Biology 10, Las Positas College
Cellular Respiration

I-Introduction
II-ATP
III-Harvesting Energy
A-Glycolysis
B-Fermentation
C-Cellular Respiration

I-INTRODUCTION
A. General
All the activities that organisms perform require energy. Most living things release the stored energy in food molecules by an O2-dependent process called cellular respiration. Cellular respiration captures energy in ATP, an energy-carrying molecule.

Sources of energy
Nutrient molecules can be glucose, storage forms of glucose, fats, or proteins. These can all be broken down into forms that yield energy. Different nutrients enter aerobic pathway at different points, -> CO2, ATP, and different waste products, depending on nutrient.

Producers – capture energy from environment -> food that all organisms use for energy. All energy from sun, except rare chemical reaction or thermal vent. Sun’s energy captured via photosynthesis.
Consumers – use energy rich molecules from producers -> energy.

Interrelationship between producers & consumers

C6 H12O6 + 6O2<-> 6 CO2 + 6 H2O + ATP

(consumers <-> producers)

II-ATP

ATP = the primary molecule used by cells to capture energy & later release it during chemical reactions.
ADP = the molecule that remains after ATP has been used to drive an energy requiring reaction.

Cells break down nutrient molecules -> ATP± O2.

+ O2 = cellular respiration
- O2 = fermentation

Energy Carrying Molecules

III-HARVESTING ENERGY
Glycolysis -> Krebs cycle -> cellular respiration or electron transport

A-GLYCOLYSIS

Glycolysis-takes place in cytoplasm of all cells.

O2 not involved.

glucose (C6) broken down to pyruvate (C3)

NAD+ picks up electrons and H atom from C3 -> NADH. NADH will be used in electron transport system.

NET:

2 ATP/glucose molecule
2 NADH

Fermentation & cellular respiration harvests energy from glycolysis.

B-FERMENTATION - cells generate ATP from chemical breakdown of nutrients without O2

Done by bacteria, yeast, animals-not as efficient for use of nutrients as aerobic metabolism.
only yields 2 ATP/ glucose - from glycolysis

C-CELLULAR RESPIRATION - takes place in mitochondria, requires O2
C6 H12O6 + 6O2<-> 6 CO2 + 6 H2O + ATP

1. C3 (pyruvate) broken down to C2 and CO2

2 NADH released

2. Krebs Cycle (in mitochondria)

C2 broken down to CO2

releases 2 ATP + 6 NADH +2 FADH2
Total energy harvest = 2 ATP, 2 FADH2, 8 NADH

3. Electron Transport Chain (in mitochondria)

Overview:

NADH, FADH2 go through electron transport chain
O2 accepts H+ from NADH & FADH2 -> H20 & ATP

Steps:

1. NADH & FADH2 give up H+ and electron to electron transport system.
2. H+ shuttled out of inner compartment, -> high H+ concentration in outer compartment & electrical gradient
3. H+ goes down concentration gradient by returning to inner compartment through ATP synthase (enzyme which forms ATP from ADP & Pi)
4. H+ & electron accepted by O2 at end of electron transport system -> H2O

Typical Total Energy Yield from 1 molecule glucose = 36 ATP