Lesson 7: Membranes

Question 1

What is the permeability of a membrane dependent on?

Answer 1

size of molecules, hydrophobic nature

Question 2

what is the function of a contractile vacuole?

Answer 2

Removes excess water to maintain a constant osmotic pressure in unicellular organisms.

Question 3

which organisms have a contractile vacuole?

Answer 3

freshwater organisms - the freshwater is hypotonic compared to them.

Question 4

What happens when a molecule is more hydrophobic when crossing the membrane layer?

Answer 4

Passes through more easily than hydrophilic molecules.

Question 5

What is the structure of integral proteins

Answer 5

transmembrane, amphipathic

Question 6

What are the two types of integral proteins?

Answer 6

channel and carrier proteins

Question 7

What is the structure of a phospholipids?

Answer 7

glycerol + 2 fatty acids + phosphate group

Question 8

What property does the phospholipid head have?

Answer 8

hydrophilic

Question 9

What property do the phospholipid tails have?

Answer 9

hydrophobic

Question 10

What does amphipathic mean?

Answer 10

having both hydrophilic and hydrophobic regions

Question 11

what is the function of channel proteins?

Answer 11

facilitated diffusion - large + polar molecules

Question 12

What is the function of carrier proteins

Answer 12

Active + passive transport: changes shape and binds to specific molecules to transfer them across the membrane

Question 13

What is active transport?

Answer 13

transport that uses energy to move molecules against the concentration gradient.

Question 14

What is passive transport?

Answer 14

transport that does not require energy.

Question 15

What is facilitated diffusion?

Answer 15

a form of passive transport that involves integral proteins.

Question 16

Where are peripheral proteins located?

Answer 16

bound to the surface of the membrane

Question 17

What is one property of peripheral proteins?

Answer 17

hydrophilic

Question 18

What is the role of aquaporins?

Answer 18

transport of water across cell membranes

Question 19

What can impact the number of auqaporins in the membrane?

Answer 19

Anti-diuretic hormone

Question 20

What cells do aquaporins act on?

Answer 20

kidney
red blood
lung

Question 21

What does membrane fluidity depend on?

Answer 21

fatty acid composition
Abundance of cholesterol

Question 22

What happens to the membrane fluidity when the fatty acid is unsaturated ?

Answer 22

increases membrane fluidity as it has kinks that prevent the fatty acids from packing too closely together.

Question 23

Why do cold blooded animals have unsaturated fatty acids?

Answer 23

To prevent fatty acids to pack too closely together in low temperatures.

Question 24

Why is membrane fluidity important?

Answer 24

carry out processes such as endocytosis and exocytosis.

Question 25

What is the function of cholesterol in low temperatures and how?

Answer 25

Increases membrane fluidity by preventing fatty acids from fitting too closely together.

Question 26

What is the function of cholesterol in high temperatures?

Answer 26

reduces fluidity

Question 27

What are aquaporins?

Answer 27

water channels

Question 28

What is the structure of aquaporins

Answer 28

four monomeric subunits, transmembrane

Question 29

what proteins does facilitated diffusion involve?

Answer 29

integral proteins - both carrier and channel

Question 30

Which protein does active transport involve?

Answer 30

carrier proteins

Question 31

What is the role of glycolipids and glycoproteins in cell recognition?

Answer 31

act as "markers" on the cell surface so cells can recognise each other.

Question 32

What is the role of glycolipids and glycoproteins in cell adhesion?

Answer 32

helps cells to stick to other cells.

Question 33

What is the role of glycolipids and glycoproteins in cell signalling?

Answer 33

function as receptors on the cell surface, binding to hormones or other signaling molecules so they can respond to environment.