Biology final exam

Activation energy

The minimum energy required to start a chemical reaction.

Active site

The region of an enzyme where the substrate binds and the reaction occurs

Adenine

A nitrogenous base found in DNA and RNA; pairs with thymine (DNA) or uracil (RNA).

Amino acid

The monomer of proteins; contains an amino group, carboxyl group, hydrogen, and R group

Anabolism / condensation

Reactions that build larger molecules from smaller ones by removing water.

Anticodon

A three-base sequence on tRNA that is complementary to an mRNA codon.

ATP (Adenosine triphosphate)

The primary energy currency of the cell.

ATP synthase

An enzyme that produces ATP using a proton gradient

Bases

Nitrogen-containing molecules that form part of nucleotides (A, T, C, G, U).

Biomolecule

Any molecule produced by living organisms (e.g., proteins, lipids).

Carbohydrate

A biomolecule made of sugars; used for energy and structure.

Carboxyl group (–COOH)

A functional group found in amino acids; acidic

Catalyst

A substance that speeds up a chemical reaction without being consumed.

Catabolism / Hydrolysis

Reactions that break down large molecules using water.

Cholesterol

A steroid lipid that stabilizes animal cell membranes.

Codon

A three-base sequence on mRNA that codes for an amino acid.

Complementary base pairing / Chargaff’s rule

A pairs with T (or U); C pairs with G.

Cytosine (C)

A nitrogenous base that pairs with guanine

Denaturation

Loss of protein shape and function due to heat, pH, or chemicals.

Deoxyribose

The sugar found in DNA

Disaccharide

A carbohydrate made of two monosaccharides.

Enzyme

A protein that catalyzes biochemical reactions.

Essential amino acids

Amino acids that must be obtained from the diet.

Fatty acids

Long hydrocarbon chains that make up lipids.

Genetic code

The set of rules by which codons specify amino acids

Glucose

A monosaccharide used as a main energy source

Glycosidic bond

A bond linking monosaccharides

Glycerol

A three-carbon alcohol that forms the backbone of lipids

Guanine (G)

A nitrogenous base that pairs with cytosine

Hemoglobin

A protein in red blood cells that transports oxygen

Histones

Proteins that DNA wraps around to form chromatin

Hydrogen bond

A weak attraction between polar molecules

Insulin

A protein hormone that regulates blood glucose levels

Lipid

A hydrophobic biomolecule including fats, oils, and phospholipids

Monomer

A small building block of a polymer

Monosaccharide

simple sugar

Nittrogen

An element essential for amino acids and nucleotides.

Nitrogenous base

A nitrogen-containing molecule in DNA or RNA.

Nucleic acid

A polymer of nucleotides (DNA or RNA).

Nucleotide

The monomer of nucleic acids; sugar + phosphate + base.

Organic molecule

A molecule containing carbon and hydrogen

peptide bond

A bond between amino acids.

Phosphodiester bond

The bond linking nucleotides in DNA/RNA

Phospholipid

A lipid with a phosphate head and fatty acid tails; forms membranes.

Polar/non-polar

Polar molecules have uneven charge; non-polar do not.

polymer

A large molecule made of repeating monomers.

Primary structure

The amino acid sequence of a protein.

Quaternary structure

Interaction between multiple polypeptide chains.

R group/side chain

The variable part of an amino acid.

rRNA

Ribosomal RNA; forms ribosomes.

Secondary structure

Protein folding into alpha helices or beta sheets.

Substrate

The molecule an enzyme acts upon.

Sulphur

An element found in some amino acids (e.g., cysteine).

Tertiary structure

The 3D shape of a single polypeptide.

thymine (T0

Transfer RNA; carries amino acids to the ribosome.

Uracil (U)

An RNA base that replaces thymine.

Active transport

Movement of molecules against a concentration gradient using energy.

Aquaporins

Channel proteins that allow water to move across membranes.

Assembly (viral)

Formation of new virus particles inside a host cell.

Bacteriophage

A virus that infects bacteria.

Capsid

The protein coat of a virus.

Cell membrane

Semi-permeable barrier surrounding the cell

Cell wall

A rigid outer layer providing support.

Central dogma

DNA → RNA → Protein.

Channel protein

A membrane protein that allows substances to pass through.

Chloroplast

Organelle where photosynthesis occurs.

Chromatin

DNA and proteins packaged in the nucleus.

Concentration gradient

Difference in solute concentration across space.

Diffusion

Movement of molecules from high to low concentration.

DNA

Deoxyribonucleic acid; stores genetic information.

Double helix

The twisted ladder shape of DNA.

Double membrane

Two lipid bilayers surrounding an organelle.

Endocytosis

Movement of materials into the cell via vesicles

Endoplasmic reticulum (rough/smooth)

Rough ER makes proteins; smooth ER makes lipids.

Equilibrium

Equal concentration of substances.

Eukaryotic cell

A cell with a nucleus and organelles.

Exocytosis

Release of materials from the cell

Facilitated diffusion

Passive transport using membrane proteins.

Fluid mosaic model

Describes membrane structure as flexible with embedded proteins.

Gene expression

The process of making proteins from genes.

Genome

An organism’s complete set of DNA.

Golgi apparatus

Modifies and packages proteins.

Hydrophobic/ Hydrophilic

Water-repelling./ water attracting

Hypertonic

Higher solute concentration outside the cell.

Hypotonic

Lower solute concentration outside the cell.

Isotonic

Equal solute concentration.

Lysosome

Organelle that digests waste.

Matrix

The inner fluid of mitochondria.

mRNA

Messenger RNA, carries instructions from DNA.

Nucleolus

Produces ribosomes.

Osmosis

Diffusion of water across a membrane.

Passive transport

Movement without energy.

Plasma membrane

Another name for the cell membrane.

Replication

Copying of DNA.

Release (viral)

Viruses exiting the host cell.

Reticulum

A network (as in ER).

Ribosome

Site of protein synthesis.

RNA

Ribonucleic acid; involved in protein synthesis.

RNA polymerase

Enzyme that synthesizes RNA.

Simple diffusion

Movement without proteins or energy.