Review

What are the 4 macromolecules? What is an enzyme? What is a polymer? What is a monomer? What is the name of the process that breaks

polymers? What is the name of the process that joins

polymer?

Enzymes

Cellular RespirationHarvesting Chemical Energy

Cellular Respiration

the process that releases energy by breaking down glucose and other food molecules in the presence of oxygen

It is the reverse of photosynthesis.

C6H12O6 + 6O2 6CO2 + 6H2O

3 main stages – each captures some of the chemical energy available in food molecules and uses it to produce ATP

Glycolysis Krebs's Cycle Electron Transport Chain (ETC)(mitochondria)

Glycolysis

Happens in the cytoplasm net gain of 2 ATP per glucose molecule main purpose is to produce pyruvic acid to be used in

the Kreb’s Cycle and to create NADH to transport high energy electrons to the electron transport chain

NAD+ – high energy electron carrier like NADP+ in photosynthesis

NAD+ accepts a pair of high energy electrons forming a molecule called NADH which holds the electrons until they can be transferred to other molecules. NADH carries electrons to the electron transport chain

Glycolysis does not require oxygen and can, therefore, supply chemical energy to cells when oxygen is unavailable.

If oxygen is not present, pyruvate is converted to lactic acid in the cytoplasm -- anaerobic respiration

Kreb’s Cycle (citric acid cycle)

At the end of glycolysis, 90% of the energy from glucose is still unused – locked in the high energy electrons of pyruvic acid.

The main purpose of this cycle is to produce NADH and FADH2 – high energy electron carriers – these carriers carry electrons to the electron transport chain.

Electron Transport Chain

The electron transport chain uses high energy electrons from the Kreb’s Cycle to convert ADP to ATP. Water is a waste product of the ETC (and of cellular respiration) just as oxygen is in photosynthesis.

Electron Transport Chain

When oxygen is not present …. Glycolysis is followed by a different pathway!

Fermentation

Fermentation

Fermentation releases energy from food molecules by producing ATP in the absence of oxygen.

Cells convert NADH to NAD+ by passing high energy electrons back to pyruvic acid.

This allows glycolysis to continue producing a steady supply of ATP

Called anaerobic because it does not require oxygen.

Two types: alcoholic fermentation and lactic acid fermentation.

Alcoholic Fermentation

Produces carbon dioxide and alcohol

This is what causes bread dough to rise – when yeast runs out of oxygen it ferments, giving off carbon dioxide gas which creates the air spaces in a slice of bread.

The alcohol evaporates.

Lactic Acid FermentationLactic acid is produced in the muscles

during rapid exercise when the body cannot supply enough oxygen to the tissues.

Without oxygen the body is unable to produce all the ATP required.

Muscle cells begin producing ATP by lactic acid fermentation.

The build-up of lactic acid causes a painful, burning sensation – sore muscles

Comparing Photosynthesis and Cellular Respiration

  Photosynthesis Cellular RespirationFunction Energy capture Energy releaseLocation Chloroplasts Mitochondria and Cytoplasm

Who does it? “green” cells – plant, algae ALL living cells

Reactants CO2 & H2O C6H12O6 & O2

Products C6H12O6 & O2 CO2 & H2OEquation 6CO2 + 6H2O C6H12O6 +

6O2

C6H12O6 +6O2 6CO2 + 6H2O

Order Happens first Happens second