Chapter 3: Biological Macromolecules Structure and Function

Biological Macromolecules

Four major classes of macromolecules: Carbohydrates, Lipids, Proteins, Nucleic Acids.

Organic molecules

All contain carbon and may also contain hydrogen, oxygen, nitrogen, and some other elements.

Macromolecule synthesis

The process of linking monomers together to form polymers.

Dehydration synthesis

A reaction where two molecules are linked together by a covalent bond, forming a dimer and releasing a water molecule.

Hydrolysis

The process of breaking polymers down into individual monomers, using water as a reactant.

Disaccharide maltose

Formed by linking two glucose molecules through dehydration synthesis.

Enzymes

Biological molecules that catalyze or speed up reactions, including hydrolysis and dehydration reactions.

Amylase

An enzyme that breaks down carbohydrates.

Lipases

Enzymes that break down lipids.

Pepsin

An enzyme that breaks down proteins.

Carbohydrates

Organic compounds found in grains, fruits, and vegetables that provide energy to the body in the form of glucose.

General formula of carbohydrates

Represented by the formula (CH2O)n.

Carbohydrate ratio

The ratio of Carbon:Hydrogen:Oxygen in carbohydrates is 1:2:1.

Monosaccharides

Simple sugars usually having 3-7 carbons, bound to a hydroxyl group, and ending with the suffix -ose.

Aldoses

Monosaccharides with a carbonyl group at the end of the carbon chain.

Ketoses

Monosaccharides with a carbonyl group in the middle of the carbon chain.

Trioses

Monosaccharides that contain three carbons.

Pentoses

Monosaccharides that contain five carbons.

Hexoses

Monosaccharides that contain six carbons.

Glucose

An important source of energy and a hexose monosaccharide.

Galactose

A hexose monosaccharide that is part of lactose, also known as milk sugar.

Fructose

part of sucrose / fruit

Monosaccharides

exist as linear chain or ring-shaped molecules

Ring structure of monosaccharides

assumed in aqueous solution

Five- and six-carbon monosaccharides

exist in equilibrium between linear and ring forms

Glycosidic bond

formed when two sugar monomers are joined by a dehydration reaction

Disaccharide formation

occurs when two monosaccharides are linked in a dehydration reaction

Example of disaccharide formation

Glucose + Fructose = Sucrose (disaccharide)

Glycosidic linkage

formed between carbon 1 in glucose and carbon 2 in fructose

1,2 glycosidic linkage

results from the glycosidic bond between glucose and fructose

Common disaccharides

maltose (grain sugar), lactose (milk sugar), sucrose (table sugar)

Polysaccharide

long chain of monosaccharides joined by glycosidic linkages

Polysaccharides

may be branched or unbranched and consist of multiple types of monosaccharides

Molecular mass of polysaccharides

could be > 10,000 amu

Starch

energy storage in plants

Cellulose

cell walls of plants

Chitin

cell walls of fungi and exoskeleton of arthropods

Glycogen

energy storage in animals

Amylose

unbranched glucose monomers in α 1-4 glycosidic bonds

Amylopectin

branched glucose monomers in α 1-4 and α 1-6 glycosidic bonds

Cellulose structure

glucose monomers linked in unbranched chains by β 1-4 glycosidic linkages

Chitin

the hard exoskeleton of arthropods and cell walls of fungi

Lipids

a diverse group of non-polar hydrocarbons

Functions of lipids

long-term energy stores, insulation, building blocks for hormones, important component of cellular membranes

Types of lipids

Fats & Oils, Waxes, Phospholipids, Steroids

Fats

contain two main components: glycerol and fatty acids

Triacylglycerol

formed by joining three fatty acids to a glycerol backbone

Ester linkage

the bonds formed between glycerol and fatty acids

Saturated fatty acids

Contain no carbon-carbon double bonds.

Saturated fatty acids

Pack tightly and are solid at room temperature (butter, fat in meats, etc.).

Saturated fatty acids

May be associated with cardiovascular disease - should be limited in your diet.

Unsaturated fatty acids

Contains at least one carbon-carbon double bond.

Monounsaturated fat

One double bond.

Polyunsaturated fat

More than one double bond.

Unsaturated fats

Most are liquids at room temperature - referred to as oils.

Cis configuration

Hydrogens on the same side of the chain.

Trans configuration

Hydrogens on opposite sides of the chain.

Cis-acids

Have a kink in the chain and cannot be packed tightly.

Cis-acids

Liquid at room temperature.

Trans-acids

Have no kink and can be created through processing.

Trans fats

Foods with trans fat may increase LDL cholesterol in humans (bad for heart).

Essential fatty acids

Required but not synthesized by the body - must be part of diet.

Alpha-linolenic acid

An example of an omega-3 fatty acid.

Omega-3 fatty acids

Found in salmon, trout, tuna; these fats are heart healthy.

Omega-3 fatty acids

Reduce risk of heart attack, reduce triglycerides in blood, lower blood pressure.

Waxes

Hydrophobic and prevent water from sticking to surface.

Waxes

Found on the feathers of some aquatic birds and on the surface of leaves from certain plants.

Phospholipid

Molecule with two fatty acids and a modified phosphate group attached to a glycerol backbone.

Phospholipids

Are amphipathic, having a hydrophobic portion and a hydrophilic portion.

Phospholipids

Major constituents of the plasma membrane.

Amphipathic molecule

The hydrophilic heads of the phospholipids face the aqueous solution while the hydrophobic tails are sequestered in the middle of the bilayer.

Steroids

Have a closed ring structure with four linked carbon rings.

Steroids

Many have a short tail.

Steroids

Are hydrophobic.

Cholesterol

The most common steroid, synthesized in the liver, and a precursor to hormones such as testosterone and estradiol, as well as vitamin D.

Lipids

Four major types of lipids that play roles in energy storage, cell structure, and signaling.

Saturated fatty acids

Fatty acids with no double bonds between carbon atoms.

Unsaturated fatty acids

Fatty acids that contain one or more double bonds between carbon atoms.

Phospholipids

Molecules that make up cell membranes, consisting of two fatty acids, a glycerol unit, and a phosphate group.

Proteins

The most abundant organic molecules in organisms, performing a diverse range of functions including regulatory, structural, protective, transport, and catalytic roles.

Enzymes

Catalysts in biochemical reactions, most of which are proteins, with names typically ending in -ase.

Catabolic enzymes

Enzymes that break down substrates.

Anabolic enzymes

Enzymes that build more complex molecules.

Digestive enzymes

Enzymes such as amylase, lipase, pepsin, and trypsin that help in the digestion of food by catabolizing nutrients into monomeric units.

Transport proteins

Proteins like hemoglobin and albumin that carry substances in the blood or lymph throughout the body.

Structural proteins

Proteins such as actin, tubulin, and keratin that construct different structures, like the cytoskeleton.

Hormones

Proteins like insulin and thyroxine that coordinate the activity of different body systems.

Defense proteins

Immunoglobulins that protect the body from foreign pathogens.

Contractile proteins

Proteins such as actin and myosin that are involved in muscle contraction.

Storage proteins

Proteins that provide nourishment in early development of the embryo and the seedling, such as legume storage proteins and egg white (albumin).

Amino acids

The monomers that make up proteins, consisting of a central carbon atom, an amino group, a carboxyl group, a hydrogen, and a side chain (R-group).

Essential amino acids

Amino acids that must be supplied in the diet for humans, including isoleucine, leucine, and cysteine.

Peptide bonds

Links formed between amino acid monomers through dehydration synthesis reactions, where the carboxyl group of one amino acid is linked to the amino group of another.

Polypeptide

A chain of amino acids joined together in peptide linkages.

Protein

A polypeptide or multiple polypeptides with a biological function, often combined with non-peptide groups.

Primary structure

The first level of protein structure, determined by the sequence of amino acids.

Secondary structure

The second level of protein structure, involving the folding or coiling of the polypeptide chain.

Tertiary structure

The third level of protein structure, the overall three-dimensional shape of a single polypeptide.

Primary structure

the unique sequence of amino acids in a polypeptide

Sickle cell anemia

a condition where a change in one amino acid (glutamic acid replaced by valine) can impact human health