Chemistry of Life Chapter 2

I. Matter and Substances A. What makes up matter? A. Atoms- smallest unit of matter that cannot be broken down by chemical means B. Structure of atoms- nucleus contains protons and neutrons, surrounded by electron clouds C. Nucleus is positive because of protons and electrons are negative- most atoms are neutral

B. An element is a substance made up of atoms that have the same number of protons 1. Atoms of an element may have a different number of neutrons- isotopes

II. Why Do Atoms Form Bonds? A. Atoms have different levels of electrons and the outermost level is the valence level B. Atoms form bonds to fill the valence shell C. A compound is a substance made of the bonded atoms of 2 or more elements

Ionic Bond Ionic Bond Covalent Bond Covalent Bond

D. Polarity occurs when one atom of a covalent bond pulls harder on the shared electrons, leaving a slightly positive region and a slightly negative region 1. The partially charged ends attract opposite charges! a. Water can dissolve sugar and salt

E. Hydrogen atoms bonded to O, N, or F have a + charge almost as great as a proton and can attract other negatively charged atoms 1. Strong bond 2. Essential in holding DNA together

Energy F. The ability to do work 1. Comes in many forms a. Light, chemical, mechanical G. The transfer of energy causes changes in state 1. Solid, liquid, gas

H. Chemical reactions involve the absorption or release of energy 1. Energy your body needs is provided by the breakdown of food, which is accompanied by a release of energy a. Metabolism refers to chemical reactions in an organism

2. Activation energy is the amount of energy needed to start a reaction a. Catalysts lower the amount of activation energy needed and allow reactions to occur in conditions where they normally would not b. Enzymes are biological catalysts 3. Oxidation Reduction reactions occur together and are the result of the transfer of electrons between atoms

III. What Makes Water Unique? A. Water has unique properties because water molecules form hydrogen bonds with each other 1. Ice Floats- frozen water has air spaces, making it less dense. Ice floating on rivers and lakes prevents the water from totally freezing, so life can exist beneath

2. Water absorbs and retains heat- large bodies of water help keep the earth’s temperature from changing too quickly 3. Water molecules stick to each other Cohesion is attraction of particles of same substance

4. Water molecules stick to other polar molecules. Adhesion is the attraction of different substances a. Cohesion and Adhesion allow water to move through the stems of plants

B. Solutions are mixtures in which ions or molecules are evenly distributed in another substance 1. Substances are transported in living things by being dissolved in water and can move easily within and between cells

C. Some water molecules break apart to form ions H+ and OH- 1. In pure water there is an equal amount of these ions 2. Acids are compounds that form extra H+ ions when dissolved in water- stomach acid 3. Bases form extra OH- ions when dissolved in water 4. Acids and Bases mixed together will neutralize each other

D. pH is a measure of how acidic or basic something is E. pH of living things must be stable- buffers maintain a stable pH

IV. What Are Biomolecules? A. The parts of a cell are made up of large, complex molecules called biomolecules 1. The basic units contain carbon atoms a. C has 4 valence electrons and covalently bonds to up to 4 atoms b. Can form rings or chains

B. Cells use carbohydrates for sources of energy, structural material, and cellular identification 1. Made of sugars that contain carbon, hydrogen, and oxygen 2. Glucose, found in animals, is a simple sugar, a monosaccharide 3. Starches are polysaccharides, they are complex sugars

C. The main functions of lipids include storing energy and controlling water movement, include fats, steroids, and waxes 1. Chains of carbons bonded to hydrogen atoms; structure repels water 2. Very efficient long term energy storage

D. Proteins perform many functions: structure, enable movement, transport, chemical reactions 1. Chains of amino acids that twist and fold into certain shapes that determines function 2. Amino Acids are the building blocks of proteins- link together with peptide bonds a. Made of an amino group, carboxyl group, and a side group that determines function (20 amino acids)

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E. All cells contain nucleic acids, which are long chains of nucleotide units 1. Nucleotides have 3 parts: sugar, nitrogenous base, phosphate group a. DNA has sugar deoxyribose, RNA has sugar ribose 2. Nucleic Acids store and transmit hereditary information 3. Transports energy in form of ATP

Macromolecules MonomerPolymer

Chemical Reaction Law of conservation of matter Law of conservation of matter 2H 2 + O 2 -> 2H 2 O 2H 2 + O 2 -> 2H 2 O