QMUL BMD116 NOTES W3

116A WEEK 3 - Cell Organelles

Learning outcomes:
1. Describe the organelles found inside a cell and their function
2. Describe how cells vary in size, shape and organelles according to
their function
3. Appreciate differences between Prokaryotic and eukaryotic
organisms

Prokaryotes
- Single celled
- Adapted to diverse environments
- Variety of growth conditions (aerobic/anaerobic/photosynthetic)
- Minimal internal organisation (no nucleus etc)
- Circular DNA molecule (nucleoid)
- No histones to protect DNA
- Divide by fission
- Are predominantly unicellular
o Archaea are predominantly unicellular
o Some bacteria like pseudomonas are usually unicellular but
they can clump together
o Multicellular bacteria like myxobacteria which forms colonies




Eukaryotes
- Larger than prokaryotes (5-100um)
- Organelles
- DNA is in chromosomes, protected by histones
- Divide by mitosis or meiosis
- Unicellular (yeast) or multicellular (fungi, plant, etc)


What is an organelle?

, Cytoplasm and the Cytosol
- Cytoplasm is the substance between a cell's membrane (its outside
layer) and its nucleus (its core). Cytosol is the fluid part of
cytoplasm. Cytoplasm also consists of organelles and other parts,
which float in the cytosol




Cytoplasm
- Remove the plasma membrane
- Cytosol + organelles (not nucleus)
- Inside the prokaryote

Cytosol
- Remove the plasma membrane
and all organelles
- Largest single compartment
- Aqueous
- Site of chemical reactions
- Site of protein synthesis

Cytoskeleton = protein filaments
(actin, microtubules, intermediate
filaments). Retains rigidity and
strength of the cell


Nucleus - electron microscope (EM) image