Transcript here

LB145
Sec 001-004
Today’s Outline
- Announcements:
StudyNotes5 AND Homework4 are due on
Tuesday Feb 19th.
Honors – come see me if you missed the
meeting.
Glycolysis and the Krebs Cycle.
CO2
H2O
Light
NADP+
ADP
+
P
i
Light
Reactions
Calvin
Cycle
ATP
NADPH
Chloroplast
O2
[CH2O]
(sugar)
Campbell 8e, Fig. 10.5
Methods of Producing ATP
GLYCOLYSIS & CITRIC ACID CYCLE
• Substrate-level phosphorylation occurs when ATP is
produced by the enzyme-catalyzed transfer of a
phosphate group from an intermediate substrate to
ADP.
Typically, a cell will
not convert 100% of
its glucose stores for
ATP production.
When the cell has
enough ATP,
glycolysis stops –
how does this
occur?
Typically, a cell will
not convert 100% of
its glucose stores for
ATP production.
When the cell has
enough ATP,
glycolysis stops –
how does this
occur?
Product Feedback Inhibition
Feedback Inhibition Regulates
Glycolysis
• During glycolysis, high levels of ATP inhibit the
enzyme phosphofructokinase, which catalyzes one
of the early reactions.
• This is called allosteric inhibition.
Enzyme Inhibition
Substrate
Competitive
inhibitor
Enzyme
Noncompetitive inhibitor
(a) Normal binding
(b) Competitive
inhibition
(c) Allosteric
inhibition
Hexokinase
• First step
• Requires ATP
• Allosteric inhibition by high concentrations of glucose-6phosphate
Pyruvate kinase
• Last step (produces ATP)
• Inhibited by high concentrations of ATP or acetyl
coenzyme A
Energy investment phase
Glycolysis: What do
you need to know?
Glucose
2 ADP + 2
P
2 ATP
used
P
4 ATP
formed
Energy payoff phase
4 ADP + 4
2 NAD+ + 4 e– + 4 H+
2 NADH
+ 2 H+
2 Pyruvate + 2 H2O
Net
Glucose
4 ATP formed – 2 ATP used
2 NAD+ + 4 e– + 4 H+
2 Pyruvate + 2 H2O
2 ATP
2 NADH + 2 H+
Glycolysis: What do
you need to know?
Track the Carbons and Phosphates:
Glucose + ATP  Fructose-P + ADP
Fructose-P + ATP  P-Fructose-P
P-Fructose-P  P-CCC + P-CCC
P-CCC + P-CCC + 2NAD+ + 2Pi P-CCC-P + P-CCC-P + 2NADH
P-CCC-P + P-CCC-P + 2ADP  P-CCC + P-CCC + 2ATP
P-CCC + P-CCC + 2ADP  Pyruvate + Pyruvate + 2ATP
NADPH
2ATP
2ATP
25 ATP
Campbell: Fig. 9-6-3
Electrons carried
via NADH and
FADH2
Electrons
carried
via NADH
Citric
acid
cycle
Glycolysis
Pyruvate
Glucose
Oxidative
phosphorylation:
electron transport
and
chemiosmosis
Mitochondrion
Cytosol
ATP
ATP
ATP
Substrate-level
phosphorylation
Substrate-level
phosphorylation
Oxidative
phosphorylation
Pyruvate Processing
• Pyruvate processing is the second step in
glucose oxidation. It is catalyzed by the
enzyme pyruvate dehydrogenase in the
mitochondrial matrix.
• In the presence of O2, pyruvate undergoes a
series of reactions that results in the product
molecule acetyl coenzyme A (acetyl CoA).
Fig. 9-10
CYTOSOL
MITOCHONDRION
NAD+
NADH
+ H+
2
1
Pyruvate
Transport protein
3
CO2
Coenzyme A
Acetyl CoA
Pyruvate Quiz
3. In the presence of oxygen, the three-carbon compound
pyruvate can be catabolized in the citric acid cycle. First,
however, the pyruvate
1) loses a carbon, which is given off as a molecule of CO2,
2) is oxidized to form a two-carbon compound called acetate,
and
3) is bonded to coenzyme A.
These three steps result in the formation of:
a) acetyl CoA, NAD+, ATP, and CO2.
b) acetyl CoA, O2, and ATP.
c) acetyl CoA and NADH.
d) acetyl CoA, NADH and CO2.
e) acetyl CoA, NADH, ATP and CO2.
Pyruvate Quiz
4. How many carbon atoms are fed into
the citric acid cycle as a result of the
oxidation of one molecule of pyruvate?
a)
b)
c)
d)
e)
3
5
2
6
4
Citric Acid Cycle / Krebs Cycle
The Citric Acid Cycle and the Krebs Cycle are the
SAME THING.
Fig. 9-11
Pyruvate
CO2
NAD+
CoA
NADH
+ H+
Acetyl CoA
CoA
CoA
Citric
acid
cycle
2 CO2
FADH2
3 NAD+
3 NADH
FAD
+ 3 H+
ADP + P
ATP
i
2
2
2
2
2
2
2
2
2
2
2
More accurately…
Krebs Cycle Quiz
5. How does the Krebs Cycle export
energy?
a) Mostly as CO2
b) Mostly as ATP
c) Mostly as FADH2
d) Mostly as NADH
e) Mostly as H2O
Krebs Cycle Quiz
6. Which statement about the citric acid cycle
is correct?
a) The citric acid cycle produces most of the ATP that is
subsequently used by the electron transport chain.
b) The last reaction in the citric acid cycle produces a
product that is a substrate for the first reaction of the
citric acid cycle.
c) The citric acid cycle oxidizes glucose to carbon dioxide.
d) The citric acid cycle depends on the availability of NAD+,
which is a product of glycolysis.
e) The oxidation of compounds by the citric acid cycle
requires molecular oxygen.
The Citric Acid Cycle
What do you need to know:
• Be familiar with the intermediates (Carbons/Oxygens).
• What molecules are produced?
• How many of each molecule is produced per
cycle?
• How many of each molecule is produced per
glucose?
• What gets recycled?
For THURSDAY:
1. For TUESDAY – SN5 and HW4