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
Properties Related to Hydrogen Bonding
Life depends on hydrogen bonds in water
 High Specific Heat = water resists changes in temp.
- helps regulate cells
 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
 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
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
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+ [ ]
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
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)
Monomer = each smaller subunit molecule
Polymer = large molecule that contains many monomers bonded together
1) Carbohydrates
- ex: sugars, starches, cellulose, glycogen
Specifics
- contain elements: 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
2) Lipids
- ex: fats, oils, cholesterol
Specifics
- contain C, H, and O
- store large amounts of energy
- cell membrane made up of phospholipids
- regulate body responses and sexual development
- are nonpolar molecules (don’t dissolve in water)
3) Proteins
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
4) Nucleic Acids
- work together to make proteins
Types:
1) DNA
2) RNA
Functions
DNA – stores info to build proteins
RNA – helps build proteins
Chemical Reactions
= change substances into different substances by breaking and forming chemical bonds
Example:
6O2 + C6H12O6
1. Reactants
6CO2
2. Direction
+ 6H2O
3. Products
Reactants = substances changed during a chemical reaction (left side)
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)
Exothermic = chemical reaction that releases more energy than it absorbs
- gives off heat (hot)
- ex: cellular respiration
Endothermic = chemical reaction that absorbs more energy than it releases
- absorbs heat (cold)
- ex: photosynthesis
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
- 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
- Reaction 1 requires more activation energy than Reaction 2
- Reaction 3 has less activation energy due to a catalyst being used