2.2 Cell membranes Flashcards
What is CF caused by?
A faulty transport protein in surface cell membranes of epithelial cells
What is the role of cell membranes
They controll what pass through them
What are the six main elements which make up the surface cell membrane
(And their role)
- Phospholipid bilayer - acts as barrier, prevents substances entering/exiting.
-
Carrier proteins - Move substances across membrane
* Channel proteins - Allows molecules that are too hydrophilic/large to pass through membrane
Glycolipids - Involved in cell signalling/recognition -
Glycoproteins - Involved in cell singalling/recognition
* Cholesterol - Steroid molecule blocks gaps in membrane
How do channel proteins move molecules
- They create a hydrophilic “tunnel” for molecules to pass through
How do carrier proteins move molecules?
- Molecules bind to protein
- Protein changes shape, moving substance across membrane.
What process are both carrier and channel proteins involved in.
Define process
Facilitated diffusion - the movement of particles form an area of high to low concentration involving transport proteins.
What does cholesterol reduce in the cell membrane?
The fluidity of the membrane
What are the 4 main ways substances pass through the cell membrane
- Diffusion
- Osmosis
- Active transport
- Exocytosis
- Endocytosis
Which particles are able to diffuse through the Phospholipidbilayer?
and example
- Hydrophobic particles
- Small particles
When does diffusion stop
When the concentration of the particle is the same either side of the membrane.
Is diffusion against or with concentration gradient?
With
Which 2 structures are involved with facilitated diffusion
- Carrier protiens
- Channel proteins
Is facilitated diffusion against or with concentration gradient?
With
Define osmosis
The movement of water particles from a solution with a lower concentration of a solute to a solution with a higher conecentration of a solute.
Define isotonic
Solute concentration is same inside cell
(Osmosis stops when isotonic)
What is the energy molecule involved in active transport + how does it work (think pumps)
- ATP (adenosine tri phosphate)
- 1 phosphate released and bonds to water - releases energy which drives shape change of carrier protein.
Differece between exo/endocystosis
Exocytosis - Transports substances out of cell in vesicles (EXITS)
Endocytosis - Transports substances into cell in vesicle (Enters)
(Both inovled in bulk transport / large molecules)
Example of Exo/Endocystosis
- Exo-Insulin into blood
- Endo - Cholesterol taken up by cells
2 forms of Endocytosis
- Phagocytosis (extensions from membrane)
- Pinocytosis (cell membrane invaginated)
Example fo Active transport in cell membrane
NA+/K+ pump
