Chapter 5, Membrane Structure, Synthesis, Transport Flashcards
Membrane Structure
Two leaflets made of phospholipid bilayers
Fluid Mosaic Model
- double layer of phospholipids
Phospholipids are _________
amphipathic
Amphipathic means
containing partial + and - charges
Fatty acid tails are _______
nonpolar
Phosphate heads are ______
polar
Each phospholipid bilayer called a
leaflet
Leaflet on outer cell called
extracellular leaflet
Leaflet on inside of cell called
Cytosolic leaflet
Selective Permeability means
-polar molecules cannot pass through hydrophobic membrane center
- non molecules can diffuse through the membrane
There are ____ embedded into phospholipid bilayer
proteins
Protein ratio varies from ___-___ times more lipid molecules than protein molecules
15-70
_____ determine the exact function of cells different membranes
proteins
_____ do the bulk of the membrane’s work
proteins
_______ membrane proteins less associated with membrane and are ____ bound to membrane
peripheral, loosely
Peripheral membranes bound by _____ or _______ bonds
hydrogen or ionic
Peripheral proteins bound to ___________ proteins also called the _______ __ _______
transmembrane proteins, heads of phospholipids
Exposed proteins of peripheral proteins are usually _____ for binding
polar
Because peripheral proteins only occur on 1/2 leaflets, membranes may be ______ with __________ ______
asymmetric, different functions
_______ proteins are more closely associated with the membrane
integral
Integral proteins often ____ the membrane
span, transverse
Exposed portions of integral proteins usually _____ for binding
nonpolar
Two types of integral proteins
- transmembrane
- lipid-anchored
Transmembrane proteins transverse the membrane with domains forming ______
a-helices (alpha)
Regions of alpha proteins occur on ______ ____ of membrane and may be bound to _________
both sides, cytoskeleton
Lipid anchored proteins have a lipid _____ attached to the protein
covalently
Lipid is inserted into phospholipid bilayer to ______ the protein
anchor
Phospholipids in the membrane are… to each other
NOT covalently bound
The phospholipids are _________________ within the membrane
free to move
Phosophlipid can move from one end of cell to other in…
less than a second
______ seconds in a eukaryotic cell
5-10
Phospholipids cannot move…
between leaflets
Special protein needed to move phospholipids between leaflets using ATP is
Flippase
most common phospholipids have an _____ number of carbons
even (18-20 in the tails)
Up to 25% of the lipids in animal cell membranes may be ___________
cholesterol
The membrane is more fluid if…
there are fewer hydrophobic interactions
There will be fewer hydrophobic interactions with… (3)
- shorter hydrocarbon chains
- more unsaturated hydrocarbon chains (more kinks in chain)
- more cholesterol makes it MORE fluid at LOW TEMP
Phospholipids cannot flip flop between leaflets because of their _______
polarity
membrane ______ can also diffuse/move throughout the membrane
proteins
Some proteins exposed to the cytoplasm attach to ______, anchoring them in place
cytoskeleton
Carbs in membranes only occur as _______ and __________
- glycolipids
- glycoproteins
Carbs in membranes only occur in the _______ leaflet of plasma membrane
exterior (extracellular)
Glycoproteins and Glycolipids in plasma membrane can act as ______
antigens, which identify cells of organisms
Glycoproteins and Glycolipids in plasma membrane can also label…
proteins with signals for cellular destinations
Glycocalyx is a
thick layer of carbs outside plasma membrane
Purpose of glycocalyx
shield cell from immune system of other cells
Phospholipids are synthesized by the
smooth ER
Phospholipids can be spread throughout the Endomembrane System by _______ _________
lateral diffusion
Membranes of nucleus, ER, golgi, plasma membrane, mitochondria, and chloroplasts are either _________ ______ or connected by ________
directly connected, connected by vesicles
Lipid Exchange proteins can…
extract lipid from one membrane, diffuse through cytoplasm, and insert it into any other membrane
The _________ and __________ both synthesize various types of proteins which are transferred to other organelles by lipid exchange proteins
mitochondria, chloroplast
Most transmembrane proteins are synthesized in …
rough ER