Cell Membranes

Question 1

What is the role of the plasma membrane?

Answer 1

Partially permeable membrane between:
the cell and its environment
Organelles and the cytoplasm

. Site of chemical reactions
. site of cell signalling

Question 2

Describe what the fluid mosaic model consists of

Answer 2

Its made up of a:

.Phospholipid bilayer
. Cholesterol
.Glycolipids and glycoproteins
.Proteins

Question 3

Whats the difference between extrinsic and intrinsic proteins?

Answer 3

Extrinsic- Partially Held on the surface of the membrane

Intrinsic - embedded embedded in the membrane

Question 4

What is the job of the phospholipid bilayer

Answer 4

It forms a barrier that limits movement of some substances in and out of the organelles so its partially permeable

, Small, fat soluble substances dissolve in the bilayer and diffuse across.

Water - soluble molecules and ions cannot easily cross over.

Question 5

What does Cholesterol do In the fluid mosaic model.

Answer 5

It fits between the tails of the phospholipid molecules. It inhibits the movement of phospholipids, Reducing fluidity of membrane, it makes it less permeable to water and ions.

increases the mechanical strength and stability of membranes

Question 6

What does the fluid mosaic model help explain?

Question 7

What does the fluid mosaic model help explain?

Answer 7

Passive and active movement between cells and their surroundings

Cell-to-cell interactions

Cell signalling

Question 8

Why is it described as mosaic?

Answer 8

The scattered pattern produced by the proteins within the phospholipid bilayer looks somewhat like a mosaic when viewed from above

Question 9

What is the function of glycolipids and glycoproteins ?

Answer 9

contain carbohydrate chains that exist on the surface (, which enables them to act as receptor molecules

bind with certain substances at the cell’s surface

Question 10

What are the three type of receptors?

Answer 10

Signalling receptors for hormones and neurotransmitters

Receptors involved in endocytosis

Receptors involved in cell adhesion and stabilisation. ( as the carbohydrate part can form hydrogen bonds with water molecules surrounding the cell

Question 11

What do Transport proteins in membranes do?

Answer 11

ransport proteins create hydrophilic channels to allow ions and polar molecules to travel through the membrane.

Question 12

What two types of transport proteins?

Answer 12

1. Channel protein
2. Carrier proteins (Carrier proteins change shape to transport a substance across the membrane)

Question 13

Whats special about transport proteins?

Answer 13

Specific to a particular ion / molecule.

Question 14

What affect does temperature have on membrane permeability?

Answer 14

As temp increases the fluidity of lipids in the membrane, this makes the cell membrane less effective to stopping polar molecules.

At too high temperatures the proteins in the membrane also denature, this disrupts the membrane structure so it no longer forms and effective barrier.

Question 15

What affect does organic solvents have on membrane permeability?

Answer 15

They dissolve the the lipids in the membrane causing it to loose its structure.

Question 16

Define diffusion.

Answer 16

The net movement, as a result of the random motion of its molecules or ions, of a substance from a region of its higher concentration to a region of its lower concentration.

Question 17

How does steeper concentration gradient affect diffusion?

Answer 17

A greater difference in concentration means that more molecules will pass over so a greater rate of diffusion

Question 18

What affect does temperature have on rate of diffusion?

Answer 18

As you increase the temp the particles have more kinetic energy so this means they will diffuse at a faster rate.

Question 19

What affect does Surface area have on rate of diffusion?

Answer 19

The greater the surface area across the greater the number of molecules that can cross at one moment so increased rate of diffusion.

Question 20

What if you have large molecules or Ions /polar molecules

Answer 20

Large molecules diffuse more slowly as they require more energy to move.

Non polar molecules diffuse directly as they are soluble in the phospholipid bilayer.

Question 20

What if you have large molecules or Ions /polar molecules

Answer 20

Large molecules diffuse more slowly as they require more energy to move.

Non polar molecules diffuse directly as they are soluble in the phospholipid bilayer.

Question 21

What type of substances require Facilitated diffusion?

Answer 21

Large polar molecules such as glucose and amino acids.

Ions such as sodium and Cl-

Question 22

What are the two proteins that help in facilitated diffusion?

Answer 22

Channel and Carrier proteins

Question 23

Whats the difference between channel and carrier proteins?

Answer 23

Channel are water filled they allow charged substances to diffuse through.

Question 24

Whats the difference between channel and carrier proteins?

Answer 24

Channel are water filled they allow charged substances to diffuse through. Ions

Carrier proteins have a fixed shape and they can switch between two shapes to allow something in or out.

Question 25

Define Active transport.

Answer 25

movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration

Question 26

Which proteins does active transport require?

Answer 26

Carrier proteins.

Question 27

Why is ATP required in Active transport?

Answer 27

The energy is required to make the carrier protein change shape, allowing it to transfer the molecules or ions across the cell membrane

Question 28

What is bulk transport into cells known as?

Answer 28

Endocytosis Requires energy

Question 29

What is bulk transport out of cells known as?

Answer 29

Exocytosis Requires energy

Question 30

What is pinocytosis?

Answer 30

Bulk intake of liquids

Question 31

How does exocytosis work

Answer 31

Substances are packaged into secretory vesicles formed by the Golgi body and they then travel to the surface membrane and fuse with the cell membrane.

Question 32

Define osmosis.

Answer 32

net movement of water molecules from a region of higher water potential to a region of lower water potential, through a partially permeable membrane

Question 33

What the water potential of Water

Answer 33

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