Transcript

Chapter 7: Cellular Respiration

How Cells Make ATP:

Energy-Releasing Pathways

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

Equation

C6H12O6 + 6O2 -->6 CO2 + 6H2O + 38 ATP

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+

Copyright Pearson Prentice Hall

Fermentation

Group Assignment:

1. Glycolysis

2. Krebs Cycle

3. Electron Transport Chain/Chemiosmosis

4. Alcoholic Fermentation

5. Lactate Fermentation


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