Lecture 7: Photon conversion into electrical energy & Electrical phenomena

Question 1

What is the role of rod photoreceptor cells?

Answer 1

Light intensity detection

Question 2

What is the role of cone photoreceptor cells?

Answer 2

Colour vision

Question 3

How are the rod and cone photoreceptor cells distributed in the retina?

Answer 3

Cones are concentrated in the fovea (small depression at the center of the retina where visual activity is the highest) but almost absent elsewhere.
Rods are present at high density throughout the retina but absent at the fovea.

Question 4

How can someone be partially colourblind?

Answer 4

Either they are missing a cone type or the spectrum of a particular cone is shifted

Question 5

What is the blindspot?

Answer 5

The location where the optic nerve passes through the retina; there are no rods or cones there

Question 6

What are opsins? Give an example.

Answer 6

Light-sensitive proteins in the photoreceptor cells. ex: Retinal

Question 7

What is phototransduction?

Answer 7

The process by which light detected by photoreceptor cells is converted to electrical impulses before these impulses are sent to the brain. GTP and GDP are used in this process. Membrane depolarization and multiple specialized proteins are involved.

Question 8

What is coulomb’s law?

Answer 8

F = keq1q2/r^2
Used to quantify the electrostatic force between charged particles

Question 9

Describe disulfide bonding.

Answer 9

• Covalent bond derived from the oxidation of two thiol (S-H) groups.
• Can occur intra- and inter- molecularly.
• Intramolecular disulfide bonds stabilize tertiary structure and intermolecular bonds stabilize the quaternary structure.

Question 10

Describe the capillary action concept.

Answer 10

• Process that occurs due to forces of cohesion (attractions within the molecules of the liquid) and adhesion (attractions between the molecules of the liquid and the surface)
• ONLY occurs when ADHESIVE forces are stronger than cohesive forces. Occurs against gravity.

Question 11

What’s surface tension ?

Answer 11

Result of cohesive forces between liquid molecules at an interface.
Leads to a surface film.

Question 12

What are surfactants ?

Answer 12

Compounds which lower surface tension by disrupting intermolecular forces at the interface.
Amphiphilic molecules.