Topic 1:Cell biology

Question 1

Explain how the villi and the alveoli are adapted to absorb molecules into the bloodstream

Answer 1

-Both have a large surface area
-villi have many microvilli and alveolar walls are not flat
-to maximise diffusion/absorption of molecules
-both have many capillaries/good blood supply
- to maintain concentration
-Both have thin walls to provide short diffusion distance
-villi have many mitochondria to provide energy for active transport
-cells of villi have microvilli to further increase surface area

Question 2

Evaluate the use of stem cells from a patients own bone marrow instead of from an embryo

Answer 2

Embryo
+ can create many embryos in a lab
painless technique
can treat many diseases
- harm/death to embryos
ethical issues
unreliable technique/ may not work
Bone marrow
+ no ethical issues/ patient can give permission
can treat some diseases
procedure is safe/ doesn’t kill donor
patient recover quickly from procedure
- risk of infection
can only treat a few diseases
procedure can be painful
Both
+ can treat disease
- risk of transfer of viral infection

Question 3

Describe how the movement of potassium ions into the guard cells causes the stoma

Answer 3

potassium ions increase concentration of solution
make cells more concentrated
water moves into the guard cells by osmosis
cell swells unevenly
as inner wall is less flexible than outer wall

Question 4

Describe why diffusion is important to animals and plants

Answer 4

importance: to take in substances for use in cell processes
products from cell processes removed
e.g. for gas exchange - respiration and photosynthesis
food molecules absorbed: glucose amino acids
water absorption in large intestine
water lost from leaves/ transpiration
water absorption by roots
mineral ions absorbed by roots

Question 5

Culturing microorganisms

Answer 5

• Petri dish and agar sterilised before use to kill unwanted bacteria
• inoculating loop passed through flame to sterilise kill other bacteria
• loop used to spread bacterium onto agar
• lid of petri dish opened as little as possible to prevent microbes from air entering
• sealed with tape to prevent microbes from air entering
• incubate to allow growth of bacteria

Question 6

Evaluate use of stem cells from embryos or from adult bone marrow for treating human diseases

Answer 6

embryos
+painless/many available
+can treat lots of diseases
+using them better than wasting
-ethical issues
-unreliable/may not work
-death to embryos

adult bone marrow
+no ethical issues
+quick recovery/safe
+tested
-risk of infection
-only treats few diseases
-painful

Question 7

Describe and explain how the villi are adapted to maximise the rate of absorption of the products of digestion

Answer 7

• many microvilli provide large surface area
• many capillaries maintain concentration
• thin walls for short distance for food to travel
• many mitochondria to provide energy

Question 8

Diffusion

Answer 8

movement of atoms moves from high to low concentration down the gradient

Question 9

Active transport

Answer 9

movement of molecules from low to high concentration requires energy from respiration against a concentration gradient

Question 10

meiosis

Answer 10

• sexual reproduction
• for gametes
• produces in ovaries/testes
• half number of chromosomes
  -haploid 23 chromosomes
  -4 cells produced and 2 divisions
• not identical

Question 11

Explain why the movement of chloride ions cause water to pass out of the cells into the mucus

Answer 11

-osmosis/diffusion
-more concentrated solution outside cell/in mucus
-water moves from dilute to more concentrated solution
-partially permeable membrane of cell