Paper 1 Cell 5

Question 1

How are alveoli specialised to maximise the diffusion of O2 and CO2?

Answer 1

• an enormous surface area
• a moist lining for dissolving gases
• very thin walls a good blood supply

Question 2

How are villi specialised to maximise diffusion?

Answer 2

• there’s millions of them in the small intestine
• they increase the surface area so that digested food is absorbed more quickly into the blood
• have a single layer of surface cells
• also have a good blood supply to assist quick absorption (concentration gradient)
• (diffusion and active transport)

Question 3

What’s a stem cell?

Answer 3

-an undifferentiated cell of an organism which is capable of dividing into to many more cells of the same type, from which certain other cells can arise from differentiation

Question 4

Where can stem cells be found in humans and what can they do?

Answer 4

• early human embryos: can be cloned and made to differentiate into most types of human cells
• adult blood marrow: can form some types of cells including blood cells

Question 5

Where can stem cells be found in a plant?

Answer 5

• in the meristems (where growth occurs)
• the meristem tissues can differentiate into any type of plant cell (throughout its entire life)
• can produce clones of whole plants quickly or cheaply
• can be used to grow more plants of a rare species or grow crops of identical plants that have desired features for farmers (eg. Disease resistance)

Question 6

What’s therapeutic cloning?

Answer 6

• An embryo could be made to have the same genetic information as the patient
• this means the stem cells produced would have the same genes and wouldn’t be rejected by the patients body

Question 7

Explain what 2 things could be cured with theoretic cloning and why?

Answer 7

• you could make insulin-producing cells for people with diabetes
• nerve cells for people paralysed by spinal injuries

Question 8

What are the risks of therapeutic cloning?

Answer 8

Stem cells grown in a lab can become contaminated with virus which could be passed onto the patient making them sicker

Question 9

Why are some people against stem cell research?

Answer 9

• don’t feel human embryos shouldn’t be used for experiments since each one is a potential human life
• while others believe curing patients who are suffering is more important than the rights of embryos
• the embryos used in research are usually unwanted ones from fertility clinics so if they weren’t used for research they’d be destroyed
• campaigners believe scientist should find another source if stem cells
• religious people feel it’s unethical as it‘d destroying a potential life, and as the embryo can’t give consent it is a human rights violation