4- Cell Membrane & Movement Flashcards
components, structures, functions, types of proteins, movements
List the structures of the cell membrane.
( size, components, arrangement, structure)
(9 marks)
- 7 nm in width (1)
- Mosaic: proteins are randomly scattered within the membrane when viewed from above. (2)
- Fluid: phospholipds & proteins can move sideways by diffusion, within their own monolayer(2)
- Bilayer
- Components: phospholipids, proteins and cholestrol
function of phospholipids in cell membrane
(2 marks)
acts as a barrier againts polar hydrophilic molecules (most water soluble molecules), allowing lipid soluble molecules in.
what are factors that affect the membrane’s fluidity?
(6 marks)
- temperature: as it increases, fluidity of membrane increases as phospholipid molecules are further apart, increasing molecules.
- kinks ( double bonds/ unsaturations): they prevent close packing (freezing) of phospholipid molecules, therefore increasing the fluidity.
- Length of fatty acids: longer fatty acids may tangle together, and make more hydrophobic interactions, decreasing their movement & fluidity.
what does the structure of cell membrane result in?
( arrangement of phospholipid molecule)
(3 marks)
hydrophobic core acts as a barrier against large, polar & hydrophilic molecules, separating between cytoplasm and outside the cell, resultig in PARTIAL PERMEABILITY.
Why can’t Na+ ions cross the membrane?
(2 marks)
as its charged (ionic) which means its soluble in water, so it cannot cross the hydrophobic core of the membrane as its insoluble in fats.
Functions of cholestrol
(4 marks)
- regulated membrane’s fluidity
- maintains movement across the membrane and prevents close packing of phospholipids, increasing membrane’s fluidity & preventing it from becoming too rigid.
- helps with mechanical stability
where are cholestrol molecules located and state its structure
(2 marks)
- between phospholipids, below their heads
- small molecules with hydrophobic tails and hydrophilic heads.
proteins according to their position in membrane
(2 marks)
peripheral and integral
difference between peripheral and integral proteins
(2 marks)
- peripheral: temporarily attached to membrane, but doesnt form a part of the lipid bilayer
- integral: permanently attached to membrane, forms a part (embedded) in lipid bilayer.
what are 2 types of integral protiens and whats the difference?
(4 marks)
intrinsic & extrinsic
1. intrinsic: present in the whole bilayer, have hydrophilic regions which are repelled by phospholipids and hydrophobic regions which helps them to stay in membrane
2. extrinsic: only found on one side of the bilayer( either inner or outer surface of membrane). Many are bound to intrinsic proteins or to phospholipids.
proteins according to their functions?
(5 marks)
- transport proteins
- adhesive proteins
- enzymes
- attachements to cytoskeleton
- identity makers
two types of transport proteins?
(2 marks
channel & carrier proteins
What are the functions of channel proteins?
(3 marks)
- They form water filled pores to allow diffusion of charged (ionic) & polar molecules through membrane by facilitated diffusion, down their concentration gradient.
- Has a bidirectional movement
How is the structure of the channel protiens suitable to its function?
(2 marks)
- They have a fixed specific shape and can be gated to control ion and exchange
- They can be closed, ensuring that cell membrane is partially permeable
What are the functions of carries proteins?
(6 marks)
- Involved in active transport
- Moves molecules & ions from high to low conc. against a conc. gradient , using ATP, by conformational change in its shape
- Could be used in passive transport as facilitated diffusion, moving down the conc. gradient WITHOUT ATP
Whats the importance of active transport in both the human body and plants?
Human body:
1. Reabsorption in kidney tubules
2. Absorption in ileam
Plants:
1. Loading sugar from photosynthesizing cells to phloen
2. Loading inorganic ions from soil to roots
Define exocytosis
Bulk movement of liquids or solids out of cell by the fusion of vesicles containing subs. with cell surface membrane, using ATP
Examples of exocytosis
- Secretory vesicles from golgi bodies carrying enzymes to cell surface membranes and releasing its contents
- Plant cells get their cell wall building materials outside of the cell membrane
Define endocytosis
Bulk movement of liquids or solids onto cells by the infolding of the cell surface membrane to form vesicles containing the substances called (phagocytic vacuoles), requiring ATP
What happens to liver cells when controlling BGC
When pancrease detects the high bgc, it releases beta cells which releases the insulin hormone “antigen”, which is a signalling molecule. It then binds with the insulin receptors found on the proteins of the cell surface membranes of the liver cells. These receptors are made up of a protein called G-protein. It combines with ATP to be broken down by “adenylyl cyclase enzyme”, releasing a 2ry messenger called cAMP which activates a series of enzyme catalyzed reactions using ATP, giving a specific response which increases the glucose channels in membrane, increasing permeability of the membrane.
Factors affecting rate of diffusion?
- Temperature
- Steepness of concentration gradient
- Nature of molecules (size)
- Surface area : volume ratio
- Diffusion distance
Whats meant by water potential
The potential energyof water molecules allowing it to move out of the solution/
The tendency of water molecules to move out of solution.
