UNIT 1: INTRODUCING BIOLOGY

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UNIT 1 INTRODUCING BIOLOGY Chapter 2 Chemistry
of life
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UNIT 1 INTRODUCING BIOLOGY Chapter 2 Chemistry
of Life   I. Atoms, Ions, and Molecules
(2.1)      
A. Living things consist of atoms of different
elements
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1. An atom is the smallest basic unit of
matter   2. An element is one type of atom   3.
An atom has a nucleus and electrons      
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 a. The nucleus has protons and neutrons   b.
Electrons are in energy levels outside the
nucleus      
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4. A compound is made of atoms of different
elements bonded together      
a. Water (H20)   b. Carbon dioxide (CO2)   c.
Many other carbon-based compounds in living
things.
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B. Ions form when atoms gain or lose
electrons 1. An ion is an atom that has gained
or lost one or more electrons a. Positive ions
-lost electron(s) b. Negative ions -gain
electron(s) 2. Ionic bonds form between
oppositely charged ions      
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1. A covalent bond forms when atoms share a pair
of electrons   a. Multiple covalent bonds   b.
Diatomic molecules      
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2. A molecule is two or more atoms held together
by covalent bonds    
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II. Properties of Water A. Life depends on
hydrogen bonds in water   1. Water is a polar
molecule   a. Polar molecules have slightly
charged regions        
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 b. Nonpolar molecules do not have charged
regions      
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c. Hydrogen bonds form between slightly positive
hydrogen atoms and slightly negative atoms.    
   
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2. Hydrogen bonds are responsible for three
important properties of water.          
a. High specific heat   b. Cohesion- attraction
between molecules of the same substance (because
of hydrogen bonds, water is very cohesive)
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c. Adhesion- attraction between different
substances. Adhesion between water and other
charged or polar substances very important
force. (responsible for capillary action)  
   
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B. Many compounds dissolve in water    
   
1. A solution is formed when one substance
dissolves in another   a. A solution is a
homogeneous mixture
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 b. Solvents dissolve other substances   c.
Solutes dissolve in a solvent      
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2. Like dissolves like   a. Polar solvents
dissolve polar solutes b. Nonpolar solvents
dissolve nonpolar solutes c. Polar substances
and nonpolar substances generally remain
separate       
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C. Some compounds form acids and bases 1. An
acid releases a hydrogen ion when it dissolves
in water a. High H concentration   b. pH less
than 7      
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2. A base removes hydrogen ions from a
solution a. low H concentration   b. pH greater
than 7      
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3. A neutral solution has a pH of 7      
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III. Carbon-Based Molecules (2.3) A. Carbon
atoms have unique bonding properties 1. Carbon
forms covalent bonds with up to four other
atoms, including other carbon atoms.      
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2. Carbon-based molecules have three general
types of structures a. Straight chain   b.
Branched chain   c. Ring      
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B. Many carbon based molecules are made of many
small subunits bonded together        
1. Monomers are the individual subunits  2.
Polymers are made of many monomers
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B. Four main types of carbon-based molecules are
found in living things.   1. Carbohydrates are
made of carbon, hydrogen, and oxygen      
a. Carbohydrates include sugars and
starches b.Monosaccharides are simple sugars
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c. Polysaccharides include starches, cellulose,
and glycogen        
d. Carbohydrates can be broken down to provide
energy for cells   e. Some carbohydrates are part
of cell structure
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2. Lipids are nonpolar molecules that include
fats, oils, and cholesterol   a. Many contain
carbon chains called fatty acids   b. Fats and
oils contain fatty acids bonded to glycerol.  
   
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c. Lipids have several different functions 1).
Broken down as a source of energy 2). Make up
cell membranes 3). Used to make hormones    
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d. Fats and oils have different types of fatty
acids   1). Saturated fatty acids   2).
Unsaturated fatty acids    
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e. Phospholipids make up all cell membranes    
   
1). Polar phosphate head   2). Nonpolar fatty
acid tails
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3. Proteins are polymers of amino acid
monomers        
a. Twenty different amino acids are used to build
proteins in organisms
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 b. Amino acids differ in side groups, or R
groups   c. Amino acids are linked by peptide
bonds    
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d. Proteins differ in the number and order of
amino acids   1). Amino acids interact to give a
protein its shape   2). Incorrect amino acids
change a proteins structure and function  
   
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4. Nucleic acids are polymers of monomers called
nucleotides        
a. Nucleotides are made of sugar, phosphate
group, and a nitrogen base.
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b. DNA stores genetic information   c. RNA builds
proteins      
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IV. Chemical Reactions (2.4)   A. Bonds break
and form during chemical reactions.   1.
Reactants are changed during a chemical
reaction   2. Products are made by a chemical
reactions.      
C6H12O6 O2 CO2 H2O
reactants
products
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B. Bond energy is the amount of energy that
breaks a bond   1. Energy is added To break
bonds   2. Energy is released when bonds form  
   
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C. A reaction is at equilibrium when reactants
and products form at the same rate.      
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D. Chemical reactions release or absorb
energy   1. Activation energy is the amount of
energy that needs to be absorbed to start a
chemical reaction.      
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 2. Exothermic reactions release more energy than
they absorb. a. Reactants have higher bond
energy than products b. Excess energy is
released by the reaction      
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3. Endothermic reactions absorb more energy than
they release. a. Reactants have lower bond
energy than products   a. Energy is
absorbed by the reaction to make up the
difference.      
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V. Enzymes (2.5) A. A catalysts lowers
activation energy 1. Catalysts are substances
that speed up chemical reactions a.
Decrease activation energy b. Increase
reaction rate      
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B. Enzymes allow chemical reactions to occur
under tightly controlled conditions.        
1. Enzymes are catalysts in living things   a.
Enzymes are needed for almost all processes   b.
Most enzymes are proteins
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C. Disruptions in homeostasis can prevent enzymes
from functioning. 1. Enzymes function best in a
small range of conditions 2. Changes in
temperature and pH can break hydrogen
bonds. 3. An enzymes function depends on its
structure        
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D. An enzymes structure allows only certain
reactants to bind to the enzyme   1.
Substrates   2. Active Site      
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E. The lock-and-key model helps illustrate how
enzymes function 1. Substrates brought
together 2. bonds in substrates weakened