transport Flashcards

1
Q

what is diffusion defined as?

A

the net movement of molecules (simple) or ions (facilitated) from a region where they are highly concentrated to one where their concentration is lower until evenly distributed

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2
Q

which molecules pass across the membrane via simple diffusion?

A

small, non-polar (lipid soluble) molecules such as oxygen and carbon dioxide

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3
Q

what does the ‘passive’ part mean in diffusion?

A

energy comes from the natural, inbuilt motion of particles, rather than an external source such as ATP.

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4
Q

what is simple diffusion?

A

the net movement of small, uncharged (non-polar) molecules from a region where they are highly concentrated to a region where their concentration is lower until they are evenly distributed

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5
Q

what is facilitated diffusion?

A

the net movement of larger, charged ions and polar molecules from a region where they are more highly concentrated to a region where their concentration is lower until they are evenly distributed, by using channel and carrier proteins that span the membrane.

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6
Q

how are simple and facilitated diffusion similar?

A

-both passive process so relies only on the inbuilt KE of the diffusing molecules (NO ATP)

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7
Q

describe what is meant by facilitated diffusion?

A

larger, polar molecules are transported along their conc gradient (from high to low) e.g. glucose, ions. It is a passive process that doesn’t require energy from ATP

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8
Q

what is required for facilitated diffusion ?

A

carriers or channels (intrinsic proteins) in the cell membrane
these allow molecules that are large and insoluble in lipids (polar) to be transported across membranes

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9
Q

what must a carrier/channel protein have?

A

a complementary shaped receptor site to the molecule

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10
Q

what happens when a molecule binds to a carrier protein?

A

it causes a shape change to the carrier that means that the molecule is transported across the membrane

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11
Q

what affects the rate of facilitated diffusion?

A

the number of complementary carriers/ channels; greater number of carriers means greater rate
also steepness of conc gradient, SA (greater capacity for carriers) and temperature

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12
Q

what is the rate of facilitated diffusion and active transport limited by?

A

the number of carriers- they reach a point of saturation (every carrier is occupied by a molecule)

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13
Q

describe what is meant by active transport?

A

molecules are transported against their concentration gradient (low to high) which requires energy (ATP) from respiration

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14
Q

how may cells carrying out high rates of active transport be adapted?

A

high number of mitochondria to provide the ATP
if resp is inhibited eg by cyanide, then active transport will cease

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15
Q

what is required for active transport?

A

carriers in the cell membrane
carriers must have a complementary shapes receptor site to the molecule being transported

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16
Q

what is the rate of active transport affected by?

A

number of complementary carriers and rate of respiration

17
Q

how is ATP used in active transport to transport molecules?

A

once a molecule binds to the receptor site of a carrier, the energy from ATP is used to change the shape of the carrier so that the molecule is moved across the membrane

18
Q

what is osmosis?

A

the net movement of water from an area of higher water potential (less negative) to an area of lower water potential (more negative) across a partially permeable membrane