Cell membranes Pt2 Flashcards
How are phospholipids arranged in a membrane?
In a bilayer, with the hydrophobic fatty acid tails in the centre and the hydrophilic phosphate heads pointing towards the outside.
What are the functions of the phospholipids in a membrane?
To be partially permeable barrier, to allow the passage of lipid-soluble substances and prevent the passage of water-soluble ones, to make the membrane flexible.
Where are intrinsic proteins positioned in a phospholipid bilayer?
They span the entire bilayer.
Where are the extrinsic proteins found in the phospholipid bilayer?
They are found on the surface or embedded in one layer.
What are the roles of intrinsic proteins?
Span the bilayer, are enzymes, carrier proteins, and channel proteins.
What are the roles of extrinsic proteins?
Provide mechanical support; in conjunction with glycolipids, act as cell receptors for hormones and other molecules.
Why is the term fluid mosaic used to describe a phospholipid bilayer membrane?
Fluid- the phospholipids are able to move relative to one another
Mosaic- describes the pattern of proteins scattered amongst the phospholipids so the role is to provide mechanical stability and regulate fluidity.
What is the role of the cholesterol in a membrane?
Restricts movement of other membrane components making membranes less fluid and providing mechanical stability.
What is the role of glycolipids?
Cell recognition/ acts as antigens
What are the roles of glycoproteins?
Receptor sites, cell adhesion in some tissues.
Does facilitated diffusion require energy from ATP?
No
Which has the higher water potential: pure water or a concentrated salt solution?
Pure water, 0 kPa.
What is active transport?
The movement of a substance across a membrane against its concentration gradient by a carrier protein using energy from ATP.
What is exocytosis?
The movement of a large amount of material out of the cell, requires ATP.
What are the two types of endocytosis?
Phagocytosis(solid) and pinocytosis(liquid)
