Summary of Biological Macromolecules

Large molecules are necessary for life, built from smaller organic molecules.
Four major classes: carbohydrates, lipids, proteins, and nucleic acids.
Organic: contain carbon and are bound to hydrogen, may contain oxygen, nitrogen, and additional minor elements.

Life is "carbon-based."
Carbon atoms bond to other carbon atoms or other elements.
Can form four covalent bonds with other atoms or molecules.
Simplest organic carbon molecule is methane (CH_4).
Can form long and branching chains, bond with nitrogen, oxygen, and phosphorus, and form rings.

Simple sugars, most common is glucose (C6H{12}O_6).
Number of carbon atoms ranges from three to six.
Names end with the suffix -ose.
Examples: trioses (three carbon atoms), pentoses (five carbon atoms), and hexoses (six carbon atoms).
May exist as a linear chain or as ring-shaped molecules
Isomers: Glucose, galactose, and fructose all have the same chemical formula (C6H{12}O_6), they differ structurally and chemically because of differing arrangements of atoms in the carbon chain

Form when two monosaccharides undergo a dehydration reaction.
Hydroxyl group (–OH) of one monosaccharide combines with a hydrogen atom of another monosaccharide, releasing a molecule of water (H_2O)
Common disaccharides include lactose, maltose, and sucrose.

Long chain of monosaccharides linked by covalent bonds.
May be branched or unbranched.
Examples: starch, glycogen, cellulose, and chitin.
Starch: Stored form of sugars in plants, made up of amylose and amylopectin (both polymers of glucose).
Glycogen: Storage form of glucose in humans and other vertebrates, made up of monomers of glucose.
Cellulose: One of the most abundant natural biopolymers, provides structural support to the cell walls of plants.
Chitin: Outer skeleton (exoskeleton) of arthropods, such as insects, spiders, and crabs, protects their internal body parts.

Hydrophobic ("water-fearing"), or insoluble in water, because they are nonpolar molecules
Functions: long-term energy storage, insulation, building blocks of hormones, constituent of plasma membrane.
Includes: fats, oils, waxes, phospholipids, and steroids.

Fat molecule (triglyceride) consists of glycerol and fatty acids.
Glycerol: organic compound with three carbon atoms, five hydrogen atoms, and three hydroxyl (–OH) groups
Fatty acids have a long chain of hydrocarbons to which an acidic carboxyl group is attached
Saturated: only single bonds between neighboring carbons in the hydrocarbon chain.
Unsaturated: hydrocarbon chain contains a double bond.
Monounsaturated: one double bond in the molecule (e.g., olive oil)
Polyunsaturated: more than one double bond (e.g., canola oil).
Essential fatty acids: required but not synthesized by the human body (Omega-3 and omega-6 fatty acids).

Steroids have a ring structure.
Hydrophobic.
All steroids have four, linked carbon rings and several of them, like cholesterol, have a short tail.
Cholesterol is mainly synthesized in the liver and is the precursor of many steroid hormones, such as testosterone and estradiol. It is also the precursor of vitamins E and K.
Waxes: hydrocarbon chain with an alcohol (–OH) group and a fatty acid.

Abundant organic molecules with diverse functions.
Structural, regulatory, contractile, or protective; may serve in transport, storage, or membranes; or may be toxins or enzymes.
Polymers of amino acids, arranged in a linear sequence.
Enzymes: catalysts in biochemical reactions, specific for the substrate.
Hormones: chemical signaling molecules.
Globular or fibrous shapes.

Monomers that make up proteins.
Central carbon atom bonded to an amino group (–NH2), a carboxyl group (–COOH), and a hydrogen atom.
R group is the only difference in structure between the 20 amino acids.
Peptide bond: covalent bond through a dehydration reaction (releasing a water molecule)
Polypeptides are formed.
Cytochrome c: Important component of the molecular machinery that harvests energy from glucose. Protein sequencing has shown that there is a considerable amount of sequence similarity among cytochrome c molecules of different species

Four levels: primary, secondary, tertiary, and quaternary.
Primary: unique sequence and number of amino acids in a polypeptide chain.
Secondary: folding patterns resulting from interactions between the non-R group portions of amino acids (alpha (α)-helix and beta (β)-pleated sheet structures).
Tertiary: unique three-dimensional structure of a polypeptide, caused by chemical interactions between various amino acids and regions of the polypeptide.
Quaternary: formed from several polypeptides (subunits), stabilized by weak interactions.
Denaturation: protein structure may change, losing its shape due to temperature, pH, or exposure to chemicals.

Key macromolecules in the continuity of life.
Carry the genetic blueprint of a cell and instructions for the functioning of the cell.
Two main types: deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).
Monomers known as nucleotides.
Each nucleotide: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group

Genetic material in all living organisms.
Double-helical structure: two strands of nucleotides bonded to each other at their bases with hydrogen bonds.
Alternating sugar and phosphate groups form the backbone.