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The Killers Are Coming! The Killers Are Coming!

A. In the 1950s bees from Africa were introduced into Brazil in an attempt to produce a strain of bees that were better at pollinating and producing honey.

B. Unfortunately, the "African bees" are more aggressive and have attacked humans and animals as they spread throughout South and Central America.

C. Now they have arrived in the United States.

I. How Do Cells Make ATP?

A. ATP is the prime energy carrier for all cells, both autotrophic and heterotrophic.

B. Comparison of the Main Types of Energy-Releasing Pathways

1. Fermentation pathways and anaerobic electron transport can release small quantities of energy without the use of oxygen.

2. Aerobic respiration is the main energy-releasing pathway leading to ATP formation; it occurs in the mitochondria.

3. All energy-releasing pathways begin with the glycolysis reactions, which occur in the cytoplasm.

C. Overview of the Aerobic Respiration

1. Fermentation produces a net yield of two ATP; aerobic respiration yields thirty-six ATP.

2. The aerobic route is summarized:

C6H12O6 + 6O2 .–––> 6CO2 + 6H2O

3. Three series of reactions are required for aerobic respiration:

a. Glycolysis is the breakdown of glucose to pyruvate; small amounts of ATP are generated.

b. Krebs cycle degrades pyruvate to carbon dioxide, and water; ATP is produced; NAD and FAD accept H+ ions and electrons to be carried to the ETS.

c. Electron transport phosphorylation processes the H+ ions and electrons to generate high yields of ATP; oxygen is the final electron acceptor.

II. Glycolysis: First Stage of the Energy-Releasing Pathways

A. Enzymes in the cytoplasm catalyze several steps in glucose breakdown.

1. Glucose is first phosphorylated in energy-requiring steps, then split to form two molecules of PGAL.

2. Enzymes remove H+ and electrons from PGAL to change NAD+ to NADH (which is used later in electron transport).

3. By substrate-level phosphorylation, four ATPs are produced.

B. The end products of glycolysis are: two pyruvates, two ATP (net gain), and two NADH for each glucose molecule degraded.

III. Second Stage of the Aerobic Pathway

A. Preparatory Steps and the Krebs Cycle

1. Pyruvate enters the mitochondria, one carbon is removed and the two-carbon fragment joins coenzyme A.

2. Acetyl CoA then joins oxaloacetate already present from a previous "turn" of the cycle.

B. Functions of the Second Stage

1. H+ and e— are transferred to NAD+ and FAD to become NADH and FADH2, respectively..

2. Two molecules of ATP are produced by substrate-level phosphorylation.

3. Most of the molecules are recycled to conserve oxaloacetate for continuous processing of acetyl-CoA.

IV. Third Stage of the Aerobic Pathway

A. Electron Transport Phosphorylation

1. NADH and FADH2 give up their electrons to transport (enzyme) systems embedded in the mitochondrial inner membrane.

2. H+ are released into the outer compartment of the mitochondrion.

3. As H+ flow back into the inner compartment, ATP synthases form ATP from ADP and unbound phosphate.

4. Oxygen joins with the "spent" electrons and H+ to yield water.

B. Summary of the Energy Harvest

1. Electron transport yields thirty-two ATP; glycolysis yields two ATP; Krebs yields two ATP, for a grand total of thirty-six ATP per glucose molecule.

2. When energy is transferred from glucose to ATP, the efficiency is about 40%.

V. Anaerobic Routes of ATP Formation

A. Fermentation Pathways

1. Anaerobic pathways operate when oxygen is absent (or limited); pyruvate from glycolysis is metabolized to produce molecules other than acetyl-CoA.

2. There is a net yield of two ATPs and NAD+ is regenerated.

3. Lactate Fermentation

a. Pyruvate molecules are converted to lactate.

b. Certain bacteria can sour milk and make it undrinkable but other bacteria have been used commercially to produce cheese, yogurt, and sauerkraut.

c. When muscle cells are very active, they convert to producing lactate temporarily.

4. Alcoholic Fermentation

a. Cellular enzymes convert pyruvate to acetaldehyde, which then accepts electrons from NADH to become alcohol.

b. Yeasts are valuable in the baking industry (carbon dioxide by-product makes dough rise) and in alcoholic beverage production.

B. Anaerobic Electron Transport

1. This pathway, found in many bacteria, influences the cycling of nitrogen, sulfur, and other elements.

2. Electrons are stripped from some organic compound and passed to inorganic elements (acceptors).

VI. Alternative Energy Sources in the Human Body

A. Carbohydrate Breakdown in Perspective

1. Excess carbohydrate intake is stored as glycogen in the liver and muscle for future use.

2. Free glucose is used until it runs low, then glycogen reserves are tapped.

B. Energy from Fats

1. Excess fats are stored away in cells of adipose tissue.

2. Fats are digested into glycerol (which enters glycolysis) and fatty acids (which enter the Krebs cycle).

3. Because fatty acids have many more carbon and hydrogen atoms, they are degraded more slowly and yield greater amounts of ATP.

C. Energy from Proteins

1. Amino acids are released by digestion and travel in the blood.

2. After the amino group is removed, the amino acid remnant is fed into the Krebs cycle.





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	The Killers Are Coming! The Killers Are Coming! A. In the 1950s bees from Africa were introduced into Brazil in an attempt to produce a strain of bees that were better at pollinating and producing honey. B. Unfortunately, the "African bees" are more aggressive and have attacked humans and animals as they spread throughout South and Central America. C. Now they have arrived in the United States. I. How Do Cells Make ATP? A. ATP is the prime energy carrier for all cells, both autotrophic and heterotrophic. B. Comparison of the Main Types of Energy-Releasing Pathways 1. Fermentation pathways and anaerobic electron transport can release small quantities of energy without the use of oxygen. 2. Aerobic respiration is the main energy-releasing pathway leading to ATP formation; it occurs in the mitochondria. 3. All energy-releasing pathways begin with the glycolysis reactions, which occur in the cytoplasm. C. Overview of the Aerobic Respiration 1. Fermentation produces a net yield of two ATP; aerobic respiration yields thirty-six ATP. 2. The aerobic route is summarized: C6H12O6 + 6O2 .–––> 6CO2 + 6H2O 3. Three series of reactions are required for aerobic respiration: a. Glycolysis is the breakdown of glucose to pyruvate; small amounts of ATP are generated. b. Krebs cycle degrades pyruvate to carbon dioxide, and water; ATP is produced; NAD and FAD accept H+ ions and electrons to be carried to the ETS. c. Electron transport phosphorylation processes the H+ ions and electrons to generate high yields of ATP; oxygen is the final electron acceptor. II. Glycolysis: First Stage of the Energy-Releasing Pathways A. Enzymes in the cytoplasm catalyze several steps in glucose breakdown. 1. Glucose is first phosphorylated in energy-requiring steps, then split to form two molecules of PGAL. 2. Enzymes remove H+ and electrons from PGAL to change NAD+ to NADH (which is used later in electron transport). 3. By substrate-level phosphorylation, four ATPs are produced. B. The end products of glycolysis are: two pyruvates, two ATP (net gain), and two NADH for each glucose molecule degraded. III. Second Stage of the Aerobic Pathway A. Preparatory Steps and the Krebs Cycle 1. Pyruvate enters the mitochondria, one carbon is removed and the two-carbon fragment joins coenzyme A. 2. Acetyl CoA then joins oxaloacetate already present from a previous "turn" of the cycle. B. Functions of the Second Stage 1. H+ and e— are transferred to NAD+ and FAD to become NADH and FADH2, respectively.. 2. Two molecules of ATP are produced by substrate-level phosphorylation. 3. Most of the molecules are recycled to conserve oxaloacetate for continuous processing of acetyl-CoA. IV. Third Stage of the Aerobic Pathway A. Electron Transport Phosphorylation 1. NADH and FADH2 give up their electrons to transport (enzyme) systems embedded in the mitochondrial inner membrane. 2. H+ are released into the outer compartment of the mitochondrion. 3. As H+ flow back into the inner compartment, ATP synthases form ATP from ADP and unbound phosphate. 4. Oxygen joins with the "spent" electrons and H+ to yield water. B. Summary of the Energy Harvest 1. Electron transport yields thirty-two ATP; glycolysis yields two ATP; Krebs yields two ATP, for a grand total of thirty-six ATP per glucose molecule. 2. When energy is transferred from glucose to ATP, the efficiency is about 40%. V. Anaerobic Routes of ATP Formation A. Fermentation Pathways 1. Anaerobic pathways operate when oxygen is absent (or limited); pyruvate from glycolysis is metabolized to produce molecules other than acetyl-CoA. 2. There is a net yield of two ATPs and NAD+ is regenerated. 3. Lactate Fermentation a. Pyruvate molecules are converted to lactate. b. Certain bacteria can sour milk and make it undrinkable but other bacteria have been used commercially to produce cheese, yogurt, and sauerkraut. c. When muscle cells are very active, they convert to producing lactate temporarily. 4. Alcoholic Fermentation a. Cellular enzymes convert pyruvate to acetaldehyde, which then accepts electrons from NADH to become alcohol. b. Yeasts are valuable in the baking industry (carbon dioxide by-product makes dough rise) and in alcoholic beverage production. B. Anaerobic Electron Transport 1. This pathway, found in many bacteria, influences the cycling of nitrogen, sulfur, and other elements. 2. Electrons are stripped from some organic compound and passed to inorganic elements (acceptors). VI. Alternative Energy Sources in the Human Body A. Carbohydrate Breakdown in Perspective 1. Excess carbohydrate intake is stored as glycogen in the liver and muscle for future use. 2. Free glucose is used until it runs low, then glycogen reserves are tapped. B. Energy from Fats 1. Excess fats are stored away in cells of adipose tissue. 2. Fats are digested into glycerol (which enters glycolysis) and fatty acids (which enter the Krebs cycle). 3. Because fatty acids have many more carbon and hydrogen atoms, they are degraded more slowly and yield greater amounts of ATP. C. Energy from Proteins 1. Amino acids are released by digestion and travel in the blood. 2. After the amino group is removed, the amino acid remnant is fed into the Krebs cycle.


		Created by Aaron Neal