The Human Body in Health and Illness, 4th edition Barbara Herlihy Chapter 4: Cell Metabolism

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. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 What raw materials are used in metabolism? The foods we eat, including carbohydrates, protein, and fat, are the sources of raw material that are metabolized inside the cell. What role does ATP play in anabolism and catabolism? Anabolism requires an input of ATP; catabolism releases energy that is eventually converted into ATP. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Metabolism (cont’d.) In Figure A, the raw materials arrive at the factory. Figure B illustrates anabolismamino acids are linked together to form a protein, like building a brick wall. Figure C illustrates catabolisma protein is broken down into individual amino acids, like knocking down a brick wall. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Carbohydrates Organic compounds composed of carbon (C), hydrogen (H), and oxygen (O) Monosaccharides: Single-sugar compounds Disaccharides: Double-sugar compounds Polysaccharides: Many-sugar compounds Carbohydrates are classified according to size. Monosaccharides and disaccharides are called sugars; polysaccharides include starches, glycogen, and cellulose. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Carbohydrates (cont’d.) Name Function Monosaccharides Glucose Fructose Galactose Deoxyribose Ribose Most important energy source Converted to glucose Sugar in DNA Sugar in RNA Monosaccharides contain three to six carbons. What are the three six-carbon simple sugars? They are glucose, fructose, and galactose. Glucose is the most important of the three and is an immediate energy source. For what are the five carbon monosacharides used? They are used in the synthesis of DNA and RNA. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Carbohydrates (cont’d.) Name Function Disaccharides Sucrose Maltose Lactose Split into glucose + fructose Split into glucose + glucose Split into glucose + galactose Disaccharides are made when two monosaccharides are linked together. They must be broken down into monosaccharides before they can be absorbed and used by the cells. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Carbohydrates (cont’d.) Name Function Polysaccharides Starches Glycogen Cellulose Digested to disaccharides, and then to monosaccharides Storage form of glucose Forms dietary fiber or roughage Polysaccharides are made of many monosaccharides linked together in straight chains or branched chains. Plant starch, glycogen, and cellulose are the three polysaccharides of interest to us. Glycogen is the form in which humans store glucose. It is also called animal starch and is stored primarily in the liver and skeletal muscle. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Uses of Glucose Burned immediately for fuel Stored as glycogen and burned as fuel later Stored as fat and burned as fuel later After you eat a sugary snack and your body digests and absorbs it, your body can use the sugars in one of the three ways listed on the slide. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Breakdown of Glucose Anaerobic catabolism: Oxygen absent Glycolysis Glucose lactic acid Aerobic catabolism: Oxygen present Glucose carbon dioxide, water, and ATP Glycolysis is an anaerobic process and occurs in the cytoplasm. Aerobic metabolism occurs within the mitochondria. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Aerobic and Anaerobic Catabolism In glycolysis, glucose is catabolized completely: a small amount of ATP is produced in the anaerobic process. In an aerobic situation, glucose is completely metabolized into carbon dioxide, water, and ATP. After glucose is broken into pyruvic acid, it moves into the mitochondria where enzymes break the pyruvic acid fragments into carbon dioxide and water. The mitochondria contains the enzymes of the Krebs cycle and those of the electron transport chain. A great deal of ATP is produced aerobically. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lipids (Fats) Lipids: Organic compounds commonly called fats and oils Most common Triglycerides Phospholipids Steroids Other relatives of lipids Lipoid substances Oils are liquid at room temperature, and fats are solid at room temperature. Refer students Table 4-2 and ask them to identify other lipid types. Examples are types of steroids (cholesterol), fat-soluble vitamins (A, D, E, and K), and lipoproteins. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lipids (Fats) (cont’d.) Triglycerides have three long chains of fatty acids attached to one small glycerol molecule. Phospholipids form when phosphorus-containing group attaches to one of the glycerol molecules. The third type of lipid is the steroid. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Uses of Lipids Source of energy Component of cell membranes and myelin sheath Synthesis of steroids Long-term storage of energy The body needs and uses lipids, but it can also put fats into long-term storage or deposit them inside blood vessels. Excess fat is deposited in adipose tissue throughout the body. Discuss LDL (bad cholesterol), VLDL, and HDL (good cholesterol). Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Proteins Most abundant organic matter in the body Participate in every body function Enzymes Hormones Hemoglobin Contractile muscle proteins Plasma proteins Antibodies Structural proteins Refer students to Table 4-4 and ask them to identify several physiological processes controlled by proteins. Examples include hemoglobin transporting oxygen and muscle proteins enabling the muscle to contract. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Amino Acids: Building Blocks of Protein All amino acids have an amine group and acid group. Joined by peptide bonds, amino acids build peptides and proteins. Every amino acid contains an amine group and an acid group. Ask students to identify the amine group and the acid group in Figure 4-5. Portion B of the slide illustrates the assembly of many amino acids to form peptides and polypeptides. Proteins are very large polypeptides. A peptide bond is formed when the amine group of one amino acid joins the acid group of a second amino acid. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Essential and Nonessential Amino Acids Essential: Must be included in diet Nonessential: Body can synthesize these Both are needed by the body. More than half of the amino acids can be synthesized by the body. Both essential and nonessential amino acids are needed by the body; these terms refer to the body’s ability to synthesize them. Refer students to Table 4-3 and ask them to identify common essential and nonessential amino acids. Examples are tryptophan (essential) and alanine (nonessential). Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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).http://www.youtube.com/watch?v=983lhh20rGY Using protein as a source of energy for ATP production is not desirable. Carbohydrates and fats are better energy sources. Gluconeogenesis is the process of breaking down protein and converting it to glucose. Why is gluconeogenesis important in understanding blood glucose regulation? The body uses gluconeogenesis to ensure that the blood glucose level does not become too low. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Urea: The Elimination of Nitrogen 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. The liver forms urea from the nitrogen released by the breakdown of amino acids. Blood transports urea to the kidneys, which eliminate it in the urine. It should be noted that ammonia (NH3) is toxic to the body. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Lesson 4-2 Objectives Describe the structure of a nucleotide. Describe the roles of DNA and RNA in protein synthesis. Describe protein synthesis. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 Amino acids must be precisely arranged for protein synthesis. Where is the pattern of amino acid assembly coded and stored? It is coded and stored within the deoxyribonucleic acid (DNA) in the nucleus of the cell. The two strands of nucleotides form a double helix of sugar-phosphate molecules. The rungs are made of one base from each side. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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 Adenine pairs with thymine, and cytosine pairs with guanine Adenine and guanine are purines. Cytosine, thymine, and uracil are pyrimidines. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Base Sequencing: Genetic Code Genetic information for protein synthesis stored on one strand Order of three bases = code for one amino acid The code for protein synthesis is encoded within the sequence of bases in one strand of DNA. Figure 4-8 shows the base sequences for single amino acids. This is the code that will later be copied by messenger RNA (mRNA). Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

mRNA: Code Copier for Protein Synthesis 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. The slide shows the code on the DNA strand that will be copied by mRNA. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

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. tRNA (transfer RNA) can read the code on the mRNA and transfers the amino acids in the proper order so that protein synthesis can be completed. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Recap: Genetic Code and Protein Synthesis DNA strand is copied onto mRNA (transcription) mRNA leaves nucleus ribosomes tRNA base-pairs with mRNA (translation) Amino acids line up in proper sequence along ribosome; peptide bonds form Protein chain terminates when all amino acids are assembled in sequence This slide and the next slide summarize the entire process of protein synthesis. DNA and RNA control protein synthesis by following the five steps listed on this slide. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.

Recap: Genetic and Protein Synthesis Transcription is the copying of the separated DNA strand onto a strand of mRNA. Translation is the reading of the mRNA code by the rRNA. At the end of the process, a complete protein has been created and is ready for the cell to use or export to another site. Copyright © 2011, 2007 by Saunders, an imprint of Elsevier Inc. All rights reserved.