Topic 2 - Cells and Control

Question 1

stages of mitosis

Answer 1

(1). interphase: the cell makes extra cell parts (such as mitochondria) and copies all of the chromosomes
2. prophase: spindle fibres form in the cell and the nuclear membrane starts to disappear
3. metaphase: chromosomes line up in the middle of the cell
4. anaphase: the chromosomes are pulled apart by the spindle fibres
5. telophase: the single chromosomes arrive at opposite ends of the cell and the membranes around each nucleus start to form again
(6). cytokinesis: the cytoplasm of the cell separates and the cell membrane divides the cell into two genetically identical diploid daughter/body cells

Question 2

mitosis feature of process

Answer 2

chromosomes duplicate before division begins
1 duplication stage
1 cell division
new cells are diploid
there is no genetic variation in the cells formed (genetically identical)
2 cells produced
PRODUCT: two genetically identical diploid daughter/body cells

Question 3

role of mitosis

Answer 3

asexual reproduction
growth and repair of cells

Question 4

cell differentiation

Answer 4

the process that a stem cell goes through to become specialised

Question 5

importance of differentiation in plants

Answer 5

to produce all the different types of cell a plant needs such as root hair cells and xylem cells

Question 6

zone of cell division

Answer 6

cells divide rapidly by mitosis (stem cells)

Question 7

zone of elongation

Answer 7

cells grow in length

Question 8

zone of differentiation

Answer 8

cells differentiate to become specialised e.g. xylem or root hair cells

Question 9

stem cells

Answer 9

undifferentiated cells which have not yet specialised

Question 10

plant stem cells

Answer 10

found in a region called the meristem
they can differentiate and become specialised into any type of cell
in the roots and shoots

Question 11

animal stem cells

Answer 11

Embryonic stem cells - can differentiate into all other types of cell in the body

Adult stem cells (found in bone marrow) can differentiate into a few different types of cells

Embryonic stem cells lose their ability to differentiate as the animal matures (as they turn into adult stem cells & normal cells)

Question 12

advantages of stem cells

Answer 12

• rebuilding bones and cartilage
• repairing damaged immune systems
• making replacement heart valves
• curing diabetes
• can treat diseases like diabetes
• organs developed from a patient’s own stem cells reduces the risk of organ rejection and the need to wait for an organ donation.

Question 13

disadvantages/risks of stem cells

Answer 13

• Risk of cultured stem cells accumulating mutations (unpredictable) > may not form the cells you want > tumours > cancer (uncontrolled cell division)
• Stem cells cultured in the lab could become infected with a virus which could be transmitted to the patient.
• Harvesting embryonic stem cells destroys the developing life
• It is difficult to harvest adult stem cells
• Will further research lead to ‘designer’ babies?
• Low number of stem cell donors

Question 14

stimulus

Answer 14

a piece of information is detected by the nervous system

Question 15

sensory receptors

Answer 15

sensory receptors detect a stimulus. Receptors are a group of cells that can detect a change in environment which is known as a stimulus. They can be of different types for example, skin receptors can detect changes in temperature and pressure whereas eye receptors can detect light.

Question 16

sensory neurone

Answer 16

carries electrical impulse back to brain and spine, from sensory receptor

Question 17

relay neurone

Answer 17

nerve cell in the CNS that makes decisions, carrying the electrical impulse from the sensory neurone to the motor neurone

Question 18

motor neurone

Answer 18

carries impulses from the CNS to the effectors

Question 19

effector

Answer 19

the body part that produces the response

Question 20

response

Answer 20

the action that happens thanks to the nervous system

Question 21

what is part of the Central Nervous System (CNS)

Answer 21

brain
spinal chord

Question 22

what is part of the Peripheral Nervous System (PNS)

Answer 22

neurons
effectors

Question 23

axon

Answer 23

conducts information to other cells, away from the cell body

Question 24

dendrites

Answer 24

contacted by other neurons

Question 25

nerve endings

Answer 25

pass impulses on to other neurons/cells

Question 26

myelin sheath

Answer 26

insulates the axon and allows impulses to transfer faster also protects axon and dendron from electrical signals from other nerve cells

Question 27

dendron

Answer 27

carries the impulse toward the cell body

Question 28

role of the synapse

Answer 28

- ensures that nerve impulse only travels in one direction - one neurone can connect to many others - many neurones can connect to just one - low level stimulation is filtered out before it reaches the CNS

Question 29

reflex definition

Answer 29

a rapid, automatic, and involuntary action not controlled by the brain's conscious thought. it is the same in all members of that species, which has evolved as a protective mechanism

Question 30

steps of what happens at the synapse

Answer 30

1. an electrical impulse arrives at the axon terminals of the pre-synaptic neurone 2. this triggers the synaptic vesicles to release neurotransmitters (chemical messengers) into the synapse 3. the neurotransmitters diffuse across the synapse (down a concentration gradient) from the pre-synaptic membrane 4. they bind to receptors on the post-synaptic membrane 5. this triggers an impulse at the dendrites of the post-synaptic neurone (6. the neurotransmitters are recycled or destroyed once an impulse is sent)

Question 31

factors affecting the speed of nervous transmission

Answer 31

- myelination - axon diameter: a wider axon allows impulses to travel faster because there's less resistance to the flow of ions inside the neurone - temperature: higher temperatures generally increase the speed of nerve transmission because chemical reactions (e.g. neurotransmitter release) happen faster. however, if it's too hot, proteins can denature, slowing or stopping transmission - presence of synapses: at synapses, transmission is slower than along axons because the signal has to be converted to a chemical message, then back to an electrical impulse

Question 32

pathway of a sensory neurone

Answer 32

Stimulus detected by sensory receptor, convened into electrical signals, travel along dendron to cell body and from cell body along axon to axon terminal. myelin sheath insulates axon ensuring signals are carried very quickly. synapse is the junction between 2 neurones. electrical signals can't pass across synapse but instead stimulates the release of neurotransmitters in pre-synaptic neurone that move across the synapse to receptors on the post-synaptic neurone and eventually to the CNS

Question 33

journey of electrical impulse

Answer 33

1. stimulus 2. sensory receptor/cell 3. sensory neurone 4. relay neurone in CNS 5. motor neurone 6. effector 7. response

Question 34

cancer is as a result of mutations/changes in cells that lead to uncontrolled cell division

Question 35

growth in organisms

Answer 35

animals: cell division and differentiation plants: cell division, elongation and differentiation

Question 36

location of different stem cells

Answer 36

embryonic stem cells: early embryos during the blastocyst stage adult stem cells: bone marrow stem cells: meristem in roots and shoots. this means plants can only grow from their shoot tips and root tips

Question 37

specialised cells found in plants

Answer 37

root hair cells palisade cells phloem companion cells stomata guard cells