Membranes and Transport

Question 1

What is the Role of Membranes?

Answer 1

Compartmentalisation (the formations of separate area), transport, cell to cell signaling, site of chemical reactions and environment

Question 2

Explain meaning of “Fluid mosaic” model

Answer 2

Fluid - Phospholipid create a viscous layer which is free to move

Mosaic - Proteins with varying size, shape and position were distributed throughout like tiles of a mosaic

Question 3

What are phospholipids mainly made of?

Answer 3

Hydrophilic head - phosphate group, phosphoester bond

Hydrophobic tail - glycerol, Ester bond, fatty acid tail

Question 4

What are some structural properties of the phospholipid bilayer?

Answer 4

• Allows membrane fluidity/flexibility
• fluidity allows for breaking/remaking of membrane (exocytosis/ endocytosis)
• Has hydrophobic/ hydrophilic layers that restrict entry and exit of substances

Question 5

How thick is a membrane on average?

Answer 5

7.5nm

Question 6

What is the role of Cholesterol in animal membranes?

Answer 6

Stability/ flexibility (Mechanical stability)

Question 7

What is active transport

Answer 7

Movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration. Also requires energy

Question 8

What is Osmosis

Answer 8

The diffusion of water across a partially permeable membrane

Question 9

What I’d Diffusion

Answer 9

It is the Net movement of particles from a region of higher concentration to a region of lower concentration. Also rellies on energy by particles

Question 10

What is Facilitated diffusion

Answer 10

Movement down a gradient across a membrane through protein channels

Question 11

What is bulk transport

Answer 11

(Endocytosis)
Active movement of large molecules
Also requires energy

Question 12

What is Ficks law?

Answer 12

Surface area x gradient
———————————
Membrane thickness

Question 13

What are the small hydrophobic molecules that can pass through the phospholipid bilayer freely?

Answer 13

O2, Co2, N2, Benzene

Question 14

What are the small uncharged polar molecules that can diffuse through the phospholipid bilayer?

Answer 14

H20, glycerol, ethanol

Question 15

What are the ions that cannot pass through the phospholipid bilayer easily?

Answer 15

H+, Na+, HCO3, K+, Ca2+

Question 16

What are the larger uncharged polar molecules that cannot pass through the phospholipid bilayer freely?

Answer 16

Amino acids, glucose, nucleotides

Question 17

What two types of proteins does facilitated diffusion use?

Answer 17

Channel proteins

Carrier proteins

Question 18

What’s the difference between integral proteins and peripheral proteins?

Answer 18

Integral - permanent

Peripheral - temporary

Question 19

What are some examples of integral proteins?

Answer 19

Channel and Carrier

Question 20

What is the structure of a channel protein?

Answer 20

• Hydrophobic R group - Non-polar amino acid outside of protein associate directly with the lipid bilayer
• Hydrophilic R groups - Polar amino acids are located internally and face aqueous solution

Question 21

What’s the roles of intrinsic carrier proteins?

Answer 21

• Passive and active transport

- Active transport often includes a change in shape

Question 22

What’s the roles of intrinsic channel proteins?

Answer 22

• hydrophilic channel

- passive movement (diffusion) of polar molecules and ions

Question 23

What’s the roles of intrinsic glycoproteins?

Answer 23

• Recognition site
• Chemical ell signalling ( e.g Neurotransmitters)
• Cell adhesion
• Embedded proteins with attached carbohydrate chains

Question 24

What’s the roles of extrinsic proteins?

Answer 24

• Hydrophilic groups on outer surfaces to interact with polar heads of phospholipids
• serve as receptors

Question 25

What is the role of Receptors?

Answer 25

• Used in Cell signalling
• Bind site for chemical signal
• E.g Hormone for transport protein

Question 26

How does Temperature affect diffusion?

Answer 26

Increases rate of diffusion when increased

Does this because increase of kinetic energy of particles

Question 27

How does Concentration gradient affect diffusion?

Answer 27

Increases rate of diffusion when increased

Does this because more substance particles to be moved from one place to the other

Question 28

How does Surface area affect diffusion?

Answer 28

Increases rate of diffusion when increased

Does this because the bigger the SA the more it can be accessed to diffuse more

Question 29

How does membrane thickness affect diffusion?

Answer 29

Decreases rate of diffusion as it increases

Does this because it’s a thicker membrane for it to cross so bigger diffusion distance

Question 30

How does water move in terms of water potential?

Answer 30

Water moves from high water potential (dilute solution) to a low water potential (concentrated solution)

Question 31

What is water potential and what is it measured in?

Answer 31

It is the pressure created by water molecules as they collide with a membrane or container
Measured in kPa or Kilo pascals

Question 32

When is water potential at its greatest? Yeah

Answer 32

Pure/distillers water (0kPa)

Question 33

How do you work our water potential in animal cells?

Answer 33

Water potential = solute potential (always be negative)

Question 34

How do u work our water potential in plant cells?

Answer 34

Water potential = solute potential (negative number) + pressure potential (positive number)

Question 35

What lowers the water potential?

Answer 35

Solute

Question 36

Solutions that have a high water potential are __________?

Answer 36

Hypotonic

Question 37

Solutions that have a low water potential are __________?

Answer 37

Hypertonic

Question 38

Solutions that have a identical water potential are __________?

Answer 38

Isotonic

Question 39

Water molecules have an uneven distribution of charge, what do we call this?

Answer 39

Polarity

Question 40

How do u work out the % change in mass?

Answer 40

Change in mass
———————— x 100
Original mass