1.5 - Nucleic Acids and Their Functions

Question 1

What is a nucleic acid made of?

Answer 1

Monomers called nucleotides

Question 2

What is the term for many nucleotides?

Answer 2

Polynucleotide

Question 3

What are the 3 components of nucleotides?

Answer 3

• phosphate group
• a pentose sugar
• a nitrogenous organic base

Question 4

How are the compenents of nucleotides combined?

Answer 4

Combined by condensation reactions

Question 5

What are the 2 types of bases?

Answer 5

Pyrimidine and purine

Question 6

What is a pryrimidine base?

Answer 6

Single ring thymine cytosine and uracil

Question 7

What is a purine base?

Answer 7

Double ring adenine and guanine

Question 8

What are heterotrophic organisms?

Answer 8

Animals that get chemical energy from food

Question 9

What are autotrophic organisms?

Answer 9

Plants that get chemical energy from light

Question 10

What is ATP?

Answer 10

Stands for adenosine-triphosphate and is an energy carrier

Question 11

What is ATP made up of?

Answer 11

Adenine, ribose sugar and 3 phosphate groups

Question 12

How does ATP distribute energy?

Answer 12

• the enzyme ATPase hydrolyses the bond between the second and third phosphate groups in ATP, removing the 3rd phosphate group, leaving only 2
• turns into ADP (adenosine-diphosphate) and an inorganic phosphate ion, with the release of energy
• its an exergenic reaction releasing 30.6kj when this bond is broken

Question 13

What are the advantages of having ATP as an energy supplier?

Answer 13

• single reaction that releases energy immediately, unlike glucoses many reactions
• only one enzyme ATPase is needed to break down ATP, whilst glucose has many
• ATP releases energy in small amounts, whilst glucose releases it all at once
• ATP provided energy for a range of reactions, increasing efficiency and control by the cell

Question 14

What are the 5 roles of ATP?

Answer 14

• metabolic processes
• active transport
• movement
• nerve transmission
• secretion

Question 15

What is the structure of DNA?

Answer 15

• 2 polynucleotide strands in a double helix
• pentose sugar is deoxyribose
• 4 bases = purine adenine and guanine, pyrimidine cytosine and thymine
• deoxyribose sugar and phosphate group forms backbone
• AT-GC complimentary base pairing (hydrogen bonds)
• DNA is tightly coiled within a chromosome
• the strands are antiparallel (parallel but facing in opposite directions)

Question 16

Why is DNA suited to its function?

Answer 16

• very stable molecule so information remains unchanged
• large molecule so carries alot of information
• the 2 strands can separate as they are held together by hydrogen bonds
• base pairs are found in the inside, therefore are protected by the sugar-phosphate backbone

Question 17

What is the structure of RNA?

Answer 17

• single stranded polynucleotide
• pentose sugar ribose
• purine base, adenine and guanine, pyrimidine base cytosine and uracil

Question 18

What are the 3 types of RNA?

Answer 18

messenger RNA (mRNA)
ribosomal RNA (rRNA)
transfer RNA (tRNA)

Question 19

What is messenger RNA?

Answer 19

• mRNA is along single stranded molecule
• synthesised in the nucleus
• carries the genetic code from the nucleus to the ribsomes in the cytoplasm

Question 20

What is ribosomal RNA?

Answer 20

• rRNA is found in the cytoplasm
• large, complex molecules
• ribosomes are made of ribosomal DNA and protein
• they are the site of translation of the genetic code into protein

Question 21

What is transfer RNA?

Answer 21

• tRNA is a small single stranded molecule
• cloverleaf shape
• molecules of tRNA transport specific amino acids to the ribosomes in protein synthesis

Question 22

What are the 2 functions of DNA?

Answer 22

• replication
• protein synthesis

Question 23

What is replication of DNA?

Answer 23

IF 2 strands of a double helix are separated , 2 identical double helixes can be formed, as each parent strand can act as a template for the synthesis of a new complimentary strand

Question 24

What is protein synthesis in DNA?

Answer 24

The sequences of bases represents the information carried in DNA and determines the sequence of amino acids in proteins

Question 25

What are the 3 types of DNA replication?

Answer 25

• Conservative replication
• Semi- conservative replication
• Dispersive replication

Question 26

What is conservative replication?

Answer 26

Where the parental double helix remains intact, and a whole new double helix is made

Question 27

What is semi-conservative replication?

Answer 27

The double helix separates into 2 strands, each of which acts as a template for synthesis of a new strand

Question 28

What is dispersive replication?

Answer 28

The 2 new helixes contain fragments from both strands of the parental double helix

Question 29

What is the genetic code?

Answer 29

• a triplet code
• 3 pairs of bases codes for one amino acid

Question 30

How many possible amino codes are there?

Answer 30

64 (4 bases cubed)

Question 31

What in mRNA ends the code?

Answer 31

Codons mark the end of a coding sequence

Question 32

What is an intron?

Answer 32

Non-coding nucleotide sequence in DNA and pre-mRNA that is removed from pre-mRNa to produce mature mRNA (useless as its just separating code)

Question 33

What is an exon?

Answer 33

Nucleotide sequence in RNA and pre-mRNA that remains present in the final mature mRNA, after introns have been removed (the important stuff)

Question 34

What are the 2 stages of protein synthesis?

Answer 34

• transcription
• translation

Question 35

What is transcription?

Answer 35

One strand of the DNA acts as a template for the production of mRNA, a complimentary part of the DNA sequence. It occurs in the nucleus

Question 36

What is translation?

Answer 36

The mRNA acts a template to which complementary tRNA molecules attach, and the amino acids they carry are linked to form polypeptide
Occurs in ribosomes in the cytoplasm