IB BIOLOGY Y1

Hydrogen bond

Weak electrostatic attraction between δ⁺ hydrogen and δ⁻ oxygen/nitrogen; gives water cohesion, high boiling point, and solvent ability.

Hydrophilic

Polar or charged substances that form hydrogen bonds with water and dissolve in it.

Hydrophobic

Nonpolar substances that cannot hydrogen bond with water and aggregate to minimize contact.

Adhesion

Attraction between water and other polar surfaces, enabling capillary action.

Cohesion

Attraction between water molecules via hydrogen bonds, creating surface tension.

Solvent

Liquid that dissolves solutes; water dissolves ionic/polar substances due to polarity.

Solute

Substance dissolved in a solvent.

Buoyancy

Upward force from fluid allowing objects/organisms to float.

Thermal conductivity

Ability of water to transfer heat energy.

Specific heat capacity

Energy required to raise temperature; high in water due to hydrogen bonds stabilizing temperature.

Viscosity

Resistance of a fluid to flow.

Condensation reaction

Formation of covalent bond between monomers with removal of water.

Hydrolysis reaction

Breaking of covalent bond using water to split polymers.

Glycosidic bond

Covalent bond linking monosaccharides in carbohydrates.

Monosaccharide

 Single sugar unit used in respiration (e.g. glucose).

Disaccharide

Two monosaccharides joined for transport/storage.

Polysaccharide

Polymer of sugars used for storage or structure.

Starch

Plant storage polysaccharide (amylose + amylopectin).

Cellulose

Structural polysaccharide with β-glucose forming strong plant cell walls.

Glycogen

Highly branched glucose storage polymer in animals.

Glycoprotein

Protein with carbohydrate chains used in cell recognition.

Antibody

Protein that specifically binds antigens.

Antigen

Foreign molecule triggering immune response.

ABO blood system

Classification based on A/B antigens on red blood cells.

Triglyceride

Lipid with 1 glycerol + 3 fatty acids for energy storage.

Phospholipid

Amphipathic lipid forming bilayers in membranes (hydrophilic head)

Steroid

 Lipid with four fused rings functioning as hormones or membrane components.

Saturated fatty acid

 No double bonds; straight chains pack tightly.

Unsaturated fatty acid

One or more double bonds; kinked, increases fluidity.

Oestradiol

Estrogen steroid hormone regulating female reproductive system.

Testosterone

Steroid hormone controlling male reproductive development.

Nucleic acid

Polymer storing genetic information (DNA or RNA).

Genetic code

Set of rules mapping codons to amino acids.

DNA

 Double-stranded helix storing genetic information via complementary base pairing.

RNA

Single-stranded molecule involved in protein synthesis.

Nucleotide

monomer of nucleic acids (phosphate + sugar + base).

Adenine

Purine base pairing with thymine (DNA) or uracil (RNA).

Uracil

Pyrimidine base in RNA replacing thymine.

Pentose

Five-carbon sugar (ribose or deoxyribose).

Pyrimidine

Single-ring base (C, T, U).

Polynucleotide

Chain of nucleotides linked by phosphodiester bonds.

Codon

Three-base sequence coding for an amino acid.

mRNA

Messenger RNA carrying genetic code from DNA to ribosome

tRNA

transfer RNA delivering amino acids via anticodon pairing.

rRNA

Ribosomal RNA forming ribosome and catalyzing peptide bonds.

Phosphodiester bond

Covalent bond linking nucleotides in backbone.

Gene

DNA sequence coding for a functional product.

Allele

 Variant form of a gene.

Chromosome

DNA packaged with proteins into a condensed structure.

Locus

Position of a gene on a chromosome.

Homologous chromosomes

Pair of chromosomes with same genes but different alleles.

Genome

Complete genetic material of an organism.

Mutation

Change in DNA sequence.

Nucleosome

DNA wrapped around histone proteins.

Histone

Protein aiding DNA packaging and gene regulation.

Non-histone chromosomal protein

 Proteins involved in gene regulation and chromosome structure.

Bacteriophage

Virus that infects bacteria.

Amino acid

Monomer with amino group, carboxyl group, and variable R group

Amino group

Functional group (−NH₂) giving basic properties.

Alpha carbon

Central carbon bonded to amino group, carboxyl group, hydrogen, and R group.

Carboxyl group

 Functional group (−COOH) giving acidic properties.

R group

Variable side chain determining amino acid properties

Peptide bond

 Covalent bond linking amino acids via condensation

Tripeptide

Chain of three amino acids.

Essential amino acids

Must be obtained from diet.

Non-essential amino acid

Synthesized by the body.

Denaturation

Loss of protein structure due to heat/pH disrupting bonds.

Primary structure

Amino acid sequence.

Secondary structure

α-helices and β-sheets via hydrogen bonding.

Tertiary structure

3D folding due to R-group interactions.

Quaternary structure

Multiple polypeptide chains combined

Integral protein

Embedded in membrane bilayer.

Conjugated protein

Protein with non-protein prosthetic group.

Non-conjugated protein

Protein composed only of amino acids.

Insulin

Hormone regulating blood glucose.

Hemoglobin

Oxygen-transport protein in red blood cells.

Collagen

Structural protein providing tensile strength.

Transcription

Synthesis of mRNA from DNA template.

RNA polymerase

 Enzyme that builds RNA from DNA template.

Coding strand

DNA strand matching mRNA sequence (5’→3’).

Template strand

DNA strand used to synthesize mRNA (3’→5’).

Gene expression

Process of producing proteins from genes.

Translation

Protein synthesis at ribosome using mRNA.

Anticodon

tRNA base triplet complementary to codon.

Degenerate code

Multiple codons code for same amino acid.

Point mutation

 Single base change in DNA.

Promoter

DNA region where transcription starts.

Telomere

Repetitive DNA protecting chromosome ends.

Post-transcriptional modification

mRNA processing after transcription.

Splicing

 Removal of introns from mRNA.

Alternative splicing

Different mRNAs produced from same gene.

5’ cap

Modified nucleotide protecting mRNA and aiding translation.

3’ poly-A tail

Adenine chain stabilizing mRNA.

A site

Ribosome site where tRNA enters.

P site

Ribosome site holding growing polypeptide.

E site

Ribosome site where tRNA exits.

Post-translational modification

Chemical changes to proteins after synthesis.

Proteolysis

Breakdown of proteins into smaller peptides.

Proteasome

Complex degrading unwanted proteins

Gene mutation

Permanent change in DNA sequence.