The membrane

Question 1

What does the plasma membrane do?

Answer 1

• The plasma membrane gives a cell shape and support
• protects the inside of the cell
• communication/contact with cells and environment
• allows the cell to control internal pressure and concentration

Question 2

What does semi-permeable mean?

Answer 2

It allows certain things in and out of the cell selectively depending on their size and polarity

Question 3

The phospholipid?

Answer 3

A phospholipid is made up of a hydrophilic, water-loving, phosphate head, along with two hydrophobic, water-fearing, fatty acid tails. A double layer forms the phospholipid bilayer is formed

Question 4

What molecules would be able to pass through the mammalian cell membrane by simple diffusion?

Answer 4

Water, Lipids, Oxygen, and Carbon Dioxide

Question 5

What is the selective permeability driven by?

Answer 5

It is driven by the hydrophobic core structure

Question 6

What helps maintain the cell’s shape?

Answer 6

Proteins in the cell membrane attached to the cytoskeletal fibre

Question 7

What is passive transport?

Answer 7

Diffusion of a substance across a membrane with no energy expended.

Question 8

What is secondary active transport/cotransport?

Answer 8

Active transport of a solute indirectly drives transport of another across a semi-permeable membrane. Area of low con, to an area of high con. (against the con. gradient)

Question 9

What is primary active transport?

Answer 9

Uses energy to move solute against its concentration gradient across the semi-permeable membrane

Question 10

What is the point of markers and signaling on the membrane?

Answer 10

• surface proteins are embedded in the cell membrane, it is what identifies the cell enabling nearby cells recognise and to communicate with each other and the environment
• includes receptor proteins for interaction of specific chemical (hormones and neurotransmitters)

Question 11

Metabolic Activities?

Answer 11

Enzyme proteins that perform metabolic activities are in the membrane

Question 12

Why is the membrane described as a mosaic?

Answer 12

The ‘mosaic’ of lipids and proteins embedded in it

Question 13

Why are they called amphipathic molecules?

Answer 13

Phospholipids are described as amphipathic molecules meaning that there are both hydrophobic and hydrophilic parts. Meaning that it is able to interact with both polar and non-polar substances

Question 14

Why is a molecule hydrophobic?

Answer 14

Don’t have a charge, so they are non-polar, doesn’t dissolve in water

Question 15

Why is a molecule hydrophilic?

Answer 15

Is charged (polar), and so has a stabilising interaction with water.

Question 16

How do they move laterally?

Answer 16

The move laterally (side to side) as it isn’t as difficult, to flip it moves their hydrophilic head through the hydrophobic tails which require a lot of energy