Biology Content (Exam Prep, Full Course)

Protein synthesis

transcription of DNA into mRNA and translation of mRNA into an amino acid sequence at ribosomes

Transcription location

occurs in the nucleus in eukaryotes

Exons

coding segments of DNA in eukaryotic genes

Introns

non‑coding segments of DNA in eukaryotic genes

Transcription of exons and introns

both are transcribed into pre‑mRNA

Translation of exons only

only exons remain after splicing and are translated into a polypeptide

Role of DNA

template for transcription

Role of mRNA

carries the genetic code from nucleus to ribosome

Role of tRNA

carries specific amino acids and matches anticodons to mRNA codons

Role of rRNA

forms ribosomes and catalyses peptide bond formation

DNA codon

triplet of bases on DNA coding strand

RNA codon

triplet of bases on mRNA complementary to DNA template strand

Anticodon

triplet on tRNA complementary to mRNA codon

Relationship between codons and amino acids

each codon specifies a particular amino acid

Coding strand

DNA strand with the same sequence as mRNA (except T→U)

Template strand

DNA strand used by RNA polymerase to build mRNA

DNA directionality

DNA is read and synthesised in the 5’ to 3’ direction

Primary structure

sequence of amino acids

Secondary structure

folding into α‑helices and β‑sheets due to hydrogen bonding

Tertiary structure

3D shape formed by interactions between R‑groups

Quaternary structure

multiple polypeptide chains forming one functional protein

Importance of protein shape

determines protein function and specificity

Induced‑fit model

enzyme changes shape slightly to fit substrate and catalyse reaction

Gene expression control

influenced by transcription factors and environmental conditions

Cellular differentiation

controlled by selective gene expression

Epigenetic changes

heritable changes in gene expression without altering DNA sequence

Epigenetics and phenotype

can cause differences between identical siblings or clones

Mutation

change in DNA sequence

Causes of mutation

errors in replication or cell division

Factors increasing mutation rate

ionising radiation

DNA methylation changes

can silence or activate genes

Cancer definition

Uncontrolled cell division

Germ cell mutation consequences

heritable and affect offspring

Somatic cell mutation consequences

affect only the individual

Inheritable mutations

can change characteristics of descendants

DNA extraction

removal of DNA from cells

PCR

technique to amplify DNA

PCR heating and cooling

denatures DNA then allows primers to bind

PCR primers

short sequences that define the region to be copied

PCR free nucleotides

building blocks for new DNA strands

PCR heat‑resistant enzymes

Taq polymerase synthesises DNA at high temperatures

Electrophoresis

technique separating DNA fragments by size

Electropherogram

graphical output showing DNA fragment sizes or sequences

DNA sequencing

determining the base order of DNA

DNA profiling

identifying individuals by unique DNA patterns

Use of DNA profiling

forensic identification and biological relationships

Ethical issues of genetic information

privacy

Plasmids and viruses as vectors

used to transfer genes into cells

Bacterial enzymes

used to cut and modify DNA

Yeasts

used for gene expression and protein production

Gene selection using probes

probes bind to complementary DNA sequences

Restriction enzymes

cut DNA at specific sequences

Gene transfer between species

inserting foreign genes into another organism

CRISPR‑Cas9

tool for precise gene editing or gene transfer

Protein design

creating new proteins for industrial or medical use

Plant cell structure

has cell wall

Animal cell structure

lacks cell wall and chloroplasts

Fungal cell structure

cell wall made of chitin

Autotrophs

produce their own food

Heterotrophs

consume organic matter

Nucleus

stores DNA and controls cell activities

Nucleolus

produces ribosomal RNA

Mitochondrion

site of aerobic respiration

Chloroplast

site of photosynthesis

Vacuole/vesicle

storage and transport of materials

Golgi body

modifies and packages proteins into vesicles

Rough ER

synthesises proteins

Smooth ER

synthesises lipids and detoxifies chemicals

Ribosome

site of protein synthesis

Lysosome

contains digestive enzymes

Cytoskeleton

provides structure and movement

Photosynthesis

converts light energy to chemical energy

Aerobic respiration

releases energy by breaking down glucose with oxygen

Fermentation in plants/yeast

produces ethanol and CO₂

Fermentation in animals

produces lactic acid

Energy comparison between aerobic respiration and fermentation

aerobic respiration releases more energy than fermentation

ATP formation

ADP + Pi forms ATP using energy

ATP conversion

ATP → ADP + Pi releases energy for metabolism

Intermediate compounds

formed between steps

Reason DNA doubles

ensures each daughter cell receives full genetic information

Binary fission

division in prokaryotes producing identical cells

Mitosis phases

prophase

Products of mitosis

two identical diploid cells

Diploid cells (homologous chromosomes?)

contain homologous chromosome pairs

Haploid cells

contain one chromosome from each pair

Meiosis

produces haploid gametes

Reason meiosis produces haploid cells

halves chromosome number for fertilisation

Crossing over

exchange of DNA between homologous chromosomes

Independent assortment

random separation of chromosomes

Fertilisation

restores diploid number

Mitosis vs meiosis

mitosis produces identical cells

Asexual vs sexual reproduction variation

asexual low variation

Cell cycle stages

G1

Hormones regulating division

hormones can stimulate or inhibit cell cycle

Carcinogens

cause mutations that disrupt cell cycle regulation

Sensory neurons

carry signals from receptors to CNS

Interneurons

process information within CNS

Motor neurons

carry signals from CNS to effectors

Nerve pathway

receptor → sensory neuron → CNS → motor neuron → effector

Synapses

junctions where neurotransmitters transmit signals