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34 Cards in this Set
- Front
- Back
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Do the majority of biochemical substances pass through the lipid bilayer? |
No because of the semi permeable barrier |
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What type of molecules can penetrate the lipid bilayer? |
Lipid soluble or lipophilic **water molecules are small enough to penetrate |
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What type of molecules can't penetrate the lipid bilayer? |
water soluble or hydrophilic |
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Where is there more Na and Cl? |
Extracellular fluid |
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Where is there more K, PO4 and proteins? |
Intracellular fluid |
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What type of substances do proteins help go in and out of the cell? |
Hydrophilic (lipophobic) |
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How do proteins help move molecules/ions across the membrane? |
They act as channels all the way through the membrane and bind with molecules which cause a conformational change to move the substances to the other side |
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What are the two basic transports? |
Passive (diffusion)- with conc. gradient Active-against conc. gradient |
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What are the two types of passive transport? |
Simple diffusion Facilitated diffusion |
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What are the types of simple diffusion? |
Osmosis (just water) Through selective protein channels Through gated channels |
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What are the types of gated channels used in simple diffusion and what do they control? |
Voltage gated channels (mem. potentials) Ligand gated channels (acetylcholine) Controls ion permeability, opened channels are caused by stimuli |
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What type of substances diffuse directly through the lipid bilayer? |
Gases (O2, N2, CO2) Alcohols |
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What type of substances readily dissolve in the bilayer? |
Small hydrophobic (lipid soluble) molecules |
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What type of molecules diffuse across the bilayer but more slowly? |
small UNCHARGED hydrophilic (water loving) molecules |
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Which molecules cannot cross the lipid bilayer and need channels? |
Ions (charged molecules) |
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Where does the selectivity come from for the protein channels? |
diameter shape nature of electrical charges/bonds |
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What is significant about voltage gated channels for simple diffusion and what are they responsible for? |
They are present in the membrane of all EXCITABLE CELLS Ex: Nerve, muscle, endocrine, egg cells Responsible for neurons ability to transmit info |
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What is the channel's threshold in voltage gated simple diffusion? |
Minimum membrane potential that causes opening of the channel |
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What are some examples of ligand gated channels in simple diffusion? |
Skeletal muscle cells Some neurons of the ANS Ex: Acetylcholine released from neuron binds to Nicotinic Acetylcholine Receptor in the skeletal muscle cells |
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What is facilitated diffusion? |
Carrier mediated diffusion where the rate CANNOT rise greater than the Vmax of the carrier protein |
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How is facilitated different from simple? |
The rate in simple is directly proportional to the lipid solubility (concentration of diffusing substance) where the rate in facilitated depends on the number of carriers present |
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What is osmosis? |
Net movement of water caused by a concentration difference of water across a membrane |
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How does water diffuse through the lipid bilayer? |
Through aquaporins (highly specialized, 13 types found in mammals) |
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What is osmotic pressure? |
Amount of pressure required to stop osmosis *pressure can influence water diffusion Hypertonic (flow out of cell-shrinking) Hypotonic (flow into cell-swelling) |
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What are the two types of Active transport? |
Primary Secondary |
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What kind of energy is involved in primary active transport? |
from the breakdown of ATP (Na/K pump) |
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What kind of energy is involved in the secondary active transport? |
energy from the concentration gradient of the driving ion **Transporter protein couples the movement of an ion (Na+ or H+) down the electrochemical gradient to the uphill movement of another molecule against the conc. gradient |
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What are the two types of transporters involved in secondary active transport? |
Co-transporters or symporters Counter-transporters or antiporters |
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What does a cotransporter/symporter do? |
moves 2 substances at the same time in the same direction Ex: Na and glucose (Na down conc. gradient to provide energy for glucose to go up conc. grad.) |
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What does a countertransporter/antiporter do? |
Moves 2 substances at the same time in the opposite direction Ex: Na+ and H+ |
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What is transcellular/epithelial transport? |
Some areas of the cell where substances must be transported from one ECF to another **active transport through cell on one side, then simple/facilitated through membrane on opposite side |
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How are impermeable molecules transported by means other than membrane proteins? |
Using the membrane itself as a carrier Endocytosis Exocytosis |
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What is endocytosis? |
Phagocytosis (removal of large particles) Pinocytosis (removal of small particles) Receptor mediated (needs receptor Ex: cholesterol) |
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What is exocytosis? |
Constitutive secretion: All cells-no signal sequence, no proteins incorporated into plasma membrane, ECM or signaling proteins Regulated secretion: Specialized cells-Need signal to stimulate fusion and release to cell exterior |
