Section 5.1 & 5.2 (JL&MP) Flashcards
What is Selective Permeability?
A feature and a function of the plasma membrane that is essential to survive by regulating the passage of some substances while preventing others from entering the cell. Supplement.
What does Amphipathic mean?
Has both a hydrophilic and hydrophobic region; phospholipids as an example
What is the Fluid Mosaic Model?
Describes the cell membrane, fluid refers to the flowing/always moving aspect of the membrane, and the mosaic depicts the proteins and other molecules on the membrane.
What type of interactions holds the fatty acid chains of the cell Membrane together?
Hydrophobic interactions
What can the proteins in the membrane be attached to?
Cytoskeleton (inside cell), or the extra-cellular matrix (outside cell)
Explain the role of cholesterol in the membrane
temperature decreases = still remain fluid - cholesterol prevents side chains from attaching (as do the kinks in tail where there are double bonds prevent them from becoming solid). Warm temps - cholesterol holds the membrane together by being a reservoir of weak bonds between lipids.
What happens when a Membrane solidifies?
its permeability changes and enzymatic proteins in the membrane may become inactive.
Describe the Evolution of Differences in Membrane Lipid Composition with respect to temperature
- Fishes that live in the extreme cold have membranes with high amounts of unsaturated hydrocarbon tails, which allows their membranes to remain fluid
- The ability to change lipid composition to adapt has evolved in organisms that live where temperatures may vary
Membrane Proteins and Their Functions
- Lipids = fabric of membrane, while proteins = function of membrane
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Integral Proteins
- Penetrate the hydrophobic interior of the lipid bilayer
Peripheral Proteins
- Not embedded in the lipid bilayer, loosely bound to the surface of the membrane
Cell-Cell Recognition
- Cell-cell recognition is a cell’s ability to distinguish one type of neighboring cell from another and is crucial to the functioning of an organism
Importance of Cell-Cell Recognition?
rejects foreign and dangerous cells, sorts cells into tissues and organs
Membrane Carbohydrates
- Short, branched chains fewer than 15 sugar units
- Some covalently bonded to lipids → glycolipids
- Some covalently bonded to proteins → glycoproteins
Supramolecular structure
Multiple molecules interacting with one another (quarternary structure) with emergent properties beyond the individual molecules (the whole is greater than the sum of the parts)
What is the most important property of a supra molecular structure
Ability to regulate transport across cells
What helps explain how membranes regulate the cells molecular traffic
The Fluid Mosaic Model
What can move across the cell membrane without the help of proteins?
Small molecules & ions
How does the selective permeability of the cell membrane affect it?
It is able to take up some small molecules and exclude others
Why can CO2, O2, and other lipids/hydrocarbons cross the membrane easily?
They are non-polar and can dissolve in the lipid bilayer
Why is it difficult for sugars like glucose to cross the membrane?
They are polar and the hydrophobic portion of the membrane makes it difficult for them to get across.
This also affects all polar molecules and ions, including water
The lipid bilayer is one part of the membrane’s selective permeability. What is another type of molecule that helps?
Proteins
Transport proteins
are proteins that facilitate the movement of molecules across the cell membrane
Transport proteins in passive transport
Channel proteins, involved in passive transport, are hydrophilic, allowing polar molecules and ions to pass through
Most aquaporins have ___ polypeptide subunits, and can allow up to ___ water molecules per second
4, 3 billion
Transport proteins in active transport
Carrier proteins hold on to their passengers and change shape to move them across the membrane against the concentration gradient
For a transport protein to be effective, it needs to be ___ (+/-) efficient at moving molecules than them crossing the membrane on their own
more effective
