Chapter 8 - Metabolism

Front 1

Metabolism

Back 1

all chemical changes occurring in living organisms.

Front 2

Catabolism

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Any metabolic process whereby cells break down complex substances into simpler, smaller ones.

- Glucagon

Front 3

Anabolism

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Any metabolic process whereby cells build up simple substances in more complex ones.

- Insulin

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ATP

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A fundamental energy molecule used to power cellular functions, known as the universal energy currency

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Aerobic Respiration

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Presence of or need for oxygen. The complete breakdown of glucose, fatty acids, and amino acids to carbon dioxide and water occurs only through aerobic metabolism.

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Aceytl CoA

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A key intermediate in the metabolic breakdown of carbohydrates, fatty acids, and amino acids.

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Glycolysis

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An anaerobic process, does not require oxygen.

- Requires 2 ATP molecules to get started.

- 1 glucose net yield: 2 NADH, 2 ATP, and 2 pyruvates

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Pyruvate

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The three carbon compound that results from glycolytic breakdown of glucose.

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NADH

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The reduced form of NAD+. Acts as an electron carrier in cells and undergoes reversible oxidation and reduction.

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Glycogen

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A very large, highly branched polysaccharide composed of multiple glucose units. Primary storage form of glucose in animals.

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Ketogenesis

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The process in which excess acetyl CoA from fatty acid oxidation is converted into the ketone bodies

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Insulin

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Produced by beta cells in the pancreas, stimulates that uptake of blood glucose into muscle and adipose cells, synthesis of glycogen in the liver, and etc.

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Glucagon

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Produced by alpha cells in the pancreas, promotes the breakdown of liver glycogen to glucose, thus increasing blood glucose.

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The energy in food is stored

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in the chemical bonds connecting its components

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Fats can enter the process of aerobic respiration by

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being converted to Acetyl CoA, but fats cannot be burned unless there are some carbohydrates as well

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Describe the overall process of catabolism and anabolism 8.3:

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Catabolism – break down of a large compound into smaller units

- Glycogen to glucose

- Triglyceride to glycerol or fatty acids

- Protein to amino acids

Anabolism – build more complex molecules from smaller ones

- Glucose + Glucose = glycogen

- Glycerol + Fatty acid = triglyceride

- Amino acid + Amino acid = protein

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The 4 steps of aerobic respiration and where in the cell they occur (carbs)

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1. Glycolysis

2. Conversion of pyruvate to Acetyl CoA

3. Citric acid (krebs) cycle

4. Electron transport chain

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Aerobic Respiration: Glycolysis

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- Occurs in the Cytosol

- 1 glucose goes in and produces 2 pyruvates.

- 2 NADH molecules are produced but moved to the electron transport chain for ATP production.

- 2 ATP is produced

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Aerobic Respiration: Conversion of pyruvate to Acetyl CoA

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- Occurs in the mitochondria

- Each pyruvate from glycolysis goes into the mitochondrial matric

- Pyruvate is converted to a 2-carbon molecule bound to Acetyl CoA

- CO2 is released and NADH is generated

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Aerobic Respiration: Citric acid (krebs) cycle

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- Mitochondria

- The acetyl CoA combines with a four carbon molecule.

- Generates ATP, NADH, and FADH2 are produced

- CO2 is released

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Aerobic Respiration: Electron transport chain

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- The NADH and FADH2 made in other steps deposit their electrons in the electron transport chain and turn into NAD+ and FAD.

- AS electrons move down the chain, energy is released and used to pump protons out of the matrix forming a gradient.

- Protons flow back into the matrix through ATP Synthase making ATP.

- Oxygen accepts electrons and takes up protons to form water.

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The conditions in which the body’s cells perform glycolysis vs aerobic respiration

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Glycolysis is an anaerobic process; does not require oxygen.

Aerobic respiration oxygen to be readily available.

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The reason why anaerobic respiration produces ATP sooner and faster, and why it produces less ATP per glucose than aerobic respiration

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Anaerobic respiration is faster because less energy is produced for every molecule of glucose broken down (2 ATP vs 3 ATP), so more glucose must be broken down at a faster rate to meet energy demands

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What happens when your body has more energy-containing molecules than it needs (how is the energy stored)?

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Biosynthetic pathways build fat stores from excess intake of energy.

- Assemble glucose into glycogen chains for storage

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How does the body convert stored energy into glucose?

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- Glycogenolysis breaks down the stored glycogen chains into individual glucose molecules

- Gluconeogenesis, body can make glucose from pyruvate, lactate, glycerol and most amino acids.

- In the liver, the cori cycle allows lactate to convert back to glucose

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Why does ketogenesis occur and why is bad?

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High active when fatty acid oxidation in the liver produces such an abundance of acetyl CoA that it overwhelms the available supply of oxaloacetate.

- Too many ketones lower the pH of blood (acetone)

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Under what conditions insulin and glucagon be high or low in general and the effects

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After a big meal insulin will be high and glucagon will be low

After a decline in blood glucose levels insulin will be low and glucagon will be high

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How do fats and proteins enter the process of aerobic respiration?

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*FATS:

- Glycerol carries a relatively small amount of energy and can be converted by the liver to pyruvate or glucose

- Fatty acids store nearly all of the energy found in triglycerides

PROTEINS:

- Deamination, strips off the amino group (-NH2), leaving a ‘carbon skeleton’

- Carbon skeleton can enter the breakdown pathway in several different ways

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Do carbohydrates turn to fat?

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If people consume more carbohydrates than they need at the time, the body stores some of these carbohydrates within cells (as glycogen) and converts the rest to fat.

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In what order will the body burn protein, fat, and carbohydrates during starvation?

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Carbohydrates, fat, protein

**Protein is not usually burned for ATP, because protein is the structural and functional basis of the body.

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Fat becomes fatty acid…

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which becomes acetyl CoA and makes ATP