Cells And Control

Question 1

List in order the stages of the cell cycle

Answer 1

Interphase, Mitosis (Prophase, Metaphase, Anaphase, Telophase), Cytokinesis (before telophase ends)

Question 2

What happens during interphase?

Answer 2

In a cell that’s not dividing, DNA is spread out in long strings. During interphase, the cell grows and increases the number of sub cellular structures such as mitochondria and ribosomes. It then duplicates its DNA, which is copied and forms X-shaped chromosomes where each arm of the X is a copy of the other.

Question 3

What happens during prophase?

Answer 3

Chromosomes condense, getting shorter and fatter. The membrane around the nucleus breaks down and chromosomes lie free in the cytoplasm.

Question 4

What happens during metaphase?

Answer 4

Chromosomes line up at the centre of the cell

Question 5

What happens during anaphase?

Answer 5

Cell fibres pull chromosomes apart. The two arms of each go to opposite ends of the cell.

Question 6

What happens during telophase?

Answer 6

Membranes form around each set of chromosomes which become the new nuclei.

Question 7

What is cytokinesis?

Answer 7

Cytoplasm and cell membrane divide to form two separate cells

Question 8

Why is mitosis important for an organism?

Answer 8

Growth, repair and asexual reproduction

Question 9

Why may organisms rely on asexual reproduction?

Answer 9

More offspring more quickly, no mate needed, only one parent needed so isolation is not a problem.

Question 10

How do cancers grow?

Answer 10

If there is a change in one of the genes controlling cell division, the cell may start dividing uncontrollably which can result in a mass of abnormal cells (tumour) which can invade and destroy surrounding tissue (cancer)

Question 11

Define growth in animals

Answer 11

An increase in cell number and size

Question 12

Give examples of specialised animal cells.

Answer 12

Sperm, egg, ciliated epithelial, red blood, white blood

Question 13

Describe how the structure of specialised animal cells is related to their function.

Answer 13

Red blood cells: no nucleus and biconcave shape to maximise space to carry oxyhaemoglobin.
White blood cells: can make antibodies.

Question 14

Why is cell differentiation important to the development of specialised cells?

Answer 14

Cell differentiation is the process by which undifferentiated (stem) cells become specialised for their function

Question 15

What is a percentile growth chart and how is it used?

Answer 15

Used to assess a child’s growth over time. 3 measurements: length, mass and head circumference. A chart shows a number of percentiles-50th percentile shows the mass etc that 50% of babies have reached by that age. Doctors investigate if a baby is above or below the top or bottom percentile or if there are abnormalities

Question 16

Describe the stages of growth in plants.

Answer 16

Mitosis happens in meristems (tips of roots or shoots). Cell elongation is where plant cells expand. Cell differentiation is where cells produced in the meristems become specialised

Question 17

Give examples of and describe specialised plant cells

Answer 17

Root hair cell: no chloroplasts, large surface area to aid diffusion, osmosis and active transport
Phloem: elongated, small pores in the end to allow transportation of food substances which uses energy from respiration
Xylem: dead cells strengthened with lignin joined end to end with no end wall to allow water uptake
Palisade: packed with chloroplasts to easily facilitate photosynthesis

Question 18

Where are stem cells found?

Answer 18

Meristems (roots and shoots) in plants
Embryos
Bone marrow in adults (stem cells partially specialised)

Question 19

What is the function of stem cells?

Answer 19

Growth, repair and development

Question 20

What is the difference between embryonic and adult stem cells?

Answer 20

Embryonic stem cells can differentiate to form any cell whereas adult stem cells can only form certain types of cell and are for repair.

Question 21

Where may stem cells be used in medicine?

Answer 21

Adult stem cells can be used to cure some diseases e.g. sickle cell anaemia can be cured with a bone marrow transplant.
Scientists have experimented with using embryonic stem cells to create specialised cells which could be used to replace damaged cells e.g. new cardiac muscle cells

Question 22

What are the benefits of using stem cells in medicine?

Answer 22

New cures for currently incurable diseases

Potential for “fixing” injuries which previously wouldn’t heal

Question 23

What are the risks of using stem cells?

Answer 23

Tumour development leading to cancer
Disease transmission from donor to patient
Rejection

Question 24

What are the brain and spinal cord made up of?

Answer 24

Spinal cord is a long column of neurones

Brain is billions of interconnected neurones

Question 25

Draw and label a diagram of the brain.

Answer 25

Use google

Question 26

What are the functions of the different parts of the brain?

Answer 26

Cerebrum: largest part, divided into cerebral hemispheres, right hemisphere controls muscles on left side of the body & vice versa. Different parts responsible for different things including movement, intelligence, memory, language and vision Cerebellum: muscle coordination and balance Medulla oblongata: unconscious activities including breathing and heart rate

Question 27

Describe CT scanning

Answer 27

Uses X-rays to produce an image of the brain. Shows main structures but not functions Shows diseased or damaged brain structures which can be used to work out function

Question 28

Describe PET scanning

Answer 28

Uses radioactive chemicals to show which parts of the brain are active (or unusually active/inactive which can be useful in studying disorders which affect brain activity e.g. Alzheimer's disease) and can be used to investigate the structure and function of the brain in real time

Question 29

What are the effects of spinal cord damage?

Answer 29

It can cause paralysis, issues with responses since brain commands are issued through the spinal cord

Question 30

What are the effects of damage to different parts of the brain?

Answer 30

Damaging some areas, such as the frontal lobe, can change personality as these areas affect that. Damage to other areas will affect the thing they control

Question 31

What are the limitations of brain and spinal cord surgery?

Answer 31

It is hard to repair damage to the CNS as neurones don't easily repair themselves. Some areas are difficult to access. Treatment may lead to permanent damage if issues occur

Question 32

List the parts of the nervous system

Answer 32

Neurones (sensory, motor and relay) | Brain and spinal cord (CNS)

Question 33

How does the nervous system detect stimuli?

Answer 33

Receptors detect it and it is converted to an electrical signal which is transported to the CNS along sensory neurones. The CNS coordinates the response. Impulses travel through the CNS along relay neurones. The CNS sends info to an effector along a motor neurone.

Question 34

Describe the structure of sensory neurones and explain how they are adapted to their function

Answer 34

One long dendron (long neurones are quicker than lots of short ones) carries nerve impulses from receptors to the cell body in the middle of the neurone. One short axon carries nerve impulses from the cell body to the CNS. Neurones may have a myelin sheath, which insulates them, speeding up the impulse

Question 35

Describe the structure of motor neurones and explain how they are adapted to their function

Answer 35

Many short dendrites carry nerve impulses from the CNS to the cell body in the middle of the neurone. One long (long neurones are quicker) axon carries nerve impulses from the cell body to effector cells . Neurones may have a myelin sheath.

Question 36

Describe the structure of relay neurones and explain how they are adapted to their function

Answer 36

Many short dendrites carry nerve impulses from sensory neurones to the cell body in the middle of the neurone. An axon carries nerve impulses from the cell body to effector cells . Neurones may have a myelin sheath.

Question 37

Describe the route that impulses take to and from the brain

Answer 37

Stimulus, receptor, sensory neurone, CNS, Motor neurone, effector, response

Question 38

Identify the main parts of the eye

Answer 38

Cornea, iris, lens, retina, rods, cones, optic nerve | In unsure of locations check google

Question 39

How is the cornea adapted to its function?

Answer 39

It refracts light into the eye. It is transparent and convex.

Question 40

How is the lens adapted to its function?

Answer 40

It focuses light onto the retina. It is elastic, allowing near and far objects to be focussed on when suspensory ligaments and ciliary muscles pull tight and relax in turn

Question 41

How is the iris adapted to its function?

Answer 41

It controls how much light enters the pupil. It receives information from the CNS to allow it to shrink the pupil in bright light and grow it in dim light

Question 42

How is the retina adapted to its function?

Answer 42

Light sensitive part- covered in rods (which are sensitive in dim light) and cones (which detect colour)

Question 43

What is colour blindness?

Answer 43

Colour-blind people can't tell the difference between certain colours. It is caused when some of the cones on the retina do not work properly and is currently incurable as cone cells cannot be replaced

Question 44

What is long sightedness and how is it corrected?

Answer 44

Occurs when the lens doesn't refract light enough our eyeball is too short so light from near objects is brought into focus behind the retina. It can be corrected by glasses with a convex lens.

Question 45

What is short sightedness and how is it corrected?

Answer 45

Occurs when the lens refracts light too much or the eyeball is too long so light from distant objects is brought into focus in front of the retina. Glasses with a concave lens correct this

Question 46

What are cataracts and how are they treated?

Answer 46

A cataract is a cloudy patch on the lens which causes blurry vision. It is treated by replacing the faulty lens with an artificial lens

Question 47

Explain the action and function of synapses

Answer 47

Synapses are the connections between neurones. The nerve signal is transferred by neurotransmitters which diffuse across the gap. Synapses slow down the transmission of nervous impulses.

Question 48

Why does the reflex arc allow a faster response?

Answer 48

You don't have to think about it as it goes through an unconscious part of the brain or the spinal cord

Question 49

Describe the structure and function of the reflex arc

Answer 49

Stimulus is detected. Impulses are sent along a sensory neurone to a relay neurone in the CNS to a motor neurone to an effector (muscle or gland)