Download Chapter 2 Notes: The Chemistry of Life

Chapter 2 Notes: The Chemistry of Life
Section 2-1: The Nature of Matter
I. Atom - From the Greek word atomos, which means “unable to
be cut”; Very small in size.
A. Structure of an atom:
1. The atomic nucleus is located at the center of the
atom and is made of:
a. Protons – positively charged
b. Neutrons – neutral
2. Electrons
a. Move around the atomic nucleus in energy
levels
b. Negatively charged
B. Sketch an atom:
II. Elements
A. An element is a pure substance made of one type of atom
1. More than 100 are known
2. Only about 24 are commonly found in organisms
3. Atomic number of an element = # protons
ex: carbon has 6 protons, so the atomic number of carbon
is 6
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4. Mass number = the sum of # protons + #
neutrons
ex: Carbon has 6 protons, 6 neutrons; the mass number
of carbon is 12
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C
Carbon
12.011
5. Isotopes – when atoms of the same element do not
have the same number of neutrons; *All isotopes of an
element have the same chemical properties
ex: carbon 13 occurs when carbon has 6 protons and 7
neutrons.
6. Elements are represented by a 1 or 2-letter symbol
(see p.1086). Be familiar with the following elements:
a. C = carbon
b. Na = sodium
c. N = nitrogen
d. O = oxygen
e. K = potassium
f. H = hydrogen
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III. Chemical Compounds
A. A chemical compound is formed by combining 2 or
more elements
1. Examples: H2O is made of 2 hydrogen atoms and
1 oxygen;
NaCl is made of 1 sodium and 1 chlorine atom
2. The chemical properties of a compound are
different from the elements that form the compound
B. Chemical bonds
1. Chemical bonds hold atoms together
2. Two types of chemical bonds:
a. Ionic – formed when 1 or more electrons are
transferred from one atom to another
ex: NaCl (salt)
b. Covalent – formed when electrons are shared
between atoms ex: H2O (water)
i. Molecule – when atoms join together with
covalent bonds
3. Van der Waals Forces – an attraction between
oppositely charged regions of molecules
Section 2-2: Properties of Water (H2O)
I. Water is a polar molecule
A. Polar molecules are formed by unequal sharing of
electrons. For example, water is negative near the oxygen and
positive near the hydrogens
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B. Hydrogen bonds
1. form between water molecules
2. not as strong as ionic or covalent bonds
3. give water its special properties
C. Special properties of water:
1. Adhesion – attraction between molecules of
different substances;
ex: capillary action
2. Cohesion – attraction between molecules of the
same substance; ex: surface tension
D. Mixtures are materials composed of 2 or more elements
or compounds that are physically mixed
1. Two types of mixtures:
a. solutions – when all components are evenly
spread in water
i. solute - substance that is dissolved
ii. solvent – the substance that dissolves the
solute (ex: water)
b. suspensions – when all components are not
completely dissolved in water
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Part Two:
Chapter 2 Notes The Chemistry of Life (continued)
Section 2-2 (continued)
I. pH scale
A. Ranges from 0-14
B. 7 is neutral; between 0-7 is acidic; between 7-14 is basic
C. acid – a compound that forms H+ in solution
D. base – a compound that forms OH- in water
E. buffer – weak acids or bases that help keep the pH in
living things near the neutral range
Section 2-3 Carbon Compounds
I. The importance of the element carbon:
A. Carbon atoms have four electrons, which makes it easy to
form large molecules, called macromolecules
B. Carbon atoms most commonly bond with C, H, O, S, P and
N (see periodic table for element names for these)
C. The bonds that are formed can be single, double, or
triple bonds
II. Types of macromolecules (large molecules)
A. Carbohydrates
1. Living things use carbohydrates as their main source of
energy, energy storage or, for structure
2. Example: sugar, also called glucose
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3. Made of C, H and O in a 1:2:1 ratio
4. Monosaccharides - single sugars
5. Polysaccharides - many sugars connected together
B. Lipids
1. Used to store energy; also make up the outer portion
of a cell
2. made mostly from C and H atoms
C. Nucleic acids
1. Store and transmit genetic information
2. Two kinds of nucleic acids:
a. DNA
b. RNA
D. Proteins
1. Functions (what they do)
a. control the rate of chemical reactions
b. control cell processes
c. form structures, like bones and muscles
d. move substances into or out of cells
e. help fight disease inside organisms
2. Made of C, H, O, and N
3. The basic part of a protein is an amino acid. Many
amino acids link together to form a protein
4. The shape of a protein (how the long chain of amino
acids fold together) is important
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Section 2-4: Chemical Reactions and Enzymes
I. Chemical reactions
A. A chemical reaction is a process that changes one set of
chemicals into another set of chemicals
ex: CO2 + H2O ----------> H2CO3
Reactants
Product
1. Reactants – the element or compound that enters
into a reaction (starting materials)
2. Products – the elements or compounds that are
produced by a reaction; the materials after a reaction
B. Energy in Reactions
1. Some reactions occur spontaneously and release
energy;
Some reactions require energy to occur
2. Activation energy – the energy required for a
reaction to occur
C. Enzymes
1. An enzyme is a protein that lowers the amount of
activation energy required for a chemical reaction to
occur
2. Active site – area on an enzyme where another
molecule can connect
3. Substrate – the molecule that connects to an enzyme
at the active site
4. Enzymes only work at certain temperature and pH
ranges!
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