Cells

Question 1

What are cancer cells?

Answer 1

Cells that are able to divide indefinitely and uncontrollably (uncontrolled cell division), resulting in tumours or flooding the blood with abnormal cells

Question 2

Why are cancer cells able to divide indefinitely

Answer 2

cellular dysfunction - there is no contact inhibition to stop cell division after initiation of proliferation

Question 3

Some possible causes of cancer

Answer 3

Chemical carcinogens, Radiation and infectious diseases

Question 4

What does a cell culture medium contain?

Answer 4

Growth factors (signalling proteins, hormones), water, sugar, anti-biotics, pH indicators, salt

Question 5

What are primary cell cultures?

Answer 5

cultures obtained directly from body tissues and have a limited number of replications.

Question 6

What are stem cell cultures?

Answer 6

cell cultures from tissues or induced and have an extensive number of replications.

Question 7

What are immortalised cell lines?

Answer 7

cell lines that have acquired the ability to propagate indefinitely. Almost all are cancerous.

Advantages:
Good control of growth environment

Disadvantages:
Hard to maintain for some cell types
Cells in culture may no longer be the same as initial explants.

Question 8

What is senescene

Answer 8

It is the lost of ability to divide and grow of a cell

Question 9

What is the cell membrane made of?

Answer 9

Phospholipid bilayer with protein channels

Question 10

What is the function of the cell membrane?

Answer 10

1. Encloses the cell and internal cellular compartments

2. Is a selectively permeable membrane that controls the movement of substances in and out of the cell.

Question 11

What is the function of the extra-cellular matrix?

Answer 11

It provides support, segregates cells from each other and regulates intercellular communication.

Question 12

Examples of membrane-enclosed organelles

Answer 12

Mitochondria, endoplasmic reticulum, chloroplasts, nucleus, Golgi apparatus, Peroxisome, vacuole

Question 13

What is the function of the cytoskeleton?

Answer 13

Maintains and changes cell shape

Question 14

What is the function of microRNA?

Answer 14

Moves around the body to communicate with other cells

Question 15

Weight composition of a cell

Answer 15

approx. 70% water and 23% biochemicals (proteins, carbohydrates, lipids and nucleic acids) and 4% of other chemicals (vitamins, phosphates etc)

Question 16

Why is water a polar molecule?

Answer 16

The oxygen nucleus is more electronegative than the hydrogen nucleus. Hence, it attracts the electrons more strongly and pulls the electron cloud/density towards itself. This results in unequal sharing of electron density between the oxygen and hydrogen atom. Hence, there is a partial negative charge on the oxygen atom and a partial positive charge on the hydrogen atom. This unequal distribution of electron density gives the water molecule a net positive dipole moment, thus making water a polar molecule

Question 17

How are amphipathic molecules soluble in water?

Answer 17

water molecules will surround the polar groups - forming a hydration shell and the number of water molecules surrounding the solute is known as the hydration number (this process is known as hydration)

Question 18

How can hydrophobic or non-polar molecules cross the cell membrane?

Answer 18

They can cross via diffusion. Polar substances cross the cell membrane through special protein molecules which forms “channels” or “carriers” (e.g. aquaporins - water channels in cells)

Question 19

What is a clathrate?

Answer 19

It is a ‘cage-like structure’ that forces hydrophobic molecules together by surrounding these molecules, forming a cage. The hydrophobic molecules are stick together by hydrophobic interaction as they do not like the environment.