8/22 exam 1: part 2 Flashcards
(24 cards)
What is passive transport?
Movement of molecules across membranes without energy input; includes diffusion, facilitated diffusion, filtration, and osmosis.
What is facilitated diffusion?
Passive transport using specific transmembrane integral proteins to move molecules down their concentration gradient.
What is active transport?
Movement of molecules across membranes using energy, typically against concentration gradients.
What is osmosis?
Net movement of solvent molecules through a semipermeable membrane into a region of higher solute concentration.
What is a channel in biological membranes?
Proteins that allow passive movement of ions, water, or solutes through the membrane down their gradient.
What is a transporter in biological membranes?
Membrane proteins that move ions or molecules across a membrane via facilitated diffusion or active transport.
What is the function of Na+-K+ ATPase?
Transports 2 K+ ions into the cell for every 3 Na+ ions pumped out, using ATP for energy.
What are cell junctions?
Interactions that hold cells together to form tissues; include anchoring, occluding, channel-forming, and signal-relaying junctions.
What kinds of molecules can diffuse through the bilayer membrane?
Small, uncharged, hydrophobic molecules like O2, CO2, N2; larger or charged molecules cannot easily diffuse.
What are the three types of coupled transport mechanisms?
Uniport, symport, and antiport.
What energy sources power facilitated transport?
ATP-driven transport, light-driven pumps (in bacteria).
What are occluding junctions?
Junctions that prevent passage of molecules between cells, e.g., tight junctions.
What is the role of cadherins in adherens junctions?
Cadherins form and maintain adherens junctions, held together by Ca+ ions.
What is the role of connexins in gap junctions?
Connexins form gap junctions, creating channels for transport of substances like calcium and ATP.
What are the principles of membrane transport?
Transport can be passive or active, relying on concentration gradients or electrochemical gradients.
What molecules have relative permeability across membranes?
Hydrophobic > small uncharged polar > large uncharged polar > ions (least permeable).
What is the glucose carrier driven by the Na+ gradient?
Located in the gut, it balances Na+ within cells by moving glucose along with Na+.
What is the mechanism of Na+-K+ ATPase in active transport?
Pumps 3 Na+ out and 2 K+ into the cell using ATP, maintaining ion balance.
What are the types of cell junctions?
Occluding, anchoring (actin and intermediate filaments), communicating, and signal-relaying junctions.
What are adherens junctions?
Form intercellular junctions between cells, mediated by cadherins.
What are gap junctions?
Protein tubes that connect adjacent cells, allowing molecule transfer; can be open or closed.
What is the clinical significance of ion channels in sensations?
Sensations like smell, touch, and taste involve ion channel signaling.
What percentage of ATP is expended by Na+-K+ ATPase in cells?
20-25% of total cell ATP, up to 60-70% in neural cells, due to Na+-K+ ATPase.
Why are principles of membrane transport important?
They underlie cell signaling, nutrient transport, and sensation like taste and pain.
