+ Chapters 2-4 Organic Molecules and Enzymes

: Chemical Constituents of Cells Organic v. Inorganic Molecules Organic molecules Contain C and H Usually larger than inorganic molecules Dissolve in water and organic liquids Carbohydrates, proteins, lipids, and nucleic acids Inorganic molecules Generally do not contain C and H Usually smaller than organic molecules Usually dissociate in water, forming ions Water, oxygen, carbon dioxide, and inorganic salts

+ 3 Inorganic Substances Water Most abundant compound in living material Two-thirds of the weight of an adult human Major component of all body fluids Medium for most metabolic reactions Important role in transporting chemicals in the body Absorbs and transports heat Oxygen (O 2 ) Used by organelles to release energy from nutrients in order to drive cell’s metabolic activities Necessary for survival

+ 4 Inorganic Substances Carbon dioxide (CO 2 ) Waste product released during metabolic reactions Must be removed from the body Inorganic salts Abundant in body fluids Sources of necessary ions (Na +, Cl -, K +, Ca 2+, etc.) Play important roles in metabolism

+ 5 Organic Substances Carbohydrates Provide energy to cells Supply materials to build cell structures Water-soluble Contain C, H, and O Ratio of H to O close to 2:1 (C 6 H 12 O 6 ) Monosaccharides – glucose, fructose Disaccharides – sucrose, lactose Polysaccharides – glycogen, cellulose

+ 6 Organic Substances Carbohydrates O (a) Monosaccharide OO O (b) Disaccharide O O O (c) Polysaccharide Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

+ 7 Organic Substances Lipids Soluble in organic solvents; insoluble in water Fats (triglycerides) Used primarily for energy; most common lipid in the body Contain C, H, and O but less O than carbohydrates (C 57 H 110 O 6 ) Building blocks are 1 glycerol and 3 fatty acids per molecule Saturated and unsaturated Glycerol portion Fatty acid portions C O OHCC H H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H H C O OHCC H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H H C H C H H C H H C H H C H H C H H C H H H C O OHCC H HH C H H C H H C H H C HH H C Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

+ Neutral Fats Triglycerides are formed from a fatty acid and glycerol (a sugar). They are the most plentiful source of stored energy to our bodies. Two types: Saturated- contain only single bonds Unsaturated- contains one(mono) or more(poly) double bonds Short, unsaturated fats are liquids (oils) and come from plants. Long, saturated fats are solid (butter and meat fat) and come from animals.

+ 9 Organic Substances Lipids Phospholipids Building blocks are 1 glycerol, 2 fatty acids, and 1 phosphate per molecule Hydrophilic and hydrophobic Major component of cell membranes C H C OH CH H Glycerol portion (a) A fat molecule O O Fatty acid H C H H H H C H H N O O O POCH O – Phosphate portion (b) A phospholipid molecule (the unshaded portion may vary) H CH C H H O (c) Schematic representation of a phospholipid molecule Water-insoluble (hydrophobic) “tail” Water-soluble (hydrophilic) “head” Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

+ 10 Organic Substances Lipids Steroids Four connected rings of carbon Widely distributed in the body, various functions Component of cell membrane Used to synthesize hormones Cholesterol (a) General structure of a steroid C C C H 2 C H 2 CC H (b) Cholesterol C CH H C HC H 2 H 2 CH C H 2 C H 3 HOC CH 3 2 C Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

+ Organic Substances Proteins Structural material Energy source Hormones Receptors Enzymes Antibodies Protein building blocks are amino acids Amino acids held together with peptide bonds 11 HN H C H C O OH S C H HH HN H C H C O C C C H H CH CH H CH CH HN H C H C O R

+ 12 Organic Substances Nucleic Acids Carry genes Encode amino acid sequences of proteins Building blocks are nucleotides DNA (deoxyribonucleic acid) – double polynucleotide RNA (ribonucleic acid) – single polynucleotide S P B Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

: Control of Metabolic Reactions Enzymes Control rates of metabolic reactions Lower activation energy needed to start reactions Most are globular proteins with specific shapes Not consumed in chemical reactions Substrate specific Shape of active site determines substrate Product molecule Active site (a) (b)(c) Substrate molecules Unaltered enzyme molecule Enzyme-substrate complex Enzyme molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

+ 14 Enzyme Action Metabolic pathways Series of enzyme-controlled reactions leading to formation of a product Each new substrate is the product of the previous reaction Enzyme names commonly: Reflect the substrate Have the suffix – ase Examples: sucrase, lactase, protease, lipase Substrate 1 Enzyme A Substrate 2 Enzyme B Substrate 3 Enzyme C Substrate 4 Enzyme D Product Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

+ 15 Factors That Alter Enzymes Factors that alter enzymes: Heat Radiation Electricity Chemicals Changes in pH

+ 16 Regulation of Metabolic Pathways Limited number of regulatory enzymes Negative feedback Inhibition Substrate 1 Substrate 2 Enzyme B Substrate 3 Enzyme C Substrate 4 Enzyme D Product Rate-limiting Enzyme A Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.