Diffusion, Osmosis, Active Transport And Cotransport, Including Plant Mass Transport

Question 1

How can substances move across membranes ?

Answer 1

. Simple diffusion
. Facilitated diffusion
. Active transport
. Co-transport

Question 2

Features of a phospholipid bilayer:

Answer 2

. Hydrophilic heads and outside of bilayer (form intermolecular forces with water)
. Hydrophobic fatty acid tails inside bilayer (form intermolecular forces with each other)
. Form a selectively permeable barrier- only small non-polar molecules can diffuse through fatty acid core
. Fluid mosaic model (phospholipids move)

Question 3

Features of a phospholipid bilayer:

Answer 3

. Hydrophilic heads and outside of bilayer (form intermolecular forces with water)
. Hydrophobic fatty acid tails inside bilayer (form intermolecular forces with each other)
. Form a selectively permeable barrier- only small non-polar molecules can diffuse through fatty acid core
. Fluid mosaic model (phospholipids move)

Question 4

What are Glycoproteins and what are their uses?

Answer 4

. They are proteins with a short carbohydrate chain
- used for cell recognition and signalling

Question 5

What are Glycolipids and what are their uses?

Answer 5

. They are phospholipids with a short carbohydrate chain
- used for cell recognition and attachment

Question 6

How does the addition of Cholesterol impact the phospholipid bilayer ?

Answer 6

. It reduces the membrane fluidity by restricting the movement of other molecules

Question 7

What is simple diffusion ?

Answer 7

. Passive movement from higher to lower concentration
. Across phospholipid bilayer
. (Non-polar molecules only )

Question 8

What is facilitated diffusion ?

Answer 8

. Passive movement from a higher to lower concentration
. Requires channel or carrier proteins (specific to substance)
. (Polar molecules and ions)

Question 9

What is osmosis ?

Answer 9

. The diffusion of water molecules from a higher to lower water potential (across a partially permeable membrane)
- limited across phospholipid bilayer (rapid movement requires channel proteins)

Question 10

Definition of water potential:

Answer 10

. The ability of water molecules to move freely (no intermolecular forces attracting to solute)

Question 11

Water potential of pure water:

Answer 11

. = 0kPa. All solutions have negative water potentials
- more solutes (more concentrated) = lower water potential

Question 12

In plants, water potential=…

Answer 12

Solute potential + hydrostatic pressure

Question 13

What is active transport ?

Answer 13

. Movement from lower concentration to higher concentration
. Requiring specific carrier proteins in the membrane
. Requiring the hydrolysis of ATP (phosphorylates carrier proteins causing a change of shape)

Question 14

What is co-transport ?

Answer 14

. It is the movement of two substances simultaneously through a carrier protein
- One substance moves against conc. gradient (active transport)
- One substance moves down conc. gradient (facilitated diffusion)
- conc. gradient above established by active transport