the krebs cycle

Question 1

what is the krebs cycle

Answer 1

a series of biochemical steps that lead to the complete oxidation of glucose, resulting in carbon dioxide, water and quite large amounts of ATP

Question 2

how are steps of the krebs cycle controlled

Answer 2

they are controlled and catalysed by specific intracellular enzymes

Question 3

where do the krebs cycle steps take place

Answer 3

in the matrix of the mitochondrion

Question 4

where is ATP produced in the krebs cycle

Answer 4

-produced in the stalked particles on the inner mitochondrial membranes in the presence of oxygen

Question 5

the link reaction

Answer 5

reaction that links glycolysis to the krebs cycle

Question 6

step 1 of the link reaction

Answer 6

the 3C pyruvate crosses into the mitochondria through the mitochondrial membrane from the cytoplasm

Question 7

step 2 of the link reaction

Answer 7

-an atom of carbon is removed from pyruvate resulting in formation of carbon dioxide molecule and 2C joins with coenzyme A to form 2C acetyl coenzyme A

Question 8

decarboxylation

Answer 8

when at atom of carbon is removed from pyruvate

Question 9

what also happens when acetyl CoA is formed

Answer 9

pyruvate is oxidised losing hydrogens to NAD resulting in reduced NADH

Question 10

dehydrogenation

Answer 10

pyruvate oxidised losing hydrogens to NAD

Question 11

step 3 of the link reaction

Answer 11

reduced NAD used later in electron transport chain to produce ATP
-energy contained in acetyl CoA released in the krebs cycle

Question 12

decarboxylases

Answer 12

enzymes that remove carbon dioxide

Question 13

dehydrogenases

Answer 13

enzymes that remove hydrogen

Question 14

equation for link reaction

Answer 14

pyruvate (3C) + CoA + NAD = acetyl CoA(2C) + CO2+ reduced NAD( NADH)

Question 15

what do all reduced hydrogen acceptors do

Answer 15

channel hydrogen through the electron transport chain to produce ATP

Question 16

1 stage of krebs cycle

Answer 16

-2C acetyl CoA combined with 4C compound to form 6C compound citric acid (citrate)
-at this point it has entered krebs cycle

Question 17

step 2 of krebs cycle

Answer 17

-6C citric acid goes through cyclical series of reactions and compound if broken down to give original 4C compound
-2 molecules of Co2 removed in process and given off as waste product

Question 18

step 3 of krebs cycle

Answer 18

-4C compound then combines with more 2C acetyl CoA and cycle begins again

Question 19

what enters for every molecule of pyruvate that enters krebs cycle

Answer 19

-three molecules of reduced NAD (NADH), one of reduced FAD and one of ATP are produced
-the NADH and FAD enter electron transport chain

Question 20

for each molecule of glucose that enters the glycolytic pathway what else enters

Answer 20

-the krebs cycle turns twice because the 6C glucose produced two 3C pyruvate molecules- each of which pass through krebs cycle