Biochemistry

Biochemistry: study of chemical composition and reactions of living matter  Inorganic compounds  Do not contain carbon  Water, salts, and many acids and bases  Organic compounds  Contain carbon, are covalently bonded, and are often large

Properties of Water  High heat capacity – absorbs and releases large amounts of heat before changing temperature  redistributes heat, maintain homeostasis  High heat of vaporization – changing from a liquid to a gas requires large amounts of heat  sweating removes heat

Properties of Water  Polar solvent properties  dissolves ionic substances, forms hydration layers around large charged molecules, and serves as the body’s major transport medium

Properties of Water  Reactivity – is an important part of hydrolysis and dehydration synthesis reactions  Cushioning – resilient cushion around certain body organs

Salts  Inorganic compounds  Contain cations other than H + and anions other than OH –  Are electrolytes; they conduct electrical currents  NaCl, CaCO 3, KCl

Acids and Bases  Acids release H + (proton donors) HCl  H + + Cl –  Bases release OH – (proton acceptors) NaOH  Na + + OH –

Acid-Base Concentration (pH)  based on concentration oh hydrogen ions in solution, expressed in moles per liter (molarity)  logarithmic (each change of 1 pH unit is a tenfold change in H + )

Acid-Base Concentration (pH)  Acidic solutions have higher H + concentration and therefore a lower pH (0–6.99)  Alkaline solutions have lower H + concentration and therefore a higher pH (7.01–14)  Neutral solutions have equal H + and OH – concentrations (pH 7.00)

Organic Compounds  Molecules unique to living systems contain carbon and hence are organic compounds  They include:  Carbohydrates  Lipids  Proteins  Nucleic Acids

Carbohydrates  contain carbon, hydrogen, and oxygen  1-2% of cell mass  Examples:  Monosaccharides  Disaccharides  Polysaccharides

Monosaccharides (simple sugars)  contain carbon, hydrogen, and oxygen (CH 2 0)  supply a source of cellular food  named by number of C in ring (hexose, pentose)  Examples:

Disaccharides (double sugars)  two monosaccharides joined via dehydration synthesis

Polysaccharides (polymers of simple sugars)  starch and glycogen  storage (plant and animal)

Lipids  Contain C, H, and O, but the proportion of oxygen in lipids is less than in carbohydrates  Examples:  Neutral fats or triglycerides  Phospholipids  Steroids  Eicosanoids

Neutral Fats (Triglycerides)  Composed of three fatty acids bonded to a glycerol molecule

Other Lipids  Phospholipids – modified triglycerides with two fatty acid groups and a phosphorus group

Other Lipids  Steroids – flat molecules with four interlocking hydrocarbon rings

Representative Lipids Found in the Body

Amino Acids  Building blocks of protein, containing an amino group and a carboxyl group  Amino group NH 2  Carboxyl groups COOH

Amino Acids

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid Dehydration synthesis Hydrolysis Dipeptide Peptide bond +N H H C R H O N H H C R CC H O H2OH2O H2OH2O N H H C R C H O N H C R C H O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid +N H H C R H O N H H C R CC H O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid Dehydration synthesis +N H H C R H O N H H C R CC H O H2OH2O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid Dehydration synthesis Dipeptide Peptide bond +N H H C R H O N H H C R CC H O H2OH2O N H H C R C H O N H C R C H O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Dipeptide Peptide bond N H H C R C H O N H C R C H O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Hydrolysis Dipeptide Peptide bond H2OH2O N H H C R C H O N H C R C H O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid Hydrolysis Dipeptide Peptide bond +N H H C R H O N H H C R CC H O H2OH2O N H H C R C H O N H C R C H O OH

Protein  Macromolecules composed of combinations of 20 types of amino acids bound together with peptide bonds Amino acid Dehydration synthesis Hydrolysis Dipeptide Peptide bond +N H H C R H O N H H C R CC H O H2OH2O H2OH2O N H H C R C H O N H C R C H O OH

Structural Levels of Proteins  Primary – amino acid sequence  Secondary – alpha helices or beta pleated sheets  Tertiary – superimposed folding of secondary structures  Quaternary – polypeptide chains linked together in a specific manner

Structural Levels of Proteins

Fibrous Proteins  Extended and strand-like proteins

Globular Proteins  Compact, spherical proteins with tertiary and quaternary structures

Nucleic Acids  Composed of carbon, oxygen, hydrogen, nitrogen, and phosphorus  Their structural unit, the nucleotide, is composed of N-containing base, a pentose sugar, and a phosphate group

Nucleic Acids  Five nitrogen bases contribute to nucleotide structure – adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U)  Two major classes – DNA and RNA

Deoxyribonucleic Acid (DNA)  Double-stranded helical molecule found in the nucleus of the cell  Replicates itself before the cell divides, ensuring genetic continuity  Provides instructions for protein synthesis

Structure of DNA

Ribonucleic Acid (RNA)  Single-stranded molecule found in both the nucleus and the cytoplasm of a cell  Uses the nitrogenous base uracil instead of thymine  Three varieties of RNA: messenger RNA, transfer RNA, and ribosomal RNA

Adenosine Triphosphate (ATP)  Source of immediately usable energy for the cell  Adenine-containing RNA nucleotide with three phosphate groups

Adenosine Triphosphate (ATP)