Biological Molecules

Question 1

What are the four main categories of biological molecules?

Answer 1

• carbohydrates
• proteins
• lipids
• nucleotides

Question 2

What is the general composition of a cell?

Answer 2

water - 70%
macromolecules - 26%
small, organic molecules - 3%
inorganic ions - 1%

Question 3

What are the functions of carbohydrates?

Answer 3

They function as:

• an energy storage
• a fuel
• a metabolist
• a structural element

Question 4

What is the difference between D and L configuration in monosaccharides?

Answer 4

In the Fischer projection, if the OH on the chiral carbon furthest from the C=O group is pointed right, it’s the D configuration. If it’s pointed to the left, it’s the L configuration.

Question 5

What is the difference between α and β glucose?

Answer 5

In α-glucose, the OH group on C1 is pointing downwards. In β-glucose, the OH on C1 is pointing upwards

Question 6

What is the difference between glucopyranose and glucofuranose?

Answer 6

In glucopyranose, there are 6 C atoms in the ring. In glucofuranose, there are 5 C atoms in the ring.

Question 7

What monosaccharides are Sucrose and Lactose made up of?

Answer 7

SUCROSE:

• α-D-glucose
• β-D-fructose

LACTOSE:

• α-D-glucose
• β-D-galactose

Question 8

What is the difference between the bonds in cellulose and starch/glycogen?

Answer 8

In cellulose, we have β-1-4 glycosidic bonds between glucose monomers, while in starch/glycogen we have α-1-4 glycosidic bonds between glucose monomers.

Question 9

Describe starch and glycogen.

Answer 9

Starch is made up of Amylose and Amylopectin. In Amylose, glucose is linked by 1-4 glycosidic bonds, which make it unbranched. In Amylopectin, glucose is linked by 1-4 and 1-6 glycosidic bonds, making it a branched chain.
Glycogen’s structure is similar to Amylopectin’s, but with more frequent branching.

Question 10

List the 4 blood types, along with the antibodies and the antigens present on them.

Answer 10

GROUP A: Anti-B antibodies and A antigens
GROUP B: Anti-A antibodies and B antigens
Group AB: no antibodies and both A and B antigens
Group O: both Anti-A and Anti-B antibodies and no antigens

Question 11

Give two examples of amino acids that are important on their own.

Answer 11

• Tyrosine is an amino acid that forms adrenaline, which triggers glycogen breakdown.
• Histidine transforms into histamine, a vasodilator.

Question 12

Give two examples of nucleotides that are important on their own.

Answer 12

• ATP: energy unit

- cAMP: secondary messenger

Question 13

What is the difference between cis and trans-unsaturated fatty acids?

Answer 13

Trans has the H atoms on opposite sides around the double bond, while cis has them on the same side.

Question 14

Describe the structure of phospholipids.

Answer 14

Phospholipids are made of up hydrophobic tails and hydrophilic heads.
The heads are made up of glycerol, a phosphate group and choline.

Question 15

Describe cholesterol.

Answer 15

It’s a steroid that can intercalate into the membrane.

• the OH group interacts with the polar lipid heads
• its steroid scaffold interacts with the fatty acids

It DECREASES FLUIDITY and INCREASES FLEXIBILITY but REDUCES PERMEABILITY for soluble molecules (many hormones are steroids).