Cellular Respiration. Key Concepts: All organisms produce ATP by releasing energy stored in glucose...

Cellular Respiration

Key Concepts:

• All organisms produce ATP by releasing energy stored in glucose

• Cellular respiration can occur without oxygen (anaerobic) or with oxygen (aerobic)

• Photosynthesis are aerobic respiration have become linked on a global scale

PS vs. CR

Sunlight Photosynthesis

6 CO2 + 6 H2O C6H1206 + O2

Aerobic Respiration

Aerobic Respiration:

• Usually main path to ATP formation• Cannot be completed without oxygen

Anaerobic Respiration:

• Fermentation • Alcoholic & Lactic Acid Pathways• Not as efficient due to no oxygen

being used

Glycolysis - Overview:

a) Process in both Aerobic & Anaerobic respiration

b) Does not involve oxygenc) Breaking down of glucosed) Occurs in the cytoplasm

Aerobic Respiration – Overview:

a) produces the most ATP per molecule of glucose

b) C6H12O6 + 6O2 6CO2 + 6H2O Glucose Carbon Dioxidec) Three stages: glycolysis, krebs

cycle, and electron transport phosphorylation

d) Final two stages occurs in mitochondria

Glycolysis – Stage 1:

a) Glucose present in the cytoplasm is partially broken down into the three carbon pyruvate molecule

b) Two NADH and four ATP are formed during the process

c) Two ATP molecules are needed at the beginning, thus there is a net of two ATP formed for every molecule of glucose1 Glucose 4 ATP formed

total2 ATP formed

net

Krebs Cycle – Stage 2

a) Pyruvate formed during glycolysis enters the mitochondria

b) For each pyruvate molecules that enter (2 formed during glycolysis), three CO2, one ATP, four NADH, and one FADH2 are formed

c) Thus at the end of the second stage there is a net yield of four ATP molecules produced for every molecule of glucose

1 Glucose 6 ATP formed total

4 ATP formed net

Electron Transport Chain – 3rd Stage:

• Takes place in the inner membrane of the mitochondrion

• Powered by electrons move through transport proteins

• Electrons moving through system push hydrogen ions into the outer compartment setting up a concentration & electrical gradient

• As the H+ ions flow back in, it drives the formation of thirty two ATP molecules for every molecule of glucose

1 Glucose 38 ATP formed total

36 ATP formed net

Aerobic Respiration Summary:

• Glucose is broken down into CO2 & H2O

• Coenzymes transfer hydrogen and electrons from substrates to electron transport systems which drive ATP formation

• O2 is final electron acceptor• Yields a net of 36 ATP molecules per

one molecule of glucose

Anaerobic Respiration:

• Do not use oxygen as final acceptor of electrons

• Two methods:– Fermentation (lactic acid & alcoholic)

Fermentation:

a) Used by many bacteria and protists that live in oxygen deprived environments

b) Muscle cells will convert to it if oxygen is unavailable

c) Begins with glycolysis and net yield of 2 ATP, but does not produce any more ATP

d) Regenerates coenzymes instead

Lactic Acid Fermentation:

• Pyruvate from glycolysis is converted into lactate (lactic acid) in order to replenish coenzymes

Alcoholic Fermentation:

• Pyruvate form glycolysis is eventually converted into ethanol in order to replenish coenzymes