chapter 004

The Human Body in Health and Illness, 4th edition

Barbara Herlihy

Chapter 4: Cell Metabolism

1

Lesson 4-1 Objectives

• Define metabolism, anabolism, and catabolism.

• Explain the use of carbohydrates, proteins, and fats in the body.

• Differentiate between the anaerobic and aerobic metabolism of carbohydrates.

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Metabolism

• Metabolism: The series of chemical reactions necessary for the use of raw material– Anabolism: Reactions that build larger, more

complex substances from simpler substances– Catabolism: Reactions that break down larger,

more complex substances into simpler substances

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Metabolism (cont’d.)

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Carbohydrates

• Organic compounds composed of carbon (C), hydrogen (H), and oxygen (O)– Monosaccharides:

Single-sugar compounds– Disaccharides:

Double-sugar compounds– Polysaccharides:

Many-sugar compounds

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Carbohydrates (cont’d.)

Name Function

Monosaccharides

Glucose

Fructose

Galactose

Deoxyribose

Ribose

Most important energy source

Converted to glucose

Converted to glucose

Sugar in DNA

Sugar in RNA

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Carbohydrates (cont’d.)

Name FunctionDisaccharides

Sucrose

Maltose

Lactose

Split into glucose + fructose

Split into glucose + glucose

Split into glucose + galactose

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Carbohydrates (cont’d.)

Name FunctionPolysaccharides

Starches

Glycogen

Cellulose

Digested to disaccharides, and then to monosaccharides

Storage form of glucose

Forms dietary fiber or roughage

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Uses of Glucose

• Burned immediately for fuel• Stored as glycogen and burned as fuel later• Stored as fat and burned as fuel later

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Breakdown of Glucose

• Anaerobic catabolism: Oxygen absent– Glycolysis • Glucose lactic acid

• Aerobic catabolism: Oxygen present– Glucose carbon dioxide, water, and ATP

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Aerobic and Anaerobic Catabolism

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Lipids (Fats)

• Lipids: Organic compounds commonly calledfats and oils

• Most common– Triglycerides– Phospholipids– Steroids

• Other relatives of lipids– Lipoid substances

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Lipids (Fats) (cont’d.)

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Uses of Lipids

• Source of energy • Component of cell membranes and myelin

sheath• Synthesis of steroids• Long-term storage of energy

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Proteins• Most abundant organic matter in the body• Participate in every body function– Enzymes – Hormones – Hemoglobin – Contractile muscle proteins – Plasma proteins– Antibodies– Structural proteins

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Amino Acids: Building Blocks of Protein

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• All amino acids have an amine group and acid group.

• Joined by peptide bonds, amino acids build peptides and proteins.

• All amino acids have an amine group and acid group.

• Joined by peptide bonds, amino acids build peptides and proteins.

Essential and Nonessential Amino Acids

• Essential: Must be included in diet• Nonessential: Body can synthesize these• Both are needed by the body.

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Uses of Proteins

• Synthesis of hormones, enzymes, antibodies, plasma and muscle proteins, hemoglobin, and most cell membranes

• If needed, can be broken down as source of energy for ATP production.

• If needed, can be broken down and converted to glucose (gluconeogenesis).

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Urea: The Elimination of Nitrogen

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• Nitrogen: Waste product of amino acid breakdown– Most nitrogen is recycled for

new amino acids.– Extra nitrogen forms toxic

ammonia (NH3).– Liver removes NH3 from blood

and converts it to urea.– Kidneys excrete urea in urine.

• Nitrogen: Waste product of amino acid breakdown– Most nitrogen is recycled for

new amino acids.– Extra nitrogen forms toxic

ammonia (NH3).– Liver removes NH3 from blood

and converts it to urea.– Kidneys excrete urea in urine.

Lesson 4-2 Objectives

• Describe the structure of a nucleotide.• Describe the roles of DNA and RNA in protein

synthesis.• Describe protein synthesis.

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Nucleotides and Nucleic Acids• Nucleotide: Composed of a

sugar, a phosphate group, and a base– Adenine– Thymine, uracil– Guanine– Cytosine

• Nucleic acids: DNA and RNA– Composed of nucleotides

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Base Pairing

• DNA is a double-stranded nucleotide (ladder).

• Rungs of the DNA ladder are formed by base pairing.– Adenine with thymine– Cytosine with guanine

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Base Sequencing: Genetic Code

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• Genetic information for protein synthesis stored on one strand

• Order of three bases = code for one amino acid

• Genetic information for protein synthesis stored on one strand

• Order of three bases = code for one amino acid

mRNA: Code Copier for Protein Synthesis

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• mRNA uses base pairing to copy the code on a DNA strand (transcription). • mRNA detaches, leaves the

nucleus, and goes to the ribosomes in cytoplasm.

• mRNA uses base pairing to copy the code on a DNA strand (transcription). • mRNA detaches, leaves the

nucleus, and goes to the ribosomes in cytoplasm.

tRNA: Code Reader for Protein Synthesis

• tRNA connects to a single amino acid in cytoplasm.

• tRNA reads code on mRNA (translation).• Amino acids are correctly aligned to form

peptides and proteins.

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Recap: Genetic Code and Protein Synthesis

1. DNA strand is copied onto mRNA (transcription)

2. mRNA leaves nucleus ribosomes 3. tRNA base-pairs with mRNA (translation) 4. Amino acids line up in proper sequence

along ribosome; peptide bonds form5. Protein chain terminates when all amino

acids are assembled in sequenceCopyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights

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Recap: Genetic and Protein Synthesis

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