1.3 Membrane Structure

Question 1

Describe a phospholipid bilayer membrane.

Answer 1

In water amphipathic phospholipids form double layers with the hydrophilic heads in contact w water (outside and inside of cell) and hydrophobic tails away from water in centre of membrane. This arrangement makes the membrane v stable

Question 2

What are three types of fatty acids?

Answer 2

Saturated (full of hydrogen), monounsaturated (missing one hydrogen creating a ‘kink’ - double bond C), polyunsaturated (missing more than one hydrogen creating multiple double bonds between C)

Question 3

What does hydrophobic mean? What does hydrophilic mean?

Answer 3

Hydrophobic means afraid of water. Hydrophilic means attracted to water.

Question 4

What is in a triglyceride fat?

Answer 4

Glycerol + three fatty acids

Question 5

What are some parts of the fluid mosaic model (what to include when drawing phos. Bilayer)

Answer 5

Integral protein (embedded in membrane), ECF and cytoplasm, Peripheral protein (found on surface), glycoprotein (sugar on integral), protein channel, cholesterol

Question 6

Describe the different models of the membrane over time

Answer 6

1920, bilayer (did not explain proteins), 1930, proposed layers of protein adjacent to bilayer, 1966, discover proteins occupy variety of space in membrane leaving phospholipid molecules free to move

Question 7

Describe the problems with the Davson-Danielli model (1966) that led to the Singer-Nicholson model

Answer 7

We discovered that transmembrane proteins existed within membranes. Proteins were found to be varied in size and shape and hydrophobic. Proteins can move within the membrane. They would not form a layer on the surface