Week 7 - Membrane Structure Flashcards
Define Cytoplasm.
Contents of the cell outside of the nucleus (includes other organelles).
Define Cytosol.
Aqueous part of the cytoplasm; does NOT include membrane bound organelles - DOES include ribosomes and cytoskeleton
Define Lumen.
Insides of organelles.
What are the 6 cell functions at the membrane?
- Compartmentalization
- Scaffold for biochemical activities
- Selectively permeable barrier
- Transporting solutes
- Responding to external signals
- Interactions between cells
Membrane lipid bilayers have what properties?
- Amphipathic (hydrophilic/polar head groups and hydrophobic tails)
- Have 2 layers (leaflets)
What is the fluid mosaic model?
Of the membrane bilayer; Lipids are FLUID and some Proteins are MOBILE; MOSAIC of many different lipids and proteins
Membrane lipids structure?
- polar, hydrophilic head group
- 2 hydrocarbon, hydrophobic tails
In an aqueous environment, phospholipids spontaneously self-associate into what?
Spontaneously self-associate into a bilayer
Hydrocarbon tails of membrane lipids interact with what?
Other hydrocarbon tails
What is in artificial lipid bilayers?
liposomes
Experimental uses of a Liposome? (3)
- Study lipid properties
- Membrane protein properties
- Drug delivery into cells
Most energetically favourable structure of a liposome?
Spherical sealed compartment formed by phospholipid bilayer
Types of membrane lipids?
- Phospholipid (i.e. Phosphoglyceride)
- Sphingolipids (less abundant)
- Steroids (i.e. Cholesterol in animal cells)
What is the Phosphoglyceride structure?
- Variable head group (R)
- phosphate group
- glycerol group
- 2 hydrocarbon tails.
Hydrocarbon tails have what structure properties?
- saturated or unsaturated (the latter with a kink from a cis double bond)
- 14-24 carbons in length
What is the Steroid (cholesterol) structure?
- polar head group
- rigid steroid ring structure (like a wedge)
- 1 non-polar hydrocarbon tail
The 1;1; ratio of cholesterol to phospholipids can decrease what?
- decrease mobility of phospholipid tails
- decrease plasma membrane permeability
Phospholipids diffuse and move in what directions?
- laterally
- within each leaflet
- rotationally
- with flexion (often)
Phospholipids RARELY diffuse in what way?
transversely (flip-flopping) without other influences
At lower temperatures, lipid bilayers become what?
become rigid (gel)
The presence of cis-double bonds allows the membrane to remain what?
remain fluid at lower temperatures
Kinks in hydrocarbon tails allow for what?
Kinks in hydrocarbon tails allow for more space and less hydrophobic interactions
Shorter hydrocarbon tails increase what?
Shorter hydrocarbon tails increase fluidity at lower temperatures (the tails interact less)
Phospholipid translocators catalyze what?
They catalyze the rapid flip-flop of phospholipids from one leaflet to the other