Chapt 7 Flashcards
Membrane Structure
Define selective permeability.
The plasma membrane will only allow certain substances to cross more easily than others.
What are the two most important components of the membrane?
Lipids and proteins
Which lipids are the most abundant?
Phospholipids
What does amphipathic mean?
It’s a phospholipid that has both a hydrophilic region and a hydrophobic region.
Describe fluid mosaic model of the membrane.
The membrane is a fluid structure with a mosaic of various proteins embedded in or attached to a double layer of phospholipids.
The head of the phospholipid is hydrophilic. T or F.
True.
The higher the number of phospholipids with unsaturated carbon tails, the longer it will remain fluid in colder temps. T or F.
True.
When a membrane solidifies its _____ changes and enzymatic proteins in the membrane become___
permeability . inactive
Name two major populations of membrane proteins.
Integral proteins and Peripheral proteins
Within the integral proteins, which type of protein spans the membrane?
transmembrane proteins
T or F. Peripheral proteins are embedded in the lipid bilayer.
False.
List some functions for membrane proteins.
- Transport 2. Enzymatic activity 3. Signal transduction 4. Cell-cell recognition 4. Intercellular joining 5. Attachment to the cytoskeleton and extracellular matrix.
Give an example of cell-cell recognition.
The immune system can reject foreign cells which want to cause disease.
The carbohydrates attached to some proteins and lipids of the plasma membrane are added as the membrane is made and refined in the ER and Golgi apparatus. The new membrane then forms transport vesicles that travel to the cell surface. On which side of the vesicle membrane are the carbohydrates?
The inner side of the transport vesicle.
How would you expect the saturation levels of membrane phospholipids to differ in plants adapted to cold environments?
Plants adapted to cold environments have more unsaturated fatty acids in their membrane so they can stay fluid longer in colder weather.
Nonpolar molecules are hydrophobic or hydrophilic?
Hydrophobic
List some nonpolar molecules
hydrocarbons, carbon dioxide, oxygen
If a molecule is nonpolar, or hydrophobic, can it dissolve in the lipid bilayer of the membrane?
Yes
What are some polar molecules?
glucose and other sugars, water
Do polar molecules pass quickly or slowly through the lipid bilayer of a membrane?
slowly
Compared to polar molecules, how quickly can a charged atom or molecule move through the membrane?
They move even slower than the polar molecules
In order to make it easier for polar molecules to pass through the lipid bilayer, what proteins can make the job easier?
transport proteins
Are transport proteins specific for certain molecules?
Yes
Two molecules that can cross a lipid bilayer without help from membrane proteins are oxygen and carbon dioxide. What properties allow this to occur?
They are nonpolar and thus can dissolve in the lipid bilayer of the membrane with transport proteins.
Why would water need a transport protein to move rapidly through the membrane and in large quantities?
Water in polar and would move too slowly through the lipid bilayer so it needs a transport protein.
Molecules have a type of energy called ___
thermal motion (heat)
What is one result of thermal motion?
Diffusion
Define diffusion.
The movement of molecules os any substance so they they spread out evenly into available space.
Define concentration gradient
The movement of a substance from where it is more concentrated to where it is less concentrated.
Does this concentration gradient process require energy
No it’s passive
The concentration gradient itself represents ___ energy and drives diffusion.
potential energy
The diffusion of water across a selectively permeable membrane is called ____
osmosis
Define tonicity.
The ability of a solution to cause a cell to gain or lose water.
Is there any movement in an isotonic solution?
No, no net movement.
