Eduqas Biology A Level Core Concepts - Cell Membranes

What are cell membranes made up of?

A phospholipid bilayer, Proteins and cholesterol

What is a glycoprotein?

A protein with a carbohydrate chain attached

What is a glycolipid?

A lipid with a carbohydrate chain attached

What functions do glycoproteins have?

- Cell recognition

- Hormone receptors

- Cell signalling and communication

What functions do glycolipids have?

- Cell recognition

- Hormone receptors

- Cell signalling and communication

Why does water need to diffuse through aquaporins?

Water molecules are polar. The hydrophobic phospholipid tails prevent water from diffusing across the bilayer. Water must therefore pass through channel proteins, specifically aquaporins

Why is the 'Fluid Mosaic' model called what it is?

Fluid: Proteins and phospholipids are free to move relative to one another

Mosaic: The membrane contains proteins of various shapes and sizes

What is the function of cholesterol in the membrane?

It is used to maintain the structure of the membrane (it prevents phospholipids from moving too close together or too far apart)

What are intrinsic proteins used for?

Transporting substances across the membrane

What are the 3 types of intrinsic protein?

Channel, Receptor and Carrier

What are intrinsic proteins?

Proteins in a membrane that sit bound in the membrane, touching the top and the bottom.

What is the function of extrinsic proteins?

Cell recognition and hormone recepting

When are carbohydrate chains added to glycoproteins?

In the Golgi body

When are carbohydrate chains added to glycolipids?

In the Golgi body

What is the function of the plasma membrane?

- Give the cell structure

- To allow substances to exit and enter the cell

- Cell to cell recognition and cell to cell signalling

How are phospholipids arranged in the cell membrane?

In a bilayer, with the hydrophobic tails facing inwards and the hydrophillic heads facing inwards

The region inside the bilayer is...

hydrophobic and non-polar

Why can't glucose diffuse across the cell membrane?

It is a polar molecule

What are the two types of protein found in the plasma membrane?

Intrinsic and extrinsic

What effect does raising the temperature have on the permeability of a membrane, and why?

It increases the permeability:

- Temperature increase leads to increase in kinetic energy

- The membrane becomes more fluid as components move more

- The membrane is therefore more permeable

Give the names of three structures surrounded by a double membrane which are found within cells

Nucleus, Mitochondria and Chloroplast