Nucleic Acids

Question 1

Nucleotide

Answer 1

• Phosphate group
• Pentose sugar
• Nitrogenous base

Question 2

Pentose sugars

Answer 2

• Deoxyribose has only a hydrogen atom at C2

- Ribose has a OH group at C2

Question 3

Nitrogenous (Organic) bases

“As Pure As a Gold double ring”

Answer 3

Pyrimidine bases:

• Cytosine (Guanine)
• Thymine (Adenine)
• Uracil (Adenine)

Double ring purine:

• Adenine (Thymine/Uracil)
• Guanine (Cytosine)

Question 4

Phosphate group

Answer 4

PO4 is bound to the pentose sugar in a nucleotide at C5 (Very electronegative)

Question 5

ATP structure

Answer 5

• Adenine
• Ribose
• Three phosphate groups

Question 6

ATP Synthesis

ADP + Pi ——> ATP

Answer 6

• Catalysed by the enzyme ATP synthetase
• *Phosphorylation of ADP (2 phosphate groups)
• The reaction requires energy (ENDERGONIC)

*Phosphorylation: The adding of a phosphate group

Question 7

ATP Hydrolysis

ATP ——> ADP + Pi

Answer 7

• Catalysed by the enzyme ATPase
• One mole of ATP liberates 30.6KJ of energy
• The reaction releases energy (EXERGONIC)

Question 8

ATP Properties/Uses

Answer 8

Universal energy currency:
-Used by all species of organism to provide energy for biochemical reactions

Intermediate energy source:

• ATP releases less energy than a glucose molecule, so energy is released in more manageable amounts
• Only one enzyme is needed to release energy from ATP

Question 9

DNA Structure

Answer 9

• Double stranded polynucleotide twisted into double helix
• Two strands are anti parallel
• One strand runs in a 5’ to 3’ direction while the other runs in a 3’ to 5’ direction

Contains:

• Phosphate group
• Deoxyribose sugar
• Nitrogenous base (Adenine/Thymine/Cytosine/Guanine)

All joined by covalent bonds through condensation reactions

Question 10

DNA Bonds

Answer 10

• Phosphodiester bond between phosphate group and the pentose sugar of neighbouring nucleotide
• Weak hydrogen bonds between bases, but structure is strong due to high number of them. H-bonds are weak as they can be broken easily during transcription

Question 11

Complementary Base Pairing DNA

Answer 11

-A Purine (2 rings) always pairs with a Pyrimidine (1 ring), making a uniform distance of 3 rings

Pairing:
Adenine - Thymine (2 Hydrogen bonds)
Cytosine - Guanine (3 Hydrogen bonds)

Question 12

RNA Structure

Answer 12

-Single stranded polynucleotide twisted into single helix

Contains:

• Phosphate group
• Ribose sugar
• Nitrogenous base (Adenine/Uracil/Cytosine/Guanine)

Question 13

Transfer RNA (tRNA)

Answer 13

• Folded into a clover leaf shape
• Amino acid binding site is at the 3’ end
• Anticodon on tRNA ( bottom end of clover structure) complementary to codon on mRNA

Found in the cytoplasm and carries the amino acids to the ribosome during translation.

Question 14

Messenger RNA (mRNA)

Answer 14

-Linear structure (Long straight strand)

Carries the DNA code from nucleus to the cytoplasm, where it associates with a ribosome

Question 15

Ribosomal RNA (rRNA)

Answer 15

• Found free in cytoplasm or bound to RER
• A component of ribosomes
• Folded into a spherical shape

Ribosomes are the site of translation (Protein synthesis)

Question 16

Differences between the 3 types of RNA

Answer 16

mRNA: Linear structure and carries DNA from nucleus to cytoplasm

rRNA: Folded into a spherical shape and are the site of protein synthesis

tRNA: Folded into a clover leaf shape and carries the right amino acids to the ribosome during translation