Ch 5 Flashcards
What model describes the structure of the cell membrane?
Fluid mosaic model
This model illustrates how membranes are composed of a flexible combination of lipids and proteins.
What are the main components of a phospholipid?
2 fatty acid chains, a glycerol molecule, a phosphate group
The fatty acid chains can be either saturated or unsaturated.
What is the function of the hydrophilic heads and hydrophobic tails in phospholipids?
Hydrophilic heads face outward; hydrophobic tails point inward
This arrangement forms a bilayer in aqueous environments.
What affects membrane fluidity?
Phospholipid type, temperature, cholesterol
Saturated fatty acids pack more closely than unsaturated fatty acids.
What are the two types of membrane proteins?
Integral proteins, peripheral proteins
Integral proteins are embedded in the bilayer, while peripheral proteins are attached to the surface.
What is the primary function of integral membrane proteins?
Transporters, receptors, enzymes, adhesion
Integral proteins can have hydrophobic and hydrophilic regions.
How does simple diffusion occur?
Net movement from high to low concentration
This process does not require a membrane but can occur if the membrane is permeable.
What is osmosis?
Diffusion of water across a semipermeable membrane
Water moves from a region of higher concentration to lower concentration.
What is the difference between hypotonic, hypertonic, and isotonic solutions?
Hypotonic: cell swells; Hypertonic: cell shrinks; Isotonic: no change
Tonicity depends on the concentration of nonpermeating solutes.
What is primary active transport?
Transport that directly uses ATP
Example: sodium-potassium pump.
What is secondary active transport?
Transport that uses an electrochemical gradient indirectly
Example: sodium-glucose transporter (SGLT).
What creates the resting membrane potential?
Combined effect of ion diffusion, selective permeability, electrical attraction
Typically around -70 mV due to K+ leakage.
What is the role of cholesterol in cell membranes?
Maintains membrane fluidity
Cholesterol prevents membranes from becoming too rigid at low temperatures.
Fill in the blank: The process of engulfing large particles by the cell membrane is called _______.
Phagocytosis
This process is also referred to as cellular eating.
True or False: Exocytosis is the process of exporting substances out of the cell.
True
Involves vesicles fusing with the plasma membrane.
What is facilitated diffusion?
Passive transport aided by integral membrane proteins
This process allows polar molecules or ions to diffuse into the cell.
What is the function of aquaporins?
Facilitate the movement of water across membranes
They enhance the rate of osmosis.
What is osmolarity?
Total osmotic concentration of all solutes in a solution
Important for understanding the movement of water between compartments.
What is the difference between channels and carriers in membrane transport?
Channels allow ions/molecules to pass; carriers change shape to transport substances
Channels can be gated or open all the time.
What happens during receptor-mediated endocytosis?
Specific substances bind to receptors and are internalized
This process is selective and efficient for certain molecules.
What is the role of the sodium-potassium pump?
Maintains concentration gradients of sodium and potassium
Keeps sodium concentration lower and potassium higher inside the cell.
What is turgor pressure?
Pressure exerted by the plasma membrane against the cell wall
Important for plant cell stability in hypotonic solutions.
Define tonicity.
Ability of a surrounding solution to affect fluid volume and pressure in a cell
It is determined by the concentration of nonpermeating solutes.
