Williamson - Metabolism

Question 1

what is catabolism

Answer 1

making energy, oxidative

Question 2

what is anabolism

Answer 2

using energy to make things, reductive

Question 3

what is produced/required in catabolism vs anabolism

Answer 3

catabolism = produces NADH
anabolism = requires NADPH
eg. glycolysis and gluconeogenesis
- makes separate

Question 4

how much ATP can be made from NADH

Answer 4

3 ATP

Question 5

how much ATP can be made from FADH2

Answer 5

2 ATP

Question 6

why are reactions which liberate CO2 very energetically favourable

Answer 6

CO2 is very stable (lower free energy than reactants)
it easily escapes from the reaction site (law of mass action)
a reaction which produces CO2 has more molecules on the right (higher entropy)

therefore it is a useful committed step eg. in the link pyruvate to acetyl CoA

Question 7

redox status

Answer 7

must be balanced if something is getting oxidised something else must be reduced

Question 8

is anabolism mainly reduction or oxidation

Answer 8

reduction
NADPH is used to reduce substrates

Question 9

what is metabolic flux

Answer 9

where did the atoms (eg. C) come from and where did they go

Question 10

where is our carbon from

Answer 10

food, ultimately photosynthesis - fixing CO2
energy for this coming from the sun

Question 11

what is an anaplerotic reaction

Answer 11

used to top up an atom (eg. carbon) in a biosynthetic pathway
ana - add
plero - more

Question 12

how can we fix carbon

Answer 12

pyruvate + CO2 –> oxaloacetate
using ATP, and pyruvate carboxylase

Question 13

what is a threshold enzyme + examples

Answer 13

enzymes which bring key elements into biosynthetic pathways
eg. pyruvate carboxylase and glutamate dehydrogenase

Question 14

characteristics of a threshold enzyme

Answer 14

• tightly regulated
• non-constitutive
• high affinity for substrate

Question 15

what is the carrier for COO

Answer 15

biotin vitamin b7

Question 16

what is the carrier for C1 (methyl)

Answer 16

s-adenosyl methionine

Question 17

what is the carrier for C1 (CH or CH2)

Answer 17

folic acid

Question 18

what is the carrier for C5

Answer 18

isopentenyl pyrophosphate

Question 19

what is the carrier NH2

Answer 19

glutamine

Question 20

what is the carrier C2

Answer 20

Coenzyme A, from vitamin B5
has a sulphur making it more reactive

Question 21

what is a vitamin

Answer 21

essential molecules we cannot make ourselves
often carriers

Question 22

what role does biotin play in the Krebs

Answer 22

it is the carrier of COO in the anaplerotic reaction of pyruvate to oxaloacetate to top up carbon in the Krebs

Question 23

how does a folate molecule bind CH2 or CH

Answer 23

with N “claw” - 2 nitrogens surround it
folate can change it oxidation states to carry the 2 forms of carbon

Question 24

where does the methyl group bind to s-adenosylmethionine

Answer 24

the sulphur of the methionine
the adenosine is a handle

Question 25

why is s-adenosylmethionine important

Answer 25

it carries methyl groups which are important in epigenetics - DNA - and histones and important for the ripening of fruit

Question 26

what is an example of C2 donation

Answer 26

link reaction fatty acid biosynthesis

Question 27

how are C5 units made

Answer 27

6 units of acetyl CoA - 1C removed as CO2

Question 28

what are C5 units used for

Answer 28

steroids eg. terpenes - plant signals also smells eg. menthol retinol haem and chlorophyll

Question 29

what is glutamate used for

Answer 29

main carrier of nitrogen nucleic bases

Question 30

what is the pentose phosphate pathway for

Answer 30

interchanging different sugars (different lengths of Cs) making biosynthetic intermediates especially making ribose

Question 31

what human cell can only do glycolysis

Answer 31

RBCs

Question 32

what is a ketone body

Answer 32

fats which are soluble in water - can cross BBB

Question 33

how does pyruvate become alanine

Answer 33

a transamination reaction (swapping a C double bond O for an C-NH2 done by alanine transaminase

Question 34

what are some differences between the pentose phosphate pathway and glycolysis

Answer 34

it uses NADPH (P = hint to biosynthesis) it releases a CO2 at the start - control

Question 35

what are the roles of acetyl CoA

Answer 35

making energy biosynthesis synthesising fatty acids

Question 36

once carbon atoms have gone from pyruvate to acetyl CoA can they go back?

Answer 36

no

Question 37

what krebs intermediate is used to make fatty acids

Answer 37

citrate (6C)

Question 38

what krebs intermediate is used to make amino acids

Answer 38

α-ketoglutarate (5C) and oxaloacetate (4C)

Question 39

what krebs intermediate is used to make porphyrins (haem, chlorophyll)

Answer 39

succinyl CoA (4C)

Question 40

does the krebs cycle go backwards

Answer 40

yes especially in photosynthetic bacteria and plants for biosynthesis

Question 41

what is the breakdown of fatty acids

Answer 41

beta-oxidation because you chop off 2 carbons at a time the first being -CH2-COOH = acetyl CoA same enzyme for different length substrates - fatty acid oxidase

Question 42

can fats be converted to sugars

Answer 42

not directly, only the glycerol headgroup which can feed into gluconeogenesis

Question 43

how are fatty acids synthesised

Answer 43

opposite of breakdown same enzyme adds 2 carbons to the chain each time

Question 44

how is nitrogen moving around compounds in AA synthesis

Answer 44

moved around from glutamate using transamination

Question 45

what does nucleotide biosynthesis use as a committed step and why?

Answer 45

ATP --> AMP this is a big free energy change favourable and less likely to go backwards = important to get right

Question 46

what are the four ways metabolism can be controlled

Answer 46

1. isozymes 2. cumulative regulation of one enzyme by multiple products/substrates 3. expressional regulation 4. change in [substrate] - metabolic flux

Question 47

what does ATP inhibit

Answer 47

energetic pathways

Question 48

what does ADP inhibit

Answer 48

biosynthetic pathways

Question 49

what is enzyme multiplicity (isozymes)

Answer 49

having multiple different isozymes with different allosteric modulators eg. lactate dehydrogenase different components H4 to M4

Question 50

what is cumulative control of a single enzyme

Answer 50

when one enzyme is regulated by multiple different substrates or products often includes kinases which temporarily phosphorylate an enzyme making it inactive eg. glycogen phosphorylase

Question 51

what is expression control of an enzyme

Answer 51

presence of a substrate removes a repressor eg. lac operon or presence of a product causes a repressor to bind

Question 52

transamination what AA forms alpha-ketoglutarate

Answer 52

glutamine

Question 53

transamination what AA forms oxaloacetate

Answer 53

arginine