Topic 3- Transport And Cell Membranes Flashcards
How does the plasma membrane appear under a light microscope
As a double line
What are the two types of protein found in the plasma membrane
Intrinsic and extrinsic proteins
What are intrinsic proteins involved in
Transporting substances across the cell membrane
What are extrinsic proteins involved so
Act as receptors as they have a specific binding site, and are involved in cell to cell signalling and cell to cell recognition
What is the main function of the plasma membrane
Cell to cell recognition and cell to cell signalling
As well as controlling what substances enter and exit the cell
What is diffusion.
The movement of molecules from and area of high concentration to an area of low concentration down a concentration gradient
What molecules use simple diffusion
Lipid soluble molecules which are non polar and uncharged
Name substances that carry out simple lipid diffusion
Lipid soluble steroids
Oxygen
Carbon dioxide
What is facilitated diffusion
Passive transport of substances across a plasma membrane with the help of an intrinsic protein either through a carrier protein or a hydrophilic pore within a protein channel
What substances use facilitated diffusion
Large water soluble polar and charged molecules or ions
What are the two kinds of transport proteins
Channel proteins and Cartier proteins
What is active transport
An active process which moves against a concentration gradient from low to high concentration requiring an input of ATP energy
Name some examples of active transport
Transport of mineral ions in the root hair cells of plants
Glucose from kidney to the blood
How can active transport be stopped
By adding a metabolic poison called cyanide which stops the atp energy being produced, without atp active transport can not occur
How does phospholipids arrange themselves in water
As a Micelle, with the hydrophilic head facing outwards and the hydrophobic tails facing inwards
Why is structure of the plasma membrane described as a fluid mosaic structure
Fluid because all the parts move relative to each other and mosaic because all proteins are dotted through out the membrane like tiles
Describe the structure of the plasma membrane
Demi phospholipid bilayer composed of intrinsic and extrinsic proteins, glycolipids, glycoproteins and cholesterol arranged in a fluid mosaic structure
Who proposed the fluid mosaic structure of the plasma membrane
Singer and Nicholson
How are phospholipids arranged in water
As a Michelle with the hydrophilic heads outside and the hydrophobic heads facing in side
What are the main functions of the plasma membrane
Provide the cells structure, cell to cell signalling and cell to cell recognition
What does lipid bilayer mean
Two layers of phospholipid
What is a phospholipid
A molecule made of a hydrophilic glycerol phosphate head and two fatty acids forming a hydrophobic tail
What is the distance across the membrane
7-8 nm
How does an intrinsic protein differ from an extrinsic protein
Intrinsic proteins lie across both layers of the bilayer. Extrinsic proteins are in one of the layers on the surface of the membrane
