Ch. 5 - The Molecules of Life
5.1 Carbon is the main ingredient of organic molecules
I. Carbon Skeletons and Functional Groups
A. Carbon is very common in living things
1. Carbon can form up to 4 bonds with other atoms due to 4 electrons in the outer shell
2. Carbon may bond with other carbon atoms
B. Carbon backbones
1. Straight chain
2. Branched chain
3. Ring
C. Classification
1. Organic molecules- most molecules that are comprised of Carbon in various shapes
(living)
2. Inorganic molecules- most non-carbon molecules (H2O, O2, and NH3) (non-living)
D. Hydrocarbons- organic molecules composed of only Carbon and Hydrogen
1. Fuels such as methane CH4 as natural gas
E. Functional Groups- group of atoms within a molecule that interacts in a predictable way;
attached to a hydrocarbon skeleton
1. Hydroxyl group- polar hydrophilic – attract water around; also know as alcohols
(like ethanol)
2. Carbonyl group- polar hydrophilic; bonds with two other molecules or atoms.
Oxygen end polar negative charge
a. If one or more of the bonds is connected to a hydrogen – it is called an
aldehyde –polar hydrophilic (vanilla bean, lemon grass)
b. If both bonds with carbon are other than hydrogen – it is called a ketone polar hydrophilic (acetone, camphor-moth balls)
3. Carboxyl group- polar, hydrophilic weak acid, (fatty acid chains, vinegar, niacin)
4. Amino group- polar hydrophilic, weak base responsible for amino acid formation (proteins)
II. Monomers and Polymers
A. Monomers- small molecular units
B. Polymers- large chains of monomers in various shapes
C. Life’s major Polymers: carbohydrates, lipids, proteins, and nucleic acids
III. Building and Breaking Polymers
A. Dehydration Synthesis- to lengthen a polymer chain
1. A hydrogen atom and a hydroxyl group from two monomers react
2. A new bond is formed and water is released.
B. Hydrolysis- to shorten a polymer chain
1. A water molecule is added to a bond between two monomers
2. The bond is broken an a H is added to one monomer and a hydroxyl group to another
monomer
5.2 Carbohydrates provide fuel and building material
I. Carbohydrates- organic compound made of a sugar molecule
A. Sugars contain C,H,O in a 1 carbon : 2 hydrogen : 1 oxygen ratio
1. Multiple of CH2O
2. Most are ring structures
II. Monosaccharides- one sugar unit molecule (end in –ose)
A. Glucose- both in straight chain and ring
1. Main fuel source for energy and to build other organic molecules
2. Molecules not used may be connected into larger molecules and stored for later use
B. Fructose
Fructose
III. Disaccharide- a double sugar formed from a dehydration reaction
A. Formation of Sucrose
1. Found in plant sap and table sugar – can be broken down easily for energy use
Glucose + Fructose  Sucrose + water
C6H12O6 + C6H12O6  C12H22O11 + H2O
IV. Polysaccharides- long polymer chains made up of simple sugars
A. Starch- polysaccharide found in plants made totally of glucose monomers
1. Found in potatoes, rice, and corn
B. Glycogen- polysaccharide found in animals made totally of glucose monomers that are highly
branched
1. Stored as granules in muscle and liver – broken down when body needs energy
C. Cellulose- made up of glucose monomers that arrange in cable-like fibers in plants
1. Chains are linked by hydrogen bonds to form tough cell walls in plants like
broccoli stems
2. Human unable to digest – functions as fiber to help keep digestive system healthy
3. Cow and termites can break down cellulose due to organism in side them to get energy
from it.
IV. Properties of carbohydrates
A. Hydrophilic – attract to water due to many hydroxyl groups
B. Monosaccharides and Disaccharides dissolve readily in water
C. Cellulose and some starches do not dissolve easily but are hydrophilic
5.3 Lipids include fats & steroids
I. Characteristics of Lipids
A. Hydrophobic- water avoiding or fearing molecules
B. Functions of lipids
1. Serves as a boundary that surrounds and contains aqueous contents of cells
2. Others serve as chemical signals or store energy as fats
II. Fats – consists of a 3 carbon backbone called glycerol (C3H8O3) attached to three fatty acids, that
contain long
hydrocarbon chains
A. Saturated fats- where all three fatty acid chains contain the maximum number of hydrogen
atoms
1. All the carbon atoms form single bonds
a. Butyric acid- C4H8O2 (antihistamine properties)
2. Found in lard and butter – they are solid at room temperature
B. Unsaturated fats- contains less than the maximum number of hydrogen atoms in one or more
fatty acid chain
1. Some of the carbon atoms are double bonded
2. Fats in fruits and vegetables and fish usually, corn, olive, other vegetable oils
3. Oleic acid- C18H34O2
a. Part of Lorenzo’s oil for clinical trial to treat childhood cerebral
adrenoleukodystrophy (ALD), a degenerative myelin disorder
b. Used commercially in the preparation of oleates and lotions,
4. Linoleic Acid - C18H32O2
a. Essential fatty acid in mammalian nutrition
b. Biosynthesis of prostaglandins (hormone) and cell membranes
C. Saturated fats in high amounts may lead to plaque (lipid material) development in arteries
1. Can lead to decrease blood flow or complete blockage of blood to the heart or brain.
D. Phospholipids- looks just like a lipid but has one of the fatty acid chains replaced with a
Phosphate group (PO4)-3 and then a R-group following the phosphate
1. Phosphates are a polar, hydrophilic, & acidic molecule
2. Phospholipids are the key component of cell membranes
3. Phospholipids have a polar,hydrophilic head (phosphate region) and a nonpolar,
hydrophobic tail (two fatty acid chains)
III. Steroids- lipid molecule where the carbon skeleton forms four fused rings
A. Lipid molecule where the carbon skeleton forms four fused rings; differ in functional groups
and locations of functional groups
B. Steroids are lipids due to their hydrophobic nature; however are different from fats
structurally & functionally
C. Sex hormones
1. Testosterone- male hormone C19H28O2
2. Estrogen- female hormone C18H24O2
D. Cholesterol – essential material found in cell membranes and starting point for other
Steroids (C27H46O)
1. LDL – low density cholesterol builds up in arteries to cause cardiovascular disease
2. HDL – high density cholesterol helps remove LDL cholesterol that clogs arteries
Cholesterol
5.4 Proteins perform most functions in cells
I. The Functions of Proteins
A. Protein- a polymer made from a set of 20 kinds of monomers called amino acids
B. Functions
1. Makes up structures hair, fur, muscle and long-term nutrient stores
2. Defend against foreign invader and serve as chemical signals
3. Controls chemical reactions
II. Amino Acids
A. Amino acid- monomer that consists of a carbon bonded to an amino group, carboxyl,
hydrogen and side chain (R)
1. Side group or R-group gives the amino acid its specific property and way interacts
2. Leucine is hydrophobic (CH3-CH3)
3. Serine is hydrophilic (OH)
III. Building a Protein
A. Polypeptide- chain of amino acids created by dehydration reaction between each amnion and
carboxyl group
B. Most polypeptide chains are at least 100 amino acids long
IV. Protein Shape
A. Influenced by the interaction between bonds between chains
B. The environment helps to determine shape like a aqueous (water) environment
1. Hydrophilic amino acids like water so will position on outside edge of protein
2. Hydrophobic amino acids repel water so they will cluster in center of protein
5.5 Enzymes are proteins that speed up specific reactions in cells.
I. Enzymes (proteins) and Activation Energy
A. Activation Energy- “start-up” energy needed to start the chemical reaction for the reactants
B. Catalysts- chemical compounds that speed up chemical reactions in the cell
C. Enzymes allow chemical reaction to occur without raising the cell’s temperature
D. Enzymes lower the activation energy in the body to allow certain products to be made
E. Characteristics of enzymes
II. How Enzymes Work
A. Substrate- the substance or substances which the enzyme acts upon
B. Enzymes are substrate specific- fit like a lock and key
C. Induced fit model explains how enzymes work
1. Active site- location where substrate binds to an enzyme
D. Enzymes remained unchanged by the substrate in a chemical reaction
E. Efficiency of enzyme is affected by temperature and pH
1. Denature- enzymes lose their ability to catalyze when T> 104 F in humans
F. –ase is the standard suffix found on enzymes like
G. Enzymes can hold molecules in closer proximity – helps form larger molecules
Induced fit model
Sucrase (enzyme) + Sucrose (substrate) becomes glucose and fructose