Ch. 7 Flashcards
What are the main macromolecules in membranes?
Lipids and proteins
What does amphipathic mean?
The molecule has both hydrophobic and hydrophilic regions
What factor influences membrane fluidity and how does it impact the membrane?
Temperature.
As temperatures cool, membranes switch from a fluid stare to a solid state as the phospholipids pack more closely
What feature of the plasma membrane allows some substances to cross more easily than others?
Selective permeability
Are membranes more fluid with more unsaturated fatty acids or saturated fatty acids?
Unsaturated fatty acids because the kinks in the tails prevent tight packing
What steroid acts as a fluidity buffer?
Cholesterol
What determines most of the membrane’s specific functions?
Proteins
What two type of proteins are part of the plasma membrane and where are each of them located?
Integral- penetrate the hydrophobic interior
Peripheral- loosely bound to the surface of the membrane
Where are membrane lipids and proteins synthesized?
The ER
Can nonpolar molecules cross the membrane easily or do they have trouble? Why?
They can cross easily because they are hydrophobic and can dissolve in the lipid bilayer
Do polar molecules and ions cross the plasma membrane with ease or difficulty? Why?
They have difficulty crossing and do it slowly because they are hydrophilic
What channel proteins assist the passage of water through the membrane?
Aquaporins
Transport proteins called_________ bind to molecules and change shape to shuttle then across the membrane
Carrier proteins
Is work or energy required to move substances down the concentration gradient?
No
The diffusion of a substance across a biological membrane
Passive transport
The ability of a surrounding solution to cause a cell to gain or lose water
Tonicity
When the cell is submersed in a solution and loses water to its environment resulting in the shrinking of the cell, what is this called?
Hypertonic
When water enters the cell faster than it leaves and the cell swells and bursts, what environment was it placed in?
Hypotonic
What environment will result in no net movement of water across the plasma membrane?
Isotonic
The control of water balance
Osmoregulation
If a plant cell and its surroundings becomes isotonic what happens?
There is no movement of water into the cell and it becomes flaccid (limp) and the plant may wilt
The passive movement of molecules down their concentration gradient with the help of transport proteins is called…
Facilitated diffusion
What kind of transport proteins can move solutes against a concentration gradient through active transport?
Carrier proteins
What is the energy supply for most active transport?
ATP
