Biological Molecules

Question 1

List all the small biological molecules and the macromolecules they form

Answer 1

sugars to polysaccharides
amino acids to proteins
nucleotides to nucleic acids (DNA, RNA)
lipids/fats associate to form membranes

Question 2

What is the general formula for carbohydrates and its main functions

Answer 2

(CH2O)n

Function as energy storage, fuel, metabolite and structural element

Question 3

Describe the two types of monosaccharides

Answer 3

Aldehyde based- aldose (C=O is at the end of the chain)

Ketone based- ketose (C=O is in the middle of the chain)

Question 4

Describe glucose as a monosaccharide

Answer 4

An aldose
It has 6 C-atoms so its a hexose
D-configuration- asymmetric C-atom most distant from the C=O group
Can exist in long chain and ring structure

Question 5

Describe the structure of a general amino acid

Answer 5

An amine group and a carboxyl acid group which form the N-terminus and a C-terminus
There’s the central/alpha carbon and attached to it are a hydrogen group and an R group
There are around 20 variations of aa side chains
Amino acids form peptides in a condensation reaction, linked by a peptide bond

Question 6

Describe the structure of proteins

Answer 6

Primary structure- covalent bonds forming polymer e.g. order of amino acid residues joined by peptide bonds
Secondary structure- Regular folded form, often stabilised by hydrogen bonds, hydrophobic, hydrophilic and van der Waals forces
Tertiary structure- overall 3D structure, stabilised by hydrogen bonds, hydrophobic, hydrophilic and van der Waals forces
Quaternary structure- the organisation of macromolecules into assemblies, often stabilised by ionic bonds

Question 7

Describe the hydrogen bonds between the DNA bases

Answer 7

There are three hydrogen bonds between cytosine and guanine

Two hydrogen bonds between adenine and thymine

Question 8

What are body fats, triglycerides and phospholipids

Answer 8

Glycerol esters with fatty acids
Act predominantly as food reserves (energy)
Triglycerides consist of glycerol joined to three fatty acids through ester bonds
Phospholipids consist of two fatty acyl chains joined to a glycerol molecule joined to a phosphate and at the end joined to a head group (choline)

Question 9

Describe cholesterol

Answer 9

Cholesterol is a steroid which can intercalate into the membrane by:
OH group interacts with polar lipid heads
Its steroid scaffold interact with the fatty acids
It decreases fluidity and increases flexibility of the membrane
Reduces permeability for soluble molecules
Cholesterol is also a building block for a range of molecules including cortisol, testosterone and progesterone

Question 10

Give examples of single-molecule diseases

Answer 10

Diabetes- the absence of a protein hormone leads to failure to regulate blood glucose
Sickle cell disease- one amino acid change in a globin chain causes haemoglobin to aggregate into polymers
Cystic fibrosis- the absence of a membrane protein that transports chloride leads to altered properties of secretions