Cells and Control

Question 1

How do you do a scientific drawing?

Answer 1

Use a sharp pencil
Use clear, unbroken lines
Draw outlines of the main features - no shading
Take up at least half of the space
Keep parts in proportion
Label important features with straight, uncrossing lines
Include a scale and the magnification

Question 2

What is a chromosome?

Answer 2

They are coiled up lengths of DNA molecules that contain genetic material. Cells normally have two copies of each chromosome, making them ‘diploid’ cells. One chromosome comes from the organism’s ‘mother’; one comes from its ‘father’.

Question 3

What is mitosis used for?

Answer 3

Growth or repairing damaged cells.

Question 4

What is mitosis?

Answer 4

A type of cell division and part of the cell cycle resulting in two daughter cells with identical chromosomes to the parent cell

Question 5

What is interphase?

Answer 5

The time when a cell is not dividing, where chromosomes are uncoiled. The cell replicates all of its subcellular structures and DNA in this period

Question 6

What are the four stages of mitosis?

Answer 6

Prophase, metaphase, anaphase, telophase

Question 7

What is prophase?

Answer 7

The first stage of mitosis, where chromosomes condense, getting shorter and fatter. The nucleus membrane breaks down and chromosomes lie free

Question 8

What is metaphase?

Answer 8

The second stage of mitosis, where the chromosomes line up at the centre of the cell

Question 9

What is anaphase?

Answer 9

The third stage of mitosis, where cell fibres pull the chromosomes apart. The two arms of each chromosome go to opposite ends of the cell

Question 10

What is telophase?

Answer 10

The fourth stage of mitosis, where membranes form around each of the sets of chromosomes. The nucleus has divided

Question 11

What is cytokinesis?

Answer 11

When the cytoplasm and cell membrane divide to form two separate cells

Question 12

How do plants and animals grow and develop?

Answer 12

Cell differentiation - cells becoming more specialised
Cell division - by mitosis
(In plants) Cell elongation - plant cells expanding

Question 13

What is cancer?

Answer 13

When a change in one of the genes controlling cell division causes a cell to start dividing uncontrollably. This can result in a mass of abnormal cells called a tumour. If it invades and destroys surrounding tissue it is called cancer

Question 14

What are stem cells?

Answer 14

Undifferentiated cells that can divide by mitosis to become new cells, which then differentiate

Question 15

What is the difference between embryonic and adult stem cells?

Answer 15

Embryonic stem cells are found in early human embryos. They have the potential to divide and produce any type of cell.
Adult stem cells are found only in some places, like bone marrow. They can only produce some types of cells so they are not as versatile.

Question 16

What are meristems?

Answer 16

A plant tissue found at the tips and roots of shoots (parts of a plant that are growing). They are the only cells in plants that divide by mitosis. They produce unspecialised cells that can divide and differentiate into any type of cell.

Question 17

How are stem cells used in medicine?

Answer 17

Adult stem cells can cure some diseases, such as sickle cell anaemia with a bone marrow transplant. Embryonic stem cells are being experimented on to see if they could produce any type of cell

Question 18

What are the potential risks with stem cells?

Answer 18

Tumour development - stem cells divide very quickly
Disease transmission - unnoticed viruses could be passed on in stem cells
Rejection - they could be recognised as foreign and trigger an immune response

Question 19

What are growth charts?

Answer 19

Charts that show a number of percentiles of growth

Question 20

What does the cerebrum do?

Answer 20

It is the largest part of the brain, divided into two cerebral hemispheres that control the opposite sides of the body. It controls higher function, including movement, intelligence, memory, language, and vision

Question 21

What does the cerebellum do?

Answer 21

It is responsible for muscle coordination and balance

Question 22

What does the medulla oblongata?

Answer 22

It controls unconscious activities like breathing and heart rate

Question 23

What are CT scans?

Answer 23

A scan using X-rays to produce and image of the brain. It shows the main structures but not their function. If it shows a diseased or damaged brain structure and the patient has lost some function, the function of a part of the brain can be worked out.

Question 24

What are PET scans?

Answer 24

A scan using radioactive chemicals to show which parts of the brain are active when the person is inside the scanner. They are very detailed and can show the brain’s structure and function in real time. They can show if areas in the brain are unusually inactive or active, show they can study disorders changing the brain’s activity

Question 25

Why can it be difficult to treat problems in the central nervous system?

Answer 25

It is hard to repair damage - neurones do not readily repair themselves and there is not yet a way to repair it
It is hard to access parts of the CNS
It can lead to permanent damage - mistakes can mean the CNS is damaged further

Question 26

What are the parts of the nervous system?

Answer 26

Brain
Spinal cord
Nerves

Question 27

What does the nervous system enable you to do?

Answer 27

Control your body

Get feedback about the world

Question 28

How does the CNS coordinate responses?

Answer 28

Sensory receptors detect a stimulus. Different receptors detect different stimuli. When a stimulus is detected information is converted to a nervous impulse and sent to the CNS. The CNS coordinates a response. Impulses travel through the CNS along relay neurones. It sends info to an effector along a motor neurone.

Question 29

How do neurones transmit information?

Answer 29

They have cell bodies with a nucleus. The cell body has extensions that connect to other neurones. Some axons are insulated with a myelin sheath, speeding up the impulse. They are connected by synapses.

Question 30

What is the structure and function of a sensory neurone?

Answer 30

They carry impulses from receptors to relay neurones. One long dendron carries nerve impulses to the cell body. One short axon carries nerve impulses from the cell body to the CNS.

Question 31

What is the structure and function of a relay neurone?

Answer 31

They carry nerve impulses from sensory neurones to motor neurones. Many short dendrites carry nerve impulses to the cell body. An axon carries nerve impulses from the cell body to motor neurones.

Question 32

What is the structure and function of a motor neurone?

Answer 32

They carry nerve impulses from relay neurones to effector cells. Many short dendrites carry nerve impulses to the cell body. One long axon carries nerve impulses from the cell body to effector cells.

Question 33

What are synapses?

Answer 33

The connection between two neurones. The signal is transferred by chemicals called neurotransmitters which diffuse across the gap. They then set off a new electrical signal in the next neurone. It is slower than transmission in one neurone, as diffusion takes time

Question 34

How do reflexes work?

Answer 34

They are automatic, rapid responses to stimuli. There is a reflex arc: stimulus - receptor - sensory neurone - relay neurone - motor neurone - effector - response. It does not involve the conscious brain so it is quicker than normal responses

Question 35

What does the cornea do?

Answer 35

Refracts light into the eye

Question 36

What does the iris do?

Answer 36

Controls how much light enters the pupil

Question 37

What does the lens do?

Answer 37

Refracts light, focusing it onto the retina

Question 38

What does the retina do?

Answer 38

Senses light as it is covered in receptor cells called rods and cones

Question 39

What does the optic nerve do?

Answer 39

Carries electrical impulses from receptors to the brain

Question 40

What does the pupil do?

Answer 40

Allows light to pass through as it enters the eye

Question 41

What is the pupil reflex?

Answer 41

In dark conditions the pupil dilates to allow for more light. In light conditions it constricts to prevent retina damage.
To constrict the pupil the circular muscles contract and the radial muscles relax
To dilate the pupil the circular muscles relax and the radial muscles contract

Question 42

What are rods and cones?

Answer 42

Found in the retina
Rods are sensitive to dim light but not colour
Cones are sensitive to colours but not good in dim light

Question 43

How and why does the lens change shape?

Answer 43

For light that is far away the lens needs to be flatter so less refraction happens. Ciliary muscles relax and suspensory ligaments become tense.
For light that is near the lens needs to be rounder so more refraction happens. Ciliary muscles contract and suspensory ligaments become slack.

Question 44

What is long sightedness caused by? How is it treated?

Answer 44

It occurs when the lens is the wrong shape and does not bend the light enough or when the eyeball is too short. Light from near objects is focussed behind the retina. Glasses with a convex lens fixes it.

Question 45

What is short sightedness caused by? How is it treated?

Answer 45

It occurs when the lens is the wrong shape and bends light too much or when the eyeball is too long. Light from distant objects is focussed in front of the retina. Glasses with a concave lens fixes it.

Question 46

What is colour blindness caused by? How is it treated?

Answer 46

Cones in the retina are not working properly so you cannot tell the difference between certain colours. There is no cure as cone cells cannot be replaced.

Question 47

What are cataracts caused by? How is it treated?

Answer 47

It is a cloudy patch on the lens, which stops light from being able to enter the eye normally. This causes blurred vision. Sometimes colours look less vivid and it is difficult to see in bright light. It can be treated by replacing the lens with an artificial one.