3.1 Carbon Provides the Framework of biological molecules
• A chemical compound containing the element carbon is called an organic molecule
o Molecules containing carbon can form straight chains, branches, rings, balls and
o They can do this because they can form up to four covalent bonds
• Molecules consisting only of carbon and hydrogen are called hydrocarbons.
o Hydrocarbons make good fuels: gasoline and propane
• Carbon and hydrogen atoms both have similar electro-negativities, therefore electrons
in these bonds are evenly distributed.
o Because they are evenly distributed, hydrocarbons are nonpolar.
• Functional groups have a C-H core, they also have definite chemical properties that they
retain no matter where they occur.
o Functional groups that are polar: hydroxyl, carbonyl (C=O), acidic carboxyl
(COOH), phosphate (PO4), and basic amino (NH2)
o Many of these groups participate in hydrogen bonding
• Isomers are organic molecules that have the same molecular or empirical formula that
exist in different forms.
o If the difference is in the actual structure of their carbon skeleton, they are called
o Steroisomer have the same carbon skeleton but differ in how the groups
attached to this skeleton are arranged in space. Enzymes in biological systems
usually recognize only a single, specific steroisomer.
▪ A subcategory of stereoisomers, called enantiomers, are actually mirror
images of each other. This is also called a chiral molecule.
▪ Chiral compounds are characterized by their effect on polarized light
• 4 classes of macromolecules:
▪ Starch. Glycogen-glucose-energy storage-potatoes
▪ Cellulose-glucose-structural support in plan cell walls- paper
▪ Chitin-modified glucose-structural support-crab shells
▪ Functional-amino acids-catalysis; transport- hemoglobin
▪ Structural-amino acids-support-Hair
o Nucleic Acids
▪ DNA-nucleotides-encodes genes-chromosomes
▪ RNA-nucleotides-needed for gene expression- messenger RNA
▪ Fats- glycerol and three fatty acids-energy storage-butter
▪ Phospholipids- glycerol, two fatty acids, phosphate and polar R groups-
cell membranes-phosphatidylcholine ▪ Prostaglandins- 5 carbon rings with 2 nonpolar tails-chemical
messengers-prostaglndin E (PGE)
▪ Steroids-4 fused carbon rings- membranes; hormones-cholesterol
▪ Terpenes-long carbon chains-pigments; structural support- rubber
• A polymer is a large molecule built by linking together a large number of small, similar
chemical subunits called monomers. Lipids are the only ones that has a chain of only
three subunits that consists of a long chain of C-H functional groups (fatty acid)
• These chains are all built in the same way, assembled via chemical reactions termed
dehydration reactions are broken down by hydrolysis reactions.
• Dehydration reaction:
o To form a covalent bond between two monomers, an –OH group is removed
from one monomer, and a hydrogen atom (H) is removed from the other.
o This chemical reaction is called condensation or a dehydration reaction because
the removal of –OH and –H is the same as the removal of a molecule of water.
o For every subunit added to a macromolecule, one water molecule is removed.
• Hydrolysis reaction:
o Reverse dehydration, a molecule of water is added instead or removed
o A hydrogen atom is attached to one subunit and a hydroxyl group to the other,
breaking a specific covalent bond in the macromolecule
3.2 Carbohydrates form both structural and energy storing molecules
• Carbohydrate are a loosely defined group of molecules that all contain, carbon,
hydrocarbon, and oxygen in the molar ratio 1:2:1. (CH2O)n
• The simplest of the carbohydrate sugars are the monosaccharides. They are simple
sugars that contain as few as 3 carbon atoms
• Five carbon sugars ribose and deoxyribose are components of nucleic acids
• The most important of the six-carbon monosaccharides for energy storage is glucose.
Glucose has a 7 energy-storing C-H bonds. Glucose can exist in the alpha and beta forms
• Fructose is a structural isomer that differs in the position of the carbonyl carbon (C=O);
galactose is a steroisomer that differs in the position of –OH and –H groups relative to
• Transport forms of sugars are commonly made by linking two monosaccharides
together to form a disaccharide. Disaccharides serve as effective reservoirs of glucose
because of the enzymes that normal use glucose in the organism can’t break the bond
linking the two monosaccharide subunits.
• In plants glucose instead forms a disaccharide with its structural isomer fructose. The
resulting disaccharide is sucrose, sucrose is the form most plants use to transport
glucose and is the sugar most humans eat.
• In mammals, glucose is linked to its steroisomer galactose, forming the disaccharide
lactose, or milk sugar. Many mammals supply energy to their young in the form of
• Polysaccharides are longer sugar polymers made up of monosaccharides that have been
joined through dehydration reactions. • Organisms store the metabolic energy contained in monosaccharides by first converting
them into disaccharides, such as maltose. These are then linked together into insoluble
storage polysaccharides called starches.
3.3 proteins are the tools of the cell
• Proteins are the most diverse group of biological macromolecules, both chemically and
• 7 catergories of protein functions
1. Enzume catalysis: enycmes are biological catalyst that facilitate specific chemical
reactions. Encymes are #D globular proteins that fit snugly around the molecules
they act on. This fit facilitates chemical reactions by stressing particular chemical
2. Defense: other globular proteins use their shapes to recognize foreign microbes
and cancer cells. White blood cells destroy forign cells, and others make
antibody proteins that attach to invading cells.
3. Transport: a variety of globular proteins transport small molecules and ions. Red
blood cells contain the transport protein hemoglobin, which transports oxygen in
the blood. On the surfaces of individual cells, membranes transport proteins help
move ions and molecules across the membrane.
4. Support: protein fibers play many important structural roles. In humans, these
fibers include keratin, the fibrin in blood clots, and collagen. The last one,
collagen, forms the matrix of skin, ligaments, tendons, cartilage and bones.
5. Motion: muscles contract through the sliding motion of two kinds of protein
filaments: actin and myosin. Proteins also play key roles in the cells cytoskeleton
and in moving materials within cells.
6. Regulation: small proteins called hormones serve as intercellular messengers in
animals, proteins also play many regulatory roles within the cell-turning on and
shutting off genes, for example. Proteins also act as receptors for extracellular
7. Storage: calcium and iron are stored in the body by binding as ions to storage
proteins found in cells
• Proteins are long linear polymers of amino acids. The sequence of the a