Topic 2 - The Brain, Eye And Nervous System

Question 1

An embryonic stem cell can (1)

differentiate into any type of cell
differentiate into only one type of cell
only be obtained from embryos
only produce haploid cells

Answer 1

differentiate into any type of cell

Question 2

Describe how the structure of a red blood cell is related to its function. (3)

Answer 2

Biconcave shape (1)
No nucleus (1)
Thin membrane (1)
Flexible/small (1)
Contains haemoglobin (1)

Large surface area/increase oxygen uptake (1)
To increase amount of haemoglobin/oxygen carrying capacity (1)
So short distance for diffusion (1)
To get through capillaries (1)
To bind oxygen (1)

Question 3

Describe the function of platelets. (2)

Answer 3

Clotting/to seal a wound/scab formed (1)
Stop bleeding (1)
Prevent infection/entry of microbes (1)
Fibrin (1)

Question 4

Mitosis and meiosis are types of cell division.
Compare these two types of cell division. (6)

Answer 4

Mitosis:
2 genetically identical diploid daughter cells produced
One division
Identical set of chromosomes
Occurs in the formation of body cells
For growth and repair (of body cells)

Meiosis:
4 genetically non-identical haploid daughter cells produced
2 divisions
Half the number of chromosomes
Occurs in the formation of gametes
For sexual reproduction
Results in genetic variation

Question 5

Corals can reproduce sexually, releasing sperm cells into the water.
The mass of DNA in one sperm cell from a species of coral is 0.5 picogram.
Suggest the mass of DNA that would be present in an unfertilised egg cell of the same species. (1)

Answer 5

0.5 picogram

Question 6

The term used to describe the number of chromosomes in an egg or sperm cell is… (1)

A diploid
B gamete
C haploid
D zygote

Answer 6

Haploid

Question 7

The base pairs in DNA are (1)

thymine with adenine, cytosine with guanine
thymine with guanine, adenine with cytosine
uracil with adenine, guanine with cytosine
uracil with thymine, guanine with cytosine

Answer 7

thymine with adenine, cytosine with guanine

Question 8

Name the bond that joins the base pairs (in DNA) together. (1)

Answer 8

Weak hydrogen bond

Question 9

After fertilisation, mitosis takes place to form an embryo.
The embryo develops into new coral.
Describe mitosis. (3)

Answer 9

Cell divides/splits (1)
2 cells produced (1)
Both diploid (1)
Both cells are genetically identical (1)

Question 10

Corals can reproduce sexually, releasing sperm cells into the water.
Describe how the embryo develops into new coral.
(3)

Answer 10

Many cell divisions (1)
Growth (1)
Differentiation/specialisation (1)
Stem cells formed (1)

Question 11

Some students investigated water movement in plant cells.
They measured the mass of five pieces of potato.
Each piece of potato was put into a different concentration of salt solution.
After one hour the pieces of potato were dried and the mass of each was recorded.
Suggest why calculating a percentage change is more useful than calculating the change in mass in this investigation. (1)

Answer 11

Better/easier comparison can be made between values

Question 12

Mitosis occurs in plant cells during growth.
Describe the division of a cell by mitosis. (3)

Answer 12

Produce 2 daughter cells (1)
Which are genetically identical (1)
And diploid (1)

Question 13

Explain how active transport and diffusion provide a plant with named substances it needs for growth. (6)

Answer 13

• active transport requires energy
• (active transport moves mineral ions) from the soil
• into root (hair cells)
• reference to pumps (in the cell membranes)
• from a low concentration to a high concentration/against their concentration gradient
• reference to mineral ions / mineral salts accept named minerals eg nitrates
• diffusion is a passive process
• gases diffuse from high to low concentration/down their concentration gradient
• gas exchange in the leaf occurs by diffusion
• carbon dioxide diffuses in
• to air spaces in leaves / into cells
• for photosynthesis / produces glucose
• oxygen diffuses in
• for respiration

Question 14

Which statement is true for DNA? (1)

DNA is made up of amino acids and bases.
DNA is made up of amino acids which give instructions to make proteins.
In DNA, the bases A and T are complementary.
Every gene in a DNA molecule contains only 3 bases.

Answer 14

In DNA, the bases A and T are complementary.

Question 15

Sperm cells are involved in fertilisation.
Define fertilisation. (2)

Answer 15

A sperm cell fuses with an egg/penetrates the egg (1)
Nuclei/genetic information combines/fuses (1)
Haploid gametes/gametes with 23 chromosomes (1)
Zygote/diploid cell/cell with 23 pairs of chromosomes produced (1)

Question 16

Describe the function of mitochondria. (2)

Answer 16

(Aerobic) respiration/using oxygen/using glucose (1)
Energy released (for movement/swimming/metabolism) (1)

Question 17

Gene mutations in DNA can produce abnormal mitochondria.
Explain how a gene mutation can produce a different protein. (2)

Answer 17

A change in a base/base sequence/order of bases/mRNA (1)
E.g. addition/deletion (1)
Change in an amino acid/order of amino acid (1)

Question 18

A person with diabetes cannot control (1)

the water content of their blood
the glucose content of their blood
their body temperature
their body mass index

Answer 18

The glucose content of their blood

Question 19

Explain how Type 1 diabetes can be controlled. (3)

Answer 19

Insulin (1)
Is injected (1)
Use a low carbohydrate diet/healthy diet (1)
Regular exercise (1)
When blood glucose levels are too high/regulate blood glucose levels (1)

Question 20

Body movement is controlled by nerve impulses.
Explain how impulses are transmitted in a reflex arc to prevent a person from injuring themselves. (6)

Answer 20

• a reflex response is an involuntary response
• reflex responses do not involve the brain
• reflex responses involve sensory neurones
• reflex responses involve relay neurones
• reflex responses involve motor neurones
• relay neurones are in the spinal cord
• impulses travel along neurones as electrical signals
• the axon is insulated by the myelin sheath
• which ensures the electrical signal does not lose energy
• at the junction between two neurones there is a synapse
• the message is carried across the synapse by neurotransmitters
• the message travels from the stimulus along the axon and dendron of the sensory neurone to the spinal cord
• the reflex arc is important to keep the body safe

Question 21

Explain how information travels along the axon of a sensory neurone. (2)

Answer 21

From receptor cells/sense organ (1)
To the brain/CNS/spinal cord (1)
As an electrical impulse (1)

Question 22

Describe the role of the myelin sheath. (2)

Answer 22

Insulates (1)
The axon (1)
Speeds up the impulse (1)

Question 23

Describe the pathway of a nerve impulse through a reflex arc. (3)

Answer 23

Receptor cells pick up a stimulus (1)
Sensory neurone sends a message to the CNS/relay neurone (1)
The message travels from the relay neurone/CNS to the motor neurone (1)
This initiates a response in the effector/muscle (1)
Message travels across synapse (by neurotransmitters) (1)

Question 24

There are many different types of cell in the human body.
Complete the sentence:
An embryonic stem cell can… (1)

differentiate into any type of cell
differentiate into only one type of cell
only be obtained from embryos
only produce haploid cells

Answer 24

differentiate into any type of cell

Question 25

Which structure of the eye contains the light receptor cells? (1)

Answer 25

Retina

Question 26

The optic nerve transfers electrical signals from the eye to the central nervous system
The optic nerve is a… (1)

relay neurone
motor neurone
sensory neurone
reflex neurone

Answer 26

Sensory neurone

Question 27

Name the region of the central nervous system responsible for vision. (1)

Answer 27

Cerebrum

Question 28

Macular degeneration is a defect of the eye that occurs when some cells of the retina begin to break down.
Embryonic stem cell therapy has been used to improve the vision of some patients with macular degeneration.
Explain how embryonic stem cells could be used to treat macular degeneration. (2)

Answer 28

Embryonic stem cells can be stimulated to produce cells of the retina (1)
Which can be transplanted into the patient’s eye to replace the damaged cells (1)

Question 29

Some research has shown that increased use of computers and other digital media can affect eyesight and reaction times.
A scientist wanted to test if prolonged use of a computer affected reaction time.
The scientist tested the reaction times of 10 people under the same environmental conditions.
These people then used a computer for three hours.
The scientist tested their reaction time again.
Give three ways that the scientist could improve this method to determine if prolonged use of a computer affects reaction time. (3)

Answer 29

Vary the time for computer usage (1)
The activity used on the computer must be the same for each person (1)
Control the intake of food/drink/drugs before and during the test (2)
Repeat the test at different times of the day (1)
Repeat the test using more people (1)

Question 30

The axon carries information along the neurone as
(1)

chemical messages
electrical impulses
neurotransmitters
hormonal responses

Answer 30

electrical impulses

Question 31

Describe the role of the myelin sheath surrounding the axon. (2)

Answer 31

Insulates the axon/neurone/impulse (1)
Allows quicker electrical conductance (1)

Question 32

There is a gap between neurones.
State the name for this gap between neurones. (1)

Answer 32

Synapse