Chemistry of Cells Section 2-3

Carbon Compounds are found in Living Things Most matter in your body that is not water is organic compounds. Organic compounds contain carbon – carbon atoms are covalently bonded to H, O and C. Four Principle Classes of Organic Compounds Carbohydrates Lipids Proteins Nucleic acids

Carbohydrates Organic compounds composed of C, H, and O in the ratio of 1:2:1. Key source of energy Found in most foods – fruits, vegetables, grains Building blocks of Carbohydrates – sugars Single sugars = monosaccharides Ex.: glucose, fructose Glucose – major source of energy

Ex.: sucrose – common table sugar – Disaccharides – double sugars formed when two monosaccharides are joined Ex.: sucrose – common table sugar – combination of glucose and fructose Polysaccharides – chains of three or more monosaccharides joined (Ex. Starch; Figure 2-8) Polysaccharides are examples of macromolecules In organisms, polysaccharides function as storehouses of energy contained in sugar Starch and glycogen – glucose molecules Cellulose – polysaccharides providing structural support for plants

Lipids Nonpolar molecules that ARE NOT soluble in water Four types – fats, phospholipids, steroids, & waxes Important part of structure & functioning of cell membranes Phospholipids – make up the lipid bilayer of cell membrane Steroids – (cholesterol) in animal cell membranes Pigments – chlorophyll – light absorbing compounds

Fats Lipids that store energy (Figure 2-9) Typical fat – contains 3 fatty acids bonded to a glycerol molecule Glycerol – alcohol with 3 C atoms Fatty acid – long chain of C with H bonded to them. Either one or two H to each C. Saturated Fatty Acid All C to 2 H atoms (end has 3 H) – all single bonds Straight molecules Most animal fats – solid at room temperature

Unsaturated Fatty Acid Some C atoms linked to only one H atom – double bonds present – these produce kinks in molecules Most plant and fish oils Generally liquid at room temperature Hydrogenated vegetable oil – contains naturally unsaturated fatty acids that have been artificially saturated – solid at room temperature – margarine & shortening

Proteins Chain of amino acids Amino acids – building blocks for proteins – 20 different found in proteins Each amino acid – different chemical structure Some polar Some nonpolar Some charged Some uncharged Proteins fold into compact shapes determined by how amino acids in the “arms” of protein interact with water and one another

Enzymes – promote chemical reactions Some proteins – structural – collagen – skin, ligaments, tendons, bone, hair, muscles, blood clots Antibodies – help body defend against infection Specialized proteins in body – ex. Proteins to make muscles contract Blood – hemoglobin – carries O2 from lungs to body tissues

Nucleic Acids Contained in ALL cells Nucleic acid – long chain of smaller molecules called nucleotides Nucleotide – made of sugar, nitrogenous base, and a phosphate Two types of Nucleic Acids DNA – deoxyribonucleic acid RNA – ribonucleic acid

DNA – Deoxyribonucleic Acid Made of 2 strands of nucleotides that spiral around each other Held together by hydrogen bonds between bases Chromosomes made of DNA Carries hereditary information

RNA – Ribonucleic Acid Single strand of nucleotides Plays several roles in cell function ex. Manufacturing of proteins

ATP Adenosine Triphosphate Carries energy in cells Single nucleotide with two extra phosphate groups MAIN ENERGY CURRENCY When food molecules are broken down inside cells, some energy temporarily stored in ATP Cells need steady supply of ATP to function