Roles and Structurers of membranes (Phospholipid bilayer)

A level Biology

Basic structure of a cell membrane in a eukaryotic cell

Phospholipid bilayer

Proteins

What is the phospholipid role in the cell membrane?

because it is mainly made out of non-polar, hydrophobic phospholipid tails, it only allows non-polar, hydrophobic, uncharged substances to enter and exit the cell

therefore it controls the movement of substances across the membrane

Lipids in a cell membrane

Phospholipids

Cholesterol

Glycolipids

Proteins in a cell membrane

Surface proteins

glycoproteins

transport proteins

Role of Cholesterol in a cell membrane

• it is a lipid that binds to the fatty acid tails of the phospholipids

• it regulates membrane fluidity

• makes cell membranes less fluid by restricting the movement of phospholipids and proteins —> which prevents water/ions from leaking out of the cell

Role of Glycolipids in a cell membrane

• they are phospholipids that are attached to a carbohydrate

• they act as recognition sites for other cells—> allowing cells to attach to one another to form tissues

Where can proteins in a cell membrane be?

Either:

on the surface of the cell membrane

or

span the entire membrane

Which proteins are found on the surface?

• Surface proteins

• Glycoproteins

Which protein is found spanning the entire membrane?

Transport proteins

Role of surface proteins in cell membrane?

• Surface proteins are found on inner or outer surface of phospholipid bilayer

• provide mechanical support for the membrane

Role of Glycoproteins in a cell membrane

• have a carbohydrate attached to them

• either act as a recognition site for foreign cells or for specific chemicals

• so specific hormones outside the cell can trigger a response inside the cell

Role of transport proteins (brief summary)

• help transport substances across membrane 

Meaning behind Fluid mosaic model

Fluid- describes how phospholipids and some proteins move in their layer of the membrane

Mosaic- describes the random scattering of proteins

What is the function of the phospholipid bilayer? (uplearn)

The phospholipid bilayer allows the diffusion of lipid-soluble substances across the membrane.

 

It also prevents the entry and exit of polar substances.

What is a glycolipid

a phospholipid that is attached to a carbohydrate

What is a glycoprotein

a protein with a carbohydrate chain attached