Nucleic Acids

Question 1

What are the components of a nucleotide?

Answer 1

Pentose sugar, phosphate plus organic base which contains nitrogen.

Question 2

What are the components of ATP?

Answer 2

Ribose sugar, adenine and three phosphate groups joined together

Question 3

Why is ATP formation endergonic?

Answer 3

Because energy is stored in the bond between the second and third phosphate.

Question 4

Why is ATP hydrolysis exergonic?

Answer 4

Energy is released when the bond is broken between the second and third phosphate

Question 5

Why is ATP known as the universal energy currency?

Answer 5

It is used by all living organisms to provide energy for nearly all reactions

Question 6

Name three cellular processes that require ATP

Answer 6

Active transport, muscle contraction, protein synthesis, cell division, bulk transport.

Question 7

Which DNA base is not present in RNA and which base replaces it?

Answer 7

Thymine is replaced by uracil

Question 8

Which bases are pyrimidines and how many rings to they have?

Answer 8

Cytosine, Thymine, Uracil, they have one ring

Question 9

Which bases are purines and how many rings to they have?

Answer 9

Guanine and Adenine, they have two rings

Question 10

What are the base pairs and how do they join together?

Answer 10

Adenine and Thymine, Cytosine and Guanine. Joined by H bonds

Question 11

How do you describe the different directions in which the two DNA strands run?

Answer 11

One runs from the 5 prime end to the 3 prime end, the other from the 3 prime end to 5 the prime end.

Question 12

What are the two functions of DNA?

Answer 12

Replication in dividing cells and coding for the order of amino acids in protein synthesis

Question 13

Which enzymes are involved in DNA replication and what do they do?

Answer 13

DNA helicase breaks the H bonds to separate the strands, DNA polymerase catalyses the condensation reaction to join the sugar phosphate backbone

Question 14

What type of DNA replication is used in cells?

Answer 14

Semi conservative replication

Question 15

What is semi conservative DNA replication?

Answer 15

When each orginal strand of DNA acts as a template to make a new strand of DNA. The molecules of DNA made will contain one original strand and one new strand.

Question 16

Which isotopes were used in Meselson and Stahl’s experiment?

Answer 16

Nitrogen 14 and 15

Question 17

If bacteria were given only N15 with which to form DNA bases, then DNA was extracted and centrifuged, where would the band be in the tube?

Answer 17

At the bottom

Question 18

If bacteria grown in N15 were allowed to divide once in N14, then DNA was extracted and centrifuged, where would the band be in the tube?

Answer 18

In the middle

Question 19

What does it mean that the DNA code is universal?

Answer 19

The same triplets of bases code for the same amino acids in all organisms

Question 20

What does it mean that the DNA code is degenerate?

Answer 20

There is more than one DNA triplet coding for each amino acid

Question 21

What do you call three bases of DNA?

Answer 21

A triplet

Question 22

What do you call three bases of mRNA?

Answer 22

A codon

Question 23

What do you call the three unpaired bases on a tRNA molecule?

Answer 23

An anticodon. This will be complementary to a codon of mRNA.

Question 24

Which areas of DNA code and which don’t?

Answer 24

Exons code, introns don’t

Question 25

What is the name for the process in which non coding parts of the mRNA are removed after transcription?

Answer 25

mRNA splicing of introns

Question 26

Which organisms do mRNA splicing of introns and which don't?

Answer 26

Eukaryotic organisms splice. Prokaryotic organisms don't, so they do not contain introns in their genes.

Question 27

Which enzymes are involved in transcription and what do they do?

Answer 27

DNA helicase breaks the H bonds to separate the DNA strands, RNA polymerase catalyses the condensation reaction to join the sugar phosphate backbone

Question 28

What do m, r and t RNA stand for?

Answer 28

messenger, ribosomal and transfer RNA

Question 29

What does it mean if a tRNA molecule is activated?

Answer 29

It has an amino acid attached. It requires energy in the form of ATP to bind the amino acid to the attachment site

Question 30

How many activated tRNA molecules can bind to a ribosome at one time?

Answer 30

Two

Question 31

What is the function of mRNA?

Answer 31

Acts as a copy of the genetic code from the DNA in the nucleus. Allows the code to travel to the ribosome for protein synthesis.

Question 32

What is the function of rRNA?

Answer 32

Ribosomes are made up of rRNA and protein.

Question 33

What is the function of tRNA?

Answer 33

tRNA molecules bring amino acids to the ribosome so that proteins can be synthesised

Question 34

Describe a tRNA molecule

Answer 34

It is a clover leaf shape, with an anticodon (three bases) at the bottom and an amino acid attachment site at the top

Question 35

Where does transcription happen? What does it mean?

Answer 35

In the nucleus. A copy of the DNA code is made in mRNA that can leave the nucleus

Question 36

Where does translation happen? What does it mean?

Answer 36

At the ribosome. The code from mRNA is used to create a sequence of amino acids and join them into a polypeptide chain

Question 37

What is a gene?

Answer 37

A section of DNA that codes for one polypeptide chain

Question 38

Which bond is formed between amino acids in translation, catalysed by ribosomal enzymes?

Answer 38

A peptide bond

Question 39

How could polypeptides be further modified after they have been produced and where would this happen?

Answer 39

Polypeptides can be further modified by the addition of carbohydrates, lipids or phosphate, or joining of multiple polypeptide chains to form a quaternary structure. Modification of proteins happens in the golgi body.