1. Biological Molecules

Question 1

Describe biological molecules ( 3 marks)

Answer 1

1. Biological molecules are carbon based
2. Sugars- polysaccharides
   Amino acids- peptides
   Nucleotides - nucleic acids (dna/ rna)
   Lipids/fats- associate to form membranes
3. Proportion of cell weights:
   Water- 70%
   Inorganic ions- 1%
   Small organic molecules- 3%
   Macromolecules- 26%

Question 2

Describe carbohydrates (3pts)

Answer 2

1. type of sugar
2. most common organic compound on earth
3. function as energy storage, fuel, metabolite and structural elements

Question 3

Describe Monosaccharides (3pts)

Answer 3

1. individual blocks of carbohydrates
2. types of sugar with a chiral centre. This means monosaccharides are enantiomers so cannot be superimposed onto each other.
3. Monosaccharides can be ketose which means they have a c=o bond in the middle or aldose which means they have a c=o bond at the end.

Question 4

Describe Glucose (4 pts)

Answer 4

1. An aldose- C=O bond at the end
2. Has 6 carbon atoms so is a hexose
3. It is D Glucose because it is asymmetric and is projecting to the right.
4. Exists as:
5. Alpha d glucose-where the OH group is at the bottom of the ring.
6. Beta d glucose- where the OH group is at the top of the ring.

Question 5

Describe Sucrose (4pts)

Answer 5

1. A disaccharide- monosaccharide+monosaccharide
2. Sucrose= glucose+ fructose
3. Plant sugar
4. H2O is released upon bond formation in a condensation reaction.

Question 6

Describe Lactose (4pts)

Answer 6

1. A disaccharide= monosaccharide+monosaccharide
2. Lactose is the milk sugar
3. Lactose= galactose+ glucose
4. H20 is released upon bond formation in a condensation reaction.

Question 7

Describe cellulose (3pts)

Answer 7

1. A polysaccharide- long chain of monosaccharides
2. Cellulose is unable to be broken down in the body due to the strong glycosidic bonds
3. B 1-4 glycosidic bonds- OH group is at the top

Question 8

Describe starch ( 4pts)

Answer 8

1. A polysaccharide- long chain of monosaccharides.
2. Storage molecule for sugars
3. a- 1,4 glycosidic bonds
4. OH groups are all at the bottom and are all facing the same direction therefore starch can be broken down in the body.

Question 9

Describe Glycogen ( 6 pts)

Answer 9

1. A polysaccharide- long chain of monosaccharides
2. Storage molecule for sugars
3. An aldose
4. Hexose- 6 carbon atoms
5. OH groups are all at the bottom and and are all facing the same direction therefore glycogen can be broken down in the body
6. Branched structure which saves space as it allows the glycogen molecules to pack closely together due to the a 1,4 and 1, 6 glycosidic bonds. This allows glycogen storage within muscles and cells in our body.

Question 10

Describe Amino Acids ( 4 pts)

Answer 10

1. Amino acids make up proteins
2. Amino acids are made up of an Amine Group, a carboxyl group and an R group which can be 20 different versions.
3. Amino acids are essential (needed in the body) or non- essential.
4. Amino acid+Amino acid= Dipeptide+ Water
   - condensation reaction
   - peptide bond

Question 11

Describe the structure of proteins (4pts)

Answer 11

Primary structure= the sequence of amino acids joined by peptide bonds

Secondary structure= The regular folded form often stabilised by hydrogen bonds
Tertiary structure= Overall 3D structure stabilised by hydrogen bonds, hydrophobic, hydrophilic and VDW forces.

Quaternary structure= Organisation of macromolecules into assemblies often stabilised by ionic bonds.

Question 12

Describe nucleotides ( 5 pts)

Answer 12

1. Nucleotides make nucleic acids (DNA and RNA)
2. Nucleotides= sugar + base+ phosphate
3. Ribonucleotide= forms RNA
4. Deoxyribonucleotide= forms DNA
5. DNA does not have an OH group on carbon 2 of the sugar whilst this exits in RNA. This makes DNA highly stable compared to RNA.
6. ATP= a nucleotide and is the main energy source

Question 13

Describe DNA (5pts)

Answer 13

1. DNA forms a double helix strand
2. Phosphate sugar backbone heads in one direction and forms an anti-parallel strand.
3. A-T interaction= 2 hydrogen bonds
4. C-G interaction= 3 Hydrogen bonds
5. The loss of oxygen in the sugar makes DNA very stable.

Question 14

Describe Body fats (6pts)

Answer 14

1. Act as food reserves for energy
2. Saturated fatty acids= no carbon double bonds
3. Unsaturated fatty acids= have carbon double bonds.
4. Unsaturated fatty acids trans= H atoms opposite
   Unsaturated fatty acids cis= H atoms on the same side
5. Glycerol+ 3 fatty acids= Triglyceride+ water
   - ester bond
6. polyunsaturated fatty acid= Many double bonds.

Question 15

Describe phospholipids (5 pts)

Answer 15

1. Made up of a hydrophilic phosphate head which is directed towards water when arranged in a bilayer and hydrophobic fatty acid tails which repel water when arranged in a bilayer
2. Phosphate head is made up of Phosphatidylcholine which is found on the inner membrane of a cell.
3. Phospholipids form bilayers but can also form transport vehicles like micelles and liposomes.
4. micelle= fats are found within the inside. Polar outer region so that it can transform.
5. Liposome= important for transporting materials. enables materials to get inside the cell as the bilayers fuse with cells.

Question 16

Describe Cholesterol (3pts)

Answer 16

1. Cholesterol is a steroid
2. Cholesterol is found within the membrane therefore:
3. decreases fluidity
4. increases flexibility of the membrane
5. Reduces permeability for soluble molecules
6. Cholesterol acts as hormone building blocks e.g in testosterone and cortisol.

Question 17

Describe single molecule diseases (3 pts)

Answer 17

Diabetes= due to defective insulin

Sickle cell anemia = A change in haemoglobin into an aggregated shape.

Cystic Fibrosis= The mutation of a protein that transports chloride ions to regulate water flow.