Chapter 5 Section 3Cellular Respiration

How do we get energy?•We all need energy

to function and we get this energy from the food we eat.

•Cellular respiration is the process by which chemical energy of “food” molecules is released and captured as ATP.

Foods•All types of food

(carbohydrates, fats, and proteins) can be used as fuel to produce ATP.

•However, glucose is most commonly used.

Cellular Respiration = Metabolism

•Metabolism is the sum of all chemical reactions that occur in the organism.

•During cell respiration, the breaking down of food contributes to metabolism.

Cellular respiration in the presence of oxygen is known as aerobic respiration.

3 Metabolic Processes of Aerobic Cellular Respiration

•1. Glycolysis which occurs in the cytoplasm.

•2. Krebs cycle/Citric cycle which occurs inside of the mitochondria.

•3. Electron transport chain which occurs inside the mitochondria membrane.

Glycolysis•Literally means “sugar breakdown”.• In glycolysis, the 6-carbon sugar, glucose

is broken down into two 3-carbon molecules called pyruvate.6 CARBON

SUGAR3 CARBON 3 CARBONPYRUVATE PYRUVATE

Glycolysis•2 ATP are used as activation energy for glycolysis.

•However, it produces 4 ATP and 2 NADH.

What is NADH?•It helps produce energy!

•Acts like a spark plug in a cell.

Krebs/Citric Cycle•Only occurs if O2 is present!

•The pyruvate from glycolysis will be used to generate a pool of chemical energy which includes:▫2 ATP▫8 NADH▫2 FADH2 - similar to NADH

Electron Transport Chain•The ETC allows the

release of large amounts of chemical energy stored in NADH and FADH2.

•The ETC produces up to 30 more ATP for the cell.

•Net gain of aerobic respiration 36-38 ATP!

If oxygen is not present, the Krebs cycle won’t function.

If Krebs cycle doesn’t function, the organism must be able to recycle NAD+ so ATP can be produced!

When the cell lacks O2,

fermentation (which is a type

of anaerobic respiration) recycles the

NAD+ so the cell can make ATP!

Fermentation does not

produce ATP!

Net gain of anaerobic

respiration is 2 ATP!

Aerobic vs. Anaerobic Respiration

•The chemical energy stored in glucose generates far more ATP in aerobic respiration (36-38 ATP) compared to anaerobic respiration (2 ATP)!

Two types of fermentation:•Lactic acid – recycles NAD+, but produces

lactic acid as a by-product.▫Bacteria, fungi and animals use this

process!•Alcoholic – recycles NAD+, but produces

alcohol as a by-product.▫All other organisms!▫Especially yeast! Root Beer