Unit 1 Revisited Watch

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Revenged
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Ok... i want to get this sorted

Active transport occurs against the conc gradient

Through carrier proteins in the membrane... simple


Diffusion occurs down a conc gradient

If the molecule is lipid soulbe it can diffuse through the phospholipid bilayer

So if the thing is water soluble it cannot diffuse through the phospholipid bilayer therefore it diffuses through channel proteins through pores (which can be opened or closed to control movement)

I thought faciliated diffusion is a special type of diffusion that uses carrier proteins to move products down a concentration gradient very efficiently without using ATP energy

Does that sound right?
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non-centrally acting
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(Original post by Revenged)
Ok... i want to get this sorted

Active transport occurs against the conc gradient

Through carrier proteins in the membrane... simple


Diffusion occurs down a conc gradient

If the molecule is lipid soulbe it can diffuse through the phospholipid bilayer

So if the thing is water soluble it cannot diffuse through the phospholipid bilayer therefore it diffuses through channel proteins through pores (which can be opened or closed to control movement)

I thought faciliated diffusion is a special type of diffusion that uses carrier proteins to move products down a concentration gradient very efficiently without using ATP energy

Does that sound right?
u got the active transport rite
u lost me when ur talkin about diffusin through sommer soluble
but i know facilitated diffusion is down diffusion grad, needs no energy but requires channel protiens- not carrier protiens.
carier protiens are used 4 active transport
( i think so neway! )
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Revenged
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my revision guide says 'faciliated diffusion requires carrier molecules'

Channel proteins are used in normal diffusion

This is confusing me!
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non-centrally acting
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(Original post by Revenged)
my revision guide says 'faciliated diffusion requires carrier molecules'

Channel proteins are used in normal diffusion

This is confusing me!
normal diffusion doesnt require anything- molecules just pass through bilayer
but facilitated requires channel protiens. in sum books it may say carrier but i think its more important 2 remember channel. carrier wont be rong, cos some channels be closed and the require a hormone to open the channel.

active transport always requires carrier protiens
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Seth
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Diffusion takes place along a concentration gradient (i.e. diffusion gradient)- gases which diffuse across the plasma membrane do not require any channel or carrier proteins. However, charged particles, which cannot pass through becuase of their lipid insolubility require channel proteins. These are selective, gated channels which speed up the rate by which ions can enter cells. Remember a concentration gradient of that particular ion is still necessary for it to diffuse through.

Facilitated diffusion is like diffusion but now includes carrier proteins. These are used to transport polar molecules, such as amino acids or glucose, which cannot diffuse through the bilayer. Once again a concentration gradient is still required to transport the molecule.

Active transport, as the name may suggest, is an active process (i.e. requires energy), and uses the ATP produced in respiration. It utilises carrier proteins, much like in facilitated diffusion, except this time it's moving the molecules against a concentration gradient .

Hope thats helped you a bit
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Revenged
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Cheers, Seth!

I was thinking on the right lines after all
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oxymoron
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Facillitated diffusion also includes channel proteins. These are proteins that help (or facillitate!) molecules which would otherwise be unable to cross the bilayer, to diffuse across - usually by creating a hydrophillic path through the otherwise hydrophobic membrane.
It is only called simple diffusion if it diffuses straight across the bilayer (eg steroids, alcohol) ... anything requiring any sort of protein for transport across the membrane is known as facillitated diffusion or active transport.
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Revenged
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(Original post by oxymoron)
Facillitated diffusion also includes channel proteins. These are proteins that help (or facillitate!) molecules which would otherwise be unable to cross the bilayer, to diffuse across - usually by creating a hydrophillic path through the otherwise hydrophobic membrane.
It is only called simple diffusion if it diffuses straight across the bilayer (eg steroids, alcohol) ... anything requiring any sort of protein for transport across the membrane is known as facillitated diffusion or active transport.
OK...

So basically anything that is lipid-soluble, e.g. ethanol, undergoes diffusion because it can move throught the phospholipid bilayer

Anything polar or water soluble, e.g. amino acids and glucose, can't diffuse through the membrane so they travel through channel proteins or carrier proteins by facilitated diffusion

So, if this is true, can only polar and water soluble (e.g. glucose and amino acids) undergo active transport against the conc gradient? Since your saying that only these would travel through carrier proteins in the membrane.
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