Nucleic Acids

Question 1

What are the monomers of nucleic acids?

Answer 1

Nucleotides

Question 2

Describe the structure of nucleotides?

Answer 2

A phosphate group, pentose sugar and organic base joins via a condensation reaction

Question 3

What are the two types of organic bases?

Answer 3

Purine and pyrimidine

Question 4

What is a purine?

Answer 4

A base with an double ring structure. Eg Adenine and Guanine

Question 5

What is a pyramidine?

Answer 5

A base with a single ring structure. Eg cytosine, thymine and uracil.

Question 6

What is the difference between a DNA and RNA nucleotide?

Answer 6

DNA= Deoxyribose, A,T,C & G
RNA= Ribose A,U,C & G

Question 7

What is an endergonic reaction?

Answer 7

A reaction requiring energy

Question 8

What is an exogonic reaction?

Answer 8

A reaction releasing energy

Question 9

What is the role of ATP?

Answer 9

Universal energy currency

Question 10

What is complementary base pairing?

Answer 10

When hydrogen bonds from between a purine and pyrimidine base pairs.

Question 11

Describe the structure of DNA

Answer 11

A DNA molecule consists of two antiparallel polynucleotide strands joined via hydrogen bonds between complimentary base pairs. The alternating phosphate groups and pentose sugars form the phosphate sugar backbone. The molecule is twisted into a double helix structure maintained by hydrogen bonding.

Question 12

Describe the structure of RNA

Answer 12

RNA is a single stranded polynucleotide that is much shorter than DNA.

Question 13

Name the three types of RNA found in cells.

Answer 13

Messenger RNA
Ribosomal RNA
Transfer RNA

Question 14

What is the structure and function of tRNA?

Answer 14

tRNA is a small single stranded molecule folded into the shape of a clover leaf. Each tRNA molecule has an amino acid attachment site CCA. At the opposite end of the tRNA molecule there is a triplet of bases called an anticodon. tRNA molecules transport amino acids to the ribosomes. The anticodon bases form a complex with complimentary bases on
the mRNA molecule (codon). This allows translation to take
place.

Question 15

What is the structure and function of mRNA?

Answer 15

mRNA is a long single-stranded molecule. It is synthesised in the nucleus and carries the genetic code from the DNA to the ribosomes in the cytoplasm. Each strand of mRNA contains the genetic code for one gene. Each gene codes for a particular
polypeptide.

Question 16

Define DNA replication

Answer 16

A process occuring during interphase where DNA is copied and doubles

Question 17

Outline the process of DNA replication

Answer 17

1.DNA molecule unwinds, hydrogen bonds between the complimentary base pairs break.
2.DNA polymerase, addition of free nucleotides to template strand
3. Formation of 2 identical DNA molcules consisting of 1 newly synethesised strand and 1 strand from the original DNA molecule.

Question 18

What is semi-conservative DNA replication?

Answer 18

Where the parental double helix seperates and each strand acts as a template strand for free nucleotides to join and from new DNA: 1 newly synthesised strand and 1 strand from original DNA molecule.

Question 19

What is conservative DNA replication?

Answer 19

Where the parental double helix remains intact and a whole new molecule is made seperate from the original strand.

Question 20

What is dispersive DNA replication?

Answer 20

Where fragments of the parental DNA strands are dispersed within two new double helix DNA molecules

Question 21

What is the structure and function of rRNA?

Answer 21

rRNA is found in the cytoplasm and is a component part of ribosomes. Ribosomes are made of rRNA and protein and are synthesised in the nucleolus of the nucleus (they leave the nucleus via the nuclear pores). Ribosomes are the site of protein synthesis by a process called translation.

Question 22

What does DNA helicase do?

Answer 22

Unzippes and unwinds the DNA strands by breaking the hydrogen bonds between the complimentary base pairs

Question 23

What does DNA polmerase do?

Answer 23

Catalyses the addition of free nucleotides to the template strand during DNA replication

Question 24

What is an genetic code?

Answer 24

The rules applies to the sequence of amino acids in a polypeptide chain.

Question 25

What is an exon?

Answer 25

The region of DNA that codes for an amino acid sequence

Question 26

Describe the triplet code for amino acids.

Answer 26

Triplet code or codon is where 3 bases code for 1 amino acid

Question 27

What is an intron?

Answer 27

A non-coding sequence of DNA found between exons.

Question 28

What is protein synthesis?

Answer 28

The formation of proteins from amino acids through the process of transcription and translation.

Question 29

Define transcription

Answer 29

The first stage of protein synthesis where mRNA is formed from a copied region of DNA and thus carries a code for a specific pilypeptide.

Question 30

Outline the process of transcription

Answer 30

1. DNA Helicase unwinds DNA molecule, hydrogen binds break 2.RNA nucelotides allign opposite complimentary DNA nucleotides 3. RNA Polymerase attaches to beginning of DNA molecule, moves along template strand forming phosphodiester bonds and synthesising an MRNA molecule 4.Behind RNA moleucle DNA rejoins 5.mRNA carries code out of nucleus and attaches to ribosome.

Question 31

Define translation

Answer 31

The second stage of protein synethesis where mRNA attached to a ribosome that reads its code whilst amino acids on tRNA molecules join to form a polypeptide chain.

Question 32

Outline the process of translation

Answer 32

1.Initation- ribosome attaches to mRNAat start codon 2.Ribosome moves along reading code, tRNA attach to specific amino acids transporting them to the ribosome where complimentary base pairing of anticodon to codon occurs. 3.Elongation- peptide bonds form between adjacent amino acids via condensation reactions, forming polypeptide chain. Amino acid activation occurs 4.Termination-This repeats until stop codon, Molecules seperate. 5. Polypeptide modification-bfolding/combining polypeptide chains to form secondary, tertiary or quaternary proteins.

Question 33

What determins the amino acids carried by the tRNA molcule

Answer 33

The sequence of bases on the anticodon. EG Anticodon squence=CCC, then complimentary codon is GGG, GGG is the amino acid glysine

Question 34

1 gene= ???

Answer 34

1 gene codes 1 polypeptide