1.5 Nucleic Acids & 1.6 ATP

Question 1

What are components of a nucleotide?

Answer 1

• pentose sugar
• phosphate group
• nitrogen-containing base

Question 2

Name pentose sugars in DNA & RNA

Answer 2

DNA: deoxyribose
RNA: ribose

Question 3

State role of DNA in living cells

Answer 3

Base sequence of genes codes for functional RNA & amino acid sequence of polypeptides
Genetic information determines inherited characteristics= influences structure & function of organisms

Question 4

State role of RNA in living cells

Answer 4

mRNA: complementary sequence to 1 gene from DNA with introns (non-coding regions) spliced out. Codons can be translated into a polypeptide by ribosomes
rRNA: component of ribosomes (along with proteins)
tRNA: supplies complementary amino acid to RNA codons during translation

Question 5

How do polynucleotides form?

Answer 5

Condensation reactions between nucleotides form strong phosphodiester bonds (sugar-phosphate backbone)

Question 6

Describe structure of DNA

Answer 6

double helix of 2 polynucleotide strands (deoxyribose)
H-bonds between complementary purine & pyrimidine base pairs on opposite strands:
adenine (A) + thymine (T)
guanine (G) + cytosine (C)

Question 7

Which bases are purine and which are pyrimidine?

Answer 7

A & G = 2-ring purine bases
T & C & U = 1-ring pyrimidine bases

Question 8

Name complementary base pairs in DNA

Answer 8

2 H-bonds between adenine (A) + thymine (T)
3 H-bonds between guanine (G) + cytosine (C)

Question 9

Name complementary base pairs in RNA

Answer 9

2 H- bonds between adenine (A) + uracil (U)
3 H-bonds between guanine (G) + cytosine (C)

Question 10

Relate structure of DNA to its function

Answer 10

• sugar-phosphate backbone & many H-bonds provide stability
• long molecule stores lots of information
• helix is compact for storage in nucleus
• base sequence of triplet codes for amino acids
• double-stranded for semi-conservative replication
• complementary base pairing for accurate replication
• weak H-bonds break so strands replicate for replication

Question 11

Describe structure of messenger RNA (mRNA)

Answer 11

• long ribose polynucleotide (but shorter than DNA)
• contains uracil instead of thymine
• single stranded & linear (no complementary base pairing)
• codon sequence is complementary to exons of 1 gene from 1 DNA strand

Question 12

Relate structure of mRNA to its functions

Answer 12

• breaks down quickly so no excess polypeptide forms
• ribosomes can move along strand & tRNA can bind to exposed bases
• can be translated into a specific polypeptide by ribosomes rRNA

Question 13

Describe structure of transfer RNA (tRNA)

Answer 13

• single strand of about 80 nucleotides
• folded into clover shape (some paired bases)
• anticodon on one end amino acid binding site on the other:
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