cells and control sample questions and answers Flashcards

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1
Q

How many pairs of chromosomes are present in a diploid nerve cell?

A

23

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2
Q

What happens immediately before mitosis in the cell cycle?

A

Checking for errors in copied DNA

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3
Q

What phase in mitosis involves the pulling of chromosomes and their copies to different ends of the cell?

A

Anaphase

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4
Q

Explain the difference between sensory, relay and motor neurones in terms of the direction that their electrical signals travel. [3 marks]

A

-sensory neurones carry electrical signals from receptors to the central nervous system

-relay neurones carry electrical signals within the central nervous system (brain and spinal cord)

-motor neurones carry electrical signals away from the central nervous system to effectors (muscles and glands)

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5
Q

Explain why reflex arc signals do not immediately go to the brain. [2 marks]

A

-because it would take longer to react if they did
-this might increase any damage to the body

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6
Q

Describe how are embryonic and adult stem cells different? [2 marks]

A

-adult stem cells are only found in specific locations like the nose and bone marrow

-embryonic stem cells make up all of an embryo

-adult stem cells can only differentiate into a small number of cell types

-embryonic stem cells can differentiate into all cell types

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7
Q

State what types of human cells are not produced by mitosis? [1 marks]

A

Gametes (sperm and ova)

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8
Q

Describe how someone with short sight can see more clearly? [3 marks]

A

-they can wear concave lenses in glasses

-they could also wear contact lenses or undergo laser surgery

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9
Q

Explain the process of accommodation. [4 marks]

A

Answer (four from):

-to focus on a near object, the lens becomes thicker

-thicker lens allows the light rays to refract (bend) more strongly

-thicker lens allows light to focus on the retina

-to focus on a distant object, the lens is pulled thin

-thinner lens this allows the light rays to refract slightly

-thinner lens allows light to focus on the retina

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10
Q

A baby boy is born in the 9th percentile for height. Explain what this means for him in terms of the rest of the population. [1 mark]

A

For every 100 boys, 91 will be taller than him and only 8 will be shorter.

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11
Q

Describe the method used to investigate the speed of reaction times. [4 marks]

A

Answer (four from):

-person A holds out their hand with a gap between their thumb and first finger

-person B holds the ruler with the zero at the top of person A’s thumb

-person B drops the ruler without telling Person A and they must catch it

-the number level with the top of person A’s thumb is recorded in a suitable table - repeat this ten times

-swap places, and record another ten attempts

-you can use the conversion table to help convert your ruler measurements into reaction time or just record the catch distance in cm

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12
Q

Describe how you could adjust this method to show the effect of stimulants in reaction times. [2 marks]

A

Answer (two from):

-both person A and B both drink a caffeinated drink after they have measured their reaction times

-wait fifteen minutes for the caffeine to have an effect on the nervous system

-repeat the experiment and compare the results

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13
Q

Describe the structure and function of the nerves in the nervous system. [6 marks]

A

-the central nervous system is made up of the brain and spinal cord

-the peripheral nervous system is a network of nerves that cover the rest of the body

-receptor cells in sense organs start electrical signals which travel along sensory neurones to the central nervous system (two marks)

-relay neurones carry electrical signals around the central nervous system

-motor neurones carry electrical signals away from the central nervous system to effectors which are muscles or glands (two marks)

-gaps between neurones are called synapses

-all neurones have extended projects called axons along which electrical signals travel

-axons are insulated by myelin sheaths to speed up the electrical signals

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14
Q

Describe the structure of DNA in a eukaryotic cell. [6 marks]

A

-DNA is made of four base pairs

-A-T, T-A, C-G, G-C

-bases are joined together by weak hydrogen bonds

-DNA is coiled into a double helix shape

-a section of DNA that codes for a protein is called a gene

-genes come in pairs called alleles

-chromosomes are long lengths of DNA which contain many genes

-an organism’s entire DNA is called a genome

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15
Q

Describe the steps in mitosis. Give their names in your answer. [6 marks]

A

-interphase - the DNA in chromosomes copies itself ready for mitosis

-prophase - the membrane around the nucleus disappears

-metaphase - chromosomes and their copies line up in the middle of the cell

-anaphase - chromosomes and their copies are pulled to different ends of the cell

-telophase - new membranes form around the chromosomes at each end of the cell

-cytokinesis - the cell membrane pinches in and eventually divides into two daughter cells

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16
Q

Describe the differences in the cells produced in mitosis and meiosis. [4 marks]

A

-mitosis produces two [1 mark] identical [1 mark] diploid [1 mark] daughter cells

-meiosis produces four [1 mark] non-identical [1 mark] haploid [1 mark] daughter cells

17
Q

Explain how and where cell differentiation in plants occurs. [4 marks]

A

Answer (four from):

-mitosis in plant cells occurs in the meristems

-these are areas in the tips of roots and shoots

-mitosis produces stem cells in meristems

-these can differentiate into any type of cell

-as the root or shoot grows further stem cells are produced

-older stem cells differentiate to become part of the shoot or root

-this means they become larger [1 mark] and form permanent vacuoles [1 mark]

18
Q

Describe how mutations in DNA are caused and explain their possible effects. [5 marks]

A

Answer (five from):

-mutations are changes in the DNA sequence of an organism

-they can be insertion, deletion, substitution or inversion of base pairs

-this can be advantageous / disadvantageous / have no effect

-mutations are caused at random, or by ionising radiation and mutagenic chemicals (carcinogens)

-rapid cell growth of mutated cells can form cancerous tumours
benign tumours grow slowly / are easily removed / do not invade other parts of the body

-malignant tumours grow rapidly / more difficult to remove / do invade other parts of the body