Chemistry of Life Unit
When water, H2O, is created, hydrogen
and oxygen share the electrons
• The oxygen has a slightly negative
charge
• The hydrogen’s have a slightly
positive charge
This uneven pattern of charge creates
a polar molecule = has a positive side
and negative side
Water Molecule
Hydrogen Bonding
Hydrogen Bond = an attraction
between a slightly positive
hydrogen atom and a slightly
negative atom, often oxygen or
nitrogen
Hydrogen Bonding
Properties Related to Hydrogen
Bonding
Life depends on hydrogen bonds in
water
• High Specific Heat = water resists
changes in temp.
- helps regulate cells
Properties Related to Hydrogen
Bonding (cont)
• Cohesion = attractive forces between
particles of the same kind
- example: surface tension of water
• Adhesion = the attractive forces
between unlike substances
- example: meniscus curve in a
graduated cylinder
Surface Tension
Meniscus Curve
Properties Related to Hydrogen
Bonding (cont)
• Capillarity = the ability of water to
move up through narrow tubes
against gravity
- due to cohesion and adhesion
- example: carnations turning a
different color in colored water
Carnations in Colored Water
Carnations in Colored Water
Solutions
The polarity of water makes it very
effective at dissolving many
substances
Solvent +
Solute
= Solution
Concentration [ ] = amount of solute in
a given amount of solvent
Saturated = no more solute will
dissolve in the solvent
Solvent + Solute = Solution
Mosquito injects a solution into
your body that prevents clotting
Solutions (cont)
Water is the universal solvent.
All processes necessary for life
take place in water.
Acids and Bases
Acid = compound that releases a
hydrogen ion (H+) when dissolved
in water
- increases the H+ [ ]
Base = compound that remove H+
ions from a solution
- lowers the H+ [ ]
Acids and Bases (cont)
pH scale = amount of H+ ions in a
solution
0 to 6 = acidic
7 = neutral
8 to 14 = basic
buffer = compound that regulates H+ [ ]
- maintains homeostasis
pH Scale
Organic Compounds
Carbon is the building block of life
- can form multiple bonds (up to 4),
including other carbon atoms
More than 90 % of the mass of all living
things are composed of combinations
of just 4 elements
1) Carbon ( C) 2) Hydrogen (H)
3) Oxygen (O) 4) Nitrogen (N)
1) Carbohydrates
Examples
sugars
starches
cellulose
glycogen
Specifics
- contain C, H, and O
- main source of usable chemical
energy for cells
- major part of plant cell wall
(made of cellulose)
- most basic are simple sugars =
monosaccharides (glucose)
- bond to form polysaccharides
1) Carbohydrates
2) Lipids
Examples Specifics
Fats
- contain C, H, and O
Oils
- store large amounts of energy
Cholesterol - cell membrane made up of
phospholipids
- regulate body responses and
control sexual development
- are nonpolar molecules (don’t
dissolve in water)
Saturated Fats (solid at room temp)
Unsaturated Fats (liquid at room temp)
3) Proteins
Examples Specifics
- contain C, H, O, and N
- made of monomers called
amino acids
- 20 different amino acids build
proteins
- specific sequence determines
structure and function
Red Blood Cells and
Sickle Cell Anemia(SEM 3500x)
4) Nucleic Acids
- work together to make proteins
Types:
1) DNA
Functions:
– stores info to build
proteins
2) RNA
– helps build proteins
Chemical Reactions
= change substances into different
substances by breaking and
forming chemical bonds
6O2 + C6H12O6
6CO2 + 6H2O
1. Reactants = substances
changed during a chemical
reaction (left side)
2. Direction
3. Products = substances made
during a chemical reaction (right
side)
Bond Energy = the amount of
energy that will break a bond
Chemical Equilibrium = when both
the reactants and products are
made at the same rate
* Chemical reactions release or
absorb energy
Types of Chemical Reactions
Activation Energy = the amount of
energy needed to start a reaction
- is very high in most chemical
reactions (especially in the body)
Activation Energy
Types of Chemical Reactions (cont)
Exothermic = chemical reaction
that releases more energy than it
absorbs
- gives off heat (hot)
- ex: cellular respiration
Exothermic Reaction
Types of Chemical Reactions (cont)
Endothermic = chemical reaction
that absorbs more energy than it
releases
- absorbs heat (cold)
- ex: photosynthesis
Endothermic Reaction
Enzymes
Catalyst = substance that reduces the
amount of activation energy that is
needed to start a chemical reaction
Catalysts are not changed during a
chemical reaction
Enzymes = a type of catalyst in living
things
Enzymes
- almost all are proteins
- work best in normal body
conditions (temp. and pH)
- specific shape allows only certain
reactants to bind
- fit like a lock and key
Lock and Key Model - Enzymes
Enzymes (cont)
- functions:
1) help bring substrates together
and chemical reactions occur
2) decrease the activation energy
of the reaction
3) increase the rate of the reaction
Enzymes reduce Activation Energy
Enzymes (cont)
- Reaction 1 requires more activation
energy than Reaction 2
- Reaction 3 has less activation energy due
to a catalyst being used