Food as Building Material

• Building blocks from the breakdown of organic

molecules are used to

– repair tissues and

– maintain tissues.

• Essential nutrients

– are substances needed by the body but

– cannot be made in the body from other molecules.

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85Essential Amino Acids

• In humans, eight essential amino acids

– must be obtained from the diet and

– are in different proportions in different foods.

• All eight essential amino acids can be consumed

by eating

– meat, eggs, or milk or

– a variety of plants, typically grains and legumes such as beans, peanuts, and peas.

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86

Figure 22.17

Complete meals

Bread and peanut butterRice and beans Rice and tofu

Beans and otherlegumes

Methionine

Valine

Threonine

Phenylalanine

Leucine

Isoleucine

Tryptophan

Lysine

87 Figure 22.17a

Essential amino acids

CornBeans and other legumes

Methionine

Valine

Threonine

Phenylalanine

Leucine

Isoleucine

Tryptophan

Lysine

88

Figure 22.17b

Complete meals

Bread and peanut butterRice and beans Rice and tofu

89Vitamins

• Vitamins

– are organic molecules,

– are required in the diet in very small amounts, and

– usually assist enzymes in catalyzing metabolic reactions.

• Too much or too little of most vitamins can cause

harm.

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90

Table 22.2 91 Figure 22.UN01 92

Minerals

• Minerals are inorganic substances required in the

diet.

• Too much or too little of most minerals can cause

harm.

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93Essential Fatty Acids

• Our cells make fats and other lipids by combining

fatty acids and other molecules.

• Essential fatty acids must be obtained in the

diet.

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94

Decoding Food Labels

• On food labels, the FDA requires

– the list of ingredients and

– key nutrition facts.

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95 Figure 22.18 96