Chapter 1- Cytology (2)

Question 1

Why are cells that make up the lens joined by gap junctions?

Answer 1

Because the lens has no blood supply. By having gap junctions, nutrients can diffuse from the lens surface to cells in its interior.

Question 2

What is the cytoplasm composed of?

Answer 2

1- Cytosol- fluid that contains mostly water but also sugars, proteins, salts, etc.

2- Cytoskeleton

3- Membrane bound organelles, e.g, mitochondria

4- Inclusions- various substances that are found in some cells but not others, e.g melanin in epithelial cells.

Question 3

What does a cytoskeleton do?

Answer 3

1- Provides shape to the cell

2- Responsible for the whole cell movement

Question 4

What are the components of the cytoskeleton?

Answer 4

1- Actin filaments
2- Intermediate filaments
3- Microtubules

Question 5

What is the function of the actin filaments?

Answer 5

Supports the cell and is also involved in its movement.

Question 6

What is the structure of the actin filament?

Answer 6

Consists of two strands of actin monomers in a tight helix.

Question 7

What is exocytosis?

Answer 7

Movement of substances out of the cell.

Question 8

What is endocytosis?

Answer 8

Movement of substance into cell, e.g, phagocytosis

Question 9

What is the function of microtubules?

Answer 9

Involved with the movements within the cell

Question 10

What is the structure of microtubules?

Answer 10

It consists of proteins being arranged into long hollow tubes.

Question 11

What are the proteins in microtubules made up of?

Answer 11

Alpha and beta tubulin

Question 12

Where are microtubules located?

Answer 12

To one side of the nucleus

Question 13

Microtubules form the structural core of what cell?

Answer 13

The cillia- finger like projections that move fluids and its contents over the cell.

Question 14

What are the intermediate filaments like and how are they organised?

Answer 14

Very tough and durable and are organised as rope-like polymers.

Question 15

Where are intermediate filaments located?

Answer 15

Where cells are subjected to mechanical stress, e.g, desmosomes.

Question 16

What is the function of the mitochondria?

Answer 16

Releases energy in the form of ATP

Question 17

What is the mitochondria made up of?

Answer 17

1- A smooth outer membrane

2- An inner membrane containing cristae- which increases the surface area allowing for faster production of ATP.

3- A matrix containing enzymes

Question 18

Why does the mitochondria possess some of its own DNA?

Answer 18

So it can make some of its own proteins needed for its function.

Question 19

Briefly describe the protein synthesis process

Answer 19

1- The gene’s DNA is transcribed onto mRNA.

2- The mRNA leaves the nucleus for the cell’s cytoplasm where it joins onto ribosomes located on the endoplasmic reticulum.

3- Proteins are then formed by amino acids joining together in the process of translation.

Question 20

What is the function of ribsomes?

Answer 20

Its where protein synthesis takes place.

Question 21

Where are the ribosomes located?

Answer 21

In the cytoplasm or in the endoplasmic reticulum

Question 22

What does the endoplasmic reticulum (ER) do?

Answer 22

Synthesises, folds and transports proteins.

Question 23

What is the function of the rough ER?

Answer 23

It makes proteins for membranes which are due for export from the cell.

Question 24

What is the structure of the rough ER?

Answer 24

It is a surface studded with ribosomes.

Question 25

Where would there be a high number of rough ER?

Answer 25

In cells that make protein for export, e.g, plasma cells (antibodies)