Cellular Respiration & Photosynthesis lecture 11

Overview of Cellular Respiration

Process by which living cells obtain energy from organic molecules and release waste products

O2 consumed and CO2 released

Primary aim to make A T P

Aerobic respiration uses oxygen

Anaerobic respiration (fermentation) does not use oxygen

Glucose metabolism

C6H12O6 + 6O2 → 6CO2 + 6H2O

Four metabolic pathways:

• Glycolysis

• Breakdown of pyruvate

• Citric acid cycle

• Oxidative phosphorylation

Glycolysis

Breakdown of glucose into 2 pyruvates

Glycolysis can occur with or without oxygen

Steps in glycolysis nearly identical in all living species

Three phases:

• Energy investment

• Cleavage

• Energy liberation

Glycolysis – Major Reactions

Net reaction and regulation of glycolysis

• Rate of glycolysis regulated by availability of substrates and by feedback inhibition

Breakdown of Pyruvate

• In eukaryotes, pyruvate is transported into the mitochondrial matrix

• Broken down by pyruvate dehydrogenase

• Molecule of CO2 removed from each pyruvate

• Remaining acetyl group attached to CoA to make acetyl CoA

• Yield = 1 NADH for each pyruvate

Intermediate Step

Breakdown of Pyruvate

Citric Acid Cycle

Metabolic cycle- takes place in the mitochondrial matric (cristae)

Acetyl is removed from Acetyl CoA and attached to oxaloacetate to form citrate (aka citric acid)

Series of steps releases 2 CO2, 1 ATP, 3 NADH, and 1 FADH2

Oxaloacetate is regenerated to start the cycle again

Details of the citric acid cycle

Oxidative Phosphorylation

• High energy electrons removed from NADH and FADH2 to make ATP in oxidative phosphorylation

• Typically requires oxygen

• Oxidative process involves electron transport chain in the inner mitochondria membrane

• Phosphorylation occurs by ATP synthase