Biological molecules 1A

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

What are examples of polymers?

Answer 3

most carbohydrates (polysaccharides), proteins (polypeptides) & nucleic acids (DNA)

Question 4

What are examples of monomers?

Answer 4

monosaccharides, amino acids & nucleotides

Question 5

What are organic compounds?

Answer 5

compounds containing carbon & hydrogen

Question 6

Why are carbon atoms the key to the organic compounds?

Answer 6

1. each carbon atom can form 4 covalent bonds, making them very stable, as these bonds are very strong & require a large energy input to break them
2. carbon atoms can form covalent bonds with oxygen, nitrogen & sulfur
3. carbon atoms can bond to form straight chains, branched chains or rings

Question 7

What elements are all carbohydrates made up of?

Answer 7

carbon, hydrogen & oxygen

Question 8

What are the different monomers that make up different carbohydrates?

Answer 8

monosaccharides: glucose, fructose & galactose

Question 9

What is glucose & the two types?

Answer 9

-it is a hexose sugar: a monosaccharide with 6 carbon atoms in each molecule
-alpha & beta glucose (isomers)

Question 10

What is an isomer?

Answer 10

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

Question 11

What is the difference in structure for an alpha & beta glucose molecule?

Answer 11

on the right hand side of the molecule: Beta glucose has OH at the top & H at the bottom; Alpha glucose has H at top & OH at bottom

Question 12

What is a condensation reaction?

Answer 12

when 2 molecules join together with the formation of a new chemical bond & a water molecule is released when the bond is formed

Question 13

How are monosaccharides formed?

Answer 13

by condensation reactions

Question 14

What is a glycosidic bond?

Answer 14

a bond formed between 2 monosaccharides as a molecule of water is released

Question 15

How are disaccharides formed?

Answer 15

when 2 monosaccharides join together

Question 16

How is maltose formed?

Answer 16

by the condensation reaction of 2 alpha glucose molecules, by a glycosidic bond & releasing a water molecule

Question 17

How is sucrose formed?

Answer 17

by the condensation reaction of a glucose molecule & a fructose molecule, by a glycosidic bond & releasing a water molecule

Question 18

How is lactose formed?

Answer 18

by the condensation reaction of a glucose molecule & a galactose molecule, by a glycosidic bond & releasing a water molecule

Question 19

How can polymers be broken down into monomers?

Answer 19

by hydrolysis reactions

Question 20

How does hydrolysis work?

Answer 20

by breaking the chemical bond between monomers using a water molecule

Question 21

What are reducing sugars?

Answer 21

a sugar which can donate electrons, the carbonyl group becomes oxidised & the sugars become the reducing agent

Question 22

What functional group is -OH?

Answer 22

hydroxyl

Question 23

What functional group is O=C-OH (COOH)

Answer 23

carboxyl

Question 24

What functional group is -NH2

Answer 24

amino group/ amines

Question 25

What functional group is -PO4

Answer 25

phosphate

Question 26

What functional group is C=O & COH?

Answer 26

carbonyl

Question 27

Which sugars are reducing sugars?

Answer 27

-include all monosaccharides, e.g. glucose, fructose -include only some disaccharides, e.g. lactose & maltose

Question 28

What is an example of a non-reducing sugar?

Answer 28

sucrose

Question 29

How do you test for reducing sugars?

Answer 29

1. add Benedict's reagent (blue) in excess to a sample & heat it in a water bath that has been brought to the boil 2. if the test is positive, it will form a coloured precipitate which will change colour from blue>green>yellow>orange>brick red

Question 30

Why does the colour change during a reducing sugars test?

Answer 30

-the Benedict's reagent turns red due to the copper (ii) ions interacting with the free carbonyl group & the donation of electrons from the reducing sugars, reducing the copper (ii) ions (copper sulfate) to copper (i) ions (copper oxide) which are red

Question 31

How can the concentration of the reducing sugar be determined from the Benedict's test?

Answer 31

-the higher the concentration, the more red the colour/ the further the colour changes; however, this is very subjective -a more accurate way of doing this is to filter the solution & weigh the precipitate

Question 32

How do you test for non-reducing sugars?

Answer 32

1. to test for non-reducing sugars, you need to break it down into monosaccharides 2. add to the solution dilute hydrochloric acid- allowing the disaccharide to be hydrolysed- & then carefully heat it into a water bath 3. neutralise it with sodium hydrogencarbonate, as Benedict's reagent will not work in acidic conditions 4. carry out the Benedict's test as you would for a reducing sugar 5. if the test is positive, it will form a coloured precipitate, & if it remains blue, it doesn't contain any sugar whatsoever