Biochem

Question 1

What is the transition state

Answer 1

The reaction intermediate species which has the greatest free energy

Question 2

Apoenzyme

Answer 2

Enzyme without a cofactpr

Question 3

Haloenzyme

Answer 3

Enzyme with a cofactor

Question 4

Tightly bound enzyme

Answer 4

Prosthetic group

Question 5

Michaelis constant

Answer 5

The formation of the enzyme-substrate comples

THIS IS WHEN THE INITIAL REACTION RATE IS HALF MAXIMUM

Question 6

Vmax

Answer 6

The maximal rate of the reaction

Question 7

When is the reaction RATE at half of its maximum?

Answer 7

The michaelis constant

Question 8

What does a high Km mean?

Answer 8

A low KM means that an enzyme only needs a little substrate to work at half-maximal velocity
A high KM means that an enzyme needs a lot of substrate to work at half-maximal velocity

Question 9

MODY and hexokinase and Km/Vmax

Answer 9

MODY (maturity-onset diabetes of the young)
caused by mutations in pancreatic glucokinase which affect KM or Vmax
reduced glucokinase activity results in reduced insulin secretion for a given blood glucose level

Question 10

Does hexokinase or glucokinase have a lower Km?

Answer 10

Hexokinase has a lower Km. This is because it is in the blood and the blood cells need lots of oxygen

Glucokinase is in the liver and pancreas, will only get rid of glucose when there is loads of it

Question 11

Co-operativity

Answer 11

the influence that the binding of a ligand to one protomer has on the binding of ligand to another protomer in an oligomeric protein

Question 12

Allosteric

Answer 12

from allo, meaning the other
a site on an enzyme which is quite different to the active site
enzymes which respond to modulators have these ‘other sites’

Question 13

Which type of enzyme produces a sigmoidal graph?

Answer 13

Allosteric

Question 14

An important example of allosteric regulation?

Answer 14

Oxygen binding to haemoglobin

Question 15

Oxygen binding to haemoglobin is controlled by what?

Answer 15

H+
CO2
2,3 bisphosphonate

Question 16

R (relaxed)

Answer 16

Binds substrate tightly; the active form

Question 17

T (tight)

Answer 17

Binds substrate less tightly; the inactive form

Question 18

DNA-RNA

Answer 18

Transcription

Question 19

RNA-protein

Answer 19

Translation

Question 20

ACGT

Answer 20

DNA

Question 21

ACGU

Answer 21

RNA

Question 22

Which direction is DNA synthesised?

Answer 22

5 –> 3 (new nucleotides added to free 3 end only)

Question 23

Retrovir

Answer 23

Analogue of thymidine

Lacks 3OH group, stops chain getting bigger

Question 24

can only add to existing nucleic acids
can not start DNA synthesis on their own
require an RNA primer to start replication

Answer 24

DNA polymerase

Question 25

Helicase

Answer 25

Unwinds DNA

Question 26

Primase

Answer 26

synthesises RNA primer

Question 27

DNA exonuclease activity

Answer 27

DNA polymerase has 3’  5’ exonuclease activity
removes incorrect nucleotide
improves error rate to one in 109  1010 base pairs

Question 28

Clover leaf structure

Answer 28

tRNA

Question 29

synthesises all mRNA

Answer 29

Poll II

Question 30

Exon

Answer 30

Coding region

Question 31

Intron

Answer 31

Non-coding region

Question 32

Degenerate

Answer 32

Many amino acids have more than one codon

Question 33

Unambiguous

Answer 33

Each codon codes for only one amino acid

Question 34

Change in a single base in DNA

Answer 34

Point mutation

Question 35

Results in a change of amino acid sequemce

Answer 35

Missense mutation

Question 36

Creates a new termination codon

Answer 36

Nonsense mutation

Question 37

Addition of a single base or 2

Answer 37

Frameshift mutation

Question 38

No change in amino acid sequence

Answer 38

Silent mutation

Question 39

Example of problem in post-translational modification

Answer 39

Alpha1-antitrypsin results from misfolding of alpha1-antitrypsin in the ER

Question 40

Targeting

Answer 40

Moving a protein to its final cellular destination

inherited recessive disorder of protein targeting
proteins normally destined for lysosomes are not properly sorted in the Golgi
end up secreted from cell
lysosomes can not properly digest material, become clogged

death before age 8

Question 41

Aminoacyl-tRNA synthetase

Answer 41

Binds amino acids to the corresponding tRNA molecules