Biochemistry

Question 1

Structure of an amino acid

Answer 1

Amino group (NH2), alpha carbon, hydrogen, carboxylic acid group (COOH), variable side chain (R)

Question 2

Functional groups of an amino acid

Answer 2

An amine group (-NH2) and a carboxylic acid acid (COOH)

Question 3

How do naturally occurring amino acids differ

Answer 3

The R group

Question 4

Which amino acid isn’t optically active

Answer 4

Glycine

Question 5

Why are amino acids optically active

Answer 5

They have a chiral carbon

Question 6

Which which optical isomer naturally occurs and what is the effect on plane polarised light

Answer 6

L-isomer rotates plane polarised light anti-clockwise (the left)

Question 7

Can amino acid acids act as a base or an acid

Answer 7

Both an acid and a base

Question 8

Does an amino acid act as an acid or a base in a solution of acid

Answer 8

Base

Question 9

Does an amino acid act as an acid or a base in a solution of base

Answer 9

Acid

Question 10

Does an amino acid act as an acid or a base in a solution of isoelectric pH

Answer 10

Zwitterion so both

Question 11

Which part of an amino acid accepts a proton

Answer 11

The lone pair on the NH2

Question 12

Which part of the amino acid donates a proton

Answer 12

Carboxylic acid

Question 13

What is the isoelectric point

Answer 13

pH at which is has no net charge. Midway between two pKa of its two functional groups

Question 14

Which amino acid has the variable group H

Answer 14

Glycine

Question 15

Charge on an amino acid in a acidic solution

Answer 15

Positive

Question 16

Are cations positive or negative

Answer 16

Positive

Question 17

What binds join amino acids in a protein

Answer 17

Peptide

Question 18

What sort of polymers are proteins

Answer 18

Condensation polymers

Question 19

Define fibrous proteins

Answer 19

Long chains of polypeptides found in bundles and insoluble in water

Question 20

Define globular proteins

Answer 20

Polypeptide chains folded into roughly spherical shapes that are soluble in water

Question 21

Example of globular protein

Answer 21

Haemoglobin

Question 22

Example of fibrous protein

Answer 22

Keratin

Question 23

Define primary structure

Answer 23

The order of alpha-amino acids in a protein

Question 24

How do you determine the order of amino acids in a protein

Answer 24

Systematically hydrolyse the protein chain and identify each amino acid

Question 25

How do you separate amino acids

Answer 25

TLC or paper chromatography

Question 26

What is a proteins secondary structure caused by

Answer 26

Caused by hydrogen bonding between the N-H and the C=O groups of the peptide links along the protein chain causing alpha helix and beta pleated sheets

Question 27

Define alpha helix

Answer 27

Hydrogen bonds formed every four amino acids forcing the chain into a cylindrical formation. Elastic and flexible.

Question 28

Define beta pleated sheets

Answer 28

Parallel regions of the protein line up allowing hydrogen bonds to form between them, leading to a flat sheet like structure.

Question 29

Where do you find beta pleated sheet proteins

Answer 29

In association with Alzheimer’s

Question 30

Define tertiary structure

Answer 30

The overall 3D shape of a protein. Maintained by hydrogen bonds, ionic interactions and disulphides bonds between R groups of amino acids

Question 31

What is the tertiary structure necessary for

Answer 31

Biochemical activity

Question 32

What is broken when a protein is denatured

Answer 32

Tertiary structure

Question 33

What are disulphides bonds

Answer 33

Between two -SH variable groups. Form strong S-S bonds

Question 34

How can sulphide bonds be broken

Answer 34

They are destroyed by heat, reduction or reaction with a base

Question 35

Define enzyme

Answer 35

Proteins that act as biological catalysts, providing an alternative reactions of lower Eact

Question 36

How do enzymes works

Answer 36

Substrates bond in an active site.

Question 37

Define lock and key hypothesis

Answer 37

Only molecules that have the right shape can fit into the active site

Question 38

What determines how a substrate will bind

Answer 38

The size and orientation of an amino acid

Question 39

How does a substrate bind to the active site

Answer 39

Hydrogen bonding, ionic bonding, and van der waals forces

Question 40

What does a stereospecific active site cause

Answer 40

An active site which bonds to only one enantiomer of a racemate

Question 41

Define enzyme inhibitor

Answer 41

A molecule that binds to an enzyme active site and decrease its activity is called an enzyme inhibitor