Steroids

Question 1

Steroids - fundamentals

Answer 1

• Organic compound with four joined rings arranged in specific
  way.
• Groups joined all over the molecule
• Have roles in membrane stability or as signalling molecules
  (hormones).
• Sterones are steroid hormones (e.g. testosterone)
• Sterols are steroid alcohols (e.g. cortisol)

Question 2

The Fungi: secosterols and ergosterols

Answer 2

• Ergocalciferol is formed in the Fungi in response to
  290-315 nm light (vitamin D2).
• Ergosterol is made by the Fungi and Protista and have
  the same role in cell membrane stabilisation therein as
  cholesterol does in the Mammalia.

Question 3

Steroids in the Animalia and their functions

Answer 3

• Cholesterol – stabilises cell membranes by retaining
  their fluidity when temperatures fall.
• Sex hormones – testosterone, progesterone, estrogens
• Corticosteroids (from adrenal cortex)
  -glucocorticoids (corticosteroids involved in glucose
  metabolism including cortisol as natural one and predisone as synthetic one.
• mineralocorticoids (corticosteroids involved in electrolyte
  homeostasis) including aldosterone.

Question 4

Steroids in the Viridiplantae

Answer 4

• Solanaceae includes: Atropa belladonna L. (deadly
  nightshade) and Capsicum annuum L. (bell peppers, chilli peppers)
• Solanum spp. produce solanine as a defence molecule against herbivory.
• Produced from cholesterol as the raw material.

Question 5

Name the steroids that stabilise cell membranes in the Animalia and the Fungi

Answer 5

cholesterol in the Animalia and ergosterol in the
Fungi.

Question 6

Name three human sex hormones.

Answer 6

testosterone, estrone (E1), estradiol (E2), estriol (E3), progesterone

Question 7

Give two examples of plant defence molecules based on steroid.

Answer 7

digoxin, solanine, oubain, oleandrin