Edexcel A Level Biology Unit 1 Notes: Topic 1-2 Vocabulary

A comprehensive set of vocabulary-style flashcards covering key concepts from water chemistry, organic molecules, cell membranes, enzymes, genetics, and cardiovascular health as presented in the notes.

Water molecule

A polar molecule with a slightly negative oxygen and slightly positive hydrogen atoms, leading to dipole character and hydrogen bonding.

Dipolar

Molecules with two poles of charge (slightly negative and slightly positive regions) causing polar interactions.

Hydrogen bond

A relatively weak attraction between a partially negative atom (like O) and a partially positive atom (like H) in nearby molecules.

Amphoteric

A substance that can act as both an acid and a base.

Solvent

A substance (often water) capable of dissolving solutes, especially ionic compounds.

Colloid

A mixture with very small particles dispersed throughout another substance that do not settle.

Emulsion

A mixture of tiny droplets of one liquid dispersed in another liquid.

Suspension

A mixture where particles are dispersed in a liquid but will settle unless stirred.

Plasma

The liquid component of blood; a solvent in transport systems.

Cytoplasm

The cell’s cytosol; a solvent within cells involved in transport and chemical reactions.

Organic compound

Compounds that contain carbon; most are found in living organisms.

Tetravalent carbon

Carbon can form four covalent bonds, enabling long chains, rings, and 3D structures.

Monosaccharide

Simple sugars with general formula (CH2O)n; e.g., triose, pentose, hexose.

Glucose

A hexose monosaccharide (C6H12O6) that is a key energy source.

Fructose

A hexose monosaccharide found in fruits; sweetest natural sugar.

Galactose

A hexose monosaccharide found in milk alongside glucose.

Ribose

A five-carbon sugar found in RNA.

Deoxyribose

A five-carbon sugar lacking an oxygen-atom on C2, found in DNA.

Glycosidic bond

Covalent bond formed between two monosaccharides via a condensation reaction.

Condensation reaction

Joining of two molecules with the elimination of water (water is produced).

Hydrolysis

A reaction that breaks a bond by adding water; reverse of condensation.

Disaccharides

Two monosaccharides linked by a glycosidic bond; examples include sucrose, maltose, lactose.

Glycosidic bond (example)

A covalent bond joining two monosaccharides in disaccharides.

Sucrose

Disaccharide formed from glucose + fructose; common in plants.

Maltose

Disaccharide formed from glucose + glucose; found in germinating seeds.

Lactose

Disaccharide formed from glucose + galactose; main sugar in milk.

Amylose

Unbranched component of starch, a polymer of glucose with 1→4 linkages.

Amylopectin

Branched component of starch with 1→4 and 1→6 glycosidic bonds.

Starch

Plant energy storage carbohydrate composed of amylose and amylopectin.

Glycogen

Animal energy storage carbohydrate; highly branched polymer of glucose.

Cellulose

Structural carbohydrate in plants; polymer of glucose with mainly 1→4 linkages.

Lipids

Organic molecules including fats and oils; hydrophobic or amphipathic components.

Fatty acids

Long hydrocarbon chains with a carboxyl group; can be saturated or unsaturated.

Glycerol

Three-carbon alcohol that forms triglycerides with fatty acids.

Triglyceride

Glycerol esterified to three fatty acids; major form of stored energy.

Saturated fatty acid

Fatty acid with only single C–C bonds; typically solid at room temperature.

Unsaturated fatty acid

Fatty acid with one or more C=C double bonds; usually liquid at room temperature.

Esterification

Condensation forming ester bonds between glycerol and fatty acids.

Phospholipid

Lipid with two fatty acid tails and a phosphate-containing head; glycerol backbone.

Amphipathic

Molecule having both hydrophilic (water-loving) and hydrophobic (water-hating) parts.

Bilayer

Phospholipid arrangement in which hydrophobic tails face inward and heads face water.

Fluid mosaic model

Current model of the cell membrane: a phospholipid bilayer with embedded proteins.

Integral protein

Membrane protein embedded within the lipid bilayer.

Peripheral protein

Membrane protein attached to the surface of the lipid bilayer.

Glycoprotein

Protein with carbohydrate groups; involved in cell recognition and signaling.

Active site

The region of an enzyme where the substrate binds to catalyse a reaction.

Lock-and-key hypothesis

Enzyme-substrate model where shapes fit exactly without changing shape.

Induced-fit hypothesis

Enzyme alters its active site to accommodate the substrate upon binding.

Activation energy

Energy barrier that must be overcome for a reaction to proceed.

Enzyme

Biological catalyst, usually a protein, that speeds up specific biochemical reactions.

Substrate

The molecule(s) that bind to an enzyme’s active site and are transformed.

Amino acid

Monomer of proteins; contains an amino group, a carboxyl group, and an R group.

Zwitterion

A molecule that has both positive and negative charges (amino acids in solution).

Peptide bond

Covalent bond formed between carboxyl and amino groups of two amino acids.

Primary structure

Linear sequence of amino acids in a protein.

Secondary structure

Folding patterns (alpha-helix, beta-pleated sheets) due to hydrogen bonds.

Tertiary structure

Overall 3D shape of a single polypeptide driven by various bonds.

Quaternary structure

Arrangement of multiple polypeptide chains into a functional protein.

Fibrous protein

Proteins with long, thin chains forming fibres; often structural (e.g., collagen).

Globular protein

Compact, roughly spherical proteins (often enzymes or hormones).

Enzyme specificity

Enzymes catalyse only particular reactions or substrates.

Nucleic acids

DNA and RNA; store and transfer genetic information.

Nucleotide

Monomer of nucleic acids; consists of sugar, a phosphate, and a base.

Purine

Two-ring nitrogenous bases (adenine, guanine).

Pyrimidine

One-ring nitrogenous bases (cytosine, thymine, uracil).

DNA

Double-stranded molecule with deoxyribose, bases A, T, C, G; held by hydrogen bonds in a double helix.

RNA

Single-stranded nucleic acid with ribose sugar; bases A, U, C, G.

Phosphodiester bond

Covalent bond linking adjacent nucleotides in a nucleic acid strand.

DNA replication

Semi-conservative process where each new DNA molecule contains one old and one new strand.

DNA helicase

Enzyme that unwinds the DNA double helix during replication.

DNA polymerase

Enzyme that adds new nucleotides to a growing DNA strand.

DNA ligase

Enzyme that joins Okazaki fragments on the lagging strand during replication.

Antiparallel

Two DNA strands run in opposite directions (5' to 3' and 3' to 5').

Codon

A sequence of three DNA or RNA bases that codes for a specific amino acid.

Start codon

Codon that signals the start of translation (AUG in RNA; TAC in DNA).

Stop codon

Codon that signals termination of translation (e.g., UAA, UAG, UGA in RNA).

Transcription

Process by which DNA is copied into mRNA.

Translation

Process by which the genetic code carried by mRNA is used to assemble a protein at ribosomes.

mRNA

Messenger RNA; carries genetic information from DNA to ribosomes for protein synthesis.

tRNA

Transfer RNA; brings specific amino acids to the ribosome during translation.

Ribosome

Ribosomal RNA and proteins; site of protein synthesis.

Mutation

A rare, random change in DNA that can alter the amino acid sequence of a protein.

Point mutation

Mutation affecting a single nucleotide pair.

Chromosomal mutation

Large-scale DNA change affecting chromosome structure or number.

Allele

Different versions of a gene.

Genotype

Genetic makeup of an individual; the combination of alleles.

Phenotype

Observable traits resulting from the genotype and environment.

Dominant

Allele that can mask the presence of a recessive allele in the phenotype.

Recessive

Allele that is masked by a dominant allele in the phenotype.

Homozygote

Individual with two identical alleles for a gene.

Heterozygote

Individual with two different alleles for a gene.

Monohybrid cross

Cross examining the inheritance of a single gene.

Thalassemia

Inherited blood disorder affecting haemoglobin chains; can be recessive.

Albinism

Recessive genetic condition causing lack of melanin pigment.

Pedigree diagram

Family tree showing inheritance patterns of traits or diseases.

Cystic fibrosis (CFTR)

Genetic disorder caused by faulty CFTR chloride channel; thick mucus in lungs and digestive problems.

Gene therapy

Treatment introducing a healthy gene to correct a genetic disorder; can be somatic or germline.

Amniocentesis

Prenatal test removing amniotic fluid to analyze fetal cells for genetic disorders.

Chorionic villus sampling

Prenatal test sampling placental tissue to detect genetic disorders earlier than amniocentesis.

Preimplantation genetic diagnosis (PGD/PGD2)

Genetic testing of embryos created by IVF before implantation.