Download 2b.-Citric-Acid-Cycle

(7) Cellular Respiration
(A) Role of ATP
&
Phosphorylation
(B)
The metabolic
pathway of
respiration:
Glycolysis and the
citric acid cycle
Cellular
Respiration
(C) The metabolic
pathway of
respiration:
electron
transport chain &
ATP synthesis
(E)
Regulation
of pathways
through
feedback
inhibition
(D)
Substrates for
Respiration
Cellular Respiration (b)
• Describe the process of the
Citric Acid Cycle
–Using the terms coenzyme,
regeneration, oxaloacetate,
FAD
Stage 2
Citric Acid Cycle
(occurs only if oxygen is present)
Pyruvate
NAD
NADH
CO2
Acetyl group
Coenzyme A
Acetyl Coenzyme A
citrate
2 CO2
oxaloacetate
ADP
ATP
3FAD
3FADH2
3NAD
3NADH
Notice the
2 is
present on
the FAD
but not the
NAD
1
• Pyruvate is broken down to an acetyl
group that
combines with coenzyme A to be transferred to the
2
citric acid cycle as acetyl coenzyme
A.
3
• Acetyl (coenzyme A) combines with oxaloacetate
to
4
form citrate
followed by the enzyme mediated steps
of the cycle.
5
• This cycle results in the generation of ATP
in one of
the steps, the release of carbon 6dioxide in 2 of the
steps and the regeneration of oxaloacetate in the
7
matrix
of the mitochondria.
8
• In three steps in the cycle, the dehydrogenase
enzyme removes H+ ions along with high energy
9
electrons.
Both become bound to NAD to form
10
NADH.
10
• A similar step also occurs, but the coenzyme is FAD.
Checklist
 Name of stage
 Location
 Starting molecule(s)
 Intermediate molecule(s)
 Final molecule(s)
 ATP
 Carbon dioxide
 Hydrogen
 Oxygen
 Any other points?
Extra info that will help you understand
(but you will not be examined on this)
Number of carbons in each molecule:
•
•
•
•
•
GLUCOSE
PYRUVATE
ACETYL CO A
OXALOACETATE
CITRATE
6
3
2
4
6
(gets broken down)
(gets broken down more!)
(2+4=6)
Investigating the activity of
dehydrogenase enzyme in yeast
• Yeast is a fungus and a living organism. All
living organisms can respire. Like us, it also
contains the enzyme dehydrogenase which
controls the release of hydrogen during
respiration.
• To show the release of hydrogen during
respiration a blue dye called resazurin is used.
The dye changes colour upon becoming
reduced (gaining hydrogen).
Blue
(Not reduced)
Pink
(partially reduced)
Colourless
(reduced)
Aim: To investigate…
Method:
Results:
Test tube
A
B
C
Colour change of resazurin dye
• Conclusion:
– What test tube changed colour the fastest?
– Describe the process which occurred in tube A:
• ______ enzymes present in the _____ have acted on
the substrate _____ and oxidised it. This rapid
release of _____has reduced the resazurin dye and
caused it to change colour.
– Explain why the reaction in test tube B was slower
than test tube A.
• Test tube was slower than A because no glucose was
added. The dehydrogenase enzymes could act upon
the little respiratory substrate already present in the
yeast.
– Explain why test tube C remained unchanged.
• Test tube C remained unchanged since boiled yeast
was added. Boiling the yeast destroys the cells and
denatures the dehydrogenase enzymes.
Cellular Respiration (b)
• Describe the process of the
Citric Acid Cycle
–Using the terms coenzyme,
regeneration, oxaloacetate,
FAD