8/22 exam 1: part 2

Question 1

What is passive transport?

Answer 1

Movement of molecules across membranes without energy input; includes diffusion, facilitated diffusion, filtration, and osmosis.

Question 2

What is facilitated diffusion?

Answer 2

Passive transport using specific transmembrane integral proteins to move molecules down their concentration gradient.

Question 3

What is active transport?

Answer 3

Movement of molecules across membranes using energy, typically against concentration gradients.

Question 4

What is osmosis?

Answer 4

Net movement of solvent molecules through a semipermeable membrane into a region of higher solute concentration.

Question 5

What is a channel in biological membranes?

Answer 5

Proteins that allow passive movement of ions, water, or solutes through the membrane down their gradient.

Question 6

What is a transporter in biological membranes?

Answer 6

Membrane proteins that move ions or molecules across a membrane via facilitated diffusion or active transport.

Question 7

What is the function of Na+-K+ ATPase?

Answer 7

Transports 2 K+ ions into the cell for every 3 Na+ ions pumped out, using ATP for energy.

Question 8

What are cell junctions?

Answer 8

Interactions that hold cells together to form tissues; include anchoring, occluding, channel-forming, and signal-relaying junctions.

Question 9

What kinds of molecules can diffuse through the bilayer membrane?

Answer 9

Small, uncharged, hydrophobic molecules like O2, CO2, N2; larger or charged molecules cannot easily diffuse.

Question 10

What are the three types of coupled transport mechanisms?

Answer 10

Uniport, symport, and antiport.

Question 11

What energy sources power facilitated transport?

Answer 11

ATP-driven transport, light-driven pumps (in bacteria).

Question 12

What are occluding junctions?

Answer 12

Junctions that prevent passage of molecules between cells, e.g., tight junctions.

Question 13

What is the role of cadherins in adherens junctions?

Answer 13

Cadherins form and maintain adherens junctions, held together by Ca+ ions.

Question 14

What is the role of connexins in gap junctions?

Answer 14

Connexins form gap junctions, creating channels for transport of substances like calcium and ATP.

Question 15

What are the principles of membrane transport?

Answer 15

Transport can be passive or active, relying on concentration gradients or electrochemical gradients.

Question 16

What molecules have relative permeability across membranes?

Answer 16

Hydrophobic > small uncharged polar > large uncharged polar > ions (least permeable).

Question 17

What is the glucose carrier driven by the Na+ gradient?

Answer 17

Located in the gut, it balances Na+ within cells by moving glucose along with Na+.

Question 18

What is the mechanism of Na+-K+ ATPase in active transport?

Answer 18

Pumps 3 Na+ out and 2 K+ into the cell using ATP, maintaining ion balance.

Question 19

What are the types of cell junctions?

Answer 19

Occluding, anchoring (actin and intermediate filaments), communicating, and signal-relaying junctions.

Question 20

What are adherens junctions?

Answer 20

Form intercellular junctions between cells, mediated by cadherins.

Question 21

What are gap junctions?

Answer 21

Protein tubes that connect adjacent cells, allowing molecule transfer; can be open or closed.

Question 22

What is the clinical significance of ion channels in sensations?

Answer 22

Sensations like smell, touch, and taste involve ion channel signaling.

Question 23

What percentage of ATP is expended by Na+-K+ ATPase in cells?

Answer 23

20-25% of total cell ATP, up to 60-70% in neural cells, due to Na+-K+ ATPase.

Question 24

Why are principles of membrane transport important?

Answer 24

They underlie cell signaling, nutrient transport, and sensation like taste and pain.