B1.1.12-13

Question 1

Define hydrophobic

Answer 1

“Water-loving” – molecules that are attracted to water.

Question 1

Define hydrophilic

Answer 1

“Water-repelling” – molecules that do not interact well with water.

Question 2

Define amphipathic.

Answer 2

A molecule that has both hydrophilic (water-loving) and hydrophobic (water-repelling) parts, like phospholipids.

Question 3

Outline the amphipathic properties of a phospholipid.

Answer 3

When placed in water, phospholipids arrange themselves into a bilayer:
The hydrophilic heads face outward, toward the water.
The hydrophobic tails face inward, away from the water.

Question 4

Identify steroid molecules from molecular diagrams.

Answer 4

Steroids have a four-ring structure (e.g., cholesterol, testosterone, oestradiol).

Question 5

State why steroid hormones are able to pass directly through the phospholipid bilayer.

Answer 5

Steroids are non-polar and can easily pass through the hydrophobic interior of the phospholipid bilayer.