Transport across membranes Flashcards
(33 cards)
What does the plasma membrane define
borders of cells and most organelles
How permeable is the membrane
Partially permeable
What does it mean if the membrane is partially permeable
the membrane allows some materials to freely enter or leave the cell/organelle while other materials cannot move freely
What does a phospholipid molecule consist of
- glycerol
- 2 fatty acids
- phosphate-linked head group
What’s the thickness of a phospholipid
5-10nm in thickness
Where does the hydrophilic phospholipid head face
outwards and the hydrophobic fatty acids faces inwards
What is cholesterol
A lipid that sits with phospholipids in the core of the membrane
Where is cholesterol not found
in bacterial cell membranes
What affect do cholesterol molecules have on the membrane
makes it more rigid
What does cholesterol help maintain
Shape of animal cells
What does the phospholipid bilayer form
the ‘fluid’ part of the ‘fluid mosaic’ model
What’s the ‘mosaic’ part made up of
various proteins, carbohydrates and lipid molecules that punctuate membranes
What’re membrane bound molecules
Large molecules embedded in the bilayer
What can the bilayer form
open pores
What do open pores allow
- diffusion of large molecules across the bilayer
- transport proteins that bind to specific molecules and carry them across the membrane
What does the glycolipid act as
A recognition site for toxins
On the plasma membrane what part points outwards
hydrophilic heads of phospholipid molecules
What part of the membrane points inwards
The hydrophobic part
What do the glycoproteins do in the plasma membrane
branching carb of a protein which acts as a recognition site for chemicals
What’s cholesterol needed for in the cell membrane
stability and flexibility
What’re the 2 proteins found in the membrane
- intrinsic
- extrinsic
What’re 2 examples of intrinsic proteins
- channel proteins
- carrier proteins
What do channel proteins provide
hydrophilic channel that allows the passive movement of polar molecules and ions
What holds channel proteins in place
interactions between hydrophobic core of the membrane and hydrophobic R-groups on the outside
