LB145 Sec

Today’s Outline -Announcements: StudyNotes5 AND Homework4 are due on Tuesday Feb 19 th. Honors – come see me if you missed the meeting. Glycolysis and the Krebs Cycle.

Light Campbell 8e, Fig H2OH2O Chloroplast Light Reactions NADP + P ADP i + ATP NADPH O2O2 Calvin Cycle CO 2 [CH 2 O] (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 ATPused formed 4 ATP Energy payoff phase 4 ADP + 4 P 2 NAD e – + 4 H + 2 NADH + 2 H + 2 Pyruvate + 2 H 2 O Glucose Net 4 ATP formed – 2 ATP used2 ATP 2 NAD e – + 4 H + 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 + + 2P i  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 25 ATP

Campbell: Fig Mitochondrion Substrate-level phosphorylation ATP Cytosol Glucose Pyruvate Glycolysis Electrons carried via NADH Substrate-level phosphorylation ATP Electrons carried via NADH and FADH 2 Oxidative phosphorylation ATP Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis

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 O 2, pyruvate undergoes a series of reactions that results in the product molecule acetyl coenzyme A (acetyl CoA).

Fig CYTOSOLMITOCHONDRION NAD + NADH+ H Pyruvate Transport protein CO 2 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 CO 2, 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 CO 2. b)acetyl CoA, O 2, and ATP. c)acetyl CoA and NADH. d)acetyl CoA, NADH and CO 2. e)acetyl CoA, NADH, ATP and CO 2.

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)3 b)5 c)2 d)6 e)4

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

Fig Pyruvate NAD + NADH + H + Acetyl CoA CO 2 CoA Citric acid cycle FADH 2 FAD CO NAD H + ADP +P i ATP NADH

More accurately…

Krebs Cycle Quiz 5. How does the Krebs Cycle export energy? a)Mostly as CO 2 b)Mostly as ATP c)Mostly as FADH 2 d)Mostly as NADH e)Mostly as H 2 O

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