Respiration Cellular 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: C 6 H 12 O 6 + O 2 > CO 2 + H 2 O + Heat

Reactants and Products of Aerobic Respiration Kreb’s Cycle *Reactants: pyruvic acid *Products: 2 ATP CO 2 H+ ions Electron Transport Chain: *Reactants: H+ ions O 2 *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: 24 2 Aerobic Respiration: # of ATP consumed: # of ATP made: Net ATP: Anaerobic Respiration: # of ATP consumed: # of ATP made: Net ATP: 00 0 GRAND TOTALS (for entire process): *Plants / Animals = 38 ATP made per molecule glucose *Bacteria / Yeast = 2 ATP made per molecule of glucose