4.2 Link reaction and Krebs cycle

Question 1

The link reaction

Where does it occur? (how does pyruvate from glycolysis get there?

Process:

1. ? (2)
2. ?
3. ?(2)

Equation?

Answer 1

Occurs in mitochondrial matrix (pyruvate actively transported from cytoplasm)

1. Oxidation
Hydrogen removed
Accepted by NAD to form NADH
2. CO2 molecule formed
3. 2-carbon acetyl group formed
Combines with coenzyme A
= acetylcoenzymeA.

Pyruvate + NAD +coA —-> acetylcoA + NADH + carbon dioxide.

Question 2

The Krebs cycle

Where does it occur?
What phosphorylation?
Process:
1. ?
2. ? (1)
3. ? (1)

Answer 2

Mitochondrial matrix
Oxidative phosphorylation

1. 2-carbon acetylcoenzymeA combines with 4-carbon molecule to form 6-carbon molecule.
2. 6-carbon molecule loses carbon dioxides and hydrogens (accepted by coenzymes)
   Gives one 4-carbon molecule and one ATP
3. Regeneration
   4-carbon molecule combines with new acetylcoenzymeA molecule

Question 3

Energy yields (from link and Krebs):

(3)

*Yield from one glucose molecule = ? because?

Answer 3

1 ATP molecule
3 CO2 molecules (waste product)
Reduced coenzymes - NADH, FADH (have potential to produce ATP)

Double quantities above, x2 pyruvate

Question 4

Coenzymes:

Define coenzyme 
Function?
Describe where each is important:
NAD? (2)
FAD?
NADP?

Answer 4

= molecules that some enzymes require in order to function.
Carry H atoms from one molecule to another
Throughout respiration
-Works with dehydrogenase enzymes
-Involved in oxidative phosphorylation
Krebs cycle
Photosynthesis

Question 5

Significance of Krebs cycle:

Breaks down? into?

Produces…carried by…to…for oxidative phosphorylation…produced

Regenerates…that would?

Source for cells to make? e.g.?(3)

Answer 5

Breaks down macromolecules into smaller ones
Produces hydrogen atoms, carried by NAD to electron transport chain, for oxidative phosphorylation, ATP produced
Regenerates 4-carbon molecule that would otherwise accumulate.
Source for cells to make substances (e.g. amino acids, fatty acids, chlorophyll)