The fluid mosaic model of cell membranes COPY Flashcards Preview

1.3 Cell membranes and transport > The fluid mosaic model of cell membranes COPY > Flashcards

Flashcards in The fluid mosaic model of cell membranes COPY Deck (11)
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1
Q

When was the fluid mosaic theory first proposed and by who

A

Singer and Nicholson 1972

2
Q

What is the fluid mosaic model?.

A

The fluid mosaic model describes the structure of the plasma membrane

As a mosaic of components

including phospholipids, cholesterol, proteins, and carbohydrates

that gives the membrane a fluid character.

3
Q

What is the structure of a fluid mosaic model

A
4
Q

Why is a cell membrane called fluid mosaic?

A
  • The reason it is described as fluid is because
    • The individual phospholipid molecules can move within a layer, relative to one another
  • The reasons it is described as mosaic is because
    • The extrinsic and intrinsic proteins embedded in the bilayer vary in shape, size and pattern
5
Q

What has the fluid misaic model for the cell surface membrane been described as

A

A see of protein icebergs floating in a sea of lipids

6
Q

What controls the level of fluidity

A

Fatty acids can be saturated or unsaturated

Phospholipids will therefore contain saturated or unsaturated fatty acid tails

The membrane is more fluid when there is

  • a high level of saturated fatty acids,
  • the fatty acids have shorter tails
  • or when there is an increase in temperature

The greater the level of steroids in the cell membrane, the less fluid it is.

Cholesterol is a steroid found in animal cells but rarely in plant cells.

It can fit between the phospholipid molecules increasing rigidiy and stability of the membrane as a whole

7
Q

What types of substance are able to dissolve in the phospholipid membrane and diffuse accross

A
  • Lipid soluable substances
  • e.g. Vitamin
  • e.g. Small molecules O2 and CO2
8
Q

What type of molecule is able to pass through the cell membrane

A

The membrane is hydrophobic which means lipid soluable molecules are able to pass the membrane more easily than water soluable substances

9
Q

What type of molecules are unable to pass through the phospholipid molecules

A
  • Water soluable substances
    • e.g Glucose
    • e.g. Polar molecules
    • e.g. Ions
10
Q

How do these water soluable substances pass through the cell membrane

A
  • They pass through intrinsic protein molecule which form water filled channels accross the membrane
  • as a result, the cell surface membrance is slectively permeable to water and some solutes
11
Q

What does the term selectively permeable mean

A

The cell membrane is permeable to watermolecules and other small molecule but no large molecules

The cell membrane is therefore a selective barrier