Lecture 13: Cell Membranes Flashcards
What are some functions of the cell membrane
-separate cells and create environment
-selectively permeable
-Cell to cell communication
-Cytoskeleton
What is the structure of the cell membrane
phospholipid bilayer
What property of phospholipid allows for the formation of the double membrane
Amphipathic
Core of hydrocarbon tails provide a hydrophobic barrier for water and charged solutes
Animal cells show lipid asymmetry: the outer leaflet of the membrane
has ______________________ while the inner layer is
richer in ________________________
glycosphingolipids and phosphatidylcholine,
phosphatidylserine (PS), phosphatidylinositol, and
phosphatidylethanolamine.
_________________ increase in the outer leaflet is an indicator of low app –> Cell stress and death
phosphatidylserine (PS)
___________ are ATPase pumps that bring the PS to the inner leaflet
Flippases
________________ are transporter pumps that move lipids from the inner to outer leaflet
Floppases
____________ are useful in cell to cell and cell to matrix interactions
glycosphingolipid
____________ tend to group together in the outer leaflet forming lipid rafts
Sphingolipids
lipid rafts are also rich in _________________ which facilitates transmembrane signaling
glycosphingolipids and cholesterol and membrane receptor
_________ are non covalently bonded with integral proteins
integral proteins
___________ lipids and proteins on the membrane form distinct units on the surface. However they are not fixed in place and can move along the surface of the membrane
Fluid mosaic model
________ have membrane spanning alpha helical domains of about 20 amino acids, some have multiple membrane spanning domains, some proteins are linked to membrane phospholipids via oligosaccharides
integral proteins
________ interact with the matrix
adhesion molecules
_____________ bind to signal molecules ligands and initiate cellular responses often using an intracellular second messenger (more in the cellular communication sessions)
receptors
What are 3 methods of the movement of water
-Pores (always open) and channels (can be closed) to allow ions, water and other molecules
-carriers facilitate transport and do not use ATP
-Pumps move substances across membrane against gradient and use ATP
What are two key functions of membrane bound proteins?
-Enzymes that participate in digestion
-Some membrane proteins interact with the cytoskeleton to anchor it and transduce signals
____________ the ability of substances to cross the membrane depends of size and charge and stability of the membrane
selectively permeable
What types of molecules need help crossing the membrane
polar molecules
Describe dynamic equilibrium in terms of the plasma membrane?
Molecules redistribute from areas of high concentration to areas of low concentration until they equalize
What are some factors that affect how easily things flow across the membrane according to flicks law
-thickness of membrane
-temperature
-solubility and polarity of solute in the membrane
-size
What are the two types of diffusion
-Simple diffusion (through a pore)
-Facilitate diffusion (through a carrier protein)
What is active transport
transport that requires energy and carrier proteins
What occurs when carrier mediated transport is saturated?
We reach v max. The speed of transport reaches its max.
*Simple diffusion is always dependent on concentration gradient
What are some control mechanisms top open ion channels
-ligand mediated
-voltage mediated
-mechanical (stretch) mediated
*can be saturated, size and charge regulate what can cross
______________ move one type of molecule, selective, saturable, unidirectional flow, regulation is through hiding from the surface of the membrane (endocytosis)
carrier proteins
_________ use atp directly, saturable, unidirectional, can move one or multiple molecules, usually regulated through endocytosis
Pumps
Secondary active carrier proteins move multiple molecules at the same time: What must occur for the protein to move
both molecules need to be in the binding site
*selective, unidirectional, saturable, endocytosis
______________ are used to speed up the movement of water.
Aquaprorins
_______________ the force of water movement
osmolarity
in osmolarity water moves to the side with _______________________
higher concentration of solutes
What two properties balance dynamic equilibrium
-ion concentration and water concentration
_____________ the principle that ions will move across the membrane to balance based on both their concentration and their charge
electrochemical gradient
- charge
- concentration
What is membrane potential?
The potential at which a specific set of concentrations of an ion would lead to a stable equilibrium
In simple terms, membrane potential means ion will move in such a way that the _____________________ and ___________ equalize
equilibrium and membrane potential equalize
What is hyperpolarization
membrane becomes more negative
-exit of cations and entrance of anions
What is Depolarization
Membrane becomes less negative (more positive)
Entrance of cations
____________move ions in the same direction
Symporters
____________ move ions in opposite directions
Antiporters
