1. THE STUDY OF CELLS - STRUCTURE
CYTOLOGY
THE STUDY OF CELLS - STRUCTURE

2. GENERAL Cell = Smallest Living Unit
Produced by Fertilization or Cell Division
Surrounded by Interstitial / Extracellular Fluid
Components:
Plasma (Cell) Membrane
Cytoplasm
Nucleus

4. THE PLASMA MEMBRANE Structure Phospholipid bilayer
self-orienting, reseals
hydrophilic heads (face outward)
hydrophobic tails (face inward)
Proteins (floating or anchored)
Cholesterol (keeps it “fluid”)
Heads are polar & therefore hydrophilic; tails are non-polar & therefore hydrophobic. Glycolipids & glycoproteins are also present in outer phospholipid layer; they form hydrogen bonds with the surrounding water, helping to stabilize the cell membrane.

5. THE PLASMA MEMBRANE Functions: Physical Barrier (Selective!) Proteins:
Fat-soluble do pass through
Water-soluble don’t
Proteins:
Channels or Carriers (transport)
Enzymes (chemical reactions)
Receptor sites (“docking” of molecules)
Anchors

6. THE PLASMA MEMBRANE
Illustration of cell membrane structure as in Martini Fig 3-2 p.50 or Marieb Fig 3.2 p.63

7. CYTOPLASM Material Between Plasma Membrane & Nucleus Components
Cytosol (fluid with solutes)
Cytoplasmic Organelles
Inclusions (stored materials)
Site of chemical reactions
Inclusions are not membrane-bound, and can’t carry out metabolic functions. Inclusions may be stored nutrients (like glycogen), secretory products, or pigment granules.

8. NUCLEUS Organelle Double Nuclear Membrane with Pores
DNA – Instructions for making proteins
Chromatin - loose; protein synthesis
Chromosomes - dense, rod-like; cell division
Nucleolus
Assembly of ribosomes

9. STRUCTURE OF THE NUCLEUS
Illustration of cell nucleus structure as in Tortora Fig 3.10 p.48 or Marieb Fig 3.21a p.83

10. CYTOPLASMIC ORGANELLES
Mitochondria
ATP synthesis (cellular energy)
Self-replicating
Contains DNA
“Little Organs” with specialized functions
Membranes isolate secretions, enzymes or toxins

11. CYTOPLASMIC ORGANELLES
Ribosomes
Site of Protein Synthesis
Free or Attached
Rough Endoplasmic Reticulum
Membrane synthesis
Making Proteins for export

12. CYTOPLASMIC ORGANELLES
Smooth ER
Lipid synthesis & breakdown
Detoxification
No ribosomes, but Smooth ER does have unique enzymes making it functionally more diverse than Rough ER. Synthesizes fatty acids & steroids (e.g. estrogen & testosterone. In Liver, enzymes help release glucose from glycogen, & deactivate or detoxify lipid-soluble drugs, alcohol, pesticides & carcinogens. In muscles cells, special Smooth ER stores Ca+ ions , triggering muscle contraction.

13. CYTOPLASMIC ORGANELLES
Golgi Apparatus
Prepares proteins for export
Makes lysosomes
Packages material to add to plasma membrane
(Gol’ je)

14. CYTOPLASMIC ORGANELLES
Lysosomes
Digestion within the cell
Defense
Recycle worn-out cells
Peroxisomes
Detoxify
Alcohol
Formaldehyde
Free Radicals
Peroxisomes contain oxidases that oxidize (remove hydrogen atom) harmful substances like alcohol & H2O2 (catalase/H2O2). Free radicals contain un-paired electrons & are therefore highly reactive. Peroxisomes also self-replicate.

15. CYTOPLASMIC ORGANELLES
Cytoskeleton
Proteins
Support & Shape
Movement inside cell
Centrioles
Form base of cilia & flagella
Form spindle

17. CYTOPLASMIC ORGANELLES
Cilia – short, numerous, move substances over free surfaces
Flagella – long, singular, move cell
Microvilli – thin folds of cell membrane, increase surface area to maximize absorption
Both cilia & flagella are projections

19. Cytoplasmic Organelles
Proteosomes
Ring of stacked proteins around central core
Break-up undesirable proteins
Vaults
Ribonucleoprotein (proteins + RNA)
May be involved in transport between nucleus & cytoplasm?
Proteasomes are sometimes described as giant “waste disposal” complexes of protein-digesting enzymes. They break up un-needed, damaged or faulty proteins via proteases. Their activity is pronounced during periods of starvation when they degrade pre-existing proteins to provide the body with small peptides for synthesis of essential proteins. Proteins called ubiquitins attach to undesirable proteins, marking them for destruction.
Vaults have been linked to multidrug resistant cancer cells. Vaults are being modified to act as a drug delivery system aimed at treating cancer & viral infections.