RespirationCellular Respiration – process in

which living organisms break down organic compounds (glucose) to make energy.

Respiration Facts:

*all animals, bacteria, and the roots of plants undergo respiration.

*respiration involves more than “breathing” – it is the creation of energy to fuel the cell.

*energy produced by respiration is in the form of ATP (adenosine triphosphate).

*two types: aerobic and anaerobic respiration

*Respiration can take two different paths, depending on whether oxygen is present.

Overview of Respiration

Pathways of Respiration

*ALL organisms begin respiration with the digestion of food....food is broken down into individual glucose molecules.

*When the cell needs energy, the glucose is taken from blood and is broken down to harvest ATP....this process is known as glycolysis.

*Glycolysis occurs in the cytoplasm and takes place with or without oxygen.

Glycolysis*enzymes in the cytosol break

glucose into four different compounds, using up two ATP in order to drive the reactions.

*the end result is a compound called pyruvic acid and 4 molecules of ATP.

*the overall energy production for glycolysis is 2 ATP molecules for every molecule of glucose used.

*pyruvic acid is used in the next series of reactions; where it goes DEPENDS on whether oxygen is present.

*If oxygen is present, pyruvic acid will diffuse into the mitochondria and undergo a series of chemical reactions known as aerobic respiration.

*If oxygen is absent, pyruvic acid will stay in the cytoplasm and undergo a different type of chemical reaction called anaerobic respiration.

Aerobic Respiration:

*After glycolysis, if oxygen is present in the cell, pyruvic acid will enter the mitochondria.

*Pyruvic acid will undergo TWO types of chemical reactions – Kreb’s Cycle and the Electron Transport Chain.

*All animals and roots of plants under this type of respiration.

*This type of respiration is very efficient – produces 20x more ATP than glycolysis.

*Overall net equation:

C6H12O6 + O2 > CO2 + H2O + Heat

Reactants and Products of Aerobic

Respiration

Kreb’s Cycle

*Reactants:

pyruvic acid

*Products:

2 ATP

CO2

H+ ions

Electron Transport Chain:

*Reactants:

H+ ions

O2

*Products:

Water

34 ATP

The whole point of aerobic respiration is to harvest high energy electrons (H+) to make more ATP (much more than glycolysis can make).

* 2 net ATP from glycolysis is not enough energy for the cell, since most complex organisms (plants and animals) use this form of respiration.

During aerobic respiration, 36 ATP molecules are made for every molecule of glucose used.

Anaerobic Respiration

When oxygen is NOT present, the pyruvic acid made at the end of glycolysis will stay in the cytoplasm.

Anaerobic respiration is very inefficient...therefore, it is the primary source of energy for smaller, less complex organisms such as yeast and bacteria.

Animals can undergo anaerobic respiration if the cell is deprived of oxygen.....exercise, muscle fatigue, heart attacks, strokes, etc.

Anaerobic respiration does NOT make any additional ATP, except for what was made in glycolysis; it only produces chemicals needed to keep glycolysis going.

Two types of anaerobic respiration:

Alcoholic Fermentation- bacteria convert pyruvic acid into

carbon dioxide and ethyl alcohol in the absence of oxygen.

- same process used in the beer / wine-making industries.

Lactic Acid

- yeast and animal cells convert pyruvic acid into carbon dioxide and lactic acid in the absence of oxygen.

- same process used in bread and cheese industry.

- lactic acid build-up in over-worked muscles causes soreness in animals.

Total Energy(per ONE molecule of

glucose) Glycolysis:

# of ATP consumed: # of ATP made: Net ATP:

2 4 2

Aerobic Respiration:

# of ATP consumed: # of ATP made: Net ATP:

0 36 36

Anaerobic Respiration:

# of ATP consumed: # of ATP made: Net ATP:

0 0 0

GRAND TOTALS (for entire process):

*Plants / Animals = 38 ATP made per molecule glucose*Bacteria / Yeast = 2 ATP made per molecule of glucose