Module 2 Flashcards
The main goal of a membrane is what?
Separating one compartment from another
List the four functions of the cell membrane.
- Physical isolation (separating ICF and ECF)
- Regulation of exchange with the environment
- Communication between cell and environment
- Structural support
In a typical cell membrane, we would expect to find roughly 55% of ____, 45% of ___, and small amounts of ___.
55% protein
45% lipids
small amounts of carbohydrates
Which of the following membranes would theoretically be the most metabolically active?
a) membrane with 35% protein comp.
b) membrane with 37% protein comp.
c) membrane with 47% protein comp.
d) membrane with 54% protein comp.
d) membrane with 54% protein comp.
Remember: the higher the protein=more metabolically active
What are the three types of lipids found in the cell membrane?
- Phospholipids
- Sphingolipids
- Cholesterol
What are some characteristics of phospholipids?
They can form bilayers, micelles, and liposomes
Amphipathic
Weak bonds
BULK OF LIPID IN CELL MEMBRANE
What is the structure of a phospholipid?
Glycerol backbone, fatty acid tail, polar head (phosphate + a molecule)
Which lipid is also known as lipid rafts?
Sphingolipids
What are some characteristics of sphingolipids?
Can form lipid rafts Sphingosine backbone Fatty acid tail Phosphate head Larger than phospholipids, fewer in # Amphipathic Common to see lipid anchored proteins attached
What is the goal of cholesterol?
Increase viscosity (gives cell membrane strength and flexibility)
If a membrane has high cholesterol content, what would we expect to happen?
a) high viscosity, decreased permeability
b) high viscosity, increased permeability
c) low viscosity, decreased permeability
c) low viscosity, increased permeability
a) high viscosity, decreased permeability
as cholesterol content increases, permeability decreases
The current cell membrane model is known as the fluid mosaic model, describe this model.
Proteins dispersed throughout membrane
Extracellular surface has glycoproteins and glycolipids
Phospholipid heads face intracellular and extracellular compartments
Lipid tails form interior layer
Cholesterol inserted in lipid layer
Where would we expect to find integral membrane proteins?
integrated within the membrane
Where would we expect to find peripheral membrane proteins?
noncovalently bonded to integral proteins
Integral proteins are also called ___ proteins.
Transmembrane
Identify roles of integral proteins.
membrane receptors cell adhesion molecules transmembrane movement enzymes mediators of intracellular signaling
Which lipid do lipid anchored proteins commonly associate with?
Sphingolipids
What is the goal of lipid rafts?
Cell signal transduction
Where would you expect to find carbohydrates on the cell membrane?
Extracellularly
Adipose tissue is 90% ___, skeletal muscle is 75% ___.
lipids, water
___ is the movement of water across a membrane in response to a solute concentration gradient.
a) tonicity
b) osmosis
c) active transport
d) osmolarity
b) osmosis
What is osmolarity?
The number of particles in solution
1OsM of glucose and 1OsM of NaCl would be ___.
a) isotonic
b) isosmotic
c) hypertonic
d) hyperosmotic
b) isosmotic (idential osmolarities)
- 8OsM of glucose would be ___ to 1.2OsM of NaCl.
a) hyperosmotic
b) isosmotic
c) hyposmotic
d) hypertonic
a) hyperosmotic
- 2OsM of NaCl is ___ to 1.8OsM of glucose.
a) hyperosmotic
b) isosmotic
c) hyposmotic
d) hypotonic
c) hyposmotic
What is tonicity?
How a solution would affect cell volume if a cell were placed in the solution
What are the three tonicity terms?
isotonic, hypotonic, hypertonic
What are the units for tonicity?
a) mg/g
b) mol
c) mOsm/L
d) it has no units
d) it has no units
What is simple diffusion?
The movement of molecules from an area of higher concentration to an area of lower concentration, typically used for small uncharged, lipophilic molecules (O2, CO2, NH3, lipids, steroids)
What are some circumstances that would make diffusion faster?
Higher concentration gradient
Over shorter distance
At higher temperatures
For smaller molecules
Simple diffusion across a membrane depends on what?
Concentration gradient across membrane Membrane surface areas Thickness of membrane Lipid solubility Composition of lipid layer
What does membrane permeability depend on?
The molecules lipid solubility
The molecules size
The lipid composition of the membrane
What is a channel protein?
Membrane spanning protein subunits that create a cluster of cylinders with a pore through the center
What determines what passes through a channel protein?
Size of the pore and charge at the center of the pore
Leak channels are typically in a ___ state, Gated channels are typically in a ___ state.
open, closed
How do carrier proteins move molecules?
They change their conformation
Contrast uniport carriers, symport carriers, and antiport carriers
Uniport carriers: transport only one kind of substrate
Symport carriers: move two or more substrates in the same direction
Antiport carriers: move substrates in opposite directions
What is active transport?
Moving molecules against their concentration gradient, uses carrier proteins, support a state of disequilibrium
Contrast between primary and secondary active transport.
Primary: energy to move molecules comes from ATPase
Secondary: uses the potential energy of one molecule to push another molecule
What is the result of the N+/K+ ATPase?
3 Na+ released into ECF, 2 K+ released into ICF
The sodium glucose transporter (SGLT) is an example of ___ transport.
Secondary active transport
A carrier having a preference for a certain substrate over another substrate is known as ___.
Competition
If a transporter will move molecule A but not molecule B, this is called ____.
Specificity
Specificity, competition, and saturation are all key properties of both active and passive _____.
Carrier mediated transport
If a macromolecule cannot fit through a carrier or channel, what type of transport is used?
a) Vesicular
b) Passive
c) Active
d) Epithelial
a) vesicular
Bringing a molecule into the cell via vesicle is known as ____.
endocytosis
What are the two types of endocytosis?
Non selective (pinocytosis) Selective (receptor mediated)
Typically, what will be seen brought into the cell via endocytosis?
Small proteins, antibodies, hormones, growth factors
Transport out of the cell is known as ___.
Exocytosis
Which mineral can regulate exocytosis?
a) Na+
b) Ca2+
c) K+
d) Fe
b) Ca2+
The apical surface is:
a) facing lumen
b) facing away from lumen
c) in contact with ECF
d) in contact with ICF
a) facing lumen
Which compartment does the basolateral membrane come in contact with?
ECF
What are the three types of epithelial transport?
Paracellular
Transcellular
Transcytosis
The ECF has a slight excess of ___, the ICF has a slight excess of ___.
cations, anions
What is membrane potential?
The electrical disequilibrium that exists between the ECF and ICF.
The membrane potential of a cell when it is not active is called what?
Resting membrane potential
What determines the membrane potential?
Na-K ATPase
What is the resting membrane potential?
-70mV
What are the two factors that influence a cell’s membrane potential?
Concentration gradients of different ions across the membrane
Permeability of the membrane to those ions
What is depolarization?
Membrane potential becomes less negative than the resting potential
What is hyperpolarization?
Membrane potential becomes more negative
