Biological Membranes

Question 1

Describe the function of Glycoproteins

Answer 1

Cell adhesion
Cell Recognition
Cell Signalling
Receptors on hormones
Receptors on Transport Proteins
Cell Adhesion

Question 2

What is meant by cell signalling

Answer 2

Communication between cells
Cell Recognition

Question 3

How do Glycoproteins act as receptors

Answer 3

Shape of receptor specific and is complementary to shape of trigger and receptor binds onto trigger

Question 4

How thick is phospholipid bilayer

Answer 4

7-10nm thick

Question 5

What is the function of the Phospholipid Bilayer

Answer 5

Forms a barrier for dissolved substances

Question 6

What is a carrier protein

Answer 6

Transport protein found within bilayer which transports lagrer molecules polar or ions down conc. gradient
Protein changes shape after molecule attaches to protein and release molecule on opposite side of memb. Also can actively transport molecules

Question 7

What are channel proteins

Answer 7

Forms pores in the memb. for smaller ions/polar molecules to diffuse through down conc. gradient

Question 8

What is endocytosis

Answer 8

Cell surrounds substance with section of P.M and memb. pinches off to form vesicle inside cell containing indigested substance

Question 9

What is exocytosis

Answer 9

Vesicle containing substance pinches off from sacs of G.A and moves towards plasma memb.

Question 10

What are the 4 factors which affect rate of diffusion

Answer 10

Thickness of exchange surface
Temp.
SA
Steepness of Conc. Gradient

Question 11

What occurs in Hypotonic

Answer 11

Animal cell bursts
———————
Plant cell - Vacuole swells
Turgid
Content push against cell wall

Question 12

What occurs in Hypertonic

Answer 12

Higher water potential** inside cell**
Water moves outside of cell

Animal - Cell shrinks
CRENATION

Plant- Cell memb. pull away from cell wall
Flaccid (PLASMOLYSIS)

Question 13

What happens to the membrane at high temperatures

Answer 13

Bilayer Melts
memb disrupted / denatures –> increases permeability thus more pigment leaks out therefore abosrbtion increases

Question 14

What affect does solvents have on permeablity

Answer 14

Increase it as solvent dissolve lipids make memb. more permeable

Question 15

What may happen at low temp to permability

Answer 15

Low permability as Phospholipids have Low K.E and ice crystals may form which may pierce the membrane thus increasing permeability

Question 16

How is cholesterol included in the bilayer

Answer 16

Function : Regulates membrane permability
They fit between Phospholipids and at high temp. they bind to fatty acid tails causing them to pack closely together making memb. more rigid and decreasing permeablity

Question 17

How does cell surface memb. contribute to cell signalling

Answer 17

Relase of signal molecules **via Exocytosis **
Glycoproteins act as receptors
Signal molecules and glycoproteins are complementary
Arttachment of signal molecule causes change
Membrane allows ENTRY OF SOME SINGAL MOLECULES

Question 18

What is at the center of the bilayer

Answer 18

It is Hydrophobic thus preventing the entry of water-soluble/polar molecules

Question 19

State some roles for membranes inside cells

Answer 19

Forms organelles
Isolation of contents of organelle
Site for attachment of enzymes

Question 20

What are the roles of membranes within cells

Answer 20

Controsl what substances enters/leaves organelles

Seperates content of organelles from cytoplasm

Forms Vesicles

Question 21

How to calibrate colourimeter and why

Answer 21

Zero colourimeter using a blank
To reduce systematic error