Chapter 1 - Biological Molecules

Question 1

What are biological molecules?

Answer 1

Particular groups of chemicals that are made up and used by living organisms

Question 2

What is covalent bonding?

Answer 2

When atoms share one or more pairs of electrons in their outermost shell

Question 3

What is ionic bonding?

Answer 3

The electrostatic force of attraction between two or more oppositely charged ions

Question 4

What is hydrogen bonding?

Answer 4

Weak electrostatic bond caused when the negative region of one polarised molecule is attracted to the positively charged region of another

Question 5

What is a polar molecule?

Answer 5

A molecule with an uneven distribution of charge

Question 6

What are monomers?

Answer 6

Small, basic molecular unit that builds polymers

Question 7

What are polymers?

Answer 7

Molecule made up of large numbers of monomer sub-units joined together

Question 8

What is polymerisation?

Answer 8

Process of making polymers by joining monomers together

Question 9

Give examples of industrial made polymers

Answer 9

Polythene and polyester

Question 10

Give examples of naturally occurring polymers

Answer 10

Polysaccharides, polypeptides and polynucleotides

Question 11

What is a condensation reaction?

Answer 11

A reaction that releases a molecule of water when it links molecules together.

Question 12

What is a hydrolysis reaction?

Answer 12

A reaction that hydrolyses the chemical bond between monomers by the addition of water

Question 13

What does the term metabolism mean?

Answer 13

All the chemical processes/reactions that take place in a living organism

Question 14

Define mole

Answer 14

The amount of a substance that contains as many particles as there are atoms

Question 15

What is a molar solution?

Answer 15

A solution that contains one mole of solute in each litre of solution

Question 16

What is an ion?

Answer 16

A charged atom that has received or lost an electron

Question 17

What is an isotope?

Answer 17

Atoms of the same element that have a different number of neutrons which results in a difference in mass

Question 18

What three elements are carbohydrates made from?

Answer 18

Carbon, hydrogen and oxygen

Question 19

What are the monomers that make up carbohydrates called?

Answer 19

Monosaccharides

Question 20

What are monosaccharides and give examples

Answer 20

Simple sugars i.e. glucose, galactose and fructose

Question 21

What are the isomers of glucose?

Answer 21

Alpha glucose and beta glucose

Question 22

What are disaccharides?

Answer 22

Pairs of monosaccharides joined together by a glycosidic bond in a condensation reaction

Question 23

Give examples of disaccharides

Answer 23

Maltose (glucose+glucose)
Lactose (glucose+galactose)
Sucrose (glucose+fructose)

Question 24

What are polysaccharides?

Answer 24

Large molecules formed from combining many monosaccharides together by glycosidic bonds formed in a condensation reaction

Question 25

Give examples of some polysaccharides

Answer 25

Starch, cellulose and glycogen

Question 26

What is a reducing sugar?

Answer 26

A sugar that can donate electrons to (or reduce) another chemical

Question 27

How do you test for reducing sugars?

Answer 27

Benedict’s Test - Add equal amounts of sample and Benedict’s reagent, mix gently and heat for 5 mins - Positive reaction=red precipitate formed of copper oxide

Question 28

How is the test for reducing sugars semi-quantitative?

Answer 28

Has variation in the colour of the precipitate formed depending on how much reducing sugar is present - Blue = none - Green = very low - Yellow = low - Orange = medium - Red = high

Question 29

How do you test for non reducing sugars?

Answer 29

1. Do the Benedict’s test and get a negative reaction 2. Add equal volumes of food sample and dilute hydrochloric acid 3. Heat for 5 mins (acid hydrolyses any disaccharides) 4. Slowly add sodium hydrogen carbonate solution and check pH with pH paper to ensure solution is alkaline 5. Re-test with Benedict’s reagent and heat for 5 mins 6. Orange-brown precipitate formed when a non-reducing sugar is present

Question 30

Where is starch located in organisms?

Answer 30

Found only in plants in the form of small grains and large amounts are found in the seeds and storage organs

Question 31

What is the role of starch?

Answer 31

It’s main role is energy storage as plants store excess glucose as starch

Question 32

How is starch produced?

Answer 32

Chains of alpha glucose monomers joined together by glycosidic bonds formed in a condensation reaction

Question 33

Starch is a mixture of...

Answer 33

2 polysaccharides of alpha-glucose: amylose and amylopectin

Question 34

Describe the structure of amylose

Answer 34

Long, unbranched chain of alpha-glucose that is wound into a tight coil

Question 35

Describe the structure of amylopectin

Answer 35

Long, branched chain of alpha-glucose monomers

Question 36

Describe how the structure of starch relates to its function

Answer 36

1. Insoluble - doesn’t affect water potential 2. Large - does not diffuse out of cells 3. Compact (when coiled) - lots of energy stored in small spaces 4. Amylopectin branches - provide more area for enzymes to act on and break down the glycosidic bonds easily so glucose is released rapidly

Question 37

Alpha glucose molecules are formed by what type of glycosidic bonds?

Answer 37

1,4 and 1,6 glycosidic bonds

Question 38

Where is glycogen located in organisms?

Answer 38

Found in animals and bacteria and is stored as small granules in the liver and muscles

Question 39

Describe glycogen’s structure

Answer 39

Shorter and more highly branched polysaccharide chains of alpha-glucose

Question 40

Describe how glycogen’s structure relates to its function

Answer 40

1. Insoluble - does not affect water potential or diffuse out of the cell 2. Compact - lots stored in small spaces 3. Lots of branches and shorter chains - more area for enzymes to act on so stored glucose can be released very quickly, important for animals with high metabolic and respiratory rates

Question 41

Describe the test for starch

Answer 41

Add iodine solution to a sample and if it reacts with starch it produces a blue-black colouration from yellow

Question 42

Describe the structure of cellulose

Answer 42

Long, straight, unbranched chains of beta-glucose that run parallel to each other that allows hydrogen bonds to form cross-linkages between chains which results in the formation of microfibrils that group together in parallel to make fibres

Question 43

What is the purpose of cellulose?

Answer 43

Provides rigidity and support to plant cells as it is a major component in the cell wall

Question 44

How does cellulose prevent the cell from bursting as water enters the cell by osmosis?

Answer 44

Experts an inwards pressure that stops any influx of water so it makes the plant cell turgid

Question 45

Why is it important that stems and leaves are in a turgid state?

Answer 45

To provide maximum surface area for photosynthesis