The Cell And Its Components

Question 1

What are the differences between euchromatin and heterochromatin?

Answer 1

Euchromatin appears white, its genes are commonly expressed. DNA is present as ‘beads on a string’ nucleosomes- with DNA wrapped around histone proteins.
Heterochromatin appears darker and is less regularly expressed, it is present as solenoid form where the nucleosomes are packed tightly together

Question 2

What is the plasma membrane mainly made of? What does amphipathic mean in relation to these molecules? How are these molecules arranged?

Answer 2

Phospholipids 
Hydrophobic (fatty acid) and hydrophilic (phosphate group) domains
In a bilayer with heads pointing out and tails in

Question 3

What is the glycocalyx? what is its function?

Answer 3

A coating of carbohydrates, it looks like a furry coat around the cell. The carbohydrates are bound to proteins (glycoproteins) and lipids (glycolipids). It is important in cellular communication, identification and adhesion.

Question 4

List 4 functions of the plasma membrane

Answer 4

Transport along cell surface, selective permeability, intercellular adhesion, intecellular recognition, signal transductance (see G proteins), endo& exocytosis, comminication.

Question 5

What are the major differences between SEM and TEM?

Answer 5

TEM in vacume, in TEM electrons pass through sample not bounce off, TEM is cross section not surface

Question 6

How can a tissue be prepared to be observed under a light microscope?

Answer 6

Preserve in FORMALIN, embed in PARAFIN so when it cools it sets hard, cut thin using a MICROTOME, stain tissue with Haematoxylin to stain nucleus blue and Eosin to stain cytoplasm & extracellular matrix pink (H&E)

Question 7

What is the role of the Smooth ER?

Answer 7

Lipid and steroid synthesis

Question 8

What does the Smooth ER look like? In what cells is it aubundant?

Answer 8

Tubular with smooth edges (no ribosomes)

aubundant in liver cells

Question 9

What type of proteins are synthesised by the ribosomes at the RER? Therefor what cells have lots of RER?

Answer 9

Secretory proteins

pancreatic cells

Question 10

What are the functions of the RER? Give 4- 1 in relation to insulin and 1 in relation to collagen

Answer 10

protein is synthesised and then moves into intercisternal space
proteins then modified (cleavage, glyosylation, disulphide bonds formation- insulin, folding, hydroxylation of lys and pro in collagen formation)

Question 11

What ribosomal subunits are in eukaryotes and what subunits are found in prokaryotes?

Answer 11

eukaryotes= 80s type of a 60s and 40s 
prokaryotes= 70s type of 50s and 30s

Question 12

Other than amino acids, what are ribosomes made of?

Answer 12

ribosomal RNA

Question 13

What is the general role of the golgi?

Answer 13

to modify, sort, concentrate and package proteins destined for secretion (or lysosomes)

Question 14

What is the face of the golgi nearest and furthest the nucleus called?

Answer 14

cis is nearest the nucleus and trans is furthest

Question 15

What do primary lysosomes look like under a TEM?

Answer 15

Filled in black circles

Question 16

What do secondary lysosomes look like under a TEM?

Answer 16

Larger, light grey circles with other circles inside them, which can be filled in black, grey or white.

Question 17

What is the differance between a primary and secondary lysosome?

Answer 17

Primary lysosomes have not fused with a endocytotic/ phagocytotic vesicle, and will not release their contents out the cell. Whereas secondary might if products are useful

Question 18

What does a peroxisome look like under a TEM?

Answer 18

grey circles with defined black outlines

Question 19

What does a peroxisome do?

Answer 19

oxidises and so detoxify toxins such as alcohol, phenol, formic acid ect.

Question 20

What is a glycogen inclusion and what does it look like under a TEM?

Answer 20

a glycogen store- looks like small black specs, bigger than ribosomes and varying in size

Question 21

Where are microfilaments distributed in the cell?

Answer 21

Around the edges

Question 22

What is the role of intermediate filaments? How are they distributed?

Answer 22

To form tough supporting meshwork in cytoplasm. Found throughout cytoplasm also also just beneath the nuclear membrane forming the nuclear lamina

Question 23

What proteins are microtubules made of?

Answer 23

Tubulin

Question 24

Where are microtubules found?

Answer 24

At sites where structures move- mitotic spindle, cila, flagella

Question 25

What arrangement do microtubules take in a flagellum?

Answer 25

“9+2” arrangement