Question
Celiac disease is an immune reaction to eating gluten, a protein found in many cereals. The diagram shows the arrangement of normal villi and villi affected by celiac disease in the small intestine.
(a) Outline the functions of the villi in the small intestine.
(b) Explain the consequences of celiac disease for absorption of digested nutrients.
(c) Wheat, barley and rye all contain gluten. Outline how a protein such as gluten is digested.
Answer/Explanation
Ans:
a)
a. increase the surface area for absorption
b. absorption of digested foods/nutrients
c. absorption of mineral ions/vitamins
b)
a. (celiac disease/gluten causes) much smaller villi/flattened villi/smaller surface area (of villi) / no villi
b. (smaller villi leads to) less efficient/less/slower/poor absorption OR nutrients/energy lost / fatigue/malnutrition may result
c. (celiac sufferers) must eat a gluten-free diet / WTTE Note that this question requires an explain not an outline
c)
a. enzymes/protease required
b. (protease/peptidase) breaks peptide bonds/bonds between amino acids
c. hydrolysis adds water molecules/breaks peptide bonds between amino acids
Question
Hormones are produced by one tissue in an organism and have their effect on a target tissue.
(a) Describe the genetic and hormonal control of male sexual characteristics in a human.
(b) Outline how the hormone auxin controls phototropism in plant shoots.
(c) Compare and contrast hormonal and nervous communication.
Answer/Explanation
Ans:
a)
a. male if (X and) Y chromosomes present
b. gene on Y chromosome/SRY promotes development of testes (from embryonic gonads)
c. testes secrete testosterone
d. testosterone stimulates sperm production/spermatogenesis
e. testosterone stimulates development (in fetus) of male genitals/primary sexual characteristics
f. testosterone stimulates development of male secondary sexual characteristics OR testosterone causes changes to become adult male during puberty Allow first alternative for mpf if two secondary sexual characteristics are named instead of the general term ‘secondary sexual characteristics’
b)
a. grows/bends towards (brightest) light/sun
b. auxin moved from lighter to shadier side (of shoot/stem tip/apex)
c. moved by auxin efflux pumps
d. auxin promotes cell elongation/cell growth / auxin causes cell wall acidification/loosening
e. more growth on shady side of stem (due to auxin concentration gradient)
f. binds to auxin receptors (in target cells) auxin/auxin receptors promote expression of genes (for growth)/for H+ secretion into wall
c)
Similarities
a. both used for communication between cells/tissues/organs/parts of the body / WTTE
b. both cause a response/change in specific/target cells OR both use chemicals that bind to receptors / hormones and neurotransmitters are both chemicals
c. both can stimulate or inhibit (processes in target cells) / WTTE
d. both can work over long distances/between widely separated parts of the body / WTTE
e. both under (overall) control of the brain/CNS / brain (has role in) sending hormones and nerve impulses
f. both use feedback mechanisms/negative feedback / both used in homeostasis
