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BIOC2600 > 16 Membrane transport > Flashcards

16 Membrane transport Flashcards

1
Q

How are the 2 aqueous phases inside and outside the cell divided?

A

by membrane, phospholipid bilayer

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2
Q

What 3 parts make up the phospholipid bilayer?

A
  • glycerol
  • phosphate group
  • 2 fatty acid chain (one saturated, one unsaturated)
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3
Q

How do diff parts of the phospholipid react to water?

A

Hydrophilic head (glycerol is an alcohol), and hydrophobic tail (FA)

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4
Q

What are the 3 types of membrane proteins?

A
  • intrinsic/integral proteins
  • extrinsic/peripheral proteins
  • transmembrane proteins
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5
Q

What is the diff between instrinsic/integral and extrinsic/peripheral proteins?

A
  • instrinsic/integral: embedded within the phospholipid bilayer
  • e.g. transport protein (ion channel, protein carrier), enzymes (usually near to the cytoplasmic domain)
  • extrinsic/peripheral proteins
  • mainly located on surface of phospholipid layers, could be extracellular or intracellular
  • e.g. antigens
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6
Q

what is an example of transmembrane proteins?

A

receptors

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7
Q

what are 2 other components found in the membrane other than membrane proteins?

A

glycolipid
* cell-cell recognition

cholesterol
* prevents the aggregation of phospholipid, increase fluidity of phospholipid bilayers (fluid-mosaic model)

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8
Q

What are 2 features of cell membrane?

A
  • asymmetry: due to glycoprotein and glycolipids (more common in extracellular region)
  • selectively permeable: only allow certain types of molecules to directly pass through
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9
Q

what is the criteria to pass through selectively permeable membranes?

A

small and non-polar
or
lipid-soluble

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10
Q

what are the 2 passive and 2 active modes of membrane transport?

A

Passive (no energy required, high to low conc)
* diffusion
* osmosis

active (atp required, against conc gradient)
* active transport
* vesicular transport

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11
Q

What are the 2 types of diffusion?

A

simple and facilitated

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12
Q

what are the 2 types of active transport?

A

primary and secondary active transport

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13
Q

what are the 2 types of vesicular transport?

A

endocytosis and exocytosis

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14
Q

What is simple diffusion?

A

directly through plasma membrane
* small and nonpolar
* or lipid-soluble molecules
* e.g. gases (O2 and CO2), fat soluble vitamins

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15
Q

can water travel through the membrane directly?

A

yes but is hard and slow with simple diffusion
facilitated diffusion is better

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16
Q

What is facilitated diffusion?

A
  • travel across membrane via specific protein channels or carriers
  • lipid-insoluble substances
  • e.g. glucose, AA, ions, and water molecules
17
Q

What is osmosis?

A
  • for water molecules
  • from high to low water potential (water molecule conc)
  • or low to high osmolarity (total conc of solutes) = osmotic pressure
  • much faster through aquaporin (also a protein channel)
  • simple diffusion of water is very slow through the lipid bilayer
18
Q

Why cant solutes (e.g. ions or glucose) diffuse across the membrane directly?

A

because they are valuable
need them, dont want to lose them, instead change the water for osmosis

19
Q

What is the relationship between water potential and osmolarity?

A

higher water potential = lower osmolarity

lower water potential = higher osmolarity

20
Q

which side has higher osmotic pressure?

A

bottom
higher osmolarity = higher osmotic pressure

21
Q

What are the 3 different tonicity of solution?

A
  • isotonic - solution conc is same as the cell
  • hypertonic - if solution conc is higher than the cell (higher osmolarity)
  • hypotonic - if solution conc is lower than the cell (lower osmolarity)
22
Q

What is ECF and ICF?

A

extracellular and intracellular fluid

23
Q

What is the osmolarity of ECF and ICF?

A

usually have the same osmolarity

24
Q

what if the following solutions are individually infused into the ECF, what is the outcome: isotonic, hypertonic, hypotonic

A
  • isotonic solution - nothing happens
  • hypertonic - water goes from inside to outside
  • hypotonic - water goes from outside to inside
25
Q

What is primary active transport? what are the 3 different types?

A
  • ion pumps using ATP = ATPase
  • P, V, F, type
26
Q

What is ABC transporter

A

ABC transporter (ATP binding cassette), e.g. P-glycoprotein & CFTR
* under primary active transport

27
Q

What is the relative conc of Na+ and K+ in ECF and ICF?

A

more Na+ in ECF than ICF
more K+ in ICF than ECF

28
Q

What is the P type ATPase

A

P type - activated by phosphorylation, e.g. Na+/K+ ATPase

29
Q

What is the mechanism of Na-K ATPase?

A

K+ out Na+ in
to build up electrochemical gradient

phosphorylation of ATP-> ADP expels Na+ to outside, then K+ binding triggers release of the phosphate group and goes back to original conformation, Na+ binds, cycle repeats

30
Q

What is the V-type ATPase?

A

V type - H+ ATPase in vesicles/vacuoles, e.g. lysosome
* once activated by ATP, moves H+ into lysosome to acidify and activates hydrolytic enzymes

31
Q

What is F type ATPase?

A

F type - H+ ATPase in mitochondrial inner membrane
* moves H+ ions into mitochondrial matrix to produce ATP
* also ATP synthase

32
Q

What are examples of ABC transporters?

A

ABC (ATP binding cassette) transporter

P-glycoprotein & CFTR
* both have similar mechanisms
* once activated by ATP
* P-glycoprotein removes lipid-soluble drugs out of the cell
* CFTR removes Cl- out of the cell

CFTR - cystic fibrosis transmembrane conductance regulator

33
Q

What is secondary active transport?

A

movement of one substance driven by the electrochemical gradient of anothre substance (often Na+ ions)

34
Q

What are the 2 types of secondary active transport?

A
  • symport (or cotransport) system = 2 substances move across the membrane in the same direction
  • antiport (or countertransport) system = 2 substances move across the membrane in opposite directions
35
Q

What is endocytosis?

A

uptake of large particles using vesicles

36
Q

What are the 3 types of endocytosis?

A
  • phagocytosis - (cell eating) uptake of solid molecules, e.g. bacteria
  • pinocytosis - (cell drinking) uptake of dissolvable molecules, e.g. DNA, protein
  • receptor-mediated endocytosis - uptake of specific molecules when recognized by specific receptors, e.g. cholesterol
37
Q

What is exocytosis?

A

secretion of large molecules using vesicles
* like endocytosis, exocytosis requires energy
* e.g. release of hormone or neurotransmitter

38
Q

Compare primary and secondary active transport

A

BIOC2600 (26 decks)

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