ions

Question 1

what is diffusion

Answer 1

the process where atoms or molecules intermingle because of their random thermal motion

Question 2

problems with diffusion in multicellular organisms

Answer 2

rapid of microscopic distances
slow over macroscopic
need circulatory systems to bring cells in diffusion range
cell membrane - barrier - allow concentration gradients

Question 3

what is osmosis

Answer 3

movement of water
across a PPM
from hypotonic soln to hypertonic soln

Question 4

tight junctions

Answer 4

stop paracellular transport
keep polarity of cell - otherwise membrane proteins would spread out
3D
tighter in stomach than in SI - SI allow water through

Question 5

what modulates transcellular transport

Answer 5

the membrane proteins

Question 6

paracellular transport

Answer 6

through TJ and lateral intercellular spaces

Question 7

transcellular transport

Answer 7

through the epithelial cells

conc grad different on either side of the cell - need different membrane proteins

Question 8

channel proteins

Answer 8

aqueous pores

allow specific solutes to pass through

Question 9

carrier proteins

Answer 9

bind to solute - conformational change of protein

transport across membrane

Question 10

do channel/carrier proteins allow faster transport

Answer 10

channel

just pass - no conformational change

Question 11

simple diffusion

Answer 11

through the membrane

no membrane proteins involved

Question 12

gating of ion channels

Answer 12

voltage
extracellular ligand
intracellular ligand
mechanically gated

Question 13

types of carrier mediated transport

Answer 13

uniport
symport
antiport- try to equilise charge, secondary AT

Question 14

Active transport

Answer 14

energy

enhances conc grad

Question 15

primary AT

Answer 15

linked directly to cellular metabolism - use ATP

Question 16

secondary AT

Answer 16

drives energy form conc grad of another substance that is actively transported

Question 17

Facilitated diffusion

Answer 17

enhances the rate a substance can flow down conc grad
equilibrate substance across membrane
passive

Question 18

primary active transporters

Answer 18

Na/K ATPase

H/K ATPase

Question 19

secondary active transporters

Answer 19

SGLT-1 co-transport
HCO3- /Cl- counter transport
Na/H+ counter transport

Question 20

facilitated diffusion transporters

Answer 20

GLUT-5
GLUT-2
these move monosaccharides across the enterocytes

Question 21

absorption of carbohydrate

Answer 21

glucose and galactose taken in by secondary active transport with na- can go uphill
this is done by SGLT-1 on apical membrane
fructose move in by facilitated diffusion via GLUT-5 - low intracellular concentration so can diffuse in
all leave by facilitated diffusion through GLUT-2, high capacity low affinity

Question 22

the need to absorb water

Answer 22

99% water that goes into GI tract is reabsorbed
powered by absorption of ions
greatest amount water absorbed in SI - jejunum
ions absorbed by passive diffusion
8L water absorbed SI, 1.4L - LI
water comes from secretions into gut

Question 23

mechanism that water is absorbed by

Answer 23

standing gradient osmosis
driven by Na
becomes more efficient as travel down intestine

Question 24

what process is iron essential for

Answer 24

ox transport - RBC
ox phhos
in excess is toxic - body cant actively excrete it
therefore need to absorb quickly but also limit absorption

Question 25

how is iron present in the diet and its absorption

Answer 25

inorganic iron - Fe2+ ferrous or Fe3+ ferric as part of haem group - Hb, myoglobin and cytochromes if eat meat can only absorb Fe2+ Fe3+ insoluble salts with hydroxide, phosphate, HCO3- vit c reduce Fe3+ to 2+ haem smaller part of diet but absorbed more readily

Question 26

Haem

Answer 26

dietry haem - bioavailable | absorbed into intect enterocyte

Question 27

what are vitamins

Answer 27

``` organic compounds cannot be manufactured by the body vital to metabolism fat soluble - A D E K - transported to brush border in micelles K taken up by AT ```

Question 28

Vitamin B12

Answer 28

liver contains large store impaired absorption = retarded maturation of RBC - pernicious anaemia most B12 is bound to proteins