Module 2 - Foundations In Biology: Nucleotides and Nucleic Acids

Question 1

Nucleotide

Answer 1

• the monomer of DNA and RNA
• contains a pentose sugar , phosphate group and nitrogenous base

Question 2

Nitrogenous base

Answer 2

• a nucleotide component
  -includes adenine,guanine,cytosine, thymine and uracil
• DNA has thymine , RNA has uracil

Question 3

DNA nucleotide

Answer 3

• The monomer of DNA and
• contains a deoxyribose sugar , phosphate group and nitrogenous base

Question 4

Polynucleotide

Answer 4

• DNA polymer
• Many nucleotides joined together via condensation reactions
• joined by phosphodiester bonds

Question 5

Phosphodiester bond

Answer 5

• bond joined two nucleotides together
• forms between a phosphate group and the pentose sugar

Question 6

Complementary base pairs

Answer 6

• the base pairs that align opposite each other and form hydrogen bonds
• A and T/U
• G and C

Question 7

Ribose

Answer 7

• pentose sugar
• found in RNA nucleotides and ATP

Question 8

Uracil

Answer 8

Nitrogenous base
- found in RNA instead of thymine

Question 9

Purines and pyrimidines

Answer 9

• purines are two carbon rings structures (e.g adenine and guanine)
• pyrimidines are one carbon rings structures (e.g. cytosine ,thymine and uracil

Question 10

tRNA

Answer 10

• found only in the cytoplasm
• single stranded but folded to create a shape that looks like a cloverleaf
• held in place by Hydrogen bonds

Question 11

mRNA

Answer 11

• a copy of a gene
• single-stranded polymer of RNA

Question 12

rRNA

Answer 12

• rRNA combines with proteins to make ribosomes

Question 13

DNA template strand

Answer 13

• a DNA strand that is used to make a new DNA copy
• both DNA strands in the double helix are used as templates in DNA replication

Question 14

DNA polymerase

Answer 14

• an enzyme in DNA replication
• joins together adjacent nucleotides

Question 15

DNA structure

Answer 15

• Stable structure - covalently bonded sugar-phosphate backbone and double helix
• Double-stranded - semi-conservative replication can occur
• weak hydrogen bonds - strand separation during replication

Question 16

DNA function

Answer 16

• large molecules - carries lots of information
• complementary base pairings - allows identical copies to be made

Question 17

DNA precipitation and extraction

Answer 17

Detergent → Breaks cell & nuclear membranes to release DNA
• Protease enzyme → Digests proteins (e.g. histones) to purify DNA
• Cold ethanol/isopropanol → Precipitates DNA (insoluble in cold alcohol → forms visible white strands)

Question 18

DNA helicase

Answer 18

• enzyme that breaks hydrogen bonds between bases
• causes the two strands to separate
• used in DNA replication and transcription

Question 19

ATP

Answer 19

• contains adenine, the pentose sugar ribose and three inorganic phosphate ion groups
• it is an immediate source of energy for biological processes

Question 20

Phosphorylation

Answer 20

• the addition of an inorganic phosphate group to a molecule
• makes the molecule more reactive (it gains energy)
• For example ADP can be phosphorylated to form ATP

Question 21

ATP hydrolase

Answer 21

Enzyme that catalyses the hydrolysis of ATP into ADP +Pi

Question 22

ATP synthase

Answer 22

Enzyme that catalyses the synthesis of ATP from ADP and Pi

Question 23

Stages of DNA replication

Answer 23

• DNA helicase breaks hydrogen bonds in double helix are used
• free-floating nucleotides align opposite to their complementary base on the template strand
• hydrogen bonds form between base pairings
• DNA polymerase joins adjacent nucleotides together, forming phosphodiester bonds

Question 24

Degenerate genetic code

Answer 24

Some amino acids are coded for by more than one triplet of bases

Question 25

Universal genetic code

Answer 25

The same triplet of bases codes for the same amino acid in all organisms

Question 26

Non-overlapping genetic code

Answer 26

Each base in a gene is only part of one triplet of bases that codes for one amino acid

Question 27

Colorimeter

Answer 27

- measures light abosrbance (how ,cut light is absorbed) or light transmission (how much light passes through) a substance - colorimetry can be used in any enzyme-catalysed reaction that involves colour change

Question 28

Introns

Answer 28

Sequences of bases in a gene that do no code for aminoacids and therefore polypeptide chains - these get removed , spliced, out of mRNA molecules before translation

Question 29

Exons

Answer 29

Sequence of bases in a gene that codes for sequences of amino acids

Question 30

Transcription

Answer 30

- DNA helicase breaks hydrogen bonds between DNA base pairs - The double helix unwinds - One strand acts as a template -Free mRNA nucleotides align opposite complementary bases - RNA polymerase joins adjacent RNA nucleotides forming phosphodiester bonds - mRNA is spliced and leaves nucleus

Question 31

Translation

Answer 31

- mRNA attaches to small subunit of ribosome at start codon - tRNA with complementary anticodon aligns opposite codon mRNA - two amino acids are joined via a peptide bond catalysed by an enzyme and ATP - Ribosome moves along mRNA until a stop codon is reached