Biological Molecules

Question 1

What is the general formula of monosaccharides?

Answer 1

(CH2O)n

Question 2

Is glusose an aldose or ketose?

Answer 2

Aldose

Question 3

What orientation does glucose have?

Answer 3

· D-glucose because the OH of carbon 2 projects to the right

Question 4

Why is the linear form of glucose important?

Answer 4

The linear form is chemically important because the aldehyde group is reactive and can react with proteins

Question 5

Why is the ring form of the monosaccharides important?

Answer 5

· sugars having five or more carbons spontaneously self-react to produce a closed or ring-containing molecule.

· The ring form is important as building blocks of molecules.

Question 6

How does D and L configuration arise?

Answer 6

Based by convention on the arrangement of groups attached to the asymmetric carbon atom farthest from the aldehyde (the carbon associated with the aldehyde is designated C1).

If the hydroxyl group of this carbon projects to the right, the aldose is a d‐sugar; if it projects to the left, it is an l‐sugar.

Question 7

How is maltose formed?

Answer 7

alpha-glucose and alpha-glucose

Question 8

How is sucrose formed?

Answer 8

alpha-glucose and fructose

Question 9

How is lactose formed?

Answer 9

alpha-glucose and galactose

Question 10

What are the glycosidic bonds that exist in cellulose, starch, and glycogen?

Answer 10

Starch, amylase (α-1-4 glycosidic bond), glycogen (α-1-4 glycosidic bond and alpha-1-6 glycosidic bond), cellulose (β-1-4 glycosidic bond)

Question 11

What is the arrangement of amino acids?

Answer 11

“Tetrahedral arrangement with chiral carbon (apart from glycine with 2 H) so enantiomers can form. “

Question 12

Why is glycine freer to move?

Answer 12

“due to small R chain group”

Question 13

How common is D and L and where are they found?

Answer 13

“L form more common. D residues comprise bacterial cell walls and therapeutics”

Question 14

Why is cis arrangement of the R-group not common?

Answer 14

“Only 0.1% has CIS so less energetically favourable. “

Question 15

Describe amino acids in different pH(3)

Answer 15

1. At acidic conditions (low pH), the amino acid acts as a base and accepts a proton.
2. At high pH, it acts as an acid an loses proton.
3. In neutral conditions, can form zwitterion, where carboxyl group loses H+, and the amine group gains the H+ This can change depending on the proportion of acid/base in R group.

Question 16

Recall the essential amino acids(9)

Answer 16

· Isoleucine

· Leucine

· Valine

· Phenylalanine

· Tryptophan

· Histidine

· Lysine

· Threonine

· Methionine

Question 17

Name the groups of amino acids(9)

Answer 17

Aliphatic, aromatic, acidic, basic, hydroxylic, sulfur-containing, amidic, non-essential and essential

Question 18

How is folding determined?

Answer 18

Rotational freedom of Ca-N and Ca-C (around alpha carbon), so folding determined by backbone of amino acid and not the peptide bond

Question 19

Give examples of amino acids being used as precurssors(2)

Answer 19

1. Tyrosine with amino acids involved and converted into adrenaline. Triggers the breakdown of glycogen 2. Loss of CO2 makes histamine from histidine- vasodilator

Question 20

Why is DNA more stable than RNA?

Answer 20

· hydroxyl group make RNA less stable than DNA because it is more susceptible to hydrolysis.

Question 21

Name the types of heads of the phsopholipids (4)

Answer 21

Phosphatidic acids Phosphatidylcholine Phosphatidylethanolamine Phosphatidylserine

Question 22

What is the role of phosphotidylserine?

Answer 22

· found in the inner membrane but when expressed outside it reprenst the cell is going through apotosis and is cleared by the cell

Question 23

What are micelle?

Answer 23

interact with surrounding water. Fats are found with the inside with outer hydrophilic heads. Detergents

Question 24

What are liposomes?

Answer 24

“enables materials to get in to the cell. Bilayer fuses with cellencapsulate hydrophilic or lipophilic drugs”

Question 25

Where is cholesterol synthesised?

Answer 25

The ER

Question 26

What is the role of cholesterol in membranes?(2)

Answer 26

· Decreases fluidity and increases flexibility of the membrane

· Reduces permeability for soluble molecules

Question 27

Give examples of single molecule diseases(3)

Answer 27

Diabetes- absence of a protein hormone leads to a failure to regulate blood glucose

Sickle cell- one amino acid change in globin chain causes haemoglobin to aggregate

Cystic fibrosis- absence of a membrane protein that transports chloride leads to altered properties.

Question 28

Summarise the different

Answer 28