Biomed final review 4
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Graphic Objective 3.
Linst and classify the components of the plasma membrane. as defined by the fluid-mosaic model.Cassify membreane proteins as peripheral or interal.
tells how easily a substance can cross the plasma membrane.
What is differential permeability
is what defines a cell.
-the cell lets some things pass (water and cell nutrients must be allowed into the cell)
-the cell does not let other things pass(guts of the cell should not leak out)(toxic substances should not leak in)
What can pass through the cell membrane?
Small uncharged moleculeslipid-soluble substances (fat-soluble)gases
What can't pass through the cell membrane?
charged ionswater-soluble molecules
Only ______ and ________ can move across the cell membrane without help.
The random motion of small particles or even molecules in a liquid or gas is called
Physical principles underlying diffusion.
Molecules in a gas or liquid can move around.
The warmer the tempertature, the more movement.
The smaller the molecule, the more movement.
This random movement is seen as diffusion: over time, the concentration of the substance will become equal in all parts of the system.
Graphic objective 13 module 4
Discuss the physical principles underlying osmosis
No energy needed
protein channels or carriers in the cell membrane facilitate the diffusion of substances.
What has to be escorted, even if the concentration is higher outside than inside.
Larger and charged molecules
What are the critical steps in the facilitated diffusion of glucose?
Step 1: Gluscose fits into "pocket" of glucose transporter.
Step 2: Protein changes shape, closing glucose pocket.
Step 3: Glucose transporter changes shape again, forces glucose into cytoplasm.
What is Active Transport?
Requires energy. Is used to move an ion against its concentration gradient.
Energy sources for active transport?
Pre-existing storage of energy in a concentration gradient.
When molecules are moved against their concentration gradient (from low concentration to high), energy is required.
Na+ is _______ outside, ________ inside.
K+ is _______ outside, _________ inside.
Na+/K+ pump moves both
against their concentration gradients (Na+ moves out, K+ moves in), splits ATP for energy to do this (ATPase).
Three Na+ ions rest in a pocket of the pump. Thes Na+ ions are expelled as _______ is split into ____ + _______, releasing the nergy needed to drive the pump. Then, two K+ ions _______ outside the cell and these are ________ inside the cell.
ATP; ADP; phosphate; bind; released
Since three positive charges are pumped out for every two allowed in, the cell is made more negative inside by the pump. We call this pump
Na+/K+ ATPase (Na+/K+ pump)
Na+ gradient: high outside cell, low inside.
K+ gradient: low outside cell, high inside.
Pump wants to move both against their gradients.
ATP is used as energy source.
3 Na+ bind to pocket in pump protein
3 Na+ expelled from cell.
ATP split to ADP + P + energy
K+ pocket exposed
2 K+ enter cell.
Pump is reset to bind 3 more Na+
What is an Antiport System?
It is a form of Active transport.When two ions move in opposite directions to drive the pump.
What is a Symport System?
It is a form of Active transport.
A molecule and an ion move in the same direction to drive the pump.
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