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cell transport > cell membrane transport methods > Flashcards

cell membrane transport methods Flashcards

1
Q

What are the two different types of transport method?

A

Passive and active

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2
Q

What are the three different types of passive transport methods?

A

lipid diffusion, facilitated diffusion and osmosis (water diffusion)

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3
Q

What are the two different types of active transport methods?

A

Active transport and bulk transport (endocytosis and exocytosis)

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4
Q

What is a passive transport method?

How do they take place?

A

A process that does not require any energy other the thermal energy of the surroundings
They take place as a result of concentration, pressure or electrochemical gradients

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5
Q

Why do substances move around within the cell?

A

They move around randomly due to thermal motion

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6
Q

What is regular diffusion?

A

A net movement of substances across a cell membrane down the concentration gradient (from an area of high concentration to low concentration)

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7
Q

Do substances diffuse in both directions across a membrane or in just one direction?

A

Both, but there is a net movement down the concentration gradient

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8
Q

What are the factors that affect the rate of diffusion and why do they affect it?
(4 things)

A
  1. The steepness of the concentration gradient - the greater the difference in concentration the faster the rate
  2. Temperature - molecules have more kinetic energy at high temperatures therefore diffuse faster
    3 The type of molecule or ion - large molecules diffuse more slowly than small ones. Non-polar molecules diffuse faster than polar molecules.
  3. Surface area - the greater the surface area, the more molecules or ions that can cross it
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9
Q

What is another name for lipid diffusion?

A

Simple diffusion

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10
Q

What is lipid diffusion?

A

When a substance can diffuse directly through the lipid bilayer part of the membrane

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11
Q

What substances can undergo lipid diffusion?

A

Hydrophobic (lipid-soluble) molecules such as steroids, and very small hydrophilic molecules such as water oxygen and carbon dioxide.

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12
Q

What is facilitated diffusion?

A

The diffusion of a substance across the membrane through a trans-membrane transport protein molecule
i.e. with the aid of transport proteins

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13
Q

Are transport proteins specific or non-specific?

A

Specific-this means that substances can only cross membranes that contains the appropriate protein

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14
Q

How do channel proteins help facilitated diffusion?

A

They form a water filled pore or channel in the membrane which allows charged substances to defuse across

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15
Q

Are the channels gated or not?

A

Gated -this means that they can be open or closed, allowing the cell to control the entry and exit ions

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16
Q

Can cells change their permeability to certain ions using channel proteins?

A

Yes - due to the gated channels they get along certain substances in but not others

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17
Q

What are some examples of ions that can defuse across the membrane through specific ion channels?

A

Na+, K+, Ca2+ and Cl-

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18
Q

How do the carrier proteins help facilitated diffusion?

A

They have binding site for a specific solutes and constantly flip between two states so the site is alternately open to opposite side of the membrane

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19
Q

Where will the substance bind?

A

On the side with the highest concentration

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20
Q

Where will the substance be released?

A

On the side with the lowest concentration

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21
Q

What type of solutes can diffuse across the membrane through specific carrier proteins?

A

Amino acids and glucose

22
Q

What is co-transport?

A

When a carrier proteins have two binding sites so can therefore carry two molecules at once

23
Q

What is an example of co- transport?

A

The sodium/glucose co-transport found in the small intestine

24
Q

What must be present for co-transport to take place?

A

Both the molecules

25
Q

What is osmosis?

A

The diffusion of water molecules from a more dilute solution to a more concentrated solution across a partially permeable membrane

26
Q

What two ways can water diffuse across the membrane?

A

Partly the phospholipids bilayer (which is an example of lipid diffusion) or partly through the protein channels called aquaporins (which is the example of facilitated diffusion)

27
Q

Why is the concentration of water in most cells very high but is not free to diffuse?

A

Because water is the solvent in all cells however most of the water is bound to solvent molecules as a hydration shell

28
Q

What is a hydration shell?

A

When the solvent is water, it is the number of solvent molecules surrounding each unit of solute

29
Q

What happens when the solution is concentrated?

A

The more concentrated the solution, the more solute molecules are in a given volume and more water molecules are bound in hydration shells so there are less free water molecules

30
Q

What happens when there is a concentration difference of solutes across the membrane?

A

There will also be a concentration difference of free water molecules across the membrane, so water will diffuse across.

31
Q

What will a dilute solution have?

3 things

A
  1. A low concentration of solute
  2. A high concentration of free water
  3. A high solute potential
32
Q

What will a concentrated solution have?

3 things

A
  1. A high concentration of solute
  2. A low concentration of free water
  3. A low solute potential
33
Q

What is an active transport method?

A

A process that needs energy to occur

34
Q

What is ATP?

A

adenosine triphosphate

35
Q

How is ATP broken down?

What is it used for?

A

ATP is broken down by removing a phosphate ion

All active processes use ATP is their immediate source of energy

36
Q

What is ATP synthesised from?

How is ATP synthesised?

A

ADP - adenosine diphosphate and phosphate (Pi)

Using hydrolosis and energy released from glucose in respiration in mitochondria

37
Q

What is hydrolysis?

A

The splitting of ATP back to ADP and the phosphate which will release energy which drives the processes.

38
Q

What is active transport?

A

The pumping of substances across a membrane by a trans membrane protein pump molecule using energy from ATP

39
Q

What protein molecule does active transport involve?

A

ATPase enzymes

40
Q

What do ATPase enzymes do?

A

They catalyse the hydrolysis of ATP to release energy

41
Q

What are ATPase enzymes?

A

Transport proteins that have an active site on their cytoplasm side

42
Q

How do ATPase enzymes aid active transport?

A

The protein binds a molecule of the substance to be transported on one side of the membrane,, changes the shape using energy from ATP spitting and releases the molecule on the other side.

43
Q

Are ATPase enzymes specific?

A

Yes - therefore there is a different protein pump for each molecule type to be transported.

44
Q

Does active transport always appear in same direction?

A

Yes

45
Q

Is active transport movement of substances down a concentration gradient or up the concentration gradient?

A

Up

46
Q

What is an example of an active transport pump?

A

the sodium/potassium ATPase (Na/K pump) which pumps sodium ions out of an animal cell and potassium ions in.

47
Q

What is the bulk transport?

A

The transport of a large macromolecules like proteins and polysaccharides using membrane vesicles.

48
Q

What is a membrane vesicle?

A

Small structures within the cell consisting of fluid enclosed by lipid bilayer

49
Q

What does the movement and fusion of vesicles require?

A

Metabolic energy in the form of ATP

50
Q

What is endocytosis?

A

Transport of substances into a cell.
Part of the membrane folds to form pockets that deepen and pinch shut to form a vesicle containing whatever material was captured outside the cell.

51
Q

What is exocytosis?

A

Transport of substances out of the cell

The part of the membrane that formed a pocket opens and releases the material that was inside the cell

cell transport (3 decks)

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