Cell metabolism 1 & 2

Question 1

steps of cellular metabolism?

Answer 1

glycolysis, krebs/TCA cycle, oxphos

Question 2

types of reactions which define metabolism?

Answer 2

redox, litigation requiring ATP cleavage, isomerisation, group transfer, hydrolytic, addition/removal of functional groups

Question 3

overall process of glycolysis?

Answer 3

glucose forms 2 three carbon pyruvate

Question 4

does glycolysis need oxygen?

Answer 4

no, it’s an anaerobic process

Question 5

two stages of glycolysis?

Answer 5

formation of a high-energy compound, splitting of high-energy compound

Question 6

step one of glycolysis

Answer 6

glucose –> glucose-6-phosphate
ATP –> ADP
enzyme is hexokinase
this is a GROUP TRANSFER

Question 7

why is step one of glycolysis important?

Answer 7

commits glucose-6-phosphate to cell as it’s negatively-charged so cannot leave cell via glucose transporters

Question 8

step 2

Answer 8

glucose-6-phosphate —-> fructose-6-phosphate
enzyme = phosphoglucose isomerase
it’s an ISOMERISATION reaction

Question 9

step 3

Answer 9

fructose-6-phosphate —> fructose-1,6-bisphosphate
ATP - ADP
enzyme = phosphofructokinase
= GROUP TRANSFER

Question 10

step 4

Answer 10

fructose-1,6-bisphosphate —> glyceraldehyde-3-phosphate and dihydroxyacetone phosphate

enzyme = aldolase
this is a HYDROLYTIC reaction

Question 11

step 5

Answer 11

dihydroxyacetone phosphate —-> glyceraldehyde-3-phosphate
enzyme = TPI

ISOMERISATION reaction

Question 12

step 6

Answer 12

glyceraldehyde-3-phosphate –> 1,3-bisphosphoglycerate
enzyme = glycerade-3-phosphate dehydrogenase
= REDOX and GROUP TRANSFER

Question 13

step 7

Answer 13

1,3-bisphophoglycerate –> 3-phosphoglycerate
ADP –> ATP
enzyme = phosphoglycerate kinase
= GROUP TRANSFER

Question 14

step 8

Answer 14

3-phosphoglycerate —> 2-phosphoglycerate
enzyme = phosphoglycerate mutase
reaction = ISOMERISATION

Question 15

step 8

Answer 15

3-phosphoglycerate —> 2-phosphoglycerate
enzyme = phosphoglycerate mutase
reaction = ISOMERISATION

Question 16

step 9

Answer 16

2-phosphoglycerate —-> phosphoenol pyruvate
enzyme = enolase
reaction = GROUP REMOVAL

Question 17

step 10

Answer 17

phosphoenol pyruvate —> pyruvate
enzyme = pyruvate kinase
ADP —-> ATP
reaction = GROUP TRANSFER

Question 18

net result of glycolysis?

Answer 18

2 pyruvate, 2 NADH, 2 ATP

Question 19

three fates of pyruvate?

Answer 19

alcoholic fermentation (anaerobic)
pyruvate —-> acetaldehyde
enzyme = pyruvate decarboxylase

acetaldehyde —> ethanol
enzyme = alcohol dehydrogenase

lactate fermentation

pyruvate —-> lactate
enzyme = lactate dehydrogenase

main concept of these two reactions is regenerating NAD+ so glycolysis can continue in anaerobic conditions

third fate:

pyruvate —-> acetyl CoA
enzyme = pyruvate dehydrogenase complex
this produces NADH

Question 20

why is NAD+ needed?

Answer 20

dehydrogenation of glyceraldehyde-3-phosphate, first step in generating ATP

Question 21

creatine phosphate?

Answer 21

ATP buffer when exercising

creatine phosphate —> creatine
ADP —> ATP
enzyme = creatine kinase

Question 22

creatine kinase?

Answer 22

the enzyme which is used to catalyse the reaction from creatine phosphate to creatine
used by athletes as a dietary supplement

Question 23

what bond in acetyl CoA?

Answer 23

thioester bond
high-energy bond that is readily hydrolysed so acetyl CoA can donate acetate to other molecules

Question 24

beri-beri

Answer 24

caused by a thiamine deficiency
symptoms include damage to peripheral nervous system, decreased cardiac output and weakness of cardiac musculature
brain is particularly vulnerable as it relies heavily on glucose metabolism

Question 25

what does each turn of the TCA/krebs cycle produce?

Answer 25

2 x CO2
3 x NADH
1 x GTP
1 x FADH2

Question 26

when is the bulk of ATP generated?

Answer 26

oxidative phosphorylation

Question 27

which other molecules can enter TCA cycle?

Answer 27

amino acids, fatty acids

Question 28

two types of amino acid

Answer 28

glucogenic - can produce glucose via gluconeogenesis
ketogenic - can produce acetyl CoA

Question 29

how many molecules can be created by the degradation of all 20 amino acids?

Answer 29

seven

Question 30

how do proteins enter the TCA cycle?

Answer 30

transamination reactions, then carbon skeleton is funnelled into cycle

Question 31

transamination reaction?

Answer 31

= transferral of amine group
nh4+ generated which is converted to urea and excreted as waste product
an amino acid and keto acid form another pair of amino acid and keto acid

Question 32

alanine metabolism?

Answer 32

alanine + a-ketoglutarate —-> pyruvate + glutamate

Question 33

NADH transportation?

Answer 33

NADH needs to be transported into the mitochondria so it can be used in oxidative phosphorylation and so NAD+ is regenerated as there is only a finite amount
the high-energy electrons are transported into the mitochondria

Question 34

two methods of NADH transport and where?

Answer 34

malate-aspartate shuttle - in kidney, lung and heart
glycerol-phosphate - in skeletal muscle and brain

Question 35

glycerol-phosphate shuttle?

Answer 35

only electrons from NADH move
glycerol-3-phosphate dehydrogenase transfers electrons from NADH to DHAP generate glycerol-3-phosphate

membrane-bound form of the same enzyme transfers electrons to FAD, these then get passed to co-enzyme Q (part of electron transport chain)