Topic 2 - Cells And Control

Question 1

What is a chromosome?

Answer 1

-contains coils of DNA

Question 2

What is a gene?

Answer 2

• short section of DNA that codes for a protein

Question 3

What is a gamete?

Answer 3

• sex cell e.g. egg & sperm

- has 23 chromosomes ( half) each

Question 4

What is a diploid cell?

Answer 4

• full amount of chromosomes ( 46)

Question 5

What is mitosis?

Answer 5

• cell reproduces by splitting to form two genetically identical daughter/ diploid cells

Question 6

Beginning Phase of mitosis

Answer 6

Interphase

- The DNA in chromosomes copies itself ready for mitosis.

Question 7

1st phase of mitosis

Answer 7

Prophase

- chromosomes condense (shorter & fatter) - nucleus membrane breaks down and spindle appearrs

Question 8

3rd phase of mitosis

Answer 8

• Anaphase

- spindle pulls chromosomes to polar parts of cell & spindle fibres get short while pulling away

Question 9

4th phase of mitosis

Answer 9

Telophase

- nucleus membrane reforms and chromosomes less condense and less visible and spindle disappears

Question 10

last (sort of) phase of mitosis

Answer 10

Cytokenesis

- cell divides into two – mitosis now complete

Question 11

How does cancer occur?

Answer 11

• small change in cells that leads to uncontrolled cell division

Question 12

What is a stem cell?

Answer 12

-undifferentiated cell which can undergo division to produce more similar cells

Question 13

What is therapeutic cloning?

Answer 13

• embryo produced with same genes as patient.

Question 14

Types of stem cells

Answer 14

• embryonic stem cells
• adult stem cells (found in bone marrow)
• meristems in plants

Question 15

Benefits of stem cells

Answer 15

• used to replace damaged or diseased body parts
• use unwanted stem cells that may have been thrown away
• further research into differentiation

Question 16

Disadvantages of stem cells

Answer 16

• hard to control stem cells to form desired cell
• people have religious & ethical objections
• expensive and time consuming

Question 17

What is the CNS?

Answer 17

• central nervous system – brain along w/ spinal cord

- controls conscience, movements, thoughts & emotions etc.

Question 18

What is the cerebral hemisphere?

Answer 18

• perform variety of functions, including consciousness, memory, intelligence & visual and sensory processing

Question 19

What is the cerebellum?

Answer 19

• structure found at bottom of brain, on rear side.

- responsible for muscle co-ordination, so can move in complex ways e.g. catching a ball

Question 20

What is the medulla oblongata?

Answer 20

• small ‘elongated’ structure found at base of the brain.

- responsible for basic autonomic (automatic) bodily functions e.g. breathing, digestion, swallowing and sneezing.

Question 21

What is a CT scan?

Answer 21

• fire X-Ray radiation at brain from different angles to generate 3D image of the brain
• used to examine bleeding within skull & damage to brain structure
• not recommended for pregnant woman or children- higher dose of radiation than X- ray

Question 22

What is a PET scan?

Answer 22

• radioactive ‘tracer’ injected into blood before scan.
• areas with greater blood flow, will be highlighted & tracer will build up
• used for identifying cancerous tumours, because use more blood than normal tissue

Question 23

What is the nervous system?

Answer 23

• allows us to react to surroundings & coordinate actions in response to stimuli.

Question 24

How does the nervous system work?

Answer 24

• Receptor cells convert stimulus into electrical impulse.
• electrical impulse travels along cells called sensory neurons to CNS
• information processed and appropriate response is coordinated
• then electrical impulse is sent along motor neurons to effectors.
• effectors carry out the response e.g. muscles contracting
• impulses travel from sensory, to relay and then motor neuron

Question 25

What is a reflex ?

Answer 25

- Automatic responses that take place before you have time to think - they don't travel through the brain

Question 26

Describe how a reflex works?

Answer 26

- stimulus is detected by receptors. - Impulses sent along a sensory neuron-- impulse passes to a relay neuron -- then a motor neuron. - motor neuron passes impulse to an effector and effector stimulates a response e. g. moving hand away from hot surface

Question 27

What is a synapse?

Answer 27

- gap between two neurons

Question 28

What is neurotransmitter?

Answer 28

- When impulse reaches end of first neuron, a chemical is released into the synapse.

Question 29

How does a neurotransmitter work?

Answer 29

- chemical released into the synapse. -neurotransmitter diffuses across the synapse. - When neurotransmitter reaches second neuron it triggers impulse to begin again in next neuron. -- Different neurotransmitters have different effects on the frequency and speed of the impulse in the second neuron.

Question 30

What is the myelin sheath?

Answer 30

- surrounds core of a nerve fiber or axon

Question 31

What is a retina?

Answer 31

- Layer of light sensitive cells found at back of eye. When light hits cells are stimulated impulses sent to brain -interprets info to create image.

Question 32

What are rod and cone cells ?

Answer 32

- found in retina Rod cells - sensitive to light -- better for seeing in low light Cone cells - allow to interpret different colours (colour vision)

Question 33

What is the cornea?

Answer 33

- see-through layer at front of eye. | - allows light through and curved surface bends (refracts) and focuses light onto retina

Question 34

What is the iris?

Answer 34

- muscles that surround pupil | - contract or relax to alter size of pupil

Question 35

What are ciliary muscles and suspensory ligaments?

Answer 35

- hold lens in place | - controls its shape & allows us to focus on objects nearer or further away

Question 36

What is the lens ( eye) ?

Answer 36

- Transparent, curved surface on front of eye. | - like cornea, reflects light onto retina.

Question 37

What is short sightedness?

Answer 37

- called myopia. - lens is too curved, distant objects appear blurry - need concave lens

Question 38

What is long sightedness?

Answer 38

- called hyperopia. - lens is too flat, so it cannot refract light enough - need convex lens

Question 39

How to focus on a near object

Answer 39

- ciliary muscles contract & suspensory ligaments loosen | - lens becomes thicker and more curved- this refracts light more

Question 40

How to focus on a distant object

Answer 40

- ciliary muscles relax & suspensory ligaments tighten | - lens becomes thinner - light is refracted less.

Question 41

What is a cataract ?

Answer 41

- clouding of the lens of the eye

Question 42

How to treat short and long sightedness?

Answer 42

- concave lenses to spread out the light to treat myopia ( short sightedness) - convex lenses to bring the rays together to treat hyperopia ( long sightedness)

Question 43

How does laser eye surgery work?

Answer 43

- used to reduce the thickness of the cornea -so it refracts light less- to treat short sightedness - used to change its curvature-so it refracts light more strongly- to treat long sightedness

Question 44

Examples of treatment for eyes?

Answer 44

- laser eye surgery - wearing glasses or contact lenses - replacement lenses

Question 45

Explain cancer

Answer 45

- it is as the result of changes in cells that lead to | uncontrolled cell division

Question 46

2nd phase of mitosis

Answer 46

- Metaphase | chromosomes line up at the equator of the cell

Question 47

Function of the myelin sheath

Answer 47

- insulates impulse from surrounding tissue | - speeds up transmission

Question 48

How is a red blood cell specialised

Answer 48

- no nucleus - so can increase its oxygen carrying capacity - contains haemoglobin --to bind to oxygen - flexible and small -- to get through capillaries