ions Flashcards

1
Q

what is diffusion

A

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

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2
Q

problems with diffusion in multicellular organisms

A

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

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3
Q

what is osmosis

A

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

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4
Q

tight junctions

A

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

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5
Q

what modulates transcellular transport

A

the membrane proteins

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6
Q

paracellular transport

A

through TJ and lateral intercellular spaces

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7
Q

transcellular transport

A

through the epithelial cells

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

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8
Q

channel proteins

A

aqueous pores

allow specific solutes to pass through

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9
Q

carrier proteins

A

bind to solute - conformational change of protein

transport across membrane

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10
Q

do channel/carrier proteins allow faster transport

A

channel

just pass - no conformational change

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11
Q

simple diffusion

A

through the membrane

no membrane proteins involved

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12
Q

gating of ion channels

A

voltage
extracellular ligand
intracellular ligand
mechanically gated

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13
Q

types of carrier mediated transport

A

uniport
symport
antiport- try to equilise charge, secondary AT

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14
Q

Active transport

A

energy

enhances conc grad

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15
Q

primary AT

A

linked directly to cellular metabolism - use ATP

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16
Q

secondary AT

A

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

17
Q

Facilitated diffusion

A

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

18
Q

primary active transporters

A

Na/K ATPase

H/K ATPase

19
Q

secondary active transporters

A

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

20
Q

facilitated diffusion transporters

A

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

21
Q

absorption of carbohydrate

A

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

22
Q

the need to absorb water

A

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

23
Q

mechanism that water is absorbed by

A

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

24
Q

what process is iron essential for

A

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

25
Q

how is iron present in the diet and its absorption

A

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

26
Q

Haem

A

dietry haem - bioavailable

absorbed into intect enterocyte

27
Q

what are vitamins

A
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
28
Q

Vitamin B12

A

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