Cell Organelles - Nucleus
- Only a few eukaryotes without nucleus; RBC's, phloem, etc.
- Contains chromosomes - form tangle known as chromatin.
- DNA carries code that instrucs cells about making proteins.
Nuclear Envelope - pair of membranes with gaps inbetween - gaps in envelope are nuclear pores.
Nucleolus - contains DNA being used to make ribsomes.
Cell Organelles - Endoplasmic Reticulum
Smooth Endoplasmic Reticulum -
- no ribosomes
- not joined to nuclear envelope
Rough Endoplasmic Reticulum -
- coverered in ribsomes
- usually joined to nuclear envelope
Cisternae - enclosed spaces formed by membranes.
Cell Organelles - Golgi Apparatus
Golgi Apparatus -
- Not stable, always moving and changing.
- Sacs join and break away all the time.
- Used in protein synthesis.
Protein Synthesis Overview -
- Protein made by ribosomes of RER.
- Vesicles carry protein and join to Golgi.
- Protein modified in Golgi, e.g. sugars added.
- Vesicles carry modified proteins.
- Secretion from cell by exocytosis.
Cell Organelles - Lysosomes
- Tiny bags of digestive enzymes.
- 0.5 micrometre diameter.
- Used for digestion - by fusion with bacteria, old/worn out organelles etc.
- Enzymes in lysosome break down large molecules into soluble substances.
- Substances disperse into the cytoplasm.
Cell Organelles - Mitochondia
- Site of aerobic respiration.
- ATP made in them.
- Lots of mitochondria in places where lots of energy is needed, e.g. muscle cells.
- Each cell makes its' own ATP as it has to provide own energy.
- Double membrane - inner membrane folded to form cristae.
- Matrix is background material.
Cell Organelles - Plasma (Cell Surface) Membrane
Plasma (Cell Surface) Membrane -
- Thin layer of phospholipid molecules.
- Hydrophobic tails (water-hating).
- Hydrophilic heads (water-loving).
- Tails closest together, heads on outside.
Cell Organelles - Centrioles
- Make and organise microtubules made of tubulin.
- Microtubules form spindle to move chromosomes in cell division.
Cell Organelles - Cytoskeleton
- Network of microfilaments.
- Gives cell mechanical strength.
- Provides 'tracks' for organelles to move along.
- ATP needed, because energy needed to pull organelles.
- Can help whole cell to move.
Prokaryotic Cells -
- Always contain -
- Circular DNA (no nucleus) - sometimes referred to as chromosome.
- Peptidoglycan cell wall - crosslinked peptidoglycan.
- ~20nm ribsomes - smaller than eukaryotic ribsomes.
- Plasma membrane.
- Sometimes contain -
- Pili - attachment to other cells or surfaces.
- Plasmid of DNA - several may be present.
- Capsule - additional protection.
- Mesosome - associated with DNA during cell division.
- Infolded plasma membrane - photosynthetic membrane.
- Flagellum - movement of cell.
- 1400 x mag.
- Use glass lenses to refract light rays.
- Living specimens.
- Unable to show objects smaller than 200nm across.
- TEM - pass electrons through thin specimen.
- Very thin specimens, and stained.
- 300,000 x mag.
- Much finer detail - better resolution.
- Dead specimens.
MAGNIFICATION = IMAGE SIZE / ACTUAL SIZE