Random

Question 1

How does crossing over occur in meiosis?

Answer 1

Homologous pairs of chromosomes pair up.
The chromatids twist around each other and areas of chromatids swap over.
The chromatids now have the same genes but a different combination of alleles.

Question 2

Fish gas exchange

Answer 2

The blood system in the lamellae is arranged in a counter current system where water flows in the opposite direction to the blood flow in the capillaries. In this system the concentration gradient is maintained.
Generally, the concentration of oxygen in the blood is lower than in the surrounding water so oxygen diffuses into the blood.

Question 3

Haemoglobin

Answer 3

Haemoglobin is a quaternary protein consisting of 4 globins and 4 haem groups altogether attached to these polypeptides.

Haemoglobin has a high affinity for oxygen (can hold up to 4 per molecule). However this depends on the partial pressure of oxygen.

Oxygen loads onto haemoglobin to form oxyhaemoglobin when there’s a large partial pressure. (Often when oxygen enters the blood capillaries at the alveoli in the lungs).
Oxyhaemoglobin unloads its oxygen when there’s a lower partial pressure. (Often when red blood cells deliver oxyheamoglobin to repairing tissues).

Question 4

Haemoglobin

Answer 4

Haemoglobin is a quaternary protein consisting of 4 globins and 4 haem groups altogether attached to these polypeptides.

Haemoglobin has a high affinity for oxygen (can hold up to 4 per molecule). However this depends on the partial pressure of oxygen.

Oxygen loads onto haemoglobin to form oxyhaemoglobin when there’s a large partial pressure. (Often when oxygen enters the blood capillaries at the alveoli in the lungs).
Oxyhaemoglobin unloads its oxygen when there’s a lower partial pressure. (Often when red blood cells deliver oxyheamoglobin to repairing tissues).