aerobic respiration

Question 1

what does the link reaction do

Answer 1

converts Pyruvate to Acetyl Coenzyme A

Question 2

what are all the steps to the link reaction

Answer 2

1) Pyruvate is decarboxylated (one carbon atom
is removed from pyruvate in the form of C02).
2) Pyruvate is oxidised to form acetate and N A D
is reduced to form reduced N A D.
3) Ace t a t e is combined with coenzyme A (CoA)
to form acetyl coenzyme A (acetyl CoA).
4) No ATP is produced in this reaction.

Question 3

what are all four components to aerobic respiration

Answer 3

glycolysis

link reaction

Krebs cycle

Oxidative Phosphorylation

Question 4

how often does the link reaction occur

Answer 4

Twice for Every Glucose Molecule

Question 5

how many pyruvate molecules are made for every glucose molecule

Answer 5

Two pyruvate molecules are made for every glucose molecule that enters glycolysis. This means the link reaction
and the third stage (the Krebs cycle) happen twice for every glucose molecule.

Question 6

in the link reaction what occurs per glucose molecule

Answer 6

Two molecules of acetyl coenzyme A go into the Krebs c y c le (see below).
• Two C 0 2 molecules are released as a waste product of respiration.
• Two molecules of reduced NAD are formed and go to the last stage (oxidative phosphorylation

Question 7

what does the krebs cycle produce

Answer 7

reduced co enzymes and ATP

Question 8

what does the krebs cycle involve

Answer 8

The Krebs cycle involves a series of oxidation-reduction reactions, which take place in the matrix of the mitochondria.
The cycle happens once for every pyruvate molecule, so it goes round twice for every glucose molecule.

Question 9

what is the first step to the krebs cycle

Answer 9

Acetyl Co A from the link reaction
com bines with a four-carbon
molecule (oxaloacetate) to form a
six-carbon molecule (citrate).
• Co enzyme A goes back to the
link reaction to be used again.

Question 10

what is the second step to the krebs cycle

Answer 10

The 6C citrate molecule is
converted to a 5C molecule.
• Decarboxylation occurs,
where C O , is removed.
• Dehydrogenation also occurs,
where hydrogen is removed.
• The hydrogen is used to
produce reduced NAD
from NAD.

Question 11

what is the third step to the Krebs cycle

Answer 11

The 5C molecule is then converted to a 4C molecule. (There arc some intermediate
compounds formed during this conversion, but you don’t need to know about them.)
• Decarboxylation and dehydrogenation occur, producing one molecule of reduced FAD and
two of reduced N A D.
• ATP is produced by the d ire c t transfer of a phosphate group from an intermediate compound
to A D P. W hen a phosphate group is directly transferred from one molecule to another it’s
called substrate-level phosphorylation. Citrate has now been converted into oxaloacetate.