Nucleic acids

Question 1

what are nucleotides?

Answer 1

monomers of DNA and RNA and are phosphate esters of pentose sugars

Question 2

what’s the role of nucleotides in metabolic pathways

Answer 2

• can regulate or fuel them due to high energy phosphate bonds
• also form coenzymes like NADP

Question 3

components in a nucleotide

Answer 3

• phosphate group bonded to C3 or C5 via condensation reaction
• pentose sugar: ribose in RNA, deoxyribose in DNA
• nitrogenous base bonded to C1: adenine (A), cytosine (C), guanine (G), and thymine (T)

Question 4

bond between phosphate and sugar in a nucleotide is

Answer 4

phosphodiester bond

Question 5

bond between base and sugar in a nucleotide is

Answer 5

glycosidic bond

Question 6

which bases are PURines and their features

Answer 6

• Guanine and Adenine
• 2 C rings

Question 7

which bases are pyrimidines and their features

Answer 7

• Cytosine and Thymine
• 1 C ring

Question 8

what’s ATP

Answer 8

• Adenosine triphosphate
• made up of 3 phosphate groups, a ribose sugar and the base adenine

Question 9

what type of reaction forms ADP + Pi from ATP (+H2O)

Answer 9

hydrolysis

Question 10

what type of reaction forms ATP (+H2O) from ADP + Pi

Answer 10

condensation

Question 11

what happens when ATP is hydrolysed

Answer 11

• small amount of energy is released which fuels many processes
• high energy bonds exist between phosphates

Question 12

what can ADP be hydrolysed to

Answer 12

AMP

Question 13

what can AMP be hydrolysed to

Answer 13

adenosine

Question 14

what’s deoxyribonucleic acid

Answer 14

• a polynucleotide containing genetic information and is found in all eukaryotic cell nuclei

Question 15

structure of DNA

Answer 15

• double helix with complementary bases, A-T, C-G
• large, storing lots of info in bases
• sugar phosphate backbone that protects the bases
• antiparallel strands join via H bonds

Question 16

how many H bonds are there between A-T

Answer 16

2

Question 17

how many H bonds are there between C-G

Answer 17

3

Question 18

what’s the 3’ and 5’ end dictated by

Answer 18

dictated by phosphate bonding to C3 or C5 of sugar

Question 19

which organisms are suitable for DNA extraction and purification

Answer 19

• strawberries
• kiwis
• peas

Question 20

outline the stages in DNA extraction and purification

Answer 20

1. macerate the tissue using mortar and pestle
2. add a strong detergent (washing up liquid)
3. add cold ethanol
4. remove salts and concentrate the DNA

Question 21

what’s the purpose of adding cold ethanol to DNA

Answer 21

allows DNA to precipitate out of solution

Question 22

what’s removing salts and concentrating the DNA

Answer 22

to purify it further

Question 23

what’s the purpose of macerating the tissue in DNA extraction

Answer 23

to break cell walls

Question 24

what’s the purpose of adding detergent in DNA extraction

Answer 24

dissolves the plasma membrane, which releases the DNA into the solution

Question 25

what's meant by DNA replication occurring by semi-conservative replication during interphase

Answer 25

each new molecule contains and old and a new strand

Question 26

Outline the process of DNA replication

Answer 26

1. DNA helicase breaks H bonds between the bases in the double helix 2. free nucleotides pair up with their complementary bases 5' to 3' ( leading strand) 3. DNA polymerase catalyses the condensation reaction forming phosphodiester bonds between DNA nucleotides 4. **DNA ligase joins okazaki fragments** (formed by DNA polymerase) of DNA together on the **lagging strand** (3' to 5') as DNA polymerase only works 5' to 3'

Question 27

what's a gene

Answer 27

- a length of DNA that codes for a polypeptide - the code leads to a specific primary structure and final protein shape

Question 28

what does the genetic code show

Answer 28

which bases code for which amino acid

Question 29

what are are the 3 features of the genetic code

Answer 29

- degenerate - universal - non-overlapping

Question 30

explain how the genetic code is degenerate

Answer 30

some amino acids coded by more than one triplet

Question 31

explain how the genetic code is universal

Answer 31

the same code in all organisms

Question 32

explain how the genetic code is non-overlapping

Answer 32

each base is only read once

Question 33

what are the two stages in protein synthesis

Answer 33

transcription and translation

Question 34

what's transcription

Answer 34

process where mRNA is produced from DNA

Question 35

outline transcription

Answer 35

1. the gene unzips and H bonds between the bases break 2. free **RNA nucleotides** bond to their complementary bases on **template strand**, forming H bonds, catalysed by **RNA polymerase**. 3. mRNA polymerase passes out of the nucleus to a ribosome 4. mRNA is a copy of the **coding strand**

Question 36

where are ribosomes made

Answer 36

nucleolus

Question 37

what are ribosomes made of

Answer 37

2 subunits, each containing roughly equal ratios of rRNA and protein

Question 38

what's translation

Answer 38

the process where mRNA is used to produce polypeptides

Question 39

outline translation

Answer 39

1. ribosome binds to mRNA 2. the **anti-codon** on tRNA molecule will bind to a complementary codon 3. tRNA will have a specific amino acid attached 4. a second tRNA molecule with attached amino acid will bind 5. the ribosome catalyses a condensation reaction, forming a **peptide bond** 6. tRNA molecules leave their amino acid to find new ones 7. this process continues until a **stop codon** is reached