Biological Molecules

Question 1

In what form do amino acids exist in exclusively?

Answer 1

L form

N —> C

Question 2

In what form do sugars exist in predominantly?

Answer 2

D form

C —> N

Question 3

What biological bond consisting of 4 atoms is planar?

Answer 3

Peptide bond

Question 4

What’s the general formula of monosaccharides?

Answer 4

(CH2O)n
- a carbon which is hydrated

Question 5

What 2 groups do monosaccharides either contain?

Answer 5

Aldehyde (aldoses)

Or ketone (ketones)

Question 6

What functional group do all monosaccharides possess in aqueous solution?

Answer 6

Hemiacetal

Question 7

What’s the name of the position next to the ring oxygen?

Answer 7

The anomeric position

Question 8

What’s the importance of the anomeric position?

Answer 8

It has two forms that can interconvert between alpha and Beta anomers.

This is often the region where two sugars link and becomes rigid.

Question 9

What reaction joins sugars together?

Answer 9

Condensation reaction

Question 10

What are three common disaccharides and their monomer units?

Answer 10

Maltose - glucose + glucose

Lactose - glucose + galactose

Sucrose - glucose + fructose

Question 11

What is the difference between glucose and galactose?

Answer 11

The OH on carbon 4 is flipped - in galactose it is above the plane of the ring.

Question 12

What is the difference between glucose and mannose?

Answer 12

The OH on carbon 2 is flipped - in mannose it is above the plane of the ring.

Question 13

How can you identify a glycosidic bond?

Answer 13

They are chiral carbons which are bonded to a heteroatom next to the ring oxygen.

Question 14

What sugar makes up cell walls?

Answer 14

Cellulose

Question 15

What word can be used to describe fatty acids?

Answer 15

Amphiphilic - has both hydrophobic and hydrophilic properties

Question 16

What the difference between oleic acid and stearic acid?

Answer 16

Oleic acid is more reactive due to the double bond in the hydrocarbon chain - molecular handle

Stearic acid is less reactive

Question 17

Why are butter/lard solids at room temperature?

Answer 17

They are saturated fats and so contain no C=C double bond

Hence possess better stacking - stronger VDW forces and so have a higher melting point

Question 18

Why are plant oil often liquid at room temperature?

Answer 18

Planet oils are alkenes and so have poorer stacking - lower melting point due to weaker VDW forces

Also have better molecular handle which is metabolised.

Question 19

What is an acyl group?

Answer 19

Central carbon bound to a methyl group and R group, with a C=O double bond.

Me — C == O
l
R

Question 20

Where are ester linkages found in Triacylglycerols?

Answer 20

Between glycerol and the fatty acids

Question 21

What are the key differences between triacylglycerols and phospholipids?

Answer 21

In phospholipids, glycerol is attached to two fatty acids, rather than 3 in TAGs.

Third site on glycerol is attached to phosphate group - which is then bound to a small polar group.

Question 22

How does a glycolipid differ to a phospholipid?

Answer 22

It contains a sugar instead of a phosphate group

Question 23

Where are glycosidic bonds found in nucelotides?

Answer 23

Between the sugar and the base

Question 24

What is a nucleoside?

Answer 24

It’s a nucleotide but without the phosphate group.

Question 25

What bases are pyrimidines? (Single ring structure)

Answer 25

Thymine

Cytosine

Uracil

Question 26

What bases are purines? (Double ring structure)

Answer 26

Adenine

Guanine

Question 27

Where are phosphoanhydride bonds found?

Answer 27

Between phosphate groups (in molecules like ATP)

Question 28

Where do phosphates join to sugars?

Answer 28

To the C5’ hydroxyl

Question 29

Where are phosphodiester bonds found?

Answer 29

Between the sugar of one nucleotide and the phosphate of another.

(Phosphodiester backbone of DNA)

Question 30

Give two important energy transport molecules - excluding ATP. What is the difference between them?

Answer 30

NADP+

NAD+

They are dinucleotide analogues of each other - with only structural difference being a phosphate group

Question 31

What 4 atoms make up more then 96% of the mass of a cell?

Answer 31

Carbon, hydrogen, nitrogen and oxygen