Case 1 - epithelial solute and water transport

Question 1

how much of our body weight does fluid account for

Answer 1

60%

Question 2

what makes up the extracellular fluid

Answer 2

the transcellular fluid, interstitial fluid, and the plasma

Question 3

what separates the extracellular fluid form the outside world

Answer 3

the epithelial cells

Question 4

what is considered outside of the body

Answer 4

anything on the apical side of the epithelium e.g GI tract, kidney tubules and salivary ducts

Question 5

diagram showing the organisation of the body compartments

Answer 5

Question 6

where does the apical membrane face

Answer 6

the outside

Question 7

where does the basolateral membrane face

Answer 7

the inside

Question 8

what do tight junctions do

Answer 8

separates the basolateral and apical membranes and also found between neighbouring cells

this allows for asymmetric expression of transport protiens

Question 9

what provide support in epithelia structure

Answer 9

desmosomes and adhering junctions provide structure

Question 10

what is tight junction permeability determined by

Answer 10

claudin family proteins

Question 11

what are phospholipid bilayers

Answer 11

have hydrophilic head groups facing aqueous environments and hydrophobic lipid tails in the lipid bilayer

Question 12

is the phospholipid bilayer permeable?

Answer 12

no, it is impermeable to ions and polar molecules

Question 13

what is permeability provided by instead

Answer 13

membrane proteins (transporters)

Question 14

what is sterol

Answer 14

provides structural integrity and provides precursors for fat soluble vitamins and steroid hormones

Question 15

what does the integral protein spanning proteins include

Answer 15

all of the cell surface receptors, G proteins, and our membrane transporters

Question 16

what are the three types of membrane transporters

Answer 16

ion pumps
ion channels
transporter

Question 17

what do ion pumps do

Answer 17

they move ions against their concentration gradients

Question 18

what do ion pumps use energy from

Answer 18

ATP hydrolysis

Question 19

do ion pumps use active transport

Answer 19

yes

Question 20

features of the sodium pump

Answer 20

2 K+ in, 3 Na+ out

Question 21

what do ion pumps do

Answer 21

creates and maintains electrochemical gradients

Question 22

what gradient generates the membrane potential and what is the membrane potential value

Answer 22

the K+ gradient and membrane potential is approx -60mV

Question 23

what gradient drives other passive transporters

Answer 23

Na+ gradient = secondary active transport

Question 24

what are ion channels

Answer 24

highly selective protein pores in the membrane (specifically dependent on protein structure)

Question 25

what is ion flow driven by in ion channels

Answer 25

driven by concentration gradient and membrane potential: electrochemical gradient - passive transport

Question 26

what may ion channels be gated by

Answer 26

intracellular or extracellular messengers, or by membrane potential changes

Question 27

what are transporter (carrier) proteins

Answer 27

highly selective carrier protein in the membrane

Question 28

is transport active or passive in carrier proteins

Answer 28

passive

Question 29

what is transporter (carrier proteins) driven by and what is another name for it

Answer 29

driven by concentration gradient alone facilitated diffusion!!!

Question 30

what is secondary active transport

Answer 30

cotransporters and exchangers

Question 31

what are the most common cotransporters

Answer 31

Na+, K+, Cl-

Question 32

what does inwards movements of Na+ drive

Answer 32

uptake of Cl- against its gradient

Question 33

what is the Na+/H+ exchanger

Answer 33

an anti porter inwards movement of Na+ drives extrusion of H+ against its gradient

Question 34

what is the composition values of intracellular fluid

Answer 34

low in Na+ and high in K+

Question 35

what is the composition values of extracellular fluid

Answer 35

high in Na+ and low in K+

Question 36

what is passive transport

Answer 36

simple or facilitated diffusion molecules move along the concentration gradient high to low concentration

Question 37

what is active transport

Answer 37

moves molecules against the concentration gradient hydrolysis of ATP - ion pumps secondary active transport

Question 38

what is different about secondary active transport

Answer 38

the gradient has usually been established by another ion

Question 39

what are aquaporins

Answer 39

pore is highly selective to water water flow is driven by osmosis

Question 40

what is osmosis

Answer 40

osmosis is the diffusion of water through a semi-permeable membrane from a region of lower total solute concentration to one of higher total solute concentration

Question 41

diagram showing transcellular transport

Answer 41

mostly glucose and Cl-

Question 42

what is the only thing to mediate active transport

Answer 42

pumps

Question 43

how may transport occur

Answer 43

via transcellular or paracellular pathways

Question 44

what are the main salivary glands

Answer 44

parotid - the largest submandibular sunlingual

Question 45

what are the cells found in the parotid gland

Answer 45

mainly serous acinar cells

Question 46

what are the cells found in the submandibular gland

Answer 46

serous and mucous acinar cells

Question 47

what are the cells found in the sublingual gland

Answer 47

mainly mucous acinar cells

Question 48

how much saliva do humans secrete in a day

Answer 48

1L

Question 49

what technically determines the pH value of saliva

Answer 49

the higher the incidence of bicarbonate

Question 50

secretion as a two stage process diagram

Answer 50

Question 50

secretion as a two stage process diagram

Answer 50

Question 51

features of the acinus part of secretion

Answer 51

secretion of Na, Cl, and HCO3 by active transport high water permeability isotonic, plasma like primary secretion

Question 52

features of the duct part of secretion

Answer 52

reabsorption of NaCl some secretions of K and HCO3 low water permeability hypotonic final saliva

Question 53

where does the saliva become hypotonic

Answer 53

the duct

Question 54

what is primary secretion performed by and what pump is responsible for setting the ion gradient

Answer 54

primary secretion by acinar cells and the sodium pump sets the ion gradient

Question 55

what happens when chlorine moves into the lumen (negatively charged ion)

Answer 55

leads to a small negative charge building up within the lumen and that then draws positive ions like Na+, paracellularly, passively down its electrochemical gradient

Question 56

what do acinar cells express in the apical and basolateral membranes and what does this do

Answer 56

express aquaporin 5 this lets water move via osmosis

Question 57

primary secretion by acinar cells diagram

Answer 57

Question 58

summary of the Na+, K+, ATPase pump

Answer 58

maintains concentration gradients for Na+ and K+ small direct contribution to membrane potential

Question 59

summary of the Na+, K+, 2CL cotransporter

Answer 59

electrically neutral uses inward gradient for Na+ to drive coupled uptake of Cl- secondary active transport

Question 60

what are examples of the Na+, K+, 2Cl- cotransporter

Answer 60

NKCC1, SLC12A2

Question 61

summary of K+ channels

Answer 61

recycles K+ and maintains membrane potential

Question 62

examples of K+ channels

Answer 62

BK ans IK1

Question 63

summary of Ca2+ activated Cl- channels

Answer 63

allows Cl- efflux down its electrochemical gradient

Question 64

example of Ca2+ activated Cl- channel

Answer 64

TMEM16A

Question 65

what drives Na+ secretion via the paracellular pathway

Answer 65

small negative potential in the lumen

Question 66

summary of the aquaporin 5 water channel

Answer 66

allows H20 efflux driven by a small osmotic gradient

Question 67

example of an aquaporin channel

Answer 67

AQP5

Question 68

modification of primary saliva by salivary duct cells diagram

Answer 68

Question 69

what is the difference between acinar and salivary duct cells

Answer 69

salivary duct cells are impermeable to water

Question 70

what is the final saliva

Answer 70

more hypotonic

Question 71

how does Na+ enter the salivary duct cell

Answer 71

passively via ENaC channels

Question 72

how does Na+ leave the salivary duct channels

Answer 72

cross the basolateral membrane via Na+,K+ ATPase

Question 73

what draws Cl- through the cell via Cl- channels

Answer 73

small positive potential on the blood sie

Question 74

what is Cl- also taken up from the saliva in exchange for

Answer 74

HCO3- via apical Cl-/HC03- exchangers

Question 75

what is intracellular HC03- generated from

Answer 75

from CO2 and water by an enzyme called carbonic anhydrase

Question 76

what extrudes H+

Answer 76

basolateral Na+/H+ exchangers

Question 77

what ensures little water reabsoprtion

Answer 77

low water permeability

Question 78

what raises the amount of saliva produced

Answer 78

stimulation of parasympathetic nervous system

Question 79

parasympathetic nervous system stimulation

Answer 79

acetylcholine raises intracellular Ca2+ acetylcholine will bind to M1 and M3 muscarinic G protein coupled receptors this activates a signalling cascade we get activation of phosphoplipase C leads to increase in inositol triphosphate the binding of this to calcium channels then leads to: triggers Ca2+ release from the endoplasmic reticulum calcium then acts as a signalling molecule to activate other ion channels

Question 80

parasympathetic nerve stimulation diagram

Answer 80

Question 81

what effect does the sympathetic nervous system have

Answer 81

noradrenaline raises intracellular cAMP

Question 82

diagram showing this effect

Answer 82

Question 83

what does raised intracellular cAMP lead to

Answer 83

protein secretion

Question 84

diagram summing up parasympathetic and sympathetic nerve activation

Answer 84