wk1: cytoplasm & organelles

What is DNA

A pair of nucleotide chains (double helix): stores genetic instructions.

What is mRNA (messenger RNA)

Single chain of nucleotides containing instructions required to make a protein.

What is tRNA (transfer RNA)

RNA that decodes mRNA by delivering amino acids to the ribosome during protein synthesis.

What is rRNA (ribosomal RNA)

RNA that constitutes ribosomes (site of protein synthesis)

Nucleus

Stores genetic information.

Nucleolus

Makes ribosomes.

Ribosome

protein synthesis

Rough Endoplasmic Reticulum (RER)

Folding/assembly of proteins.

Smooth Endoplasmic Reticulum (SER)

Lipid and steroid synthesis; detoxification of drugs.

Golgi Apparatus

Modifies, sorts, and transports proteins.

Mitochondria

Produces energy (ATP).

Peroxisome

Regulates biochemical pathways involving oxidation.

Lysosome

Removes unwanted materials from the cell.

Vacuole

Stores water and nutrients.

Vesicle

Transport of materials.

Cytoskeleton

Provides structure, support, and transport within the cell.

Red blood cells structure:

Biconcave, no nucleus, flexible — maximises surface area and haemoglobin space for oxygen transport

Muscle cells structure:

Long, cylindrical, multinucleated with many mitochondria and myofibrils — built for repeated powerful contraction

Neuron cell structure:

Long axon, many dendrites, myelin sheath — designed for rapid long distance electrical signal transmission

Goblet cell structure?

Cup shaped, packed with secretory vesicles — designed to store and rapidly release mucus for lubrication and protection

Sperm cell structure?

Streamlined with flagellum — built to swim to and penetrate an egg

Adipocyte cell structure?

Large central lipid droplet pushing nucleus to the edge — maximises fat storage capacity for energy, insulation and cushioning

How many cells do humans have?

~30 trillian cells and ~200 different types

Centrioles

Support the spatial arrangement of the cell: they are cylindrical structures composed of cytoskeletal microtubules. 2 centrioles at right angles = 1 centrosome

Mitotic Spindle =

a structure formed during cell division that separates chromosomes into daughter cells. It is composed of spindle fibres and microtubules.

Order of proliferation

Fertilised zygote (totipotent) → blastocyst (pluripotent) → ectoderm/mesoderm/endoderm (multipotent) → differentiated cells (unipotent).

Ectoderm (multipotent - outer) →

Neuron or Epithelial cell

Mesoderm (multipotent - middle) →

Red blood cells or Cardiomyocytes

Endoderm (multipotent- inner) →

Liver cells or pancreas cells

What are the structural components of the nucleus?

Nuclear envelope, nuclear pores, nucleolus, chromatin, chromosomes, histone proteins, and nuclear matrix/nucleoplasm.

Nuclear envelope =

double membrane that encloses the nucleus (protective barrier)

Nuclear pores =

Passages that allow communication between the nucleus and cytoplasm

Nucleolus =

responsible for ribosome synthesis and assembly

Chromatin =

Heterochromatic (inactive, highly condense) or Euchromatin (active, dispersed)

Chromosome =

Formed when chromatin condenses during cell division.

Histone protein =

a type of protein that helps package and stabilise DNA into chromatin

Nucleoplasm =

The viscous fluid within the nucleus, where the chromatin and nucleolus are suspended.

Cytosol

Watery intracellular fluid surrounding the nucleus.

Organelles

specialised structures within a cell that carry out a specific function

Cytoplasm

Collective cytosol and intracellular organelles.

Cytoskeleton structure and function?

Protein framework (filaments or slender tubes) throughout the cell. Supports membrane, aids shape, supports the positioning and movement of organelles and enables cell movement.

Microtubule

Composed of hollow tubulin tubes; resists compression, aids movement of organelles, and is involved in cell division.

Microfilament

Composed of actin, faciliates cell movement and changes in cell shape, involved in muscle contraction and cell division.

Intermediate Filament

Varied protein composition; aids movement of materials through cytoplasm, and anchors organelles in place.

What is the structure and function of DNA?

DNA is a double helix of nucleotides that carries genetic information essential for growth, development, and reproduction, serving as the blueprint for protein

What is the structure and function of RNA?

RNA is a single-stranded molecule composed of nucleotides, serving as a template for translation and conveying genetic information from DNA.

What is transcription?

DNA uncoils (gene sequence exposed) → enzymes bind and create a single-stranded mRNA copy → mRNA copy is transported into the cytoplasm

What is translation?

In the cytoplasm, mRNA docks onto a ribosome → ribosome reads the mRNA → tRNA brings amino acids → amino acids are linked to form proteins.

What is a codon?

A sequence of three nucleotides on the mRNA strand that specifies a particular amino acid and serves as a stop signal during protein synthesis.

initiation =

mRNA enters cytoplasm and binds to ribosome → start codon is recognised and tRNAs begin delivering AA

elongation =

amino acids link together to form a polypeptide chain (protein)

termination =

When the stop Condon is reached, the polypeptide chain is released from the ribosome

Redundancy =

reduces the chance that a DNA mutation will change the amino acid it codes for as multiple codons can create the same AA