates ATP?

Answer 35

catabolic processes
-directly (substrate level phosphorylation)

-reoxidation of NADH/FADH2 (oxidative phosphorylation; generates free energy change that os used to drive ATP synthesis)

Question 36

how can a reaction occur with a delta G >0?

Answer 36

coupling must occur in order to make the overall delta G of the rxn <0

Question 37

what is phosphate transfer potential?

Answer 37

free energies of hydrolysis for phosphate-containing compounds