TRANSPORT ACROSS MEMBRANES Flashcards

1
Q

When is there a high water potential?

A

When the solution has a high water concentration (not much solute dissolved into it)

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2
Q

When is there a low water potential?

A

The solution has a low water concentration (lots of solute dissolved in it)

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3
Q

What does pure water have a water potential of?

A

0 kPa, the value decreases as more solute is added

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4
Q

What is osmosis?

A

The movement of water molecules from an area of high water water potential to an area of low water potential across a semi-permeable membrane, down a water potential gradient

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5
Q

State of an animal cell when there is a high water potential (hypotonic):

A

Lysis: Swells and bursts in a hypertonic solution because water enters the cell

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6
Q

State of an animal cell when in an isotonic solution:

A

No change

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7
Q

State of an animal cell in a solution with low water potential (hypertonic):

A

Cell shrinks and shrivels as water moves out

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8
Q

State of a plant cells when in a hypotonic solution (higher water potential):

A

Water enters cell, protoplast swells and cell becomes turgid

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9
Q

State of plant cells when in an isotonic solution (same water potential in and outside of the cell):

A

No water enters or exits the cell, no change in the protoplast, cell is in incipient plasmolysis

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10
Q

State of plant cells when in an hypertonic solution (lower water potential):

A

Water leaves cell, protoplast shrinks and cell becomes plasmolyed

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11
Q

What is diffusion?

A

The net movement of particles from an area of high concentration to an area of low concentration, down a concentration gradient, across a semi-permeable membrane

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12
Q

What is facilitated diffusion:

A

Net movement of particles from an area of high concentration to a low concentration, down a concentration gradient, across a semi-permeable membrane, uses the assistance of carrier proteins and channel proteins- glucose moves by this

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13
Q

What are channel proteins?

A

Transmembrane proteins that facilitate the movement of substances across a cell membrane, they form a hydrophilic pathway through which specific molecules, typically ions or polar molecules, can pass

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14
Q

What are carrier proteins?

A

Transmembrane proteins that facilitate the transport of specific substances across a cell membrane. Unlike channel proteins, that provide a continuous pathway, carrier proteins bind to the substance on one side of the membrane, they undergo a conformational change and release the substance on the other side- cam occur through facilitated diffusion

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15
Q

Why is the fluid mosaic model fluid?

A

Fluid- because the phospholipid molecules in the bilayer are constantly moving

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16
Q

Why is the fluid mosaic model mosaic?

A

The proteins are all different shapes and sizes

17
Q

Key components of the fluid mosaic model:

A
  • phospholipid bilayer
  • cholesterol- adds stability
  • proteins- may be intrinsic and extrinsic
  • glycoproteins
  • glycolipids
18
Q

Role of phospholipid bilayer in the fluid mosaic model:

A

Hydrophilic heads face outwards (towards water) and hydrophobic tails face inwards (away from water
This arrangement creates a hydrophobic centre in the bi-layer so that water soluble substances cannot pass through
However, lipid-soluble substances can dissolve in the bilayer and pass directly through the cell membrane

19
Q

Role of cholesterol in the fluid mosaic model:

A
  • provide stability to cell membranes
  • consist of a hydrophilic and hydrophobic region, the hydrophobic regions bind to phospholipid fatty acid tails, causing them to pack more closely together
  • reduces fluidity of the cell membranes
20
Q

Role of intrinsic proteins in the fluid mosaic model:

A
  • embedded through both sides of the phospholipid bilayer
  • these proteins include channel and carrier proteins which transport large molecules and ions across the membrane
21
Q

Role of extrinsic proteins in the fluid mosaic model:

A

Only present on one side of the phospholipid bilayer, provide support to the membrane or may be involved in cell signalling

22
Q

Role of glycoproteins and glycolipids:

A
  1. Cell adhesion- attachment of cells to one another
  2. Cell recognition- allows cells to recognise one another
  3. Cell signalling- allows communication between cells