1.5 - Nucleic acids and their functions

Question 1

What do you call DNA, RNA and ATP?

Answer 1

Nucleotides

Question 2

What does each nucleotide contain?

Answer 2

• a phosphate group
• pentose sugar
• a nitrogenous base

Question 3

What are the four nitrogenous bases in DNA and are they purine or pyrimidine?

Answer 3

Thymine (pyrimidine)
Adenine (purine)
Cytosine (pyrimidine)
Guanine (purine)

Question 4

What does pyrimidine and purine mean?

Answer 4

pyrimidine is a single ring
purine is a double ring

Question 5

what does ATP stand for?

Answer 5

adenosine triphosphate

Question 6

What is the structure of adenosine triphosphate?

Answer 6

3 phosphate, ribose and adenine

Question 7

How is adenosine diphosphate formed?

Answer 7

when the high energy bond between the 3rd and 2nd phosphate group is broken via hydrolysis by the enzyme ATPase, 30.6kj of energy is released

Question 8

What is the reaction for ATP to ADP and vice versa? (its reversible)

Answer 8

ATP + water ⇌ ADP + Pi + 30.6 kj energy

Question 9

What is adding a phosphate group to ADP called? And what is this reaction called?

Answer 9

Phosphorylation, it’s an endergonic reaction (energy is used)

Question 10

What kind of reaction is hydrolysis?

Answer 10

An exergonic reaction (energy is given out)

Question 11

Where is ATP produced?

Answer 11

in the cytoplasm, mitochondria (matrix and inner membrane) and in chloroplasts

Question 12

What is universal energy currency?

Answer 12

used for energy in all cells in all living organisms

Question 13

What does ATP provide energy for?

Answer 13

Metabolic processes (builds large molecules from smaller molecules)
Active transport
Muscle contraction/movement
Nerve impulse transmissions
Secretion (packaging and transport of secretary products into vesicles)

Question 14

What are the advantages of ATP?

Answer 14

-hydrolysis of ATP to ADP is a single reaction that releases immediate reactions (efficient and only needs 1 enzyme)
-releases energy in small amounts vs glucose which contains large amounts of energy
- soluble and easily transported
- universal energy currency

Question 15

What does the DNA structure consist of?

Answer 15

• of two polynucleotide strands that are arranged into a double helix
• anti-parallel
• held together by H-bonds that form between complimentary nitrogenous bases (ATGC)
• The h-bonds are weak but collectively are very strong

Question 16

When comparing RNA to DNA what are the 7 things that should be listed?

Answer 16

1.Name
2.strand number
3.Chain length
4.Pentose sugar
5.Organic bases
6.Chemical stability
7.Function

Question 17

What is the full name of DNA? RNA?

Answer 17

Deoxyribonucleic acid, Ribonucleic acid

Question 18

What is the function of DNA? RNA?

Answer 18

-carries genetic information
-transfers information from DNA to ribosomes, makes up ribosomes w/proteins, involved in protein synthesis

Question 19

What is the chemical stability of DNA? RNA?

Answer 19

-very stable
-less stable

Question 20

What is mRNA? What does it do?

Answer 20

-a single stranded molecule, synthesised in the nucleus
-copies and then carries genetic infor from DNA to ribosomes in cytoplasm

Question 21

What does each strand of mRNA contain the genetic code for?

Answer 21

each strand of mRNA contains genetic code for 1 gene and each gene codes for a particular polypeptide

Question 22

What does rRNA make up? What does it do?

Answer 22

-ribosomal RNA and protein make ribosomes
-ribosomes are the site of translation of the genetic code into protein.

Question 23

What is tRNA? What does it do?

Answer 23

-small molecule winded intto a cloverleaf shape, has an anticodon at one end and an amino acid at the other
-transfers correct amino acid to the growing polypeptide during translation

Question 24

What happens during replication?

Answer 24

-DNA helicase breaks the H-bonds between the bases causing the double helix to unwind and separate into 2 strands
-the exposed bases bind to free floating nucleotides (forming phosphodiester bond)
-1 strand acts as a template for new molecule so newly synthesised DNA contains 1 parent strand and a complimentary newly synthesised strand

Question 25

What were the three theories on DNA replication?

Answer 25

conservative replication semiconservative replication dispersive replication

Question 26

What were the steps in Meselson's and Stahl's 'beautiful experiment' which proves semiconservative replication?

Answer 26

1. Bacteria (e.coli) was grown for a generation in heavy nitrogen agar, when Dna was centrifuged the Dna band settled low down the tube 2. then grown for the 1st generation in light nitrogen agar, when the dna was centrifuged, the dna band settled at a mid-point on the tube (hybrid DNA) 3. after 2nd generation in light agar, Dna band extracted formed a lighter band at the top of the tube

Question 27

How is conservative replication ruled out?

Answer 27

b/c after bacteria was grown for one generation in light nitrogen, only one dna band was produced - if it was conservative replication two bands would have been seen - one in the light position, one in the heavy position

Question 28

How is dispersive replication ruled out?

Answer 28

half of the DNA after grown for two generations was half heavy, weight and half light

Question 29

What is meant by the term semi-conservative replication?

Answer 29

each new DNA molecule consists of 1 original template strand and one newly synthesised strand which ensures the genetic info is accurately passed on during cell division

Question 30

Where does transcription occur?

Answer 30

in the nucleus

Question 31

Where does translation occur?

Answer 31

at ribosomes

Question 32

Where does post-translational modification occur>

Answer 32

in Golgi apparatus prior to packaging of the protein into vesicles

Question 33

What are the 5 steps to transcription?

Answer 33

1. DNA acts as a template for the production of mRNA 2. DNA helicase acts on a specfic region of DNA, breaking the H-bonds between the DNA strands causing them to unwind exposing free nucleotide bases 3. Free RNA nucleotides pair to exposed bases on the template strand and RNA polymerase joins them by forming H-bonds. 4. This contunues until RNA polymerase reaches a stop codon when RNA detaches and production of mRNA is complete. 5. mRNA carries DNA code out of nucleus through a nuclear pore to the cytoplasm and attaches to a ribosome.

Question 34

Define what an intron is

Answer 34

non-coding nucleotide sequence in DNA and pre-mRNA that is removed from pre-mRNA to produce mature mRNA

Question 35

Define what an exon is

Answer 35

nucleotide sequence on one strand of the DNA molecule and the corresponding mRNA that codes for the production of a specific polypeptide

Question 36

where do amino acids come from?

Answer 36

come from proteins, made by plants which animals eat and is passed on

Question 37

What are the 5 steps of translation?

Answer 37

1. Initiation (a ribosome attaches to a start codon at 1 end of the mRNA molecule) 2. A tRNA molecule w/a comp anticodon to the 1st codon binds to the 1st attachment site on ribosome. 3. Elongation (2nd tRNA molecule joins to 2nd attachment site + a risbomal enzyme catalyses the formation of a peptide bond between 2 amino acids) 4. 1st tRNA is released + ribosome now moves 1 codon along the mRNA which exposes a free attachment site and another tRNA molecule joins and process repeats. 5. Termination (amino acid added until the ribsoome reaches a stop codon, ribosome detaches from mRNA molecule + polypeptide is released).