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Chapter 2 Matter—anything that occupies space and has mass (weight) Energy—the ability to do work ◦ ◦ ◦ ◦ Chemical Electrical Mechanical Radiant Elements—fundamental units of matter ◦ 96 percent of the body is made from four elements Carbon (C) Oxygen (O) Hydrogen (H) Nitrogen (N) Atoms—building blocks of elements Elements – composed of atoms of the same kind Compound—composed of two or more atoms of different kinds chemically combined Figure 2.4 Atoms are united by chemical bonds During chemical reactions chemical bonds are broken, atoms rearrange, and new chemical bonds form. ◦ A chemical bond is simply the force of attraction between two atoms. Groups of atoms bonded together are referred to as a “molecule”. Some bonds result in creating molecules that are polar (like mini-magnets). Water is a polar molecule Figure 2.8b Polar substances dissolve in water; nonpolar substances do not (“like dissolves like”). Because water is polar, its molecules are very attracted to each other. ◦ This strong inter-molecular attraction in water is called “hydrogen bonding”. This gives water very high surface tension. + H H O – Hydrogen bonds + H O – – H O H + – + + H H O – (a) + H (b) Figure 2.9 Organic compounds ◦ Large, complex molecules (macromolecules) ◦ Must contain carbon and hydrogen ◦ Includes carbohydrates, lipids, proteins, nucleic acids Inorganic compounds ◦ Smaller molecules ◦ Lack carbon in combination with hydrogen ◦ Tend to be simpler compounds ◦ Includes water, salts, and some acids and bases Living things contain BOTH organic and inorganic compounds. Dehydration synthesis—monomers (building blocks) are joined to form polymers through the removal of water molecules Biologically important to growth and repair Figure 2.13a Hydrolysis—polymers are broken down into monomers through the addition of water molecules Opposite of dehydration synthesis Biologically important in digestion Figure 2.13b Carbohydrates ◦ Contain carbon, hydrogen, and oxygen in a 1:2:1 ratio ◦ General formula CH2O ◦ Include sugars and starches ◦ Classified according to size Monosaccharides—simple sugars ex: glucose C6H12O6 Disaccharides—two simple sugars joined by dehydration synthesis ex: maltose C12H22O11 Polysaccharides—long-branching chains of linked simple sugars ex: starch and glycogen Figure 2.14a–b Figure 2.14c Figure 2.14d Lipids ◦ Contain carbon, hydrogen, and oxygen Carbon and hydrogen outnumber oxygen ◦ Insoluble in water (not polar!) ◦ Important components of cell membranes Common lipids in the human body ◦ Neutral fats (triglycerides) Found in fat deposits Source of stored energy Composed of three fatty acids and one glycerol molecule Saturated fatty acids contain only single covalent bonds Unsaturated fatty acids contain one or more double covalent bonds Glycerol 3 fatty acid chains (a) Formation of a triglyceride Triglyceride, or neutral fat 3 water molecules Figure 2.15a Figure 2.16a Figure 2.16b Common lipids in the human body (continued) ◦ Phospholipids Contain two fatty acids rather than three Form cell membranes Polar “head” Nonpolar “tail” Phosphorus-containing group (polar end) Glycerol backbone 2 fatty acid chains (nonpolar end) (b) Phospholipid molecule (phosphatidylcholine) Figure 2.15b Common lipids in the human body (continued) ◦ Steroids Include cholesterol, bile salts, vitamin D, and some hormones Cholesterol is the basis for all steroids made in the body High levels of cholesterol can lead to heart disease Excess saturated fats are converted to cholesterol in the body Figure 2.15c Proteins ◦ Account for over half of the body’s organic matter Provide for construction materials for body tissues Play a vital role in cell function Act as enzymes, hormones, and antibodies ◦ Contain carbon, oxygen, hydrogen, nitrogen, and sometimes sulfur ◦ Built from amino acids (monomers) Amino acid structure ◦ Contain an amine group (NH2) ◦ Contain an acid group (COOH) ◦ Vary only by R groups 20 different kinds Amine group Acid group (a) Generalized structure of all amino acids (b) Glycine (the simplest amino acid) (c) Aspartic acid (an acidic amino acid) (d) Lysine (a basic amino acid (e) Cysteine (a sulfurcontaining amino acid) Figure 2.17a-e Proteins can bend and fold into interesting shapes. The shape of a protein is vital to its function. ◦ If a protein loses its shape it can’t do its job. (a) Primary structure. A protein’s primary structure is the unique sequence of amino acids in the Amino polypeptide chain. acids Hydrogen bonds Amino acids (b) Secondary structure. Two types of secondary structure are named alpha-helix and betapleated sheet. Secondary structure is reinforced by hydrogen bonds. Dashed lines represent the hydrogen bonds in this figure. Alphahelix -pleated sheet Figure 2.18a-b Figure 2.18c-d ◦ Function in structure and also as antibodies or enzymes ◦ Can be denatured (unraveled) by heat or pH changes ◦ This will make the protein non-functional Heme group Globin protein (b) Hemoglobin molecule composed of the protein globin and attached heme groups. (Globin is a globular or functional protein.) Figure 2.19b Proteins that act as biological catalysts Increase the rate of chemical reactions ◦ Bind to substrates at an active site ◦ Their SHAPE is critical to their function! ◦ Enzyme function is affected by pH, temperature and concentration Energy is Water is absorbed; released. bond is H2O formed. Substrates (S) e.g., amino acids + Product (P) e.g., dipeptide Peptide bond Active site Enzyme-substrate complex (E-S) Enzyme (E) 1 Substrates bind to active site. Enzyme changes shape to hold substrates in proper position. 2 Structural changes occur, resulting in the product. Enzyme (E) 3 Product is released. Enzyme returns to original shape, ready to catalyze another reaction. Figure 2.20 Built from nucleotide monomers which contain: ◦ Pentose (5 carbon) sugar ◦ A phosphate group ◦ A nitrogenous base A = Adenine G = Guanine C = Cytosine T = Thymine U = Uracil. Deoxyribose Phosphate sugar Adenine (A) (a) Adenine nucleotide (Chemical structure) KEY: Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Figure 2.21a Deoxyribonucleic acid (DNA) ◦ The genetic material found within the cell’s nucleus ◦ Provides instructions to make every protein in the body ◦ Organized by complimentary (paired) bases to form a double-stranded helix held together by hydrogen bonds ◦ Contains the sugar deoxyribose and the bases adenine, thymine, cytosine, and guanine ◦ Replicates (duplicates) before cell division Hydrogen bond Deoxyribose sugar Phosphate (d) Diagram of a DNA molecule KEY: Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Figure 2.21c-d Ribonucleic acid (RNA) ◦ Carries out DNA’s instructions for protein synthesis ◦ Created from a template of DNA ◦ Organized by complimentary bases to form a singlestranded helix ◦ Contains the sugar ribose and the bases adenine, uracil, cytosine, and guanine ◦ Three varieties are messenger, transfer, and ribosomal RNA Adenosine triphosphate (ATP) ◦ Composed of a nucleotide built from ribose sugar, adenine base, and three phosphate groups ◦ Supplies chemical energy used by all cells ◦ Energy is released by breaking high energy phosphate bonds ◦ ATP is replenished by oxidation (breakdown) of food fuels; primarily sugars Adenine High energy bonds Ribose Phosphates (a) Adenosine triphosphate (ATP) Adenosine diphosphate (ADP) (b) Hydrolysis of ATP Figure 2.22a-b (a) Chemical work. ATP provides the energy needed to drive energyabsorbing chemical reactions. Solute Membrane protein (b) Transport work. ATP drives the transport of certain solutes (amino acids, for example) across cell membranes. Relaxed smooth muscle cell Contracted smooth muscle cell (c) Mechanical work. ATP activates contractile proteins in muscle cells so that the cells can shorten and perform mechanical work. Figure 2.23a-c