Ultrastructure

Question 1

explain why electron microscope is capable of finer resolution than other microscopes

Answer 1

resolution improves as wavelength decreases
with a voltage of 100,000 the wave length of electrons is 0.004nm which is much smaller than the wavelength of violet light used in a light microscope.

Theoretical limit of resolution for light M = 0.2um
electron m = 0.002nm

Question 2

describe the structure and function of membranes

Answer 2

S- made of phospholipid molecules with hydrophobic tails and hydrophilic heads - are amphipathic that forms a bilaminar membrane. within the membrane are protein molecules - mostly mobile some are freely membrane, some moved by cell. alpha helix part of molecule sits in membrane as hydrophobic. Proteins may be glycosilated with oligosaccharides and polysacchariseds that give them specificity for function.
F - Has selective permeability and is a relatively impermeable barrier to most water soluble molecules
transport of materials along cell surface
endocytosis and exocytosis
intercellular adhesion
intercellular recognition
signal transduction.

Question 3

explain structure and funciton of rough endoplasmic reticulum

Answer 3

flattern pillows of cisternae with an intracisternal space with fluid
have many ribosomes

sites of protein synthesis

Question 4

smooth endoplasmic reticulum

Answer 4

found in liver, mammary gland, and in ovary testis and adrenal gland that have lipid biosynthesis
likely to be continuous with the rought endoplasmic reticulum

Question 5

Golgi apparatus

Answer 5

a stack of saucers with cis and trans faces
vesicles join at cis face and proteins are processed and separated to be secreted by cell
cis face is the outer side of the C shape

F- to modify, sort (aboriginal women), concentrate and package proteins synthesised on the rough endoplasmic reticulum
proteins secreted through different routes, may have to wait for signal to be released

Question 6

Lysosomes

Answer 6

dark staining

contain powerful hydrolytic enzymes such as proteases, nucleases and lipase.

generated by the goli apparatus
protect their own membrane by a glycolyx
Peroxisomes in liver and kidney that detoxify alcohol and other toxic molecules (dark staining)

Question 7

mitochondria

Answer 7

F- generation of potential energy by oxidative phosphorylation - are the site of cells energy production
double membrane - inner membrane is folded into cristae. with enzymes oxidative reactions of respiratory chain to synthesis ATP (inner membrane impermeable to small ions)
can divide as have own genetic information matrix contains many enzymes and mitochondrial DNA genome
outer membrane permeable by all molecules of

Question 8

actin filaments

Answer 8

microfilaments - 5-9 nm diameter 
coil of two actin filaments together 
mainly cortical in distribution 
forms a network underlying the plasma membrane of animal cells 
edge of epithelial cells in microvilli 
seen on scanning electron micrographs

Question 9

intermediate filaments

Answer 9

diameter of 10nm from keratin, vermentin and other proteins
common in epithelial cells
form tough supporting meshwork in cytoplasm found just beneath inner nuclear membrane forming the nuclear lamina
help bind cells togther
used to find origin of cancer cells.
mutant keratin gene can result in blistering in skin

Question 10

microtubules

Answer 10

long hollow cylinders made from protein tubulin
diameter - 25nm
found at sites where structures are moved e.g. in nerve fibres, mitotic spindles, cilia and flagella (have 9+2 structure)

Question 11

Define limit of resolution

Answer 11

The minimum distance that two objects can be distinguished.