Bio 178 Lecture 15Cellular Respiration

http://biology.clc.uc.edu/courses/bio104/cellresp.htm

Reading

• Chapter 9

Quiz Material

• Questions on P 184

• Chapter 9 Quizzes on Text Website (www.mhhe.com/raven7)

Outline

• Cellular Respiration

Glucose catabolism

ATP Synthase

Glucose Catabolism

Methods for Making ATP

1. Substrate-Level Phosphorylation

ADP + Pi ATP

Pi comes from a phosphate-bearing intermediate molecule.

Example - Glycolysis.

2. Aerobic Respiration

ATP synthase makes ATP using energy provided by electron transfer. O2 = final electron acceptor.

Substrate-Level Phosphorylation

Aerobic Respiration

Processes Involved in Eukaryotic Respiration1. GlycolysisSugar splitting anaerobic process.

• Location

Cytoplasm

• Energetic Products2 ATP net & 2 NADH net produced by substrate level phosphorylation.

2. Aerobic Respiration• Pyruvate oxidation

• Krebs cycle

• Electron transport chain

GlycolysisGlucose + 2 ADP + 2 Pi + 2 NAD+ 2 Pyruvate + 2 ATP + 2 NADH + 2 H+ + 2 H2O

10 enzyme catalyzed steps can be divided up into 3 major stages:

1. Glucose PrimingGlucose is prepared for cleavage using 2 ATP.

2. Cleavage

Fructose 1,6-bisphosphate (6C) 2 X 3C molecules.

3. Energy HarvestingThe 2 X 3C molecules are converted into 2 pyruvate (3C), releasing 2 NADH and 4 ATP by substrate-level phosphorylation.

Principle Stages of Glycolysis

Glycolysis Pathway

Glycolysis Pathway

Glycolysis (Cntd.)• Bookkeeping1. ATP

4 ATP - 2 ATP = 2 ATPnet

2. NADH

2 NADH

• NAD+ Regeneration

Glycolysis depletes cellular NAD+ stores. The cell uses 2 methods to recycle NAD+ (transfer electrons and H+):

1. Aerobic respiration

2. Fermentation

Pyruvate Fate

FermentationAllows glycolysis to continue in the continued presence of glucose.

2 types:

• Ethanol - Yeast2 Pyruvate (3C) 2 Acetaldhyde (2C) + 2 CO2 2 Ethanol (2C) (+ 2 NAD+)

Toxic to yeast at 12%

• Lactic Acid - Animals2 Pyruvate (3C) 2 Lactate (3C) (+ 2 NAD+)

When lactate is produced faster than it is removed Muscle fatigue

Fermentation

Acetyl-CoA Production• FunctionOxidation of pyruvate to produce NADH

• Overall Reaction

Pyruvate (3C) + CoA + NAD+ Acetyl-CoA (2C) + CO2 + NADH

Catalyzed by pyruvate dehydrogenase

Coenzyme A is a cofactor• Location

Pyruvate is shuffled into the mitochondrion. Acetyl co-A is made in the mitochondrial matrix.

Acetyl-CoA used either in fat synthesis or ATP generation