Lecture 5 - cellular energy

How do we describe energy?

• Gibbs free energy

• Amount of energy in a system to do work

• In chemical reaction, change in energy during reaction will determine of reaction can proceed, Gfinal - Ginitial

Describe the 2 types of reactions?

• exergonic, energy is released, G < 0, catabolic, breaks down molecules

• Endergonic, energy is released, G > 0, anabolic, builds molecules

Describe activation energy?

• Energy required for a full reaction to occur

• Heat can be used to over come this

• Ea determines the rate of reaction

Describe the effect of enzymes on activation energy?

• Enzymes are proteins which lower activation energy, speed is faster

• Doenst affect the change in energy

• Has an active site where substrate binds to promote reaction

Describe ATP hydrolysis?

• ATP hydrolysis releases energy to drive endogonic reactions

• Coupling Ender and endo provides enegry for endergonic reaction

How is ATP created?

• Cellular respiration

• C6 H12 O6+ 6O2 —> 6CO2 + 6H2O

• Same equation as burning glucose

• Break down of glucose in multiple steps harvests ATP

Describe NADH?

• Electron carrier for cell

• NAD+ is reduced to NADH, gains 2 electrons and 1 proton

• NADH is used in the last phase of cellular respiration, powering electron transport

Describe the mitochondria?

• Produces a lot of ATP

• Contains ribosomes and small DNA molecules

• Has double membrane, matrix and inter membrane space

• Enzymes of citric acid cycle in matrix

• Electron transport chain is in inner membrane

Brief explanation of cellular respiration?

• Has 3 major stages

• Stage 1: glycosis - mostly NADH, little ATP

• Stage 2: Pyruvate oxidation and citric acid cycle - mostly NADH, little ATP

• Stage 3: oxidation of phosphorylation, lots of ATP

Describe glycosis?

• Takes place is cytosol

• 1 glucose (6 carbons) is broken down into 2 pyruvate (3 carbons each)

• Produces so 2 NADH and 2 ATP net

Describe 2A pyruvate oxidation?

• Pyruvate moves into mitochondrion

• Produces Acetyl-CoA and CO2

• Produces 1 NADH per pyruvate but no ATP

Describe 2B citric acid cycle?

• Also called kerbs cycle

• For 1 Acetyl CoA, it produced 2 CO2, 1 FADH2, 3 NADH, 1 ATP

Describe stage 3 - Ox Phos?

• Input is NADH and FADH2

• Output is 26-28 ATP per glucose molecule

• Consist of electron transport chain and chemiosis which forms ATP

About Ox phos?

• 4 ATP net from glycosis, pyruvate oxidation and citric acid cycle

• 26-28 ATP from OX phos

• Max 30-32 ATP per glucose molecule