Chapter 6 Biology 100 Tri-County Technical College Pendleton, SC

What is respiration? u process by which living organisms take glucose and other nutrients and make ATP u Aerobic respiration –utilizes oxygen in the process u Anaerobic respiration –is done without oxygen u C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP

The first step is glycolysis u Glycolysis is a pathway of reactions that takes glucose (6C) and splits it into two pyruvate molecules (3C). u Raw material for glycolysis -- glucose u Products-- –pyruvate –2 molecules of ATP –reduced NAD (NADH)

What happens to products of glycolysis? u pyruvate –converted to acetyl-CoA and carbon dioxide u 2 molecules of ATP –used by the cell for energy u NADH and FADH 2 –is used by electron transport system to make ATP –the NAD+ is reused

Kreb’s Cycle u same as citric acid cycle u acetyl-CoA enters the cycle (raw material) u the cycle is a series of oxidation-reduction reactions u Products –2 ATP’s –reduced NAD (NADH) and FAD (FADH 2 ) –carbon dioxide

So far not much energy u 2 ATP’s from glycolysis u 2 ATP’s from Kreb’s cycle u not enough to cuss a cat with u most of the energy comes from the Electron Transport System

Electron Transport System u Raw materials –NADH and FADH 2 from the other pathways –oxygen u What is it? A series of oxidation-reduction reactions involving cytochromes. u Products –A lot of ATP (32 molecule/original glucose) –water (water of metabolism)

The Overall Scheme Glucose Glycolysis 2 Pyruvates, NADH, 2ATP Acetyl-CoA Citric Acid Cycle Carbon dioxide NADH FADH 2 2 ATP Electron Transport System 32 ATP, water, NAD+, FAD+

Oxygen and Carbon Dioxide u Oxygen is needed –final acceptor of electrons and hydrogen ions to produce water u Carbon dioxide is a waste product –generated at the entrance to the Citric Acid Cycle and during the cycle itself

Where Do These Take Place? u Glycolysis (Universal pathway) –in the cytoplasm - eukaryotic cells –in the cytoplasm - prokaryotic cells u Citric Acid (Kreb’s) cycle –in the inner membranes of the mitochondria - eukaryotic cells –inner surface of cell membrane - prokayotic cells

Where, ctd? u Electron transport system –inner surface of cell membrane - prokaryotic cells –Inner membranes of mitochondria -- eukaryotic cells u Eukaryotic cells are more specialized in their specific functions.

Aerobic vs. Anaerobic u Aerobic respiration is what we have been discussing. u Anaerobic respiration=inorganic atom/molecule other than OXYGEN as FEA u Some prokaryotes utilize anaerobic respiration u Without oxygen ETS for aerobic respiration WILL NOT WORK

Aerobic vs. Anaerobic u Considerably less ATP is produced by anaerobic respiration –aerobic respiration ATP/glucose –anaerobic respiration – equivalent ATP/glucose –Fermentation yields only 2 ATP per glucose u In muscle tissue, pyruvic acid is converted to lactic acid –muscle fatigue

Fermentation u A special kind of anaerobic respiration carried out by yeasts and some bacteria. u Instead of going into the Kreb’s cycle, pyruvic acid is converted to ethyl alcohol and carbon dioxide u Basis of multi-billion dollar fermentation industry

Synthesizing Information u Obligate aerobe is organism that requires oxygen for cellular respiration and CAN”T live without it u Obligate anaerobe is organism that cannot use oxygen and is poisoned by it u Facultative anaerobe is organism that uses oxygen if available (in fact, prefers it) but can switch to alternate pathway if oxygen is unavailable

How are fats metabolized? u Glycerol and fatty acids u Glycerol is converted to one of the intermediates of Glycolysis. u Fatty acids are broken down into two carbon pieces and each piece is converted to acetyl-CoA which enters the Kreb’s cycle u Energy is produced as with glucose.

Protein metabolism u Amino group is removed from amino acids u The result is a keto acid u Keto acids enter the respiratory cycle as pyruvic acid or as one of the other types of molecules found in the Kreb’s cycle. u The amino group is converted to ammonia

What to do with ammonia? u Ammonia is very toxic u some organisms eliminate ammonia u others, such as us, convert ammonia into urea and uric acid which are much less toxic –both are eliminated by the kidneys in urine