Topic 3- Transport in membranes

Question 1

What are cell membranes composed of?

Answer 1

Phospholipid bilayer, proteins, glycoprotein, glycolipids

Question 2

What is the fluid mosaic model?

Answer 2

Fluid refers to the components as constantly moving

Question 3

What substances would not be able to pass through the cell surface membrane?

Answer 3

Polar, charged, large molecules, water soluble

Question 4

What substances would be able to pass through the cell surface membrane?

Answer 4

Non-polar, uncharged, small molecules, lipid soluble

Question 5

Describe the phospholipid bilayer.

Answer 5

The hydrophobic tails face each other
The hydrophilic heads turn towards the water

Question 6

Why do proteins allow the transport of some substances?
What substances would be able to move?

Answer 6

Proteins have hydrophilic channels in the middle
Glucose, polar, small

Question 7

What are the functions of intrinsic proteins?

Answer 7

Transport- channel/carrier proteins

Question 8

What are the functions of extrinsic proteins?

Answer 8

Enzymes
Receptors
Antigens

Question 9

What are glycoproteins?

Answer 9

Carbohydrate chains attached to proteins

Question 10

What is the function of glycoproteins?

Answer 10

Receptors for hormones
Antigens

Question 11

What are glycolipids?

Answer 11

Carbohydrate covalently bonded to a lipid

Question 12

What is the function of glycolipids?

Answer 12

Act as recognition sites
Help maintain the stability of membrane

Question 13

What is the function of cholesterol?

Answer 13

Restricts movement of components in the cell membrane
Help keeps cell membrane strong and rigid by making it less flexible
Prevents loss of water and dissolved ions

Question 14

Define simple diffusion

Answer 14

Movement of particles down a concentration gradient

Question 15

What 6 factors affect the rate of diffusion?

Answer 15

Temperature
Surface Area
Concentration gradient
Size of diffusing molecule
Thickness of exchange surface
Water solubility

Question 16

What is Fick’s Law?

Answer 16

surface area x difference in concentration gradient/ thickness of exchange surface

Question 17

How can the diffusion rate be increased?

Answer 17

Increase the surface area
Increase the concentration gradient
Short diffusion pathway

Question 18

Define facilitated diffusion

Answer 18

Passive process
Uses carrier proteins/channels
Transport charged/polar molecules
Down a con gradient
Limited to number of carrier proteins (saturated)

Question 19

Define osmosis

Answer 19

Movement of water molecules from a high water potential to a low water potential across a partially permeable membrane

Question 20

Define active transport

Answer 20

Movement of substances against a concentration gradient
Requires ATP
Requires carrier protein

Question 21

What is the unit of pure water?

Answer 21

0kPa

Question 22

What is endocytosis?

Answer 22

Movement of large amounts of material into the cell
Transported via vesicles (made from plasma membrane)

Question 23

What is exocytosis?

Answer 23

Movement of large amounts of material out of the cell
Transported via vesicles (made from plasma membrane)

Question 24

What are the two groups of lipids?

Answer 24

Triglycerides and phospholipids

Question 25

How are triglycerides formed?

Answer 25

Condensation reaction between one molecule of glycerol and three molecules of fatty acids Bonds between the -OH group of glycerol and the -COOH group of the fatty acid are called ester bonds. 3 molecules of water are also released

Question 26

Why are lipids insoluble in water?

Answer 26

The hydrocarbon chains of fatty acids are hydrophobic so repel water molecules.

Question 27

What is the structure of glycerol?

Answer 27

Contains 3 hydroxyl -OH groups

Question 28

What is the structure of a fatty acid?

Answer 28

They are made up of a carboxylic acid group (-COOH) and a hydrocarbon chain of varying lengths.

Question 29

What are the two kinds of fatty acids?

Answer 29

Saturated- single bonds between carbon atoms Unsaturated- double bonds between carbon atoms

Question 30

What are the lipids found in cell membranes called?

Answer 30

Phospholipids

Question 31

What is the structure of a phospholipid?

Answer 31

One glycerol molecule bonded to two fatty acids and a phosphate group held together by ester bonds

Question 32

What are the properties of triglycerides?

Answer 32

Insoluble Storage molecule Source of energy

Question 33

Explain the properties of triglycerides.

Answer 33

Insoluble- fatty acid tails are hydrophobic = prevents osmotic lysis Storage molecule- due to the large ratio of energy storing carbon-hydrogen bonds compared to carbon atoms

Question 34

What are the properties of phospholipids?

Answer 34

Bilayer of cell membrane- hydrophilic (glycerol and phosphate group) head and hydrophobic (fatty acid) tail

Question 35

What is the emulsion test for lipids?

Answer 35

Dissolve in alcohol Pour into water + result = milky emulsion should appear