CB2: Cells And Controls

Question 1

Why do we need mitosis?

Answer 1

To survive and grow

Question 2

How many chromosomes do somatic cells have?

Answer 2

23 pairs
46
Diploid

Question 3

What happens in mitosis?

Answer 3

It makes two identical daughter cells which contains the same numbers of chromosomes as in the parent cells

Question 4

What can mitosis be used for as well as growth and repair?

Answer 4

Asexual reproduction

Question 5

Describe interphase

Answer 5

All the sub-cellular structures double up- 46 into 92 chromosomes, for example, so there’s one copy for each new cell and they are diploid

Question 6

Describe prophase

Answer 6

The chromosomes condense and get shorter and fatter

The nucleic envelope breaks down and the chromosomes are free in the cytoplasm

Question 7

Describe Metaphase

Answer 7

The chromosomes line up at the centre of the cell

Question 8

Describe Anaphase

Answer 8

Cell fibres pull the chromosomes apart, separating to opposite poles of the cell

Question 9

Describe telophase

Answer 9

Membranes form around each set of chromosomes

They become the nuclei of the new daughter cells

Question 10

Describe cytokinesis

Answer 10

The cell cleaves and divides forming two new daughter cells

Question 11

Name the three ways organisms can grow

Answer 11

Cell elongation
Cell differentiation
Cell division

Question 12

What is differentiation?

Answer 12

Cells eg stem cells change and specialise to their function

Allows us to work more efficiently as organisms and therefore grow quicker

Question 13

Cell elongation

Answer 13

Cells in plants get longer, making the plant bigger and helping it to grow
Helps the plant grow in height

However cell division does happen in meristems at the tips of roots and shoots

Question 14

What is cancer?

Answer 14

A change in the genes that controls cell division could lead to the cells dividing uncontrollably which can result in a large ball of abnormal cells called a TUMOUR
The tumour can invade and destroy tissue causing cancer

Question 15

Percentile charts

Answer 15

Used to monitor growth and find any problems eg obesity or dwarfism

Question 16

Why is cell differentiation important

Answer 16

Allows undifferentiated cells like stem cells to specialise and adapt to a role eg nerve cells having long and thin strands to transport messages around the body
They are useful because they fulfil a specific job in the body and allow organisms to work for efficiently

Question 17

What are stem cells

Answer 17

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

Question 18

Where are adult stem cells found

Answer 18

Bone marrow (which can replenish itself) and the spinal cord

Question 19

Where else can stem cells be found

Answer 19

Embryos

Question 20

What can embryonic stem cells do

Answer 20

They are pluripotent and are bale to differentiate into any type of somatic cell
This is because their original use is to differentiate and grow an early embryo and give it human features

Question 21

Why are adult stem cells less useful than embryonic stem cells

Answer 21

Because they can only differentiate into certain somatic cells eg blood and skin cells and are less versatile: can change into less things

Question 22

What are meristem

Answer 22

Plant stem cells that can differentiate into anything much like embryonic stem cells and are found in areas of high and fast growth in the plant eg roots and shoots and behind root tips

They can differentiate into any specialised cell eg xylem (transports water) or phloem (transports food)

Question 23

How can adult stem cells treat disease

Answer 23

Bone marrow transplants can treat sickle cell anaemia as the cells can differentiate into new blood cells

Question 24

How can embryonic stem cells be used in medicine

Answer 24

They can be extracted and used to treat anything eg can make new cardiac muscle cells which can be transported to someone with heart disease

Question 25

What are potential risks with working with stem cells?

Answer 25

1) Rejection: the body could recognise the stem cells as foreign and trigger an immune response, meaning that the stem cells would not work as the body will get rid of them
2) Tumour potential: stem cells divide and reproduce quickly meaning that there is potential for a tumour to develop if there is a loss of control in rate of mitosis
3) Infection: if the stem cells from a donor are infected the virus could be passed on to the patient and make them sicker

Question 26

What controversy is there over the use of embryonic stem cells?

Answer 26

Some argue that an embryo is a chance for a new life and destroying it after 14 days is against morality

Question 27

What is a receptor

Answer 27

A cell on a sensory organ that is able to sense a stimulus

Question 28

What is a stimulus?

Answer 28

A change in the environment eg pressure, light and sound

Question 29

What does the nervous system do?

Answer 29

Coordinate responses to stimuli and react to or protect you from them

Question 30

What is the reflex arc?

Answer 30

SRSSRSMER- Stimulus, receptor, sensory neurone, synapse, relay neurone, synapse, motor neurone, effector muscle and response

Question 31

What is the difference between the reflex arc and a normal response?

Answer 31

Reflex arc is faster because the impulse doesn’t go to the brain and therefore doesn’t require thinking which takes time

Question 32

What is a synapse?

Answer 32

A gap between neurones

Question 33

What happens with the synapse?

Answer 33

Neurotransmitters are produced when the impulse goes down a neurone and diffuse across the synapse to the next neurone.
This slows the impulse as it takes time for diffusion of the neurotransmitters

Question 34

What is the CNS made from?

Answer 34

Brain and spinal cord

Question 35

What is the PNS made from?

Answer 35

Nerves

Question 36

How is the eye protected by reflex?

Answer 36

Very bright light can damage the eye.
Receptor cells in the eye sense the change in environment (stimulus) and circular muscles in the iris contract and make the pupil smaller so less damage is done to it

Light receptors-sensory neurone-CNS-relay neurone-motor neurone-effector circular muscle which contracts in response

Question 37

Describe sensory neurone stucture

Answer 37

Connected to receptor cells
One long dendron
One short axon
Cell body
Many short axon terminals transport impulse to CNS

Question 38

Describe the structure of a relay neurone

Answer 38

Many short dendrites transport impulse to the cell body

An axon carries impulse to the motor neurone

Question 39

Describe the structure of a motor neurone

Answer 39

Can have a myelin sheath- fatty layer of electrical insulation (makes impulse faster)
Short dendrites carry impulse from CNS to cell body
One long axon carries impulse to effectors which demonstrate a physical response

Question 40

What is the acronym for the reflex arc?

Answer 40

SMELLY - stimulus
RECTUM - receptor
SMELLY - sensory neurone
SMELLY - synapse
RECTUM - relay neurone
SMELLY - synapse
MEN - motor neurone
EAT - effector muscle/gland
RECTUM - response (contraction or secretion)

Question 41

A chef touches a hot tray. A reflex reaction causes him to move his hand away immediately. Describe the pathways of his reflex arc.

Answer 41

Firstly the receptor cells on chef’s skin sense a stimulus which is heat.

This triggers an electrical impulse. It is passed on to the sensory neurone which carries it through its dendron and axon to a synapse where neurotransmitters are produced and diffuse across the gap to the next relay neurone. The neurone then carries the impulse down to another synapse where the same thing happens. The impulse is then carried from the synapse to the motor neurone which passes the impulse to the effector muscle which contracts, meaning that the chef is away from danger as his response.