Metabolism

1
Metabolism Starvation

• CHEM 124 FALL 2002
• By Cari, Naomi, Abbey

2
Nutritional Requirements

• Fiber
• Indigestible
• Keeps digestive tract flowing
• Micronutrients
• Only need small amounts for good health
• Vitamins Minerals
• Macronutrients
• Need large amounts for good health
• Carbohydrates, Lipids, Proteins

3
Carbohydrates

• Most dominant energy source
• Simple carbohydrates
• Monosaccharides (glucose)
• Disaccharides (sucrose)
• Complex carbohydrates
• Cellulose
• Starches

4
Lipids

• Concentrated source of energy
• Provides twice the amount of energy as an equal
  mass of carbohydrates
• Essential fatty acids
• Linoleic acid
• Linolenic acid

5
Proteins

• Production of new tissue
• Maintains Repairs cells for production of
• Enzymes
• Hormones
• Other nitrogen compounds the body needs
• There are several Essential amino acids that the
  body doesnt produce

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Catabolism of Food

• Stage One
• Digestion
• Stage Two
• Acetyl Coenzyme A
• Stage Three
• Catabolic Pathway
• Citric Acid Cycle

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Metabolism of Carbohydrates

• Broken down to glucose, fructose, galactose.
• Absorbed in small intestine carried to liver.
• Liver turns fructose galactose into glucose.
• Glycolysisseries of 10 reactions by which
  glucose is oxidized to pyruvate.
• Pyruvate is either reduced to ethanol or lactate
  or oxidized to Acetyl CoA.

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Metabolism of Fats

• Glycerol is hydrolyzed in two steps as shown
  below
• Fatty acids cannot be used for energy until they
  are converted to fatty acyl CoA as shown below
• Enter mitochondria for ?-oxidation
• Oxidation

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Amino Acid Metabolism

• Net effect of transamination is for the use of
  nitrogen to form glutamate aspartate.
• Oxidative deamination is source for NH4 NADH,
  which eventually produces 2 ATP.
• Urea Formation

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Citric Acid Cycle
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Citric Acid Cycle aka Kreb Cycle

• The Principle process for generating the reduced
  coenzymes NADH and FADH2 which are necessary for
  reduction of O2 and APT synthesis in e- transport
  chains.
• Carbon skeletons from amino acids are transformed
  into intermediates of the citric acid cycle.
• It is also a source for intermediates of
  biosynthesis.

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Starvation

• Bone marrow of healthy (left) to starving (right)
• There are 3 stages of Starvation

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Stage One

• Glucose produced from glycogen in the Liver
• Glycogen only lasts a few hours
• When used up fats and some proteins are broken
  down into glucose

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Stage Two

• Fat is primary energy source
• Liver breaks down fatty acids into ketone bodies
• After a week the brains starts to use ketones and
  glucose for energy

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Interrupts Biochemistry

• Glycolysis decreases.
• Oxaloacetate is decreased, but more than normal
  is needed to perform gluconeogenesis.
• Lack of oxaloacetate reduces activity of the
  Krebs cycle.
• Acetyl CoA builds up and excess is converted to
  ketone bodies.

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Stage Three

• Fat reserves are depleted.
• Proteins become primary source of energy.
• Muscles rapidly deplete.
• Nonessential proteins are used up first.

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Biochemical Problems at Stage 3

• Kidneys take over Gluconeogenesis from the Liver.
• Once nonessential proteins are used up the
  essential proteins get used.
• Eventually cell function stops.

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Overall Effect

• Pancreas reduces insulin secretions.
• Metabolic rate is decreased.
• Many organs begin to shrink.
• Villi in gut shrink which means less capacity to
  absorb nutrition.
• Total body shut down and DEATH.

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Questions

• What are the primary energy sources for regular
  metabolism and for each stage of starvation?
• What is the main purpose of the Krebs Cycle?
• What is the fate of pyruvate in the metabolism of
  carbohydrate?
• List three nutritional requirements and give an
  example of each.
• Carbohydrate, Fats, and Proteins must be broken
  down into this enzyme before it can be used to
  make energy.