Membranes Flashcards
What is the function of the plasma membrane?
To allow the passage of necessary molecules, protecting the cell
What are the four components of cellular membranes
Phospholipid bilayer, transmembrane proteins, interior protein network, cell surface markers
What are integral membrane proteins?
Span the lipid bilayer, nonpolar regions are embedded in the interior, polar regions protrude
What do integral proteins do?
playing critical roles in movement of molecules across bilayer and the transduction of energy and signals.
What is the 6 major functions of membrane proteins
transport,
enzymatic activity,
Receptor proteins (signal transduction)
cell-cell recognition,
intercellular joining (tight junctions)
attachment to the cytoskeleton and extracellular matrix
desmodomes
gap junctions
Why is membrane fluidity important?
for permeability and enzyme function
What factors impact the membrane fluidity?
Membrane composition and temperature
What roles do unsaturated fatty acids have in membranes
unsaturated fatty acids make membranes more fluid, and the kinks from the double bonds keep them from packing tightly
most membranes contain steroids like cholesterol which can increase or decrease membrane fluidity based on temperature
How does cholesterol act as a temperature buffer?
At cool temps; cholesterol maintains fluidity by preventing tight packing via double bonds
at warm temps: cholesterol restrains the movements of phospholipids, making it less fluid
How does selective permeability regular cells molecular traffic
small, nonpolar molecules can cross the membrane directly
large, polar molecules do not cross the membrane easily
what are the types of passive transport?
simple diffusion, osmosis, facilitated diffusion
what are the types of active transport?
Primary active, secondary active
What are the types of transport proteins
can be channel, carrier, pump, or cotransporter
What are 2 energy sources Active Transport:
ATP and the electrochemical gradient
What is passive transport
it is the movement of molecules down the concentration gradient (no energy)
what is osmosis
osmosis is the net diffusion of water across a membrane toward a higher solute concentration
what is tonicity
the ability of a solution to cause a cell to gain or lose water
depends on concentration of non-penetrating solutes
what is an isotonic solution
it is when the solute concentration is the same on the inside of the cell, therefore no net water movement occurs across the membrane
what is a hypertonic solution
it is when the solute concentration is greater on the outside than the inside of the cell; causing water to rush out and shrink
what is hypotonic solution
when the solution solute concentration is less than the inside of the cell; causing water to rush in and gain size
what is facilitated diffusion?
they are passive carrier mechanisms that move molecules from higher to lower concentrations
What is active transport?
they are energy dependent carrier mechanisms that move charged or polar molecules against their concentration gradient
what are channel proteins
What are membrane carbohydrates
they are either glycolipids or glycoproteins and face the extracellular side of the membrane
they are important for cell-cell recognition and communication
Most lipid and some proteins move:
laterally
what are the 3 conditions that detemne the direction of flow in a membrane
relative concentration on either side, voltage differences, and gated channels that may be opened or closed
What drives the diffusion of K + through its channel (not the pump)
there is a higher concentration on the inside of the cell which drives the K+ out. However, the excessive positive charge on the outside of the cell impedes the diffusion of K+ out of the cell
what do peripheral proteins do
cell-cell recognition, acting as enzymes, transportation
what is a membrane pore
b-sheet barrel, allows water and small polar molecules to pass throguh
what are the membrane components that move substances by facilitated diffusion
channel proteins, carrier proteins, porin (aquaporin)
what is a co-transporter?
is a form of active transport because it is using the energy from one concentration gradient to transport another molecule across the membrane against its concentration gradient
What are three specific protein types that transport sodium and what type of transport are they?
Na+ Channel: Facilitated diffusion (passive)
Na+/K+ Pump: Primary Active Transport
Na+/ glucose cotransporter: Seconary Active Transport
Is ATP required for movement of glucose in a glucose transporter
no
Is ATP required for the movement of glucose in a Na+/Glucose Transporter
no, its energy is supplied by the electrochemical gradient
true or false: phospholipids and integral membrane proteins can move laterally along the plane of the plasma membrane
true
true or false: in simple diffusion, the concentration of one substance affects the diffusion of another
false
true or false: alpha helices and beta-sheets describe the tertiary structure of proteins
false, it describes the secondary
True or false: DNA is found in the nucleus, mitochondria,and chloroplasts of eukaryotic cells
True
what is the role of the ecm in animals
support, adhesion, movement, regulation
