biological kinetics/transport (midterm 1) - equations should be studied too

Question 1

what initiates signaling for ligand and receptor binding kinetics

Answer 1

ligand binding to a membrane bound receptor

Question 2

where is there an equilibrium between

Answer 2

free ligand, free receptor, and ligand-receptor complex

Question 3

what is the cell membrane

Answer 3

thin film of non-covalently bound lipids (bilayer) and proteins, allowing free movement of molecules

Question 4

what are lipids composed of that make them amphiphilic

Answer 4

hydrophilic head (water soluble) and hydrophobic tails (lipid soluble), which form the lipid bilayer together

Question 5

what molecules struggle to cross the lipid bilayer of the cell membrane

Answer 5

larger, hydrophilic molecules

Question 6

how can the struggling molecules pass through the membrane

Answer 6

using protein channels

Question 7

what molecules go down the concentration gradient by passive diffusion

Answer 7

hydrophobic molecules (small) - oxygen, CO2, nitrogen

Question 8

what cannot transit across the lipid bilayer

Answer 8

large, neutral, polar molecules (like glucose) and charged molecules (ion - Na+, K+, Ca++)

Question 9

what does the cell membrane do for the extracellular environment

Answer 9

maintains ionic and chemical differences between the extracellular environment and the cell’s cytosol

Question 10

what are lipids composed of

Answer 10

choline, phosphate, glycerol (head), fatty acid tails

Question 11

how can transport be accomplished

Answer 11

diffusion (simple or facilitated) or active transport (requires energy)

Question 12

what does diffusion speed depend on

Answer 12

molecular/pore diameter

Question 13

what is the charge of sodium channels

Answer 13

strongly negatively charged, allowing dehydrated sodium ions to pass through the membrane

Question 14

what is the charge of potassium channels

Answer 14

uncharged, allowing hydrated potassium to pass, but preventing larger hydrated sodium to pass through

Question 15

what is bulk flow

Answer 15

solute diffusion

Question 16

when does diffusion dominate

Answer 16

when the Peclet number is less than 1

Question 17

when does bulk flow dominate

Answer 17

when the Peclet number is greater than 1

Question 18

what are voltage gated channels

Answer 18

the molecular conformation of the protein channel changes in response to the electrical potential across the cell membrane

Question 19

what causes a voltage gated channel to open/close

Answer 19

a strong negative, intracellular charge = closed
loss of this charge = open
“all or none” response

Question 20

what are chemical gated channels

Answer 20

the molecular conformation of the protein channel changes in response to ligand binding

Question 21

what is a patch-clamp technique

Answer 21

ion current flow through protein channels where a micropipette is brought into contact with a single cell, then small suction force is applied to the other end of the micropipette, sealing the cell membrane to the tip

Question 22

what is facilitated diffusion

Answer 22

diffusion of solute through a gate which opens/closes randomly due to thermal energy (Brownian motion)

Question 23

what type of diffusion does glucose and amino acids use

Answer 23

facilitated diffusion because glucose has to enter the cytoplasm for metabolism, but can’t diffuse on its own

Question 24

what is the concentration of water in cells controlled by

Answer 24

the relative amount of molecules on either side of the selectively permeable cell membrane

Question 25

if the molecular content is too high within the cell, what happens

Answer 25

water will move into the cell to reduce overall molecular concentration

Question 26

if the molecular content is too low within the cell, what happens

Answer 26

water will move out of the cell to increase overall molecular concentration

Question 27

what are the types of active transport

Answer 27

primary and secondary

Question 28

what is primary active transport

Answer 28

energy is used directly, as in the consumption of ATP->ADP

Question 29

what is secondary active transport

Answer 29

energy is derived from another source, such as a concentration gradient established by primary active transport

Question 30

how are ions moved across the plasma membrane

Answer 30

by ion channels and active transport proteins

Question 31

what occurs in a Na+-K+ pump (in all eukaryotic cells - primary active transport)

Answer 31

3 Na+ are pumped out of the cell and 2 K+ are pumped into the cell, with both transports occurring against the established concentration gradient

Question 32

what occurs in a calcium pump (primary active transport)

Answer 32

pushes Ca++ either out of the cell or into organelles

Question 33

what occurs in a hydrogen pump (primary active transport)

Answer 33

gastric glands release H+ as HCl; kidney renal tubules release H+ into the urine to control overall body hydrogen ion concentration

Question 34

what are the two forms of secondary active transport

Answer 34

cotransport and countertransport

Question 35

what is cotransport

Answer 35

established concentration gradient of substance X also carries substance Y in the same direction (down X’s gradient)

Question 36

what is countertransport

Answer 36

established concentration gradient of substance X carries substance Y in the opposite direction (up X’s gradient)