Cell Ultrastructure

Question 1

Plasma Membrane

Answer 1

• phospholipids are amphipathic
• the bilayer for as a relatively impermeable barrier to most water-soluble molecules
• protein molecules dissolved in the lipid bilayer mediated most of the other functions of the membrane
• glycocalyx - oliosaccharides and polysaccharide side chains on the outside of the plasma membrane

Question 2

Functions of the plasma membrane

Answer 2

• selective permeability
• transport of materials along cell surface
• endocytosis and exocytosis
• intercellular adhesion and recognition
• signal transduction

Question 3

Endoplasmic Reticulum 
(is continuous and encloses a single lumen)

Answer 3

sER 
- no ribosomes 
- found in liver, mammary gland, ovary, testis and adrenal gland
rER 
- ribosomes synthesise proteins

Question 4

The Golgi Apparatus

Answer 4

cis face - receives vesicles from rough ER
trans face - exports vesicles (signal mediated diversions for lysosomes or regulated secretion - not for constitutive secretion)
The Golgi Apparatus functions to modify, sort, concentrate and package proteins synthesised on the rER

Question 5

Lysosomes

Answer 5

• are generated by the Golgi apparatus
• contain many hydrolytic enzymes to break down anything in the cell that is defunked
• fuse with ,aerial requiring digestion

Question 6

Peroxisomes

Answer 6

• detoxify (oxidise) a number of molecules including alcohol, phenols, forming acid and formaldehyde
• abundant in the liver and kidney

Question 7

Mitochondrion

female lineage - always inherited from mother

Answer 7

Matrix
- 100s of enzymes 
- mitochondrial DNA genome (has bacterial like replication - endosymbiosis theory) 
Inner Membrane (cristae)
- enzymes for oxidative phosphorylation (ATP synthesis) 
- impermeable to small ions e.g. H+ 
Outer Membrane 
- permeable by all molecules

Question 8

Actin Filaments

Answer 8

Microfilaments
- 5-9nm in diameter
Intermediate filaments
- 10nm in diameter
- tough supporting mesh work in cytoplasm
- cancer source can be traced by looking at filament type in cancer cell
Microtubules
- 25nm in diameter
- hollow cylinders made of protein tubulin
- found where structures move (nerve fibres, mitotic spindle, cilia and flagella)
- 9+2 arrangement in cilium or flagellum

Question 9

The limit of resolution

proportional to wavelength

Answer 9

The minimum distance at which two objects can be distinguished (seen as distinct)
Theoretical limit of resolution
- light microscope is 0.2um
- electron microscope is 0.002nm