Cell membrane structure

What fat is found inside a cell membrane?

Phospholipid

How are phospholipids arranged?

• Phosphate head : Hydrophilic - point outwards and interact with water

• Fatty acids : hydrophobic - point inwards towards each other

What are all the components of the cell membrane?

What do phospholipids do in a cell membrane?

Allows lipid soluble molecules to pass through but not soluble

Why is the model called ‘ fluid mosaic model’ ? 

Fluid - phospholipids can move relative to each other making it a flexible structure. 

Mosaic - proteins are embedded in the membrane that vary in shape, size and pattern. 

What is the function of the cell membrane?

• Forms a boundary

• allows different conditions to be established

• allows substances in and out of the cell

What is cholesterol used for in cell membranes?

makes membrane more rigid and stable

What is glycoprotein/ glycolipid? 

Role in hormone receptors or in cell to cell recognition. 

Where is the intrinsic protein embedded? 

span on the bilayer from one side to the other 

What is the function of an intrinsic protein?

• carrier proteins to transport water soluble materials across the membrane.

• some are channel proteins

• Some are enzymes

• structural support 

Where is extrinsic protein embedded?

• partly embedded / found at edges

• never extend completely across the bilayer 

What is the function of the extrinsic protein?

• mechanical support to membrane

• act with glycolipid as cell receptors for molecules such as hormones

• binding site

How do carrier proteins work? 

1. Protein changes shape so molecule gets released inside of membrane 

2. once molecule released, protein will return to its original shape. 

How do channel proteins work?

1. allows water-soluble ions and molecules (glucose/amino acids) to pass through

2. selective - only opens in presence of a specific ion

3. consists of pore lined with polar groups

What is the function of the glycoalyx?

glycolipid and glycoprotein that surrounds the membrane

What are the factors that affect the permeability of the plasma membrane?

• Temperature

• organic solvents

• pH

How does temperature affect the permeability of the plasma membrane?

• increased temp- phospholipids have more kinetic energy and vibrate mored - increasing fluidity and permeability of plasma membrane.

What happens to plasma membrane if temperatures too high? 

• channel and carrier proteins denatured affecting the membrane permeability 

• cell will break down eventually 

How does organic solvents affect the permeability of the plasma membrane?

• organic solvents dissolve membranes disrupting cells - increases fluidity and permeability of plasma membrane 

How are phospholipids different from triglycerides?

P has 2 fatty acid tails and not 3

P has phosphates

How do you calculate the ares of a red blood cell and explain how you calculated this value.

Surface area x 2

Phospholipids are in a bilayer in a cell membrane (2)

Why do phospholipids form a bilayer?

due to amphipathic nature, hydrophilic head and hydrophobic tail.