2.4 Membranes Flashcards
What is the current model of the membrane structure called?
fluid mosaic model
What is the bilayer of the membrane structure?
the phospholipid bilayer
What is the 3-carbon compound called in the phospholipid bilayer?
glycerol
What are two of the carbons in the 3-carbon compound attached to?
non-polar fatty acids
What is one of the carbons in the 3-carbon compound attached to?
highly polar organic alcohol group with a phosphate
What are the hydrophilic ends?
alcohol-phosphate
What are the hydrophobic ends?
fatty acids
Which ways do the hydrophilic ends face?
outward
Which way does the hydrophobic ends face?
inward
Why does the membrane remain fluid and flexible?
Because the fatty acid ends are not attracted to one another
What helps maintain the overall structure of the membrane?
Hydrogen bonds with water
What are glycoproteins?
composed of carbohydrate chains attached to peripheral proteins; recognize like cells and are involved in immune response
What are integral proteins?
completely penetrate lipid bilayer; control entry and removal of specific molecules
What does the cholesterol do?
helps regulate membrane fluidity and stability
composed of carbohydrate chains attached to peripheral proteins; recognize like cells and are involved in immune responsibility
glycoprotein
completely penetrate lipid bilayer; control entry and removal of specific molecules
integral proteins
helps regulate membrane fluidity and stability
cholesterol
What are the six membrane protein functions?
Hormone binding sites Enzymatic Action Cell Adhesion Cell-to-Cell Communication Channels for Passive Transport Pumps for Active Transport
What are the 3 types of passive transport?
diffusion, facilitated diffusion, and osmosis
What is diffusion?
Particles moving from a region of high concentration to a region of low concentration
What are 3 characteristics of facilitated diffusion?
Involves a carrier protein (non-channel protein) that helps carry substances across membrane Does NOT require energy Rate is dependent on number of carrier proteins available
What is osmosis?
Movement of water across a partially permeable membrane to balance solute concentration
What proteins does osmosis use?
aquaporins
What are the 3 characteristics of a hypertonic solution(concentration, movement, and shape)?
Concentration of solutes is more outside the cell than inside Water flows out of cell The cell shrivels and becomes “flacid”.
What are the 3 characteristics of a hypotonic solution(concentration, movement, and shape)?
Concentration of solutes is less outside the cell than in. Water flows in The cell swells with water, becomes “turgid”, and dies.
What are the 3 characteristics of a isotonic solution(concentration, movement, and shape)?
Concentration is the same inside and out No net movement The cell stays the same
What is water potential?
the tendency of water to leave one place in favor of another place
How will water move?
Water will always move from and area of higher (less negative) water potential to an area of lower water potential (more negative).
Compare big/polar and small/non-polar in which can cross the membrane passively?
It is difficult (not impossible) for large or polar molecules to cross membranes passively. It is relatively easy for smaller and non-polar molecules to cross membranes passively
What are 2 characteristics of active transport(movement and requirement)?
Movement of substances against a concentration gradient Requires energy (ATP)
What is step 1 of the sodium-potassium pump?
Specific protein binds to three intracellular sodium ions
What is step 2 of the sodium-potassium pump?
Binding of sodium ions causes phosphorylation by ATP
What is step 3 of the sodium-potassium pump?
Phosphorylation changes shape of protein, pushing sodium ions out of cell
What is step 4 of the sodium-potassium pump?
Two extracellular potassium ions bind to a different part of protein, which causes release of phosphate group
What is step 5 of the sodium-potassium pump?
Loss of phosphate group restores original shape causing release of potassium ions into cell
What does endocytosis do?
Allows macromolecules to enter the cell
When does endocytosis occur?
Occurs when portion of plasma membrane is “pinched” off to enclose a substance, forming a vesicle
Where does the vesicle go in endocytosis?
This vesicle enters the cytoplasm and the substance makes its way where it is needed
Why do the ends of the plasma membrane reattach after endocytosis?
Ends of the plasma membrane reattach because of the hydrophobic and hydrophilic properties of the phospholipids and the presence of water
What is step 1 of exocytosis?
Protein produced by ribosomes of rough ER enters the lumen of the ER
What is step 2 of exocytosis?
Protein exits ER and enters the cis side of the Golgi apparatus (vesicle is involved)
What is step 3 of exocytosis?
As protein moves through the Golgi apparatus, it is modified and exits on the trans side inside a vesicle
What is step 4 of exocytosis?
Vesicle with modified protein moves to membrane and fuses with it; contents are secreted out of cell
What are the 4 parts of the membrane?
proteins, carbohydrates, lipids, and cholesterol
What is number 1?
peripheral protein
What is number 2?
phospholipid
What is number 3?
tail
What is number 4?
head
What is number 5?
peripheral protein
What is number 6?
channel protein (integral protein)
What is number 7?
cholesterol
What is number 8?
glycoprotein
