Lecture 7 - Membrane Transport

Question 1

what is the difference between simple diffusion and facilitated diffusion?

Answer 1

• simple diffusion: requires membrane permeability and favourable gradient conditions
• facilitated diffusion: requires a protein to help get the molecule across the membrane

Question 2

what is the difference between passive transport and active transport?

Answer 2

• passive transport: down a concentration gradient, no energy needed, transport proteins may or may not be needed
• active transport: against a concentrations gradient, requires energy input, transport protein “pumps” are required

Question 3

what is a uniporter?

Answer 3

carrier that transports a single solute

Question 4

what is an antiporter?

Answer 4

carrier that transports two solutes in the opposite direction across the membrane

Question 5

what is a symporter?

Answer 5

carrier that transports two solutes in the same direction across the membrane

Question 6

def: transporter that alternates between two conformations, bind one or more solute molecules, undergoes a conformational change that transfers the solutes to the other side

Answer 6

carrier protein

Question 7

def: water filled pore thorough which specific ions or small molecules can diffuse, form hydrophilic channels through

Answer 7

transmembrane channel

Question 8

def: highly specific channel that can conduct almost a million ions per second, bidirectional, flow determined by electrochemical gradient

Answer 8

ion channel

Question 9

def: passage of a variety of hydrophilic solutes, determined by pore size; some antibiotic resistance has been linked to mutations in certain bacterial porins

Answer 9

porin

Question 10

def: water flows through this channel at a rate of several billion per second, amino acid residues discriminate against other ions of similar size

Answer 10

aquaporin

Question 11

what ions are ion channels normally selective for?

Answer 11

Na+, K+, Ca2+, Cl-

Question 12

def: open and close in response to changes in membrane potential

Answer 12

voltage-gated

Question 13

def: triggered by the binding of specific substances to the channel protein

Answer 13

ligand-gated

Question 14

def: respond to mechanical forces that act on the membrane

Answer 14

mechanosensitive-gated

Question 15

what structural features make a channel a specific to a particular ion?

Answer 15

1. ion specific associations (amino acid side chains and the polar backbone)
2. constriction in the centre to serve as a size filter

Question 16

which kind of body cells have aquaporins?

Answer 16

specialized cells in the kidney

Question 17

what does the Glucose transporter GLUT1 do?

Answer 17

facilitated diffusion of glucose by a uniport carrier protein

Question 18

where is GLUT1 found?

Answer 18

on all mammalian plasma membranes

Question 19

GLUT1 process is __________ - can function in either direction depending on the ____________ ________

Answer 19

reversible, concentration gradient

Question 20

T or F: Glucose is rapidly phosphorylated inside the cell which keeps the intracellular concentration of glucose low and this maintains a concentration gradient

Answer 20

True

Question 21

intracellular or extracellular = higher potassium concentration

Answer 21

intracellular

Question 22

where is the highest concentration of Ca2+?

Answer 22

extracellular

Question 23

where is the highest concentration of Na+?

Answer 23

extracellular

Question 24

where is the highest concentration of Cl-?

Answer 24

extracellular

Question 25

def: solute accumulation is coupled directly to an exergonic chemical reaction (such as ATP hydrolysis)

Answer 25

direct (primary) active transport like ATPases or ATPase pumps

Question 26

what do ATPases do?

Answer 26

- harness the energy of ATP hydrolysis to move ions or small molecules against a concentration gradient/electrical potential - active transport

Question 27

where are P type ATPases mostly found?

Answer 27

on the plasma membrane

Question 28

which class of P type ATPases are found in all organisms?

Answer 28

P1

Question 29

Which classes of P type ATPases are found only in eukaryotes?

Answer 29

P2-P5

Question 30

what do P1, P2, P3, P5 transport?

Answer 30

cations or heavy metals

Question 31

what does P4 transport?

Answer 31

- lipids - acts as a flippase to help maintain membrane asymmetry

Question 32

what do all types of ATPase pumps have in common?

Answer 32

they all have one or more ATP binding sites on the cytosolic membrane leaflet

Question 33

P-Type ATPases are members of a large family and are ____________ Phosphorylated by ATP on a specific ____________ acid residue

Answer 33

reversibly, aspartic

Question 34

what is most energy consumed by the brain (2/3) used to do?

Answer 34

maintain Na+/K+ that maintains the membrane potential required for the transmission of nerve impulses

Question 35

what do V-type ATPase pumps do?

Answer 35

pump protons(H+) into organelles

Question 36

what's an example of a V-type ATPases?

Answer 36

- vacuoles - vesicles - lysosomes - endosomes - Golgi complex

Question 37

what are V-type ATPases like structurally?

Answer 37

- 2 multi-subunit components - integral component embedded in the membrane - peripheral component that juts out from the membrane surface

Question 38

where are v-class proton pumps in animal cells?

Answer 38

endosomal and lysosomal membranes

Question 39

what do F-type ATPases do?

Answer 39

transport protons in bacteria, mitochondria, and chloroplasts

Question 40

F-type ATPases: __________ flow of H+ up their concentration gradient _______ ATP

Answer 40

endergonic, hydrolysis

Question 41

F-type ATPases: _________ flow of H+ down their concentration gradient is used to _________ ATP

Answer 41

exergonic, synthesize

Question 42

T or F: can F-type ATPases act in the reverse direction

Answer 42

true

Question 43

where are F-type proton pumps found in eukaryotes?

Answer 43

inner mitochondrial membrane

Question 44

what does the ABC in ABC type ATPases stand for?

Answer 44

ATP binding cassette transporters

Question 45

what were the first kind of ABC type ATPases discovered?

Answer 45

importers, involved in the uptake of nutrients

Question 46

what do all ABC type ATPases have?

Answer 46

- 2 nucleotide (ATP) binding domains - 2 transmembrane domains

Question 47

why are ABC transporters medically important?

Answer 47

some of them pump antibiotics or drugs out of cells and render the cell resistant to the drug

Question 48

tumours that are resistant to growth inhibiting drugs have a high concentrations of what kind of transporter?

Answer 48

ABC transporter: MDR transport protein

Question 49

unlike most ABC transporters, MDR protein transports a _______ ______ of ________ ________ drugs

Answer 49

wide range of chemically dissimilar drugs

Question 50

T or F: Does indirect active transport rely on ATP ?

Answer 50

Yes, because the Na+ or H+ concentration gradient necessary for this process is generated by ATPase pump

Question 51

in co transport, can a molecule move on its own?

Answer 51

no, the favoured reaction is coupled with the unfavourable reaction in order to drive the unfavourable reaction against a concentration gradient