Lecture 3: Cellular organisation II – Protein Synthesis and Mitosis (EPBIOL259)

Proteins

Polymers of amino acids joined by peptide bonds, essential for virtually all cellular functions.

Amino Acids

The building blocks of proteins, with a general structure of H\text{_2N-CH(R)-COOH}, where R is the side chain.

Peptide Bond

The bond formed between two amino acids, releasing water in a condensation reaction, to form a dipeptide or polypeptide.

Enzymes

Proteins that function as biological catalysts in metabolic pathways.

Receptor (Membrane Protein)

Proteins that bind chemical messengers like hormones on the cell surface.

Nucleic Acids

Organic polymers that carry genetic information and are essential for protein synthesis; includes DNA and RNA.

DNA (deoxyribonucleic acid)

A double helix nucleic acid residing in the nucleus, containing genes and a sugar-phosphate backbone.

RNA (ribonucleic acid)

A single-stranded nucleic acid that carries out orders from DNA, containing ribose sugar and uracil.

Transcription

The process of copying a gene's code from DNA into a complementary mRNA strand.

Translation

The process where mRNA is read by ribosomes to assemble an amino acid sequence into a protein.

Codons

Three-nucleotide units on mRNA that specify specific amino acids or STOP signals.

Ribosomes

Molecular machines that read mRNA and assemble amino acids into polypeptides during translation.

Anticodon

A three-nucleotide sequence on tRNA that is complementary to a codon on mRNA, ensuring correct amino acid delivery.

G1 Phase (First Gap Phase)

The interval between cell division and DNA replication, involving protein synthesis, cell growth, and centriole replication.

S Phase (Synthesis Phase)

The phase during which DNA replication occurs, forming two identical DNA strands.

G2 Phase (Second Gap Phase)

A brief interval between DNA replication and cell division, where centriole replication completes and enzymes for cell division are synthesized.

Mitosis

The process of nuclear division in somatic cells, consisting of Prophase, Metaphase, Anaphase, and Telophase, resulting in two genetically identical daughter cells.

Cytokinesis

The division of the cytoplasm that overlaps with telophase and completes cell division.

Prophase

The first stage of mitosis where chromosomes condense, the nuclear envelope breaks down, and spindle fibers form.

Metaphase

The stage of mitosis where chromosomes align along the cell's equator.

Anaphase

The stage of mitosis where centromeres split, and sister chromatids are pulled to opposite poles of the cell.

Telophase

The final stage of mitosis where chromatids arrive at poles, new nuclear envelopes form, and chromatin decondenses.

Chromosome

Tightly condensed structures of chromatin, each consisting of two sister chromatids joined at the centromere before cell division.

Chromatid

One of two identical copies of a chromosome, joined at the centromere, that separate during anaphase of mitosis.

Centromere

The constricted region where two sister chromatids are joined.