General Biology Reviewer: Biomolecules, Enzymes, and Energy Transformation

Comprehensive vocabulary flashcards covering the core topics of carbohydrates, lipids, proteins, nucleic acids, enzymes, and energy transformations based on the General Biology Reviewer.

Carbohydrate

An organic molecule generally made of carbon, hydrogen, and oxygen; many simple carbohydrates have a hydrogen-to-oxygen ratio close to $2:1$.

Saccharide

A sugar unit; derived from the Greek word sakkharon, meaning "sugar."

Monosaccharide

The simplest carbohydrate, consisting of one sugar unit; examples include glucose, fructose, and galactose.

Glucose

A six-carbon monosaccharide that is a major fuel for cellular respiration.

Fructose

A monosaccharide commonly found in fruits and honey.

Galactose

A monosaccharide that combines with glucose to form lactose.

Ribose

A five-carbon sugar found in RNA and in ATP.

Deoxyribose

A five-carbon sugar in DNA; it has one less oxygen atom than ribose.

Aldose

A monosaccharide containing an aldehyde functional group, such as glucose in its open-chain form.

Ketose

A monosaccharide containing a ketone functional group, such as fructose in its open-chain form.

Disaccharide

A carbohydrate made by joining two monosaccharides; examples include sucrose, lactose, and maltose.

Sucrose

Table sugar, made from glucose and fructose.

Lactose

Milk sugar, made from glucose and galactose.

Maltose

A sugar made from two glucose units, often formed during starch breakdown.

Oligosaccharide

A short chain of a few monosaccharide units; some occur on cell surfaces and help cell recognition.

Polysaccharide

A long chain of many monosaccharides; examples include starch, glycogen, cellulose, and chitin.

Glycosidic bond

The covalent bond that joins sugar units together.

Dehydration synthesis (condensation)

A reaction that joins smaller molecules while releasing a water molecule.

Hydrolysis

A reaction that breaks a bond by adding water; digestion uses hydrolysis to break many large food molecules into smaller units.

Starch

A plant storage polysaccharide made of glucose.

Glycogen

The main storage polysaccharide in animals; it is stored especially in liver and skeletal muscles.

Cellulose

A structural polysaccharide in plant cell walls; humans cannot digest it with their own enzymes.

Chitin

A structural polysaccharide found in arthropod exoskeletons and fungal cell walls.

Dietary fiber

Carbohydrate material that resists digestion in the human small intestine and supports normal digestive function.

Anselme Payen

A French chemist who isolated and named diastase in 1833, an early enzyme preparation that breaks down starch.

Emil Fischer

A chemist whose late-19th-century work clarified the structures and stereochemistry of sugars, including glucose and fructose.

Eduard Buchner

Showed in 1897 that fermentation could occur in a cell-free extract, helping establish that biochemical reactions can be carried out outside intact living cells.

Lipid

A hydrophobic or partly hydrophobic biomolecule that includes fats, oils, phospholipids, steroids, and waxes.

Hydrophobic

"Water-fearing"; describes substances that do not mix well with water.

Hydrophilic

"Water-loving"; describes substances that interact readily with water.

Triglyceride (triacylglycerol)

A lipid made of one glycerol molecule joined to three fatty acids; it is a major long-term energy store.

Glycerol

A three-carbon alcohol that forms the backbone of triglycerides and many phospholipids.

Fatty acid

A molecule with a carboxyl group and a hydrocarbon chain; it is a component of many lipids.

Saturated fatty acid

A fatty acid whose carbon chain has no carbon–carbon double bonds; many saturated fats are solid at room temperature.

Unsaturated fatty acid

A fatty acid with one or more carbon–carbon double bonds; these bonds often cause bends in the chain.

Monounsaturated fat

A fat containing fatty acids with one carbon–carbon double bond.

Polyunsaturated fat

A fat containing fatty acids with two or more carbon–carbon double bonds.

Cis configuration

A double-bond arrangement in which groups are on the same side; it often bends a fatty acid chain.

Trans fat

A fat containing trans-configured unsaturated fatty acids; industrially produced trans fats increase cardiovascular risk and should be limited.

Hydrogenation

The addition of hydrogen to unsaturated bonds; partial hydrogenation can produce trans fats.

Phospholipid

A lipid typically containing glycerol, two fatty acids, and a phosphate-containing head group; it is a major component of cell membranes.

Phospholipid bilayer

Two layers of phospholipids arranged with hydrophilic heads facing watery environments and hydrophobic tails facing inward.

Steroid

A lipid with four fused carbon rings; examples include cholesterol and steroid hormones.

Cholesterol

A sterol in animal cell membranes and a starting material for steroid hormones, bile acids, and vitamin D.

Sterol

A steroid-like lipid that has a hydroxyl group; cholesterol is an example.

Wax

A water-resistant lipid often made of a long-chain fatty acid joined to a long-chain alcohol.

Adipose tissue

Connective tissue that stores fat, cushions organs, and helps insulate the body.

Essential fatty acid

A fatty acid humans must obtain from food because the body cannot make enough of it; linoleic acid and alpha-linolenic acid are essential.

Michel Eugène Chevreul

A 19th-century French chemist who studied fats and oils and helped show that fats can be separated into glycerol and fatty acids.

Fluid mosaic model

A cell membrane model proposed by S. J. Singer and G. L. Nicolson in 1972 establishing that membranes contain a lipid bilayer.

Protein

A biomolecule made of one or more folded polypeptide chains that performs structural, transport, signaling, defense, movement, or catalytic roles.

Amino acid

The building block of proteins; a typical amino acid has a central carbon bonded to an amino group, carboxyl group, hydrogen, and variable R group.

Amino group

The functional group $\text{--NH}_2$ in the standard amino-acid diagram.

Carboxyl group

The functional group $\text{--COOH}$ in the standard amino-acid diagram.

R group (side chain)

The variable part of an amino acid that gives it its distinctive chemical properties.

Essential amino acid

An amino acid that humans cannot synthesize in sufficient amounts and must obtain from the diet.

Non-essential amino acid

An amino acid the body can normally synthesize in sufficient amounts.

Conditionally essential amino acid

An amino acid that may need to be obtained from food in certain situations, such as illness, stress, or rapid growth.

Peptide bond

A covalent bond joining the carboxyl group of one amino acid to the amino group of another, with water released during formation.

Polypeptide

A chain of amino acids linked by peptide bonds.

Primary structure

The specific linear sequence of amino acids in a polypeptide.

Secondary structure

Local folding patterns, mainly alpha helices and beta-pleated sheets, stabilized largely by hydrogen bonds in the backbone.

Alpha helix

A spiral-shaped secondary structure of a polypeptide.

Beta-pleated sheet

A folded, sheet-like secondary structure formed by aligned sections of a polypeptide chain.

Tertiary structure

The overall three-dimensional shape of one polypeptide, stabilized by interactions among side chains.

Quaternary structure

The arrangement of two or more polypeptide subunits in one functional protein.

Denaturation

A change in a protein's shape that disrupts its normal function; heat, extreme pH, or chemicals can cause it.

Fibrous protein

A protein with an elongated shape, often providing strength or support; examples include collagen and keratin.

Globular protein

A compact, roughly spherical protein; examples include many enzymes and hemoglobin.

Collagen

A fibrous structural protein abundant in connective tissues such as tendons, ligaments, and skin.

Keratin

A structural protein found in hair, nails, and the outer layer of skin.

Hemoglobin

A protein in red blood cells that transports oxygen.

Antibody

An immune-system protein that recognizes and binds a particular antigen.

Hormone

A chemical messenger; some hormones, such as insulin, are proteins or peptides.

Jöns Jacob Berzelius

Introduced the term "protein" in 1838 in a letter to Gerardus Johannes Mulder, derived from Greek proteios, meaning "primary" or "of first importance."

Frederick Sanger

Determined the amino-acid sequence of insulin in the 1950s, helping establish that proteins have specific sequences.

Christian Anfinsen

Conducted work in the 1950s–1960s supporting the principle that a protein's amino-acid sequence contains information important for its folding.

Nucleic acid

A large biomolecule made of nucleotide units that stores, transmits, and helps express genetic information; DNA and RNA are nucleic acids.

Nucleotide

The monomer of nucleic acids, made of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Nucleoside

A nitrogenous base attached to a sugar, without the phosphate group.

Pentose

A sugar containing five carbon atoms; ribose and deoxyribose are pentoses.

Nitrogenous base

A nitrogen-containing ring molecule in a nucleotide; DNA uses A, T, C, and G, while RNA uses A, U, C, and G.

Purine

A nitrogenous base with a double-ring structure; adenine and guanine are purines.

Pyrimidine

A nitrogenous base with a single-ring structure; cytosine, thymine, and uracil are pyrimidines.

DNA (deoxyribonucleic acid)

Usually a double-stranded molecule that stores hereditary information; its sugar is deoxyribose.

RNA (ribonucleic acid)

Usually single-stranded and involved in gene expression and protein synthesis; its sugar is ribose.

Double helix

The twisted-ladder shape of DNA, with paired bases inside and sugar-phosphate backbones on the outside.

Complementary base pairing

Specific base matching: DNA adenine pairs with thymine, and cytosine pairs with guanine; in RNA, adenine pairs with uracil.

Gene

A DNA sequence that contributes to a functional product, such as a protein or functional RNA.

Genome

The complete genetic material of an organism or cell.

Replication

The process of copying DNA before cell division.

Transcription

The process of using a DNA template to make RNA.

Translation

The process by which ribosomes read mRNA codons to assemble amino acids into a polypeptide.

mRNA (messenger RNA)

Carries a protein-coding message from DNA to ribosomes.

tRNA (transfer RNA)

Brings amino acids to the ribosome and matches its anticodon with an mRNA codon.

rRNA (ribosomal RNA)

Forms a major part of ribosomes and helps catalyze peptide-bond formation.

Codon

A sequence of three nucleotides in mRNA that specifies an amino acid or a translation stop signal.

Anticodon

A three-nucleotide sequence in tRNA that pairs with a complementary mRNA codon.

Mutation

A change in the DNA sequence; its effects can be neutral, harmful, or beneficial.

Friedrich Miescher

Isolated a phosphorus-rich substance from cell nuclei in 1869 and called it "nuclein," an early discovery leading to the identification of nucleic acids.