Biological Macromolecules Study Guide

Comprehensive vocabulary flashcards covering the four major biological macromolecules: proteins, lipids, carbohydrates, and nucleic acids, as well as the reactions that synthesize and break them down.

Amino acids

The monomer building blocks of proteins, consisting of a central carbon, an amino group ($-\text{NH}_2$), a carboxyl group ($-\text{COOH}$), a hydrogen atom, and a variable R group.

R group (side chain)

The variable group attached to the central carbon of an amino acid that provides each of the $20$ common amino acids with its unique chemical properties.

Essential amino acids

Amino acids that the human body cannot produce on its own and must obtain through dietary food sources.

Primary protein structure

The linear sequence of amino acids in a polypeptide chain, recognized visually as a straight chain.

Secondary protein structure

Local folding of a polypeptide chain into alpha helices or beta pleated sheets, recognized visually as spirals or folded sheets.

Tertiary protein structure

The overall three-dimensional shape of a single polypeptide chain folded into a complex shape.

Quaternary protein structure

The protein structure formed when two or more folded polypeptide chains or subunits join together.

Peptide bond

A covalent bond connecting amino acids together, formed between the amino group of one amino acid and the carboxyl group of another.

Disulfide bridges

Strong covalent bonds formed between sulfur-containing R groups that help maintain and stabilize protein structure.

Enzymes

Biological catalysts, usually proteins, that speed up chemical reactions by lowering the required activation energy without being consumed.

Contractile proteins

Proteins, such as actin and myosin, that allow muscles to contract and relax to produce movement.

Immunoglobulins

Antibodies that help the immune system recognize and defend against foreign substances such as bacteria and viruses.

Hormones

Chemical messengers that travel through the bloodstream to communicate with target cells and regulate activities like growth and metabolism.

Insulin

A protein hormone produced by beta cells in the pancreas that lowers blood glucose levels by promoting glucose uptake and storage in cells.

Structural proteins

A functional class of proteins that provide physical support and strength to biological tissues.

Lipids

Biological molecules composed primarily of carbon, hydrogen, and oxygen that are nonpolar, hydrophobic, and not considered true polymers.

Fatty acids

Lipid molecules consisting of a long hydrocarbon chain attached to a carboxyl group ($-\text{COOH}$) at one end.

Saturated fatty acids

Fatty acids lacking carbon-carbon double bonds; they are typically solid at room temperature and commonly found in animal fats.

Unsaturated fatty acids

Fatty acids containing one or more carbon-carbon double bonds; they are typically liquid at room temperature and found in plant oils and fish.

Steroids

Lipids characterized by a core structure composed of four fused carbon rings, such as cholesterol, testosterone, and estrogen.

Phospholipids

Amphipathic lipids featuring a hydrophilic phosphate head and two hydrophobic fatty acid tails, forming the bilayer of plasma membranes.

Triglycerides

Lipids consisting of one glycerol molecule joined to three fatty acid chains by ester bonds, serving as long-term energy storage.

Waxes

Highly hydrophobic lipids formed by a long-chain fatty acid linked to a long-chain alcohol, functioning as waterproof, protective coatings.

Trans fats

Fats that increase LDL ("bad") cholesterol, decrease HDL ("good") cholesterol, and elevate the risk of heart disease and stroke.

Carbohydrates

Biological molecules made of carbon, hydrogen, and oxygen with an approximate hydrogen-to-oxygen ratio of $2:1$ and general formula $(\text{CH}_2\text{O})_n$.

Monosaccharides

The simplest single-sugar carbohydrates (such as glucose, fructose, and galactose) that cannot be broken down further by hydrolysis.

Sucrose

A disaccharide composed of one glucose unit linked to one fructose unit.

Lactose

A disaccharide composed of one glucose unit linked to one galactose unit.

Maltose

A disaccharide composed of two glucose units linked together.

Polysaccharides

Long chains of monosaccharides linked together that function in biological energy storage or structural support.

Starch

A storage polysaccharide used by plants to store excess glucose.

Glycogen

A storage polysaccharide used by animals to store glucose, primarily found in the liver and muscles.

Cellulose

The most abundant natural biopolymer, composed of parallel unbranched glucose chains held by hydrogen bonds to provide rigidity in plant cell walls.

Chitin

A structural polysaccharide that provides strength, support, and protection in fungal cell walls and arthropod exoskeletons.

Nucleic acids

Macromolecules composed of nucleotides that store, transmit, and express genetic information, containing the highest proportion of phosphorus.

Nucleotide

The building block of nucleic acids, composed of a phosphate group, a five-carbon sugar, and a nitrogenous base.

Phosphodiester bond

The covalent linkage connecting the $3'$ carbon of one sugar to the $5'$ carbon of another nucleotide via a phosphate group.

Purines

Two-ring nitrogenous bases found in nucleic acids, specifically adenine (A) and guanine (G).

Pyrimidines

One-ring nitrogenous bases found in nucleic acids, specifically cytosine (C), thymine (T), and uracil (U).

DNA (deoxyribonucleic acid)

A nucleic acid containing deoxyribose sugar and bases A, T, C, and G; it is usually double-stranded and stores hereditary genetic information.

RNA (ribonucleic acid)

A nucleic acid containing ribose sugar and bases A, U, C, and G; it is usually single-stranded and functions to help make proteins.

Dehydration synthesis

A chemical reaction (condensation reaction) that builds polymers from monomers by removing a molecule of water, requiring an input of energy.

Hydrolysis

A chemical reaction that breaks polymers down into smaller subunits by adding a molecule of water, often releasing energy.