Nucleic acids and ATP

Question 1

Name the pentose sugars in DNA & RNA

Answer 1

Deoxyribose
Ribose

Question 2

State the role of DNA in living cells

Answer 2

Base sequence of genes codes for functional RNA& amino acid sequence for polypeptides

Genetic information determines inherited characteristics = influences structure and functions of organisms

Question 3

State the role of mRna (Type of RNA)

Answer 3

Complementary sequence to 1 gene from DNA with introns (non coding regions) spliced out. Codons can be translated into a polypeptide by ribosomes

Question 4

State the role of rRNA (type of RNA)

Answer 4

Component of ribosomes (along with proteins)

Question 5

State the role of tRNA( type of rna)

Answer 5

Supplies complementary amino acid to mRNA codons during translation

Question 6

Describe the structure of DNA

Answer 6

Double helix of 2 polynucleotide strands (Deoxyribose)
H-bonds between complementary purine and pyrimidine base pairs in opposite strands:
Adrenaline(A) +Thymine(T)
Guanine(G) + Cytosine(C)

Question 7

Which bases are purine and which are pyrimdine

Answer 7

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

Question 8

Name the complementary base pairs in DNA

Answer 8

2 H-bond between
Adrenaline(A) + Thymine (T)

3 H-bonds between Guanine(G)+Cytosine(C)

Question 9

Name the complementary base pairs in RNA

Answer 9

2 H bonds between
Adrenaline (A) + Uracil (U)
3 H bonds between
Guanine(G) + Cytosine (C)

Question 10

Name the complementary base pairs in RNA

Answer 10

2 H bonds between
Adrenaline (A) + Uracil (U)
3 H bonds between
Guanine(G) + Cytosine (C)

Question 11

Relate the structure of DNA to its functions

Answer 11

Sugar-phosphate backbone& many H bonds provide stability
Long molecules stored lots of information
Helix is compact for storage in nucleus
Base sequence of triplets codes for amino acids
Double stranded for semi conservative replication
Complementary bare pairing for accurate replication
Weak H-bonds break so strands separate for replication

Question 12

Describe the structure of messenger RNA (mRNA)

Answer 12

Long ribose polynucleotide (but shorter than DNA)
Contains Uracil instead of thymine
Single stranded and linear (no complementary base pairing)
Codon sequence is complementary to exons of 1 gene from 1 DNA strand

Question 13

Relate the structure of messenger RNA to its functions

Answer 13

Breaks down quickly so no excess polypeptides forms
Ribosomes can move along strand & tRNA can bind to exposed bases
Can be translated into specific polypeptide by ribosomes

Question 14

Describe the structure of transfer RNA(tRNA)

Answer 14

Single strand of about 80 nucleotides
Folded into clover shape
Anticodon on one end ,amino acid binding site on the other
anticodon binds to complementary mRNA codon
Amino acid corresponds to anticodon

Question 15

Order DNA, mRNA and tRNA according to increasing length

Answer 15

tRNA mRNA DNA

Question 16

why did scientists initially doubt that DNA carried genetic code

Answer 16

Chemically simple molecule with few components

Question 17

Why is DNA replication described as semi conservative

Answer 17

Strands from original DNA molecule act as a template
New DNA molecule contains 1 old strand and one new strand

Question 18

Outline the process of semi conservative DNA replication

Answer 18

Dna helicase breaks h bond between pairs
Each strand acts as a a template
Free nucleotides from nuclear sap attattch to exposed bases by compmetary base pairing
DNA polymerase catalyses condensation reactions that join adjacent nucleotides on new strand
H bond reforms

Question 19

Describe the Meselson-Stahl experiment

Answer 19

Bacteria were grown in a medium containing heavy isotope N15 for many generations

Some bacteria were moved to a medium containing light isotope N14.Samples were extracted after 1&2 cycles of DNA replication

Centrifugation formed a pellet. Heavier DNA (bases from N15) settled closer to the bottom of the tube

Question 20

Explain the role of ATP in cells

Answer 20

ATP hydrolyse catalyses ATP—> ADP + Pi
Energy released is coupled to metabolic reaction
Phosphate group phosphorlates compounds to make them more reactive

Question 21

HOW is ATP resynthesysed in cells

Answer 21

ATP synthase catalyses condensation reaction between ADP & Pi
During photosynthesis & respiration

Question 22

Explain why ATP is suitable as the energy currency of cells

Answer 22

High energy binds between phosphate groups
Small amounts of energy released at a time = less energy wasted as heat
Single step hydrolysis=energy available quickly
Readily resynthesised

Question 23

Describe the basic function of DNA in all living cells

Answer 23

Holds genetic information which codes for polypeptides

Question 24

Describe the basic function of RNA in all living cells

Answer 24

Transfers genetic information from DNA to ribosomes

Question 25

Name the two types of molecule from which a ribosome is made

Answer 25

RNA and proteins

Question 26

DRaw and label a dna molecule and an RNA nucelotide

Answer 26

pg 15 in bio with olivia

Question 27

Describe the differnces between a DNA nucelotide and an RNA Nucelotide

Answer 27

DNA nucelotide is deoxyribose whilst in RNA it is rbose
The base for DNA nucelotide is thymine whilst the base for RNA is Uracil

Question 28

Describe how nucelotides join together to form polynucelotides

Answer 28

Condensation reactions,removing water between phosphate group of one nucleotide and deoxyribose/ribose of another forming phospodiester bionds

Question 29

Why did many scientists intially doubt that DNA carried the genetic code

Answer 29

The relative simplictiy of DNA- chemically simple molecule with few componenets

Question 30

Describe the structure of DNA

Answer 30

• Polymer of nucleotides(polynuxelotide)
• Each nucelotide(Nltd) formed from deoxyribose, a phosphate group and a nitrogen containing organic base
• Phosphodiester bonds join adjacent nltds
• 2 polynltd chains held together by hydrogen bonds between specific complemetary base pairs- adenine/thyminand cytosine/guanine
• Double helix

Question 31

Describe the strcuture of MRNA

Answer 31

• Polymer of nltds (polynltd)
• each nltd formed from ribose or a phosphate group and a nitrogen containing organic base
• Bases-Uracil adenine cytosine and guanine
• Phosphodiester bonds join adjacent nltds
• Single helix

nltd=nucelotide
plural with a s at the end

Question 32

Compare and contrast the strcuture of DNA and mRNA

Answer 32

• The pentose sugar in DNA is Deoxyribose whilst in mRNA it is ribose
• DNA has the base Thymine mRNA is Uracil
• DNA is double helix mRNA is single helix
• Long(many nltds) in DNA whilst in mRNA it is short (fewer nltds)
• DNA has hydrpgen bonds/base pairing whilst in mRNA there are none

nltd=nucelotide

Question 33

Suggest how the structure of DNA relates to its function

Answer 33

• Two strands-both can act as templates for semi conservative replication
• Hydrogen bonds between basesare weak-strands can be separated for replication
• Complemmntary base pairing-accruate replkcation
• Many strong bonds between bases- stable/strong molecule
• Double helix with sugar phosphate backbone-protects bases/ hydrogen bonds
• long molecule-stores ots of genetoc information that codes for polypeptides
• double helix)coiled)-compact

Question 34

Suggest how you can use incomplete informatoion about the frrquency of bases on DNA starnds to find the frequency of othe rbases

Answer 34

1. % of adenine in strand 1= % of thymine in strand 2 (and vice versa)
2. % of guaninein strand 1 = % of cytosine in strand 2 (and vice versa)
   because of pecifc ciomplemnatry base pairing between 2 strands