cell structure

• production + secretion of proteins (pt. 1)

  1. nucleus stores the DNA which codes for the production of proteins and the nucleolus which manufactures ribosomes required for protein synthesis - DNA is copied into a molecule of mRNA via transcription
  2. the mRNA strand moves out through a nuclear pore and attatches to a ribosome on the RER
  3. the ribosome 'reads' the genetic instructions contained within the mRNA and uses it to synthesise a protein via translation
• production + secretion of proteins (pt. 2)

  1. processed proteins are then transported to the golgi apparatus in vesicles, which then fuse with the golgi apparatus, releasing proteins
  2. the golgi apparatus modifies the proteins, preparing them for secretion - the modified proteins then leave in vesicles
  3. the vesicles containing the final proteins fuse with the cell plasma membrane, releasing the proteins
• cytoskeleton - contains microtubules and microfilaments


  importance:

  • strengthening + support

  ↳ provides cell with mechanical strength helping to maintain shape of

  cell and supports organelles, keeping them in position

  • intracellular movement

  ↳ cytoskeleton aids transport by forming tracks by which organelles

  can travel along

  • cellular movement

  ↳ enables movement via flagella + cillia which contain microtubules

  that are responsible for moving them
• nucleus

  ↳ largest organelle within an animal cell

  • contains genetic info in chromosomes
  • surrounded by a nuclear envelope that contains pores
• nucleus functions

  • controls the cells activities - DNA contains instructions for protein synthesis
  • synthesis of ribosomes - nucleolus makes ribosome RNA
  • exchange between cytoplasm - substances can enter/leave nucleus vis nuclear pores
• cell plasma membrane

  ↳ made of phospholipid bilayer and proteins
• cell plasma membrane functions

  • controls movement of substances - partially permeable
  • cell signalling: receptors can detect signals from other cells
  • isolates cytoplasm from extracellular environment
• prokaryote ⍟ e.g bacteria


  • single celled organism without a nucleus
  • no membrane bound organelles
• eukaryote ⍟ e.g muscle fibres


  • have membranes around their organelles
  • often have specific functions
• microfilaments


  • solid strands mostly made of the protein actin
  • can cause some cell movement and movement of some organelles by moving against each other
• microtubules


  • tubular (hollow) strands made mostly of the protein tubulin
  • organelles and other cell contents are moved along these fibres using ATP to drive the movements
• mitochondria

  • surrounded by double membrane, inner membrane folded to form cristae
  • the liquid known as the matrix, contains mitochondrial DNA, respiratory enzymes, lipids and proteins
• mitochondria function

  • site of aerobic respiration to produce ATP
• ribosomes

  ↳ found in all cells, in cytosol

  • made of rRNA and proteins
  • consists of large subunit - joins amino acids and small subunit - has mRNA binding site
• ribosome function

  • site of translation/protein synthesis
• golgi apparatus

  ↳ planar stack of membrane-bound flattened sacs

  • molecules processed/modified in cisternae
  • vesicles bud off trans face
• golgi apparatus functions

  • processes proteins for export
  • synthesis of glycoproteins
• chloroplasts

  ↳ vesicular plastid with double membrane

  • membrane-bound compartments - thylakoids: flattened discs stacked to form grana, contain photosystems with chlorophyll
  • stroma: fluid filled matrix
• chloroplast function

  • site of photosynthesis to convert solar energy into chemical energy
• lysosome

  ↳ sac surrounded by single membrane, specialist vesicles

  • contain hydrolytic enzymes
• lysosome functions

  • exocytosis of digestive enzymes and other waste materials
  • used in immune system cells
• endoplasmic reticulum

  • cisternae - network of flattened sacs extending from cell membrane and connects to nuclear envelop
• rough er

  • many ribosomes attached to surface for processing of proteins
• smooth er

  • no ribosomes
  • synthesis and storage of lipids
• what are bacterial + fungal cell walls made of?

  bacterial - peptidoglycan (murein)

  fungal - chitin
• plant cell wall

  ↳ made of cellulose microfibrils for mechanical support

  • support and separates adjacent cell walls
• flagella

  ↳ hollow helical tube made of flagellin

  • rotates to propel organism
• cilia

  ↳ hairlike protrusions on eukaryotic cells

  • move back/forth to sweep foreign substance/pathogens away + enable cell to move
• outline how a student could prepare a tissue mount for a light microscope


  1. obtain thin slice of tissue
  2. place tissue in drop of water
  3. stain tissue on slide to make structures visible
  4. add coverslip slowly, at 45° to avoid trapping air bubbles
• describe how light microscopes work

  1. lenses focus rays of light and magnify the view of a thin slice of a specimen
  2. different structures absorb different amounts and wavelengths of light
  3. reflected light is transmitted to the observer via the objective lens and eyepiece
• how does a SEM work


  1. beam of electrons focused onto specimens using electromagnetic lenses
  2. reflected electron hit a collecting device and are amplified to produce an image on a photographic plate
• how does a TEM work

  1. high energy beam of electrons pass through thin slice of specimen
  2. more dense structures appear darker as they absorb more electrons
  3. image focused on photographic plate using magnetic lenses
• how does a laser scanning microscope work


  1. laser beam focused on small area on samples surface using objective lenses
  2. fluorophores in the sample emit photons
  3. photomultiplier tube amplifies the signal onto detector and image is produced pixel by pixel
• why do samples need to be stained?


  • coloured dye binds to structures
  • facilitates absorption of wavelength of light
  • differential staining: contrast between stained areas distinguishes structures
• explain how to use graticule + micrometer

  1. place micrometer on stage to calibrate graticule
  2. line up scales on graticule and micrometer and count how many divisions are in 100 micrometers
  3. length of one graticule division = 100 microm / no. of divisions
  4. use calibrated values to calculate actual length of structures
• centrioles

  • hollow cylinders containing a ring of microtubules
  • involved in cell division