3.8 - Nucleic Acid

Question 1

What are the 2 types of nucleic acids?

Answer 1

RNA and DNA

Question 2

What is the role of DNA?

Answer 2

Storage and transfer of genetic information and polypeptide synthesis

Question 3

What elements are present in:

1. Carbohydrates
2. Lipids
3. Proteins
4. Nucleic Acids

Answer 3

1. Carbs: CHO
2. Lipids: CHO
3. Proteins: CHONS
4. Nucleic Acid: CHONP

Question 4

What are the monomers of nucleic acids?

Answer 4

Nucleotides

Question 5

What are the 3 components of nucleic acids?

Answer 5

• Pentose monosaccharide
• Phosphate group (PO4 2-), inorganic acidic
• Nitrogenous base (1 or 2 carbon rings + nitrogen)

Question 6

How are nucleotides linked bonded?

Answer 6

• Condensation reactions forming phosphodiester bonds to make a polynucleotide
• Phosphodiester bonds:
  
  • Phosphate at 5’ of one nucleotide forms a covalent bond with hydroxyl group of 3’ (on a sugar) of another nucleotide.
  • This is known as a sugar phosphate backbone (a base is attached to each sugar)
• They can be broken by hydrolysis

Question 7

Describe the features of the 4 DNA nucleotides

Answer 7

Purines

• Bases adenine and guanine
• Larger bases and double carbon ring structure

Pyrimidines

• Bases thymine and cytosine
• Smaller bases and single carbon ring structure

Question 8

Describe the structure of the DNA.

Answer 8

• Hydrogen bonds form between the complementary base pairs on two antiparallel polynucleotides
• Known as antiparallel because the strands run in opposite directions - 5’ to 3’ and 3’ to 5’
• The molecule twists to form a helix

Question 9

What are the base pairing rules?

Answer 9

• Adenine - Thymine (2 H-bonds)
• Cytosine - Guanine (3 H-Bonds)
• Smaller pyrimidines bond to larger purines to maintain distance and keep the backbone strands parallel

Question 10

What are the structural differences between DNA and RNA?

Answer 10

• Both polynucleotides
• Both have a sugar, phosphate and nitrogenous base
  
  • Common nitrogenous bases: adenine, guanine, cytosine
• Sugar: RNA has ribose | DNA has deoxyribose
• Bases: RNA has uracil instead of thymine (which is in DNA)
• 3 types of RNA: mRNA, tRNA, rRNA

Question 11

What is the role of RNA?

Answer 11

• Transfer genetic info of DNA to proteins that make up enzymes
• DNA is too large to leave the nucleus for protein synthesis, mRNA copies a section of the strand to leave the nucleus.
• RNA leaves to ribosome to perform protein synthesis

Question 12

What is the different base in RNA?

Answer 12

Uracil instead of thymine A-U

Question 13

What happens to RNA after protein synthesis?

Answer 13

• RNA molecule degrades in cytoplasm
• Phosphodiester bond hydrolysed
• RNA nucleotides released and reused.