Membrane Transport

Question 1

What is membrane transport?

Answer 1

movements of solutes across the cell membrane
- either from ECF to ICF or ICF to ECF

Question 2

Why is membrane transport important?

Answer 2

maintaining homeostasis
ex: move glucose into cells which allows us to make ATP
ex: absorb nutrients across the wall of the gut

Question 3

What is in the phospholipid bilayer?

Answer 3

phospholipids, proteins, cholesterol, glycoproteins, glycolipids

Question 4

What is a carrier protein?

Answer 4

water soluble solutes bind to the transmembrane proteins which undergo a conformational change in order to deliver the solute to the opposite side of the membrane. This protein illustrate specificity.

Question 5

What is a receptor protein?

Answer 5

These integral proteins protrude toward the ECF, and ligands will bind to them

Question 6

What is an enzyme?

Answer 6

These integral proteins may be protrude to either the ECF or ICF side of the membrane. They aid in catalyzing reactions.

Question 7

What is a glycoprotein/glycolipid?

Answer 7

These integral membrane proteins serve as “identity markers”, allowing cells to recognize other cells. The sugar portion of these proteins is exposed to the ECF.

Question 8

What is a channel protein?

Answer 8

These transmembrane proteins allow water soluble solutes to pass thru, provided the solute is small enough, without needing to undergo a conformational change. These proteins illustrate specificity.

Question 9

What does the bumper cars analogy represent?

Answer 9

random thermal motion
- molecule move randomly and collide with each other –> transfer energy –> energize molecules to areas of lower energy (or fewer molecules) due to gradience

Question 10

What are the 3 driving forces?

Answer 10

chemical driving force, electrical driving force, and electrochemical

Question 11

What is the chemical driving force?

Answer 11

aka concentration, based on concentration of number of particles, move from higher concentration to lower concentration

Question 12

What is electrical driving force?

Answer 12

based on electrical charges
- move towards opposite charge and similar repel

Question 13

What is electrochemical?

Answer 13

combination of chemical and electrical

Question 14

How do you determine the strength of gradience?

Answer 14

its the difference between ICF and ECF

Question 15

In an excitable cell, what net charge is in the ICF? ECF?

Answer 15

ICF - negative
ECF - positive

Question 16

Which solutes can freely diffuse across the plasma membrane?

Answer 16

hydrophobic, lipophilic, nonpolar, and small polar (ie oxygen, CO2, fat soluble vitamins, fatty acid)

Question 17

Which solutes require a transmembrane protein to cross the plasma membrane?

Answer 17

hydrophilic, lipophobic, large polar (ie water, proteins, cations, H+, glucose, amino acids, anions)

Question 18

What are the types of passive transport?

Answer 18

simple diffusion, facilitated diffusion, osmosis

Question 19

What are the types of active transport?

Answer 19

primary, secondary

Question 20

What is simple diffusion?

Answer 20

high concentration to low concentration, with the gradient (down, or along the gradient)

Question 21

What is facilitated diffusion?

Answer 21

high concentration to low concentration, goes through transmembrane proteins

Question 22

What is osmosis?

Answer 22

diffusion of water, moves from high concentration of water (low concentration of solutes) to low concentration of water (high concentration of solutes), requires aquaporin

Question 23

What is tonicity?

Answer 23

describes the behavior of cells when placed in a solution , comparing 2 areas in terms of concentration of solute or number of particles

Question 24

What is a hypotonic solution?

Answer 24

low amount of solutes (high concentration of water), water will enter cell, cell grows and could burst

Question 25

What is hypertonic solution?

Answer 25

higher amount of solutes (lower concentration of water), water leaves cell, cell shrinks

Question 26

What is isotonic cell?

Answer 26

equal amounts of solutes

Question 27

What are the type of active transports?

Answer 27

Primary - inorganic ions (Na+, K+, Cl-), Secondary - organic molecules (glucose) and ions (Na+)

Question 28

What is primary active transport?

Answer 28

low concentration to high concentration, against gradient
requirements: carrier protein = ATPase = pump
only active transport that uses ATP

Question 29

What are examples of primary active transporter?

Answer 29

Na+-K+ pump, Ca2+ -ATPase, H+-ATPase (proton pump), H+-K+ ATPase

Question 30

What is the equation for the hydrolysis of ATP?

Answer 30

ATP–> ADP + P (release energy)
aka ATP + ATPase –> ADP + carrier protein +energy

Question 31

What is secondary active transport?

Answer 31

co-transport (symport) - both molecules are moving in same direction
counter-transport (antiport) - solutes moving in opposite direction (1 in, 1 out)

Question 32

What are leak channels?

Answer 32

protein channels that are always open

Question 33

What is exocytosis?

Answer 33

via a vesicle from golgi apparatus releasing contents into ECF

Question 34

What are the types of endocytosis?

Answer 34

-phagocytosis
- pinocytosis
- receptor - mediated

Question 35

What is phagocytosis?

Answer 35

movement of solid material into cell –> enters phagosome (phagocytic vesicle) –> fuses with lysosome (phagolysosome) –> releases enzymes –> digestion

Question 36

What is pinocytosis?

Answer 36

movement of liquid (ECF) into a cell –> forms endosome (vesicle)

Question 37

What is receptor-mediated endocytosis?

Answer 37

receptors bind to specific molecule in ECF –> creates a clathrin coated vesicle –> vesicle fuses with lysosome (endolysosome)
- When the pit pinches off, the resulting vesicle is a clathrin coated vesicle which directs the vesicle to a region of cell to tell what vesicle to do like an “address”

Question 38

What happens is epithelial transport is hindered?

Answer 38

disease can occur (ie example with normal solute and water transport in cystic fibrosis)