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Biochemistry The Molecules of Life Chemistry in Living Systems • Elements: simplest form of a substance - cannot be broken down any further without changing what it is • Atom: the actual basic unit composed of protons, neutrons, and electrons The Atom • Just like cells are the basic unit of life, the ATOM is the basic unit of matter. • They are very small. If placed side by side one million would stretch a distance of 1cm. • The atom is made up of 3 particles. Particle Charge PROTON + NEUTRON NEUTRAL ELECTRON - • Electrons are not present within the atom, instead THEY REVOLVE AROUND THE NUCELUS OF THE ATOM & FORM THE ELECTRON CLOUD • Draw a helium atom. Indicate where the protons, neutrons and electrons are. ATOMIC # = 2 (PROTONS) ATOMIC MASS = 4 (PROTONS & NEUTRONS) PROTONS NEUTRONS - ELECTRONS + + - ISOTOPES • • • atoms of the same element that HAVE A DIFFERENT NUMBER OF NEUTRONS Some isotopes are radioactive. This means that their nuclei is unstable and will break down at a CONSTANT RATE over time. There are several practical uses for radioactive isotopes: 1. CARBON DATING 2. TRACERS 3. KILL BACTERIA / CANCER CELLS Common Elements • The cell is a COMPLEX CHEMICAL FACTORY containing some of the same elements found in the nonliving environment. • carbon (C), hydrogen (H), oxygen (O), and nitrogen (N) are present in the greatest percentages in living systems • Most atoms are found in living systems as molecules (2 or more non-metal atoms bonded together). TWO TYPES OF COMPOUNDS • Organic - Contain C, H, and O in some ratio (usually referred to as chemicals of life) – Carbohydrates, Proteins, Lipids, Nucleic Acids • Inorganic - usually "support" life - no specific ratio of C, H, and O – Water (H2O), Carbon Dioxide (CO2) Interactions Within Molecules • Intramolecular forces: chemical bonds within a molecule – Covalent bonds: 2 non-metal atoms share electrons equally – Polar Covalent bonds: when one atom attracts electrons more than the other, it creates a partial negative charge Interactions Between Molecules • Intermolecular forces: forces of attraction between molecules – Hydrogen Bonding: a weak bond between an atom with a partial negative and a hydrogen atom with a partial positive charge. – Hydrophobic Interactions: when non-polar molecules group together to stay away from the polar molecules. Functional Groups • An atom or group of atoms attached to a molecules that gives the molecules particular chemical and physical properties. Macromolecules • Molecules that are large and complex • Often made up of repeating subunits called monomers. • Carbohydrates: contain carbon, hydrogen, oxygen in a 1:2:1 ratio – Monosaccharides: one sugar (glucose, fructose, galactose. Fun Bio Challenge: You must be able to draw these! – Disaccharides: two monosaccharides join together forming a glycosidic linkage. – Polysaccharides: many monosaccharides join together. • Starch: alpha glycosidic linkage between monomers. Stored energy found in plants • Glycogen: alpha glycosidic linkage between monomers. Stored energy found in animals • Cellulose: beta glycosidic linkage between monomers. Provides structural support in plant cell walls. • Lipids: made of C, H and O atoms, but have fewer oxygen atoms and are mainly hydrophobic – Provides longer-term energy for animals – Triglycerides: made of one glycerol and 3 fatty acids joined by an ester linkage • Saturated fatty acids: no double or triple bonds • Unsaturated fatty acids: one double or triple bond • Polyunsaturated fatty acids: more than one double or triple bond. – Phospholipids: a lipid made of a glycerol bonded to two fatty acids and an “R” group • “Head” is hydrophilic, “tail” is hydrophobic – Steroids: lipids that have four carbon based rings attached to each other • Cholesterol • Estrogen • Testosterone – Waxes: long carbon-based chains that are solid at room temperature. Macromolecules Continued… Proteins • contain the elements carbon, hydrogen, oxygen, and nitrogen • composed of MANY amino acid subunits • It is the sequence of the amino acid that forms the primary structure of proteins. • The basic amino acid form has a carboxyl group on one end, a methyl group that only has one hydrogen in the middle, and a amino group on the other end. • Attached to the methyl group is a R group. • Uses for Proteins: – As enzymes that catalyze chemical reactions in the body – Structural support in bones, tendons, skin, hair, nails – Transporting chemicals in the body – Locomotion for animals: muscle contraction – Hormones – antibodies • There are 20 common amino acids with 8 of them being essential amino acids that cannot be made in the body and must be consumed. Protein Structure • Primary Structure: the sequence of amino acids connected together through peptide bonds • Secondary Structure: coil-like alpha helix shapes and folded beta sheets due to hydrogen bonds • Tertiary Structure: 3D shapes of proteins • Quaternary Structure: multiple polypeptide chains arranged together Macromolecules continued… Nucleic Acids • Two types: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) • Contain genetic information • Made up repeating nucleotide monomers. • Each monomer contains: – A phosphate group – A sugar with five carbons (deoxyribose or ribose) – A nitrogenous base (Adenine, thymine, guanine, cytosine in DNA and in RNA the same but thymine is replaced by uracil) • A polymer of nucleotides is a strand that joins adjacent nucleotides with a phosphodiester bond (between the phosphate and the hydroxyl groups) • DNA is two strands twisted in a double helix • The two strands are held together by hydrogen bonds • Thymine always bonds with adenine (with 2 H-bonds) and cytosine always bonds with guanine (with 3 Hbonds). These are called complementary base pairs.