Unit 1 - Cell Transport Flashcards
Functions of Cell Membranes
a) controls what enters and exits the cell to maintain homeostasis
b) provides protection and cell support
Types (2) of Cellular Transport
a) passive
b) active
Passive Transport
cells do NOT use energy = movement of substance across membrane wout energy
1) simple diffusion
2) facilitated diffusion
3) osmosis
Active Transport
cells DO use energy
1) protein pumps
2) endocytosis
3) exocytosis
Passive Transport Diffusion
random movement of particles from an area of high concentration to low concentration and will continue until all mol r evenly spaced = equilibrium but mols will still move
ie. sugar or salt dissolving in water ( Koolaid)
Rate of diffusion
depends on the concentration difference or concentration gradient that exists between 2 areas or across membrane = the larger the gradient the faster the rate of diffusion
Passive Transport
simple vs facilitated diffusion
-membranes have selective permeability, which means that some mols can diffuse rapidly while others r unable to without assistance. two major factors include the charge and size of ions.
Simple Diffusion
is the ability of substances to move across a membrane unassisted
Small, non-polar mols
can pass through the lipid bilayer and do so by squeezing through. do not need proteins from transport ie. oxygen or carbon dioxide.
Small, polar mols
these mols can pass through bilayer without the help of proteins but they do so with a little more difficulty = slower process
ie. water or glycerol
Large, non-polar mols
rings can pass through but it is also a slow process
ie. carbon ring
Large, polar mols and Ions
the size and charge of large polar mols make it too difficult to pass through the non-polar region without the help of transport proteins
ie. simple sugars or Na+
Facilitated Diffusion
large polar and charged mol need assistance for a transport protein. specific to the solute which then travels down its concentration gradient
- spontaneous = no energy
Types (2) of Facilitated Diffusion
a) channel proteins
b) carrier proteins
Channel Proteins
from hydrophilic pathways in the membrane through which water and certain ions can pass
Carrier Proteins
a protein that bins to a mol and transports it across lipid bilayer (uncharged mols)
-mol attaches to proper protein
-conforms shape
-release mol inside cell
Facilitated Transport (channel protein)
some channel proteins r regulated by hormones, pressure, and electric charge it also opens and closes.
Example of channel protein
aquaporin channel is highly specific to water mols. It allows water mols to diffuse quicker across the membrane by interacting with partial charges of mol.
Osmosis
net movement of water across selective permeable membrane and moves w concentration gradient. which moves from high water concentration to low water concentration
Isotonic Solution
the concentration of a solute is = inside and outside of the cell. The movement of water mols in and out of cell is also =.
Hypertonic Solution
the concentration of solute is higher outside the cell than in; so water moves out of cell. Cell Shrinks
Hypotonic Solution
concentration os solute is lower in the solution then in the cell; water mols will move into cell. May Rupture
active transport
movement os substance across membrane against gradient using pumps
- carrier protein “pump”
- “costs” energy = ATP
Primary Active Transport
- single mol transported in PAT
- used energy from ATP
- ions like Na+, Ca
-transmembrane proteins r unique - sodium-potassium pump
- calcium pump in muscles
- protein pump in stomach
Sodium Potassium Pump
1) cytoplasmic Ns+ bonds to SPP
2) Na+ binding stimulates phosphorylation by ATP
3) K+ is released and Na+ sites r receptive again
4) phosphorylation cause the protein to change its conformation expelling Na+ out of cell
5) loss of phosphate restores protein’s origal state
6) extracellular K+ binds to the protein causing a relase of phosphate group
Secondary Active Transport
-two types of mols use SAT
-The concentration gradient of the driving ion provides the energy for the transport of driven ion/mils against its CG
-Symports and Antiports
-Glucose-sodium pump, Na+/Ca+2 exhchanger
Bulk Transport
-some mols r too large or polar
-so cells use speical methods that involve the cell membrane folding in on itself creating vesicles
-endocytosis (pinocytosos/phagocytosis/receptor assisted endocytosis)
-Exocytosis
Endocytosis
Cell membrane folds inwards on itself enclosing matter from ECG and moves into cell
3 types:
a) pinacytosis
b) phagocytosis
c) receptor assisted enocytosis
a) pinocytosis
-occurs when a small amt of ECF containing dissolved substance is moved into the cell
-also know as cell drinking
b) phagocytosis
-occurs when large amt of ECF containing large matter like bacteria or organic matter is moved into the cell (cell eating )
- only in amoeba or macrophages
c) receptor assisted endocytosis
-occurs when specifi mols attach to specific protein receptor sites and r moved into the cell
-v specific
-cholesterol taken into cell
Exocytosis
opposite of endocytosis (vesicle remove substance from inside cell)
- vesicle moves to the cell membrane and fuses its membrane to the cell membrane and once fused vesicles empties its contents into the ECF (restores lost sie decreased by endocystosis)
