Topic 1

Question 1

what are polymers?

Answer 1

large, complex molecules composed of long chains of monomers joined together.

Question 2

what are monomers?

Answer 2

small, basic molecular units.

Question 3

give a few examples of monomers

Answer 3

monosaccharides, amino acids, and nucleotides

Question 4

what 3 elements do all carbohydrates contain?

Answer 4

carbon, hydrogen, and oxygen

Question 5

what monomers are carbohydrates made of? and give some examples

Answer 5

monosaccharides; such as glucose, fructose, and galactose

Question 6

glucose is a monosaccharide with — carbon atoms in each molecule which means that it is a — sugar.

Answer 6

six, hexose

Question 7

what are the two different types of glucose? and how are they different?

Answer 7

alpha glucose and beta glucose. the only difference is that the OH and H groups are reversed.

Question 8

what are isomers?

Answer 8

molecules with the same molecular formula as each other, but with the atoms connected in a different way.

Question 9

how are monosaccharides joined together?

Answer 9

by condensation reactions.

Question 10

what is a condensation reaction?

Answer 10

when two molecules join together with the formation of a new chemical bond, and a water molecule is released when the bond is formed.

Question 11

what is the bond called that forms between two monosaccharides?

Answer 11

a glycosidic bond

Question 12

what are two monosaccharides bonded together called?

Answer 12

a disaccharide

Question 13

what monosaccharides are the following disaccharides made from?
- sucrose
- lactose
- maltose

Answer 13

• glucose and fructose
• glucose and galactose
• alpha glucose and alpha glucose

Question 14

what reaction can break apart polymers?

Answer 14

hydrolysis

Question 15

how does hydrolysis break up monomers?

Answer 15

hydrolysis breaks the chemical bond between monomers using a water molecule (it’s the opposite of a condensation reaction).

Question 16

what is the general term for all monosaccharides and disaccharides?

Answer 16

sugar

Question 17

what are the two different classifications of sugars?

Answer 17

reducing and non-reducing

Question 18

what is the food test for sugars?

Answer 18

the Benedict’s test.

Question 19

describe the method of testing for reducing sugars

Answer 19

1) add the blue Benedict’s reagent to the sample and heat it in a water bath at boiling (100 degrees Celsius)
2) if the test is positive it will form a coloured precipitate (solid particles suspended in the solution)
3) the higher the concentration of reducing sugar, the further the colour change goes (blue - green - yellow - orange - brick red). This can then be used to compare the amount of reducing sugar in different solutions. a more accurate way of doing this is to filter the solution and weight the precipitate.

Question 20

what are reducing sugars in term of monomers/polymers

Answer 20

reducing sugars include all monosaccharides and some disaccharides.

Question 21

how do you test for non-reducing sugars?

Answer 21

1) if the result of the reducing sugars test is negative, there still may be non-reducing sugars present. To test for these, they must first be broken down into monosaccharides.
2) to do this get a new sample of the test solution and add dilute hydrochloric acid to it. Then carefully heat it in a water bath at 100 degrees Celsius. next, neutralise the solution with sodium hydrogencarbonate, and then carry out the Benedict’s test the same way as for a reducing sugar.
3) if the test is positive, a coloured precipitate will form, however, if the test is negative, the solution will stay blue, which means it doesn’t contain any reducing or non-reducing sugars.

Question 22

give one example of a non-reducing sugar

Answer 22

sucrose

Question 23

what is a polysaccharide?

Answer 23

lots of sugars joined together

Question 24

how are polysaccharides formed?

Answer 24

when more than two monosaccharides are joined together by condensation reactions.

Question 25

name three polysaccharides

Answer 25

starch, glycogen, and cellulose

Question 26

how is starch used?

Answer 26

starch is used by plants to store energy.

Question 27

how do plants store and use glucose?

Answer 27

when a plant has excess glucose, it is stored as starch. as soon as the plant needs more glucose for energy, it breaks down starch to release the glucose.

Question 28

what two polysaccharides of alpha-glucose is starch made up of?

Answer 28

amylose and amylopectin

Question 29

describe amylose and explain how it is adapted for storage

Answer 29

amylose is a long, unbranched chain of alpha-glucose. the angles of the glycosidic bonds give it a coiled structure, like a cylinder. this makes it compact and therefore good for storage because more can fit into a smaller space.

Question 30

describe amylopectin and explain how it is adapted for storage

Answer 30

amylopectin is a long, branched chain of alpha-glucose. the side branches allow the enzymes that break down the molecule to get at the glycosidic bonds easily. this means that the glucose can be released quickly.

Question 31

explain why starch being insoluble means that it is good for storage

Answer 31

starch being insoluble in water means that it doesn't cause water to enter cells by osmosis, which would make them swell. therefore starch is good for storage.

Question 32

how do you test for starch?

Answer 32

add iodine dissolved in potassium iodide solution to the test sample. if starch is present, the solution will turn from a browny-orange to a dark blue/black colour.

Question 33

why would you need to test for starch?

Answer 33

if you do an experiment on the digestion of starch and want to find out if there is any left

Question 34

how is glycogen used?

Answer 34

glycogen is the main energy storage material in animals.

Question 35

what is glycogen in terms of polymers?

Answer 35

glycogen is a polysaccharide of alpha-glucose.

Question 36

why do animals need glycogen?

Answer 36

animals store excess glucose as glycogen. glucose is used as an energy source.

Question 37

describe the structure of glycogen and how it is adapted to storage

Answer 37

the structure of glycogen is very similar to the structure of amylopectin, except that it has many more side branches. this means that stored glucose can be released quickly, which is important for energy release in animals. the molecule is also very compact so it is good for storage.

Question 38

what is cellulose used for?

Answer 38

cellulose is the major component of cell walls in plants.

Question 39

what is cellulose made from?

Answer 39

long, unbranched chains of beta-glucose.

Question 40

what is the structure of cellulose?

Answer 40

when beta-glucose molecules bond, they form straight cellulose chains. these cellulose chains are linked together by hydrogen bonds to form strong fibres called microfibrils. the strong fibres mean cellulose provides structural support for cells (like in plant cell walls).

Question 41

what are the two different types of lipids?

Answer 41

triglycerides and phospholipids

Question 42

what is the difference in terms of structure between triglycerides and phospholipids?

Answer 42

triglycerides have three fatty acids bonded to one glycerol, however phospholipids have two fatty acids bonded to one glycerol which is bonded to one phosphate group.

Question 43

what are fatty acids? how can they be saturated or unsaturated?

Answer 43

fatty acids are hydrocarbons. they can be saturated if there are no carbon - carbon double bonds. they can be unsaturated if there is one or more carbon - carbon double bond (this causes the hydrocarbon chain to kink).

Question 44

how do fatty acids and phosphate groups interact with water?

Answer 44

fatty acids are hydrophobic so they repel water (are insoluble). phosphate groups are hydrophilic so they are soluble in water.

Question 45

how does a glycerol molecule bond to fatty acids? what bond does this form?

Answer 45

condensation reactions, creating an ester bond

Question 46

what makes up fatty acids on a molecular level? (draw a fatty acid)

Answer 46

O = C - R (R is the hydrocarbon tail) | OH

Question 47

what are the function of triglycerides and phospholipids?

Answer 47

triglycerides are good for storage and phospholipids make up the bilayer of cell membranes.

Question 48

why are triglycerides good for storage?

Answer 48

the fatty acids tails have high chemical energy potential that is released when broken down. (when broken down they release lots of energy.) The fatty acids tails are also insoluble. this means they do not affect water potential so they do not damage the cell.

Question 49

why are phospholipids good as the cell membrane bilayer?

Answer 49

they have soluble heads (phosphate group) and insoluble tails (fatty acids). this means that water soluble substances can not pass through. essentially meaning that the phospholipids control what comes in and out of the cell.

Question 50

what is used to test for lipids?

Answer 50

ethanol - the emulsion test.

Question 51

what are the steps for testing for lipids?

Answer 51

add ethanol to the test substance. shake for approximately one minute. add the solution to water. a milky emulsion will show if any lipids are present. the more lipids there are, the more obvious the emulsion will be.