unit 2: steps of the kreb's cycle

Question 1

overall formula for the kreb’s cycle

Answer 1

acetyl coenzyme A + oxaloacetate + 3 NAD+ + ADP + Pi + FAD -> 3 NADH + ATP + FADH2 + 2 CO2 + oxaloacetate

Question 2

kreb’s step 1 inputs

Answer 2

oxaloacetate + acetyl coA

Question 3

where does the acetyl coA come from in the first step of the kreb’s cycle?

Answer 3

acetyl coA is created in pyruvate oxidation

Question 4

kreb’s step 1 outputs

Answer 4

citrate + coenzyme A-SH

Question 5

kreb’s step 1 function

Answer 5

addition of -CH2COO group and carbonyl (on oxaloactetae) is converted to -OH (creating citrate)

Question 6

kreb’s step 2 inputs

Answer 6

citrate

Question 7

kreb’s step 2 outputs

Answer 7

isocitrate + H2

Question 8

kreb’s step 2 facilitative enzyme

Answer 8

isomerase

Question 9

kreb’s step 2 function

Answer 9

new isomer is created (from citrate) where -OH moves to one of the peripheral carbons with a COO- group instead of the central carbon (replaced with H) – creates isocitrate

Question 10

kreb’s step 3 inputs

Answer 10

isocitrate + NAD+

Question 11

kreb’s step 3 ouputs

Answer 11

alpha-ketoglutarate + NADH + H+ + CO2

Question 12

kreb’s step 3 facilitative enzyme

Answer 12

dehydrogenase

Question 13

kreb’s step 3 function

Answer 13

OH group is converted to carbonyl group again; NAD+ is reduced to NADH; CO2 is also produced

Question 14

kreb’s step 4 inputs

Answer 14

alpha-ketoglutarate + NAD+ + coenzyme A-SH

Question 15

kreb’s step 4 outputs

Answer 15

succinyl coezyme A + CO2 _ NADH + H+

Question 16

kreb’s step 4 facilitative enzyme

Answer 16

dehydrogenase

Question 17

kreb’s step 4 function

Answer 17

COO- group beside the carbonyl (on a-ketoglutarate) is replaced with -coA-S (bonds with S); succinyl coA and CO2 are produced; NAD+ is reduced to NADH

Question 18

kreb’s step 5 inputs

Answer 18

succinyl coA + Pi + ADP + GDP

Question 19

kreb’s step 5 outputs

Answer 19

succinate + GTP + ATP + coA-SH

Question 20

kreb’s step 5 facilitative enzyme

Answer 20

kinase

Question 21

kreb’s step 5 function

Answer 21

phosphate is added to GDP to create GTP (phosphate comes off to form ATP from ADP); S-coA group comes off of succinyl coA to create succinate, which has a COO- in place of S-coA and a carbonyl group

Question 22

kreb’s step 6 inputs

Answer 22

succinate + FAD+

Question 23

kreb’s step 6 outputs

Answer 23

fumarate + FADH2

Question 24

kreb’s step 6 facilitative enzyme

Answer 24

dehydrogenase

Question 25

kreb’s step 6 function

Answer 25

FADH2 is produced when 2 H are removed from the two middle carbons, creating a C=C double bond with two COO- groups on each carbon

Question 26

kreb’s step 7 inputs

Answer 26

fumarate + H2O

Question 27

kreb’s step 7 outputs

Answer 27

malate

Question 28

kreb’s step 7 facilitative enzyme

Answer 28

isomerase

Question 29

kreb’s step 7 function

Answer 29

-OH and -H are added to the C=C double bond between the two middle carbons, each carbon still has a COO- group on it

Question 30

kreb’s step 8 inputs

Answer 30

malate + NAD+ + H+

Question 31

kreb’s step 8 outputs

Answer 31

oxaloacetate + NADH

Question 32

kreb’s step 8 facilitative enzyme

Answer 32

dehydrogenase

Question 33

kreb’s step 8 function

Answer 33

-OH group on malate is converted to carbonyl group again and H is added to NAD+ to create NADH (oxidation of NAD+); recreates oxaloacetate, which is ready to accept the next acetyl coA