LB145Sec 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.

Light

Campbell 8e, Fig. 10.5

H2O

Chloroplast

LightReactions

NADP+

PADP

i+

ATP

NADPH

O2

CalvinCycle

CO2

[CH2O](sugar)

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.

(a) Normal binding (c) Allosteric inhibition

(b) Competitive inhibition

Noncompetitive inhibitor

Competitive inhibitor

Substrate

Enzyme

Enzyme Inhibition

Hexokinase

• First step• Requires ATP• Allosteric inhibition by high concentrations of glucose-6-

phosphate

Pyruvate kinase

• Last step (produces ATP)• Inhibited by high concentrations of ATP or acetyl

coenzyme A

Energy investment phase

Glucose

2 ADP + 2 P 2 ATP used

formed4 ATP

Energy payoff phase

4 ADP + 4 P

2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+

2 Pyruvate + 2 H2O

2 Pyruvate + 2 H2OGlucoseNet

4 ATP formed – 2 ATP used 2 ATP

2 NAD+ + 4 e– + 4 H+ 2 NADH + 2 H+

Gly

coly

sis:

Wha

t do

you

need

to k

now

?

Gly

coly

sis:

Wha

t do

you

need

to k

now

? 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

Mitochondrion

Substrate-levelphosphorylation

ATP

Cytosol

Glucose Pyruvate

Glycolysis

Electronscarried

via NADH

Substrate-levelphosphorylation

ATP

Electrons carriedvia NADH and

FADH2

Oxidativephosphorylation

ATP

Citricacidcycle

Oxidativephosphorylation:electron transport

andchemiosmosis

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 3

Pyruvate

Transport protein

CO2Coenzyme A

Acetyl CoA

Pyruvate Quiz3. 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 Quiz4. How many carbon atoms are fed into

the citric acid cycle as a result of the oxidation of one molecule of pyruvate?a) 3b) 5c) 2d) 6e) 4

Citric Acid Cycle / Krebs Cycle

The Citric Acid Cycle and the Krebs Cycle are the SAME THING.

Fig. 9-11

Pyruvate

NAD+

NADH

+ H+Acetyl CoA

CO2

CoA

CoA

CoA

Citricacidcycle

FADH2

FAD

CO22

3

3 NAD+

+ 3 H+

ADP + P i

ATP

NADH

More accurately…

2

2

2

2

2

2

2

22

2

2

Krebs Cycle Quiz

5. How does the Krebs Cycle export energy?a) Mostly as CO2

b) Mostly as ATPc) Mostly as FADH2

d) Mostly as NADHe) Mostly as H2O

Krebs Cycle Quiz6. 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