Chapter 4 Transport Across Cell Membrane Flashcards
(22 cards)
How are phospholipids laid out in the cell surface membrane?
Hydrophilic head of phospholipids layer point to the out side of membrane
Hydrophobic tails point into centre of cell membrane
Functions of phospholipids?
Allow lipid soluble substances enter and leave cell
Prevent water soluble substances entering/leaving cells
Make membrane flexible
Why do some proteins never extend over the bilayer?
Act as either mechanical support to membrane or alongside glycolipids as cell receptors for molecules
When di some proteins extend completely over bilayer?
Protein channels that form water filled tubes
Carrier proteins
What are protein channels?
Water filled tubes allow water soluble ions to diffuse across membrane
What are protein carriers?
Bind to ions/molecules then change shape in order to move molecules across membrane
Function of proteins in membrane
Provide support
Act as channels
Act as receptors
Functions of cholesterol
Reduce lateral movement of phospy
Make membrane less fluid
Function of glycomipids
Act as recognition site
Help maintain stability of membrane
Helps cell to attach one another
What is ment by passive
Energy comes from natural inbuilt motion of particles rather then external
What is facilitated diffusion?
Only occurs between different concentration of same substances
Diffusion is facilitated by channels and carriers
What are protein channels
Water filled hydrophilic channels across membrane
Allow water soluble molecules through
What are carrier proteins ?
Molecule specific to protein is present it binds with protein
Causes change shape so molecules are released
What is water potential ?
Pressure created by water molecules
What is water potential of pire water?
0
How to find water potential of cell?
Place them in series of solutions of different water potential
Where this is no net gain/loss water potential is the same
Factors affecting rate of osmosis?
Higher the water potential m, the faster the rate of reaction
Thickness of exchange surface
The larger the surface area the faster
In active transport what is ATP used for?
Dorectly move molecules
Individually move molecules using concentration
Why is active transport not considered passive?
Metabolic energy required
Substance move againts c gradient
I
What is the sodium potassium pump?
Sodium ions actively removed from cell while potassium ions are actively taken in from surroundings
What does epithelial cells lining ileum contain?
Microvilli
How to increase transport across membrane ?
Increase number of protein channels and carriers
