Biological Molecules

Question 1

Glucose + Fructose =

Answer 1

Sucrose

Question 2

Glucose + galactose =

Answer 2

Lactose

Question 3

Glucose + glucose =

Answer 3

Maltose

Question 4

Difference between alpha and beta glucose

Answer 4

In alpha = OH group below H

Question 5

What is a condensation reaction?

Answer 5

Joining of two molecules with the formation of chemical bond and elimination of molecule of water

Question 6

What is a hydrolysis reaction?

Answer 6

Breaking of a chemical bond between two molecules involving use of water molecule

Question 7

How is a glycosidic bond formed?

Answer 7

Condensation reaction between two monosaccharides

Question 8

What is starch a mixture of?

Answer 8

Amylose and amylopectin

Question 9

Describe amylose

Answer 9

Poly (1-4) alpha glucose chain

Coils up into a helix held together by hydrogen bonds

Question 10

Describe amylopectin

Answer 10

Poly (1-4) alpha glucose chain with (1-6) branches

Multiple ends so can be hydrolysed quickly by amylose enzymes

Question 11

Describe glycogen

Answer 11

Poly (1-4) alpha glucose chain with (1-6) branches

Question 12

Purpose of glycogen having multiple ends?

Answer 12

It can be hydrolysed very quickly by enzymes to mobilise glucose for energy

Question 13

Describe cellulose

Answer 13

Poly (1-4) beta glucose chain

Alternate glucose molecules inverted to form straight chain

Question 14

How does cellulose give strength to plant cells and young plants?

Answer 14

Hundreds of chains linked by hydrogen bonds to form cellulose microfibrils which are strong and rigid

Question 15

What is the test for reducing sugars

Answer 15

Add Benedicts reagent
Shake and heat
A precipitate indicates reducing sugar

Question 16

How can you decipher concentration of reducing sugar from Benedicts test

Answer 16

Concentration increases going down

Green
Yellow
Orange
Brick red

Question 17

What is the test for non reducing sugars

Answer 17

Test for reducing sugars
Boil with dilute hydrochloric acid to hydrolyse glycosidic bond
Neutralise with sodium hydrogen carbonate
Test for reducing sugars again

Question 18

How can two organisms have similar % of bases but be very different

Answer 18

• different genes
• different order
• different amino acid coded for

Question 19

How can % of bases tell you an organism has single stranded DNA

Answer 19

A doesn’t = T

No base pairing

Question 20

Describe the structure of proteins

Answer 20

Polymer of amino acids
Joined by peptide bond
Formed by condensation
Primary structure is order of amino acids
Secondary structure is folding due to H bonds
Tertiary structure is 3-D folding due to H bonds, disulfide bonds, ionic bonds
Quaternary is more than one polypeptide chain

Question 21

How are proteins digested in the gut?

Answer 21

Hydrolysis of peptide bonds
Endopeptidases break polypeptides into smaller chains
Exopeptidases remove terminal amino acids
Dipeptidases hydrolyse

Question 22

How is starch adapted for plant cells

Answer 22

Insoluble - doesn’t affect water potential
Large molecule - cannot leave cell
Helical - compact

Question 23

What is the test for reducing sugars ?

Answer 23

Heat with Benedicts

Precipitate formed

Question 24

What is the test for proteins ?

Answer 24

Biuret test (add NaOH and CuSO4) 
Purple

Question 25

What is the organ that produces amylase?

Answer 25

Small intenstine, pancreas

Question 26

Describe the role of dna polymerase

Answer 26

joins nucleotides

Question 27

Other than being smaller, give two ways in which prokaryotic DNA is different from
eukaryotic DNA.

Answer 27

Circular
Not associated with proteins
No introns

Question 28

How is the DNA of the virus is different from that of other organisms?

Answer 28

No base pairing

single stranded

Question 29

Describe the structure of proteins

Answer 29

1. Polymer of amino acids;
2. Joined by peptide bonds;
3. Formed by condensation;
4. Primary structure is order of amino acids;
5. Secondary structure is folding of polypeptide chain due to hydrogen bonding;
   Accept alpha helix / pleated sheet
6. Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide
   bonds;
7. Quaternary structure is two or more polypeptide chains.

Question 30

Describe how proteins are digested in the human gut

Answer 30

Hydrolysis of peptide bonds;

2. Endopeptidases break polypeptides into smaller peptide chains;
3. Exopeptidases remove terminal amino acids;
4. Dipeptidases hydrolyse / break down dipeptides into amino acids

Question 31

How are cellulose molecules adapted for their function in plant cells?

Answer 31

Long and straight chains linked together by many hydrogen bonds
To form fibrils
To provide strength

Question 32

What is the difference between starch and cellulose molecules?

Answer 32

Position of hydrogen and hydroxyl groups on carbon 1 are inverted
Cellulose is beta glucose, starch is alpha glucose

Question 33

Give two ways in which ATP is a suitable source of energy to use in cells

Answer 33

Releases relatively small amount of energy /
little energy lost as heat;
Releases energy instantaneously;
Phosphorylates other compounds, making them
more reactive;
Can be rapidly re-synthesised;
Is not lost from/does not leave cells

Question 34

Suggest one advantage to a bacterium of secreting an extracellular protease in its
natural environment

Answer 34

They are able to digest protein

So they can absorb amino acids for growth

Question 35

Describe the action of membrane-bound dipeptidases and explain their
importance.

Answer 35

Hydrolyse (peptide bonds) to release amino
acids;
2. Amino acids can cross (cell) membrane;