Cells and Organelles

Question 1

What processes are nuclear lamins involved in?

Answer 1

nuclear structural support, chromatin organisation, anchoring nuclear pore complexes

Question 2

what is the major microtubule organising centre called and where is it located

Answer 2

the centrosome, near the nucleus

Question 3

what structures are responsible for the movement of vesicles and organelles around the cell

Answer 3

microtubules

Question 4

___ move cargo to the periphery, ___ move cargo to the cell body

Answer 4

kinesics, dyneins

Question 5

cilia and flagella are both composed of microtubules and ___ arranged into a structure called an ___

Answer 5

dynein, axoneme

Question 6

what is kartageners syndrome

Answer 6

Defective cilia and
flagella associated with a condition called Kartageners syndrome, which are
the result of mutations in the dynein motor proteins.
Individuals with Kartageners syndrome will suffer recurrent respiratory infections, and
males will suffer from infertility.

Question 7

what is a cell junction

Answer 7

These are transmembrane protein complexes that interact with similar proteins
on adjacent cells, linking not only the cell to each
other but linking to each other’s cytoskeletons as
well.

Question 8

what are the 3 different types of cell junctions

Answer 8

anchoring, occluding
which are also called tight junctions, and communicating or Gap
Junction,

Question 9

what do anchoring junctions do

Answer 9

Anchoring junctions provide
mechanical stability to groups of epithelial cells so that they
can function cooperatively.

Question 10

what junctions does the actin cytoskeleton interact with

Answer 10

adherens junction (joins cells together) and focal adhesions (connects cells to the underlying extracellular matrix

Question 11

what junctions does the intermediate filament network interact with

Answer 11

desmosomes (connects cells to each other) and hemidesmosomes (connects to the extracellular matrix)

Question 12

what is the name of the condition where defects in cell junctions are apparent and what are the effects of this

Answer 12

Defects
In junctions are apparent in individuals with epidermolysis bulosa simplex
In this condition, defects in the Hemidesmosome complex
disrupts the dermo-epidermal layer, resulting in severe blistering.

Question 13

what are 2 functions of tight junctions

Answer 13

Tight junctions are a specialised cell cell contact that have two
functions.
The junctions create a seal preventing diffusion of molecules between
adjacent cells, thereby creating a barrier function for epithelial cells.
They also create a barrier within epithelial cell membranes, which
prevents mixing of membrane proteins, creating two distinct membranes.
The apical and basolateral membranes.

Question 14

what are gap junctions, what are they composed of

Answer 14

intercellular channels that connect the cytoplasm of adjacent
cells.
They permit the passage of inorganic irons and other small
molecules. Gap junctions are composed of connexins, which are a large
family of different proteins.

Question 15

during what stage of development are gap junctions found in large numbers

Answer 15

embryogenesis

Question 16

what types of muscle are gap junctions important in and why

Answer 16

cardiac and smooth, involved in contraction

Question 17

what can defective gap junctions result in

Answer 17

Gap junctions are composed of connexins, which are a large
family of different proteins.
Mutations in different connexins that result in defective gap junctions results
in a range of clinical manifestations.
Mutations in connexin-26 for example, results in deafness and
Vohwinkel syndrome, which is a disorder of the skin, resulting
in thick honeycomb-like callouses and a build up
of abnormal fibrous tissue on the hands and feet

Question 18

give examples of cell junctions and their roles in skin

Answer 18

The importance of junctions can be shown using skin as
an example.
Adherens junctions act to hold epithelial cells together.
Desmosomes provide strength for the epidermal keratinocytes.
, tight junctions provide a seal in the stratum granulosum
and hemidesmosomes are responsible for the integrity
of the dermo-epidermal Junction. And, of course, gap junctions
allow for the passage of small molecules in between cells.

Question 19

give an example where a cells’ shape is adapted to its function

Answer 19

Plasma cells, for example, are immune cells whose sole function
is to produce immunoglobulin.
which are antibodies as you might predict, and as you
can see in this electron micrograph, the Plasma cell has
an extensive rough endoplasmic reticulum consistent with its function.

Question 20

what is responsible for the extensive Ca storage in muscle cells

Answer 20

Muscle cells contain an elaborate and specialised ER called a
sarcoplasmic reticulum to fulfil this function.

Question 21

A molecule that has a polar and non-polar end

A lipid made up of a phosphate polar head group and two fatty acids chains (one usually saturated, the other unsaturated)

Microfilament-based membrane protrusions that help cells move

Very small spikes of microfilament-based protrusions of the plasma membrane involved in cell motility

Answer 21

A molecule that has a polar and non-polar end

= amphipathic
A lipid made up of a phosphate polar head group and two fatty acids chains (one usually saturated, the other unsaturated)

= phospholipid
Microfilament-based membrane protrusions that help cells move

= lamellipodia
Very small spikes of microfilament-based protrusions of the plasma membrane involved in cell motility

= filopodia

Question 22

what is a glycocalyx

Answer 22

a layer of carbohydrate that covers cells. Many functions including cell recognition. Cells lining the gut have a thick glycocalyx where digestive enzymes reside

Question 23

what are lipid rafts

Answer 23

lipid rafts: cholesterol-rich domains that compartmentalise function by concentrating molecules, eg act as ‘signalling platforms’ by concentrating signalling receptors

Question 24

what is the gate and fence function of tight junctions

Answer 24

The ‘gate’ regulates paracellular permeability, that is, things moving inbetween cells

The ‘fence’ function prevents membrane components on the apical surface from mixing with membrane components in the basolateral membrane. This results in cell polarity. All epithelial cells have cell polarity which means that they have functionally different sides to them.