Biology/Biochemistry

Question 1

What is a biomaterial?

Answer 1

A biomaterial is a non-viable material used in a medical device, intended to interact with biological systems.

Question 2

What is biocompatibility?

Answer 2

The ability of a material to perform with an appropriate host response in a specific application.

Question 3

Reliability/probability of success

Answer 3

r = 1-f

Question 4

What is a hydrogen bond?

Answer 4

The attractive interaction of a hydrogen atom with an electronegative atom (e.g. nitrogen or oxygen) from another molecule or chemical group- must be covalently bonded

Question 5

Strength of hydrogen bond

Answer 5

5-30 kJ/mole- stronger than the van der Waals interaction

Question 6

What is a stereoisomer?

Answer 6

Stereoisomers are isomeric molecules that have the same molecular formula and sequence of bonded atoms, but with different 3D orientation in space. Structural isomers share the same molecular formula, but the bond connection and/or their order between different atoms/groups differs. In stereoisomers, the order and bond connections of the constituent atoms remains the same, but their orientations in space differ.

Question 7

pH formula

Answer 7

pH = -log(10)[H+]

Question 8

What is a zwitterion?

Answer 8

A zwitterion is a molecule with a positive and negative electrical charge on different atoms within the molecule. In some amino acids, zwitterions exist due to non-uniform distribution of ions at atoms/molecules. Zwitterion properties of an amino acid can be modulated by pH.

Question 9

What is an L-isomer?

Answer 9

A stereoisomer that rotates polarised light left (laevorotatory). All proteins in all species are made up of the same set of 20 L-amino acids).

Question 10

Hydrophobicity

Answer 10

Water unfriendly- contains a large number of CH2 or phenyl (benzene C6H6) rings groups

Question 11

Hydrophilicity

Answer 11

Water friendly- contains a large number of OH, COOH, NH2 or any group which can carry charge (polar molecules)

Question 12

Aldehyde

Answer 12

Has a C=O group at the end of the molecule

Question 13

Ketone

Answer 13

Has a C=O group at some other point along the chain

Question 14

Three main physiological functions of lipids

Answer 14

1) Building blocks of phospholipids and glycolipids that are important in biological membranes
2) Derivatives serve as hormones and intracellular messengers
3) Fuel storage

Question 15

Describe the formation of peptide by amino acids and identify the pepetide bond

Answer 15

Two amino acids bond together by a peptide bond. Water will be released during this process.

Question 16

Describe the structure of haemoglobin

Answer 16

Haemoglobin consists of 2 alpha and 2 beta chains containing a Haem group. In an alpha-helix, the protein chain is coiled like a loosely coiled spring. In a beta-pleated sheet, the chains are folded so that they lie alongside each other.

Question 17

What holds a protein into its tertiary structure?

Answer 17

The tertiary structure of a protein is held together by interactions between the side chains- the “R” groups. There are several ways this can happen.

Question 18

Primary structure

Answer 18

The sequence of amino acids in a protein is called the primary structure. The peptide bonds lie in the same plane and define the polypeptide backbone.

Question 19

Secondary structure

Answer 19

The secondary structure is governed by the rotations, or folding of the polypeptide chains. The two most common types of folding are the alpha helix and the beta pleated sheet.

Question 20

Tertiary structure

Answer 20

Refers to the 3D structure of an amino acid or protein. The folded structure is maintained by electrostatic interactions, H-bonding and in some cases sulphide links. For a protein in water, its 3D structure is determined by the hydrophobicity/hydrophilicity of the amino acids.

Question 21

Quarternary structure

Answer 21

Refers to the spatial arrangement of chains of a protein relative to one another (like haemoglobin, which has a number of polypeptide chains). The chains are held together by van der Waals forces.

Question 22

Describe the common pathway of blood clotting

Answer 22

Active X-factor from either intrinsic or extrinsic pathways triggers the reaction from prothrombin to thrombin. Thrombin then triggers the reaction for fibrinogen to turn into fibrin (loose) and fibrin (tight).

Question 23

Acute Inflammation

Answer 23

Relatively short duration (minutes- days). Main characteristics are exudation (accumulation) of fluid and plasma proteins which cause swelling (oedema) and migration of white blood cells called neutrophils.

Question 24

Chronic Inflammation

Answer 24

Generally characterised by the presence of a second class of white blood cells, macrophages, monocytes and lymphocytes. New blood vessels and connective tissues start to proliferate.

Question 25

Granulation tissue

Answer 25

Specialised tissue which is hallmark of healing inflammation. Can occur from 3-5 days after implantation. In early stages proteoglycans preodominate but replaced by collagen.

Question 26

Foreign body reaction

Answer 26

Composed of foreign body giant cells and components of granulation tissue, i.e. macrophages, fibroblasts and capillaries. Relatively flat prostheses, e.g. breast implants have a foreign body reaction which is composed of macrophages of one or two cells thickness. Rough surfaces have macrophages and foreign body giant cells.