Cells and Control

Question 1

What are rods and cones

Answer 1

The light sensitive cells in the retina

Question 2

How do rods and cones differ?

Answer 2

Rods detect in dim light but only black and white. Cones don’t work in dim light but detect colour

Question 3

What does the cornea do?

Answer 3

Refracts light

Question 4

Explain refraction

Answer 4

As the light wave moves from matter with different density it bends

Question 5

What is the pupil

Answer 5

The hole made by the iris which controls how much light enters the retina

Question 6

What does the lens do?

Answer 6

Refracts light

Question 7

How does the lens work?

Answer 7

It changes shape to focus the light onto the retina.
To look at distant objects the ciliary muscle relaxes and the suspensory ligaments pull tight which elongates the lens.
To look at near objects the ciliary muscle contracts and the suspensory ligaments relax so the lens becomes more rounded.

Question 8

What is the conjunctiva

Answer 8

Protective membrane at front of eye

Question 9

What is a cataract

Answer 9

A cloudy patch on the lens which stops light being able to enter the eye and causes blurred vision

Question 10

What is colour blindness

Answer 10

People can’t differentiate colours due to defects in the cone cells, most commonly red/green

Question 11

Where does the image fall in the eye in long sightedness

Answer 11

Behind the retina

Question 12

Where does the image fall in the eye in short sightedness

Answer 12

In front of the retina

Question 13

What is a concave lens?

Answer 13

One that is hollowed out each side - like a cave

https://www.bbc.co.uk/bitesize/guides/zt7srwx/revision/1

Question 14

What is a convex lens

Answer 14

One that is rounded each side

Question 15

What is long sightedness?

Answer 15

Can’t focus on near objects. The eyeball is too short or the lens the wrong shape and doesn;t bend the light enough. The image falls behind the retina.

Question 16

What is short sightedness

Answer 16

Can’t focus on far objects. The eyeball is too long or the lens the wrong shape and bends the light too much. The image falls in front of the retina.

Question 17

What is the retina

Answer 17

The light sensitive part of the eye

Question 18

What is the nerve for the eye called

Answer 18

Optic nerve

Question 19

What does the optic nerve do?

Answer 19

Light falling on the rods and cones causes electrical impulses to be created which the optic nerve carries to the brain.

Question 20

What is a chromosome

Answer 20

Coiled up lengths of DNA molecules which form the genetic material found in the cell nucleus

Question 21

What chromosomes does a body cell have?

Answer 21

23 pairs of chromosomes altogether with two copies of each (total 46) one copy from the father and one from the mother

Question 22

How do cells divide?

Answer 22

Mitosis

Question 23

What is mitosis

Answer 23

The part of the cell cycle called cell division where one cell divides to form two identical daughter cells

Question 24

Why is cell divsion needed

Answer 24

For growth and repair of damaged cells.
It also enables asexual reproduction.

Question 25

What is the cell cycle

Answer 25

The cell cycle consists of the interphase and mitosis and cytokinesis

Question 26

What is the Interphase

Answer 26

In a non dividing cell DNA is spread in long strings. Before divsion the cell has to grow and increase the numbers of subcellular structures eg ribosomes/mitochondria. It then duplicates it’s DNA so there is a copy for each new cell. The chrmosomes go from being shaped like I to X.