Lecture 17 Membranes 2 Flashcards
(23 cards)
Membrane fluidity is controlled by:
Fatty acid composition
Cholesterol content
What characteristics of fatty acids influence membrane fluidity?
Length of fatty acid chain Saturation levels (Tm, rigidity) Position of double bonds, especially cis position (produces a bend, effects Tm, provides more fluidity)
How can one observe the dynamics of membrane molecules?
Fluorescence recovery after photo-bleaching (FRAP) technique
What does the rate of the recovery of fluorescence depend on?
Depends on the lateral mobility of the fluorescent labeled component
How do proteins move in lipid bilayers?
They move laterally but do not flip flop
Where does glycosylation occur?
On the extracellular surface of the plasma membrane
What does glycocalyx participate in?
Participates in cell adhesion, lymphocyte homing, and many others
What is a Glycoalyx?
An outer filamentous coating of carb-rich molecules on the surface of certain cells
How are RBC’s identified by cells?
By the cells extracellular carbohydrates
List the membraneous internal compartments of eukaryotic cells?
Peroxisomes
Mitochondria
Endoplasmic Reticulum
Golgi Apparatus
Membranes must be able to separate and join together so that cells and compartments are able to:
Take-up
Transport
Release molecules
Receptor-mediated endocytosis (RME) “budding”
Invaginated membrane breaks off and fuses to form a vesicle
Receptor-mediated endocytosis (RME) “fusion”
Fusion of a vesicle to a membrane is a key for neurotransmitter release into the synaptic cleft
Involves SNARE proteins
Define SNARE
Protein that gathers the appropriate membranes to initiate fusion process
Mitochondrial Fission
“pinching” of the mitochondria
Not a simple process
DRP 1 = protein involved
Mitochondrial Fusion
Result of collision
Occurs between identical organelles
Excludes all other intracellular membranes
What does it mean when we say that mitochondrial fusion is a salvageable process?
If a ‘sick’ mitochondria is not able to be repaired, its components can be savaged
What are the requirements for innermembrane fusion?
A sufficiently large electrochemical gradient across the inner membrane
Elevated GTP levels
The vast majority of the mitochondrial proteins are encoded for by ________ (nuclear genome/mito-genome)
Nuclear Genome
During protein import into the mitochondria, what sequence may be considered as a “matrix targeting signal”?
The N-terminal signal sequence
After mitochondrial proteins are unfolded, they are threaded through an ________
“import pore”
Inner and outer membranes are frequently close together. During protein import into the mitochondria, a _______ channels forms between two membranes.
A transient channel
During protein import into the mitochondria, when is ATP required?
ATP is required only if a protein crosses the inner membrane (matrix membrane)
