Summary:
Cellular respiration - the process by which your cells transfer the energy in organic compounds to ATP. The byproduct of this reaction is water and carbon
dioxide. It occurs in the cells mitochondria, which are the
energy producers for the cell.
Summary: Each cell converts the energy in the chemical
bonds of nutrients to chemical energy stored in ATP
May be aerobic or anaerobic Most cells use aerobic respiration 3 pathways that are exergonic and release
energy: Aerobic respiration Anaerobic respiration Fermentation
Aerobic Respiration
Most eukaryotes and prokaryotes To obtain energy from glucose
Requires oxygen Nutrients are catabolized to CO2 and H2O
Glucose + Oxygen Carbon Dioxide + Water + Energy (in bonds of
ATP)
Aerobic Respiration
A redox process Glucose is oxidized to form Carbon Dioxide Oxygen is reduced, forming water
The electrons produced are used to form ATP
Aerobic Respiration 3 stages:
1. Glycolysis
2. Citric Acid (Krebs) Cycle
3. Electron Transport Chain and Chemiosmosis
Aerobic Respiration
*In eukaryotes, glycolysis occurs in cytosol and remaining 2 steps occur in mitochondria.
* In bacteria, all stages occur in cytosol working with plasma membrane.
Glycolysis
Occurs in cytosol Glucose converted to two 3-carbon
molecules of pyruvic acid ATP and NADH are formed
NADH - temporarily stores large amounts of free energy
Energy from NADH ultimately participates in reactions that form ATP
Net production of 2 ATP Animation of Glycolysis
Advantages of Glycolysis
The process of glycolysis is so fast that cells can produce thousands of ATP molecules in a few milliseconds.
Glycolysis does not require oxygen.
Citric Acid Cycle (Krebs Cycle) Pyruvic Acid from Glycolysis moves into
mitochondria. Pyruvic acid breaks apart
1 molecule of CO2 is produced 2 other Carbon atoms form acetyl CoA
Acetyl CoA combines with 4 carbon molecules to produce citric acid.
Citric Acid Cycle (Krebs Cycle) Citric Acid is broken down
CO2 released Electrons transferred to energy carriers.
Carbon Dioxide is a waste product ATP, NADH and FADH2 are produced 2 ATP are produced/glucose
Electron Transport Chain and Chemiosmosis Electrons from Krebs cycle are passed to
NADH and FADH2 in Electron Transport Chain
Enzymes present in mitochondrial membrane As NADH and FADH2 pass along enzymes, they
give up electrons (energy) = chemiosmosis H+ ions are transported across membrane and
come in contact with ATP synthase ADP + Pi = ATP
End of chain – electrons combined with oxygen and hydrogen to form water
Via chemiosmosis, 34 ATP produced.
ATP synthesis continues until ADP stores are depleted
Aerobic Respiration – End Results One glucose gives maximum of 36-38 ATP’s Glycolysis produces 2 ATP molecules 2 ATP molecules are produced in the citric
acid cycle Remainder of ATP is produced in the
electron transport system (32 or 34) Efficiency is about 40%; remaining energy is
disseminated as heat
Other nutrients (besides glucose) provide energy More energy is gained from burning fats than
glucose Lipids contain 9 kcal/gram Lipids are broken down and glycerol enters
glycolysis Fatty acids are converted to acetyl CoA and enter
the citric acid cycle Proteins are broken down to amino acids
Proteins contain 4 kcal/gram
Anaerobic Respiration and Fermentation do not Require Oxygen Anaerobic Respiration
Various inorganic substances serve as the final electron acceptor
Yield is only the 2 ATP molecules from glycolysis Types of Fermentation
Alcohol Lactate
Alcoholic Fermentation
Alcoholoic fermentation Alcoholic fermentation produces ethanol
Pyruvate is converted to ethanol Ethanol is a potentially toxic waste product Yeast carry out alcoholic fermentation when
oxygen deprived
Pyruvic acid + NADH -> alcohol + CO2 + NAD+
Lactate Fermentation
Bacteria and some fungi carry out lactate fermentation
Strenuous exercise in mammals results in lactate fermentation as well
Yields only the 2 ATP molecules from glycolysis
Pyruvic acid + NADH -> lactic acid + NAD+