BIOCHEMISTRY - i hate it too its ok but you need to know it :(

Question 1

What are enzymes?

Answer 1

Biological catalysts which speed up the rate at which a reaction reaches equilibrium but does not affect the position of equilibrium, by lowering the activation energy and stabilising the transition state

Question 2

Enzymes without a cofactor

Answer 2

apoenzymes

Question 3

Enzymes with a cofactor

Answer 3

holoenzymes

Question 4

What does a substrate bind to?

Answer 4

Enzyme’s active site

Question 5

Induced fit

Answer 5

Binding of the substrate induces a conformational change in the shape of the enzyme, resulting in a complementary fit

Question 6

What are phosphorylation reactions carried out by?

Answer 6

Protein kinases

Question 7

Vmax

Answer 7

maximal rate of reaction at unlimited substrate concentration
intersection of the straight line with the Y axis

Question 8

Km

Answer 8

Michaelis constant = 50% Vmax
intersection of the straight line with the X axis

Question 9

Competitive enzyme inhabition

Answer 9

Binds to active site
Vmax remains the same
Km varies

Question 10

Non-competitive enzyme inhabition

Answer 10

Bind to site other than active site
Km stays the same
Vmax varies

Question 11

Cholesterol

Answer 11

Present in cell membranes
Component of myelin sheath
Precursor molecule for steroid hormones, vitamin D and bile acids

Question 12

Triglycerides

Answer 12

Present in all cell membranes - lipid bilayer
Highly concentrated energy stores

Question 13

Nucleoside

Answer 13

base + sugar

Question 14

Nucleotide

Answer 14

nucleoside + phosphate

Question 15

Purines

Answer 15

Adenine and guanine

Question 16

Pyrimidines

Answer 16

Uracil, thymine and cytosine

Question 17

Where does phosphodiester bond?

Answer 17

3’ OH group and 5’ triphosphate

Question 18

Base pairing

Answer 18

A-T
C-G

Question 19

What direction does DNA replication occur in?

Answer 19

always 5’-3’

Question 20

What is DNA replication catalysed by?

Answer 20

DNA polymerases

Question 21

What is required for DNA replication?

Answer 21

RNA primer

Question 22

Leading strand

Answer 22

always has 3’ end free

Question 23

Lagging strand

Answer 23

replicated in short fragments called Okazaki fragments

Question 24

What unwinds DNA?

Answer 24

helicase

Question 25

RNA

Answer 25

single stranded, contains a stem loop

Question 26

3 main classes of RNA

Answer 26

rRNA, tRNA, mRNA

Question 27

rRNA

Answer 27

ribosomal combines with proteins to form ribosomes where protein synthesis takes place

Question 28

tRNA

Answer 28

transfer carries amino acids to be incorporated into protein anticodons consist of 3 nucleotides

Question 29

mRNA

Answer 29

messenger - stable RNAs carries genetic information for protein synthesis

Question 30

What are RNA polymerases?

Answer 30

multi-subunit complexes

Question 31

How many types of RNA polymerases do prokaryotic cells have?

Answer 31

1

Question 32

How many types of RNA polymerases do eukaryotic cells have?

Answer 32

3 Pol I, II, III Pol II synthesises all mRNA

Question 33

Transcription order

Answer 33

1. RNA polymerase binding 2. DNA chain separation 3. Transcription initiation 4. Elongation 5. Termination

Question 34

RNA polymerase binding

Answer 34

Detects initiation sites on DNA (promoters) Requires transcription factors

Question 35

DNA chain separation

Answer 35

Unwinding of DNA

Question 36

Transcription initiation

Answer 36

Selection of first nucleotide of growing RNA Requires addition general transcription factors

Question 37

Elongation

Answer 37

Addition of further nucleotides to RNA chain RNA synthesised in a 5'-3' direction

Question 38

Termination

Answer 38

release of finished RNA

Question 39

TFIID

Answer 39

general transcription factor required for all Pol II transcribed genes

Question 40

Why are specific transcription factors required?

Answer 40

for specific regulation of transcription

Question 41

Exons

Answer 41

coding regions

Question 42

Introns

Answer 42

non-coding regions

Question 43

How are introns removed after transcription?

Answer 43

By splicing before translation into the protein