Topic 1:Cell Biology

Question 1

Caveats to the cell theory: Striated Muscle Fibres

Answer 1

-Muscle cells fuse to form fibres that may be very long (>300mm)

-They have multiple nuclei despite being surrounded by a single, continuous plasma membrane

-Challenges the idea that cells always function as autonomous units

Question 2

Caveats to the cell theory: Asceptate Fungal hyphae

Answer 2

-Some fungi are not partitioned by septa and hence have a continuous cytoplasm along the length of the hyphae

-Challenges the idea that living structures are composed of discrete cells

Question 3

Caveats to the cell theory: Giant Algae

Answer 3

-Certain species of unicellular algae may grow to very large sizes

-Challenges the idea that larger organisms are always made of many microscopic cells

Question 4

Metabolism, give example of how paramecium does this

Answer 4

Living things undertake essential chemical reactions

Food particles are enclosed within small vacuoles that contain enzymes for digestion

Question 5

Reproduction (with paramecium example)

Answer 5

Living things produce offspring, either sexually or asexually

Paramecia divide asexually (fission) although horizontal gene transfer can occur via conjugation

Question 6

Sensitivity (with paramecium example)

Answer 6

Living things are responsive to internal and external stimuli

Paramecia are surrounded by small hairs called cilia which allow it to move

Question 7

Homeostasis (with paramecium example)

Answer 7

Living things maintain a stable internal environment

Essential gases enter (e.g. O2) and exit (e.g. CO2) the cell via diffusion

Question 8

Excretion (with paramecium example)

Answer 8

Living things exhibit the removal of waste products

Solid wastes are removed via an anal pore, while liquid wastes are pumped out via contractile vacuoles

Question 9

Nutrition (with paramecium example)

Answer 9

Living things exchange materials and gases with the environment

Paramecia engulf food via a specialised membranous feeding groove called a cytostome

Question 10

Growth (with paramecium example)

Answer 10

Living things can move and change shape or size

Question 11

How do cells and tissues that are specialised for gas or material exchanges increase their surface area to optimise material transfer

Answer 11

intestinal tissue of the digestive tract may form a ruffled structure (villi) to increase the surface area of the inner lining

Alveoli within the lungs have membranous extensions called microvilli, which function to increase the total membrane surface

Question 12

Magnification of an image =

Answer 12

Image size (with ruler) ÷ Actual size (according to scale bar

Question 13

Actual Size of an organism =

Answer 13

Image size (with ruler) ÷ Magnification

Question 14

Differentiation

Answer 14

Process during development where newly formed cells become more specialised and distinct from one

Each cell contains the entire set of genetic instructions for that organism. The activation of different instructions (genes) within a given cell by chemical signals will cause it to differentiate

Question 15

What are the two key qualities of stem cells?

Answer 15

1. Self Renewal – They can continuously divide and replicate
2. Potency – They have the capacity to differentiate into specialised cell types

Question 16

Totipotent

Answer 16

Can form any cell type, as well as extra-embryonic (placental) tissue (e.g. zygote)

Question 17

Pluripotent

Answer 17

Can form any cell type (e.g. embryonic stem cells)

Question 18

Multipotent

Answer 18

Can differentiate into a number of closely related cell types (e.g. haematopoeitic adult stem cells)

Question 19

Unipotent

Answer 19

Can not differentiate, but are capable of self renewal (e.g. progenitor cells, muscle stem cells)

Question 20

Outline Stargardt’s Disease, how it can be treated via the use of stem cells.

Answer 20

An inherited form of juvenile macular degeneration that causes progressive vision loss to the point of blindness, Caused by a gene mutation that impairs energy transport in retinal photoreceptor cells

-Treated by replacing dead cells in the retina with functioning ones derived from stem cells

Question 21

What are the three ways stem cells can be derived?

Answer 21

1. Embryos (may be specially created by therapeutic cloning)
2. Umbilical cord blood or placenta of a new-born baby
3. Certain adult tissues like the bone marrow (cells are not pluripotent)

Question 22

Discuss the disadvantages/ethical concerns of stem cell therapy

Answer 22

1. Using multipotent adult tissue may be effective for certain conditions, but is limited in its scope of application
2. Stem cells derived from umbilical cord blood need to be stored and preserved at cost, raising issues of availability and access
3. The greatest yield of pluripotent stem cells comes from embryos, but requires the destruction of a potential living organism
4. Sometimes involves the use of oncogenic retroviruses and transgenes, increasing the risk of health consequences (i.e. cancer)