Unit 1, Topic 2

Allosteric enzymes

enzymes that change conformation in response to a modulator

Alpha helix

polypeptide chain coiled into a helix with hydrogen bonding occurring to maintain the arrangement

Alternative RNA splicing

removal of non-coding introns from a primary mRNA transcript to leave only the coding exons; several different mature transcripts can be produced from a single primary transcript

Beta-pleated sheets

polypeptide chain arranged in rows with the chain folding in parallel or anti-parallel arrangements

Conformation

structural arrangement of the polypeptide chains within a protein; it can be altered by factors such as pH and the binding of ligands and modulators

Co-operativity

changes in binding of a target molecule to one subunit of a multiunit polypeptide changes the affinity of the other subunits for the target molecule

Disulfide bridge

a strong covalent bond that stabilises the tertiary and quaternary structures of many proteins

Endoplasmic reticulum (ER)

a network of membrane tubules within the cytoplasm of a eukaryotic cell, continuous with the nuclear membrane

Exon

section of RNA that is usually retained during splicing

Glycoprotein

a protein with a carbohydrate added by post

Golgi apparatus

a series of flattened membrane discs that packages proteins into membrane

Hydrogen bonds

attractions between polar molecules in which hydrogen is bound to a larger atom, such as oxygen or nitrogen

Hydrolases

a class of enzyme that use water to break chemical bonds

Intron

a section of RNA usually removed during splicing

lonic bonds

a type of chemical bonding that involves the electrostatic attraction between oppositely charged ions

Ligand

a substance that can bind to a protein! the protein has a shape complementary to the ligand to allow binding

London dispersion force

a temporary, weak attraction between atoms and molecules

Lysosome

a modified Golgi vesicle containing hydrolytic enzymes

Modulators

these bind to a secondary site on an enzyme to alter its conformation; positive modulators activate enzymes and negative modulators deactivate them

Monomer

a molecule that can bind chemically to other monomers to form a polymer

Non-coding RNA gene

a gene that codes for RNAs other than messenger RNA, so do not encode protein

Phospholipid

component of cell membranes

Polymer

a macromolecule composed of many repeated subunits (monomers)

Post-translational modification

chemical modification of proteins as they move through the Golgi

Prosthetic group

a non-protein unit tightly bound to a protein and necessary for its function

Protein kinases

catalyse the transfer of a phosphate group from a donor molecule (usually ATP) to an acceptor

Protein phosphatases

an enzyme that removes a phosphate group from its substrate

Protein structure

different levels of arrangement of polypeptides within a protein

Primary structure

sequence in which amino acids are found within a protein

Secondary structure

hydrogen bonding occurring within a polypeptide forming alpha helices or beta-pleated sheets

Tertiary structure

bonding of many types occurring between the R groups of amino acids within a protein

Quaternary structure

the arrangement of multiple folded polypeptides connected together

Proteolytic cleavage

a major form of post-translational modification! it occurs when a protease cleaves one or more bonds in a target protein to activate, inhibit or destroy the protein's activity

Proteome

the entire set of proteins expressed by a genome; it is much larger than the genome R groups

Basic R group

contains an amine functional group and produces a basic solution because the extra amine group is not neutralised by the acidic group

Acidic R group

contains an acidic functional group and produces an acidic solution because the extra acid group is not neutralised by the amine group

Polar R group

group that prefers to exist in a watery environment

Hydrophobic R group

composed mostly of carbon and hydrogen, and tend to be repelled from water

Rough endoplasmic reticulum (RER)

organelle made up of membranes with ribosomes attached

Signal sequence

a short stretch of amino acids at one end of the polypeptide that determines its eventual location in a cell

Smooth endoplasmic reticulum (SER)

a membranous organelle found in most eukaryotic cells; its main functions are the synthesis of lipids and steroid hormones

Turns

secondary structure that reverses the direction of a polypeptide chain

Vesicles

small membrane-bound compartments filled with liquid