Plasma Membrane Flashcards
(26 cards)
What makes up the structure of cell membrane?
- Phospholipids (75%) – main component
- Cholesterol (20%) – attached between phospholipids and between
layers - Polar Glycolipids in the external layer (5%)
What is cholestrol and what is it derived from?
Steroid lipid
derived from squalene
What is membrane fluidity important for?
Movement of membrane components required for cell
movement, growth, division, secretion and the formation of cellular junctions
What does cholestrol do to the first few hydrocarbon groups of phospholipids?
Immobilises them
This makes the lipid bilayer less deformable and decreases its permeability to small
water-soluble molecules
What is a glycoprotein?
A lipid covelantly bonded to an oligosaccharide - form glycocalyx
What is the function of a Glycocalyx?
- Required for detection of ‘self’ in immunity
- Aids in cell- cell adhesion
- Makes RBCs slippery and protects the GI from drying out
- Plays an important role in the pathogenesis of many vascular
diseases (e.g., diabetes, atherosclerosis, and sepsis)
What are the 4 different types of membrane proteins?
- Transporters
- Anchors
- Receptors
- Enzymes
What is the phopholipd bilayer permeable to?
non-polar molecules like O2 and C02
What is the phospholipd bilayer impermeable to?
Ions and large molecules like Na+ and glucose
Slightly permeable to small uncharged polar molecules - eg. water
What is passive transport and what are the 2 types?
Transport that requires no energy going down concentration gradient
- Diffusion through lipid bilayer
- Channel/carrier mediated facilitated diffusion
What do diabetic patients lack ability to regulate?
GLUT
Osmosis is a type of what?
Facilitated diffusion
(water passes through aquaporin protein channels)
What are the 2 types of active transport?
- Primary active transport (uses
energy from the hydrolysis of ATP) - Secondary active transport (uses
energy stored by an ionic
concentration gradient) - co transport
Transport charged ions against conc gradient
What is symport?
Where molecules in co-transport travel in the same direction (used for Ca2+ regulation and H+ regulation)
What is antiport?
Where molecules go in opposite directions in co-transport
What are the 3 types of endocytosis?
- Receptor mediated endocytosis
- Phagocytosis
- Pinocytosis
What is receptor mediated endocytosis used for?
The uptake of LDL, some vitamins, proteins and hormones
Clathrin is a protein for
enriching membrane
domains
What is phagocytosis carried out by?
- Macrophages
- Neutrophils
What is Pinocytosis (to drink)?
- Small droplets of extracellular fluid are taken in
- No receptors are needed
- All solutes in the extracellular fluid are brought in (non-
selective)
Where does Pinocytosis occur?
In most cells but especially absorptive cells in the intestines and kidney
What is exocytosis very important in?
- Secretory cells (digestive enzymes and hormones)
- Nerve cells (neurotransmitters)
What is trancytosis?
- Combination of endo and exocytosis
- Substances are passed through a cell
- Is common in endothelial cells which line the blood vessels
What is a tight junction?
Junction that prevents anything passing through the extra cellular
space between them.
E.g. cells lining the digestive tract.
What are adherens junctions?
- Plaque which attaches to
membrane proteins and
the microfilaments of
the cytoskeleton - Often form adhesion
belts that resist seperation during contraction and maintain cellular position
