Module 2 | Genes and Health

Question 1

2.1 Know the properties of gas exchange surfaces in living organisms.

Answer 1

-Surface area to volume ratio.
-Thickness of surface.
-Difference in concentration (concentration gradient).

Question 2

2.1 Understand how the rate of diffusion is dependent on these properties.

Answer 2

To maintain a high rate of diffusion:
-Large surface area to volume ratio.
-Reduced surface thickness (decreased diffusion distance).
-Steep concentration gradient.

Question 3

2.1 Understand how rate of diffusion can be calculated using Fick’s Law of Diffusion.

Answer 3

Fick’s Law of Diffusion:

Rate of Diffusion ∝ Surface area x Concentration Gradient / Diffusion Distance

Question 4

2.1 Understand how the structure of the mammalian lung is adapted for rapid gaseous exchange.

Answer 4

The lungs contain many alveoli with a one cell layer thick epithelium, which provides a large surface area. In the lungs, alveoli are surrounded by an extensive network of capillaries which providing a large surface area for gas exchange. capillaries have a one cell layer thick endothelium; as both the alveoli and this network of capillaries have walls that are just one cell layer thick, they provide a short distance for diffusion. A high concentration gradient is maintained by circulation, as there are large numbers of red blood cells which allows large volumes of oxygen to bind with haemoglobin, as well as ventilation. This means that rapid gas exchange by diffusion can occur as Fick’s Law states that Rate of Diffusion ∝ Surface area x Concentration Gradient / Diffusion Distance.

Question 5

2.2 Know the structure and properties of cell membranes.

Answer 5

The cell membrane consists of mainly phospholipids and protein (transport proteins, receptor proteins, enzymes, structural and recognition proteins). The phospholipids form a bilayer, and the proteins float in the phospholipids, constantly changing position as shown in the fluid mosaic model. Proteins may span the bilayer or be located in only one layer.

Question 6

2.2 Understand how models such as the fluid mosaic model of cell membranes are interpretations of data used to develop scientific explanations of the structure and properties of cell membranes.

Answer 6

In the fluid mosaic model, fluid refers to the movement of the phospholipids in the plane of the membrane, and mosaic refers to the random association of proteins of different shapes and sizes within the membrane.

Question 7

2.3

Question 8

2.4

Question 9

2.4

Question 10

2.4

Question 11

2.4

Question 12

2.4

Question 13

2.4

Question 14

2.5 Know the basic structure of mononucleotides.

Answer 14

Deoxyribose or ribose sugar linked to a phosphate and a base (thymine, uracil, cytosine, adenine or guanine).

Question 15

2.5 Know the structure of DNA.