nucleic acids

Question 1

what 3 components make up the basic structure of a nucleotide?

Answer 1

• phosphate group
• pentose sugar
• nitrogenous base

Question 2

which bases are purines?

Answer 2

• adenine
• guanine

Question 3

which bases are pyrimidines

Answer 3

• uracil
• thymine
• cytosine

Question 4

how are nucleotide chains in DNA held together?

Answer 4

• hydrogen bonds that form between complementary base pairs
• two hydrogen bonds between adenine and thymine
• three bonds between guanine and cytosine

Question 5

what are the structural differences between RNA and DNA?

Answer 5

• single vs double stranded
• uracil vs thymine
• fits through nuclear pores vs doesnt
• deoxyribose vs ribose

Question 6

what is the difference in pairing in DNA vs RNA?

Answer 6

A+T in DNA
A+U in RNA

Question 7

what bonds base pairs?

Answer 7

hydrogen bonds

Question 8

why can’t DNA leave the nucleus?

Answer 8

doesnt fit through nuclear pores

Question 9

why are there free RNA in the cytoplasm?

Answer 9

• repair of nucleic acids
• metabolic functions (ATP synthesis)

Question 10

what bonds forms polynucleotides?

Answer 10

phosphodiester bonds

Question 11

how is DNA formed?

Answer 11

• two antiparallel strands of nucleotides are linked by hydrogen bonds between complementary base pairs
• coils to form a double helix which is strong (vital for reliable info carriage)

Question 12

how many bonds form between A+T?

Answer 12

2

Question 13

how many bonds form between G+C?

Answer 13

3

Question 14

what is semi conservative replication?

Answer 14

in a replicated DNA molecule, one strand is from the original DNA and one is newly formed

Question 15

replication process

Answer 15

• strands unwind and unzip with DNA helicase
• each strand is a template
• primase catalyses formation of primer from RNA nucleotides
• DNA polymerase joins DNA nucleotides from 5’ to 3’ end (leading strand - made continuously)
• lagging strand is made from okazaki fragments placed between 2 primers
• DNA ligase reforms the hydrogen bonds

Question 16

why is DNA in long strands?

Answer 16

more information

Question 17

why are there complementary base pairs?

Answer 17

faithful DNA replication and formation of hydrogen bonds

Question 18

Why are hydrogen bonds useful?

Answer 18

easy to break and replace

Question 19

what is a codon?

Answer 19

triplet code

Question 20

what is an amino acid coded by

Answer 20

base triplet code

Question 21

what is meant by degenerate?

Answer 21

more than one codon per amino acid

Question 22

why is kiwi blended in extraction?

Answer 22

separate cells

Question 23

why is liquid detergent added?

Answer 23

it breaks open cell surface membranes and releases DNA

Question 24

why is solution heated?

Answer 24

breaks proteins around DNA

Question 25

why is alcohol added?

Answer 25

less dense so causes DNA to rise

Question 26

what is transcription and where does it occur?

Answer 26

- DNA codes for RNA and forms mRNA molecules - occurs in nucleus

Question 27

what is translation and where does it occur?

Answer 27

- conversion of mRNA into amino acids - occurs in the ribosomes

Question 28

what is mRNA?

Answer 28

- messenger RNA - copy of the coding strand

Question 29

what is tRNA?

Answer 29

- transfer RNA - each one is specific for one amino acid

Question 30

process of transcription

Answer 30

- hydrogen bonds are broken between base pairs - DNA uncoils into coding strand (sense strand runs 5' to 3') and template strand (antisense strand runs 3' to 5') - free nucleotides line along the complementary bases of the antisense strand and create phosphodiester bonds with adjacent nucleotides - this forms mRNA which is almost identical to sense strand

Question 31

which way does RNA polymerase move

Answer 31

3' to 5' of template strand but 5' to 3' end of the new mRNA molecule

Question 32

process of translation

Answer 32

- ribosome binds to mRNA and moves in 5' to 3' direction until a start codon - read one codon at a time - anticodons on tRNA are complementary to mRNA and carry a speciifc amino acid - peptidyl transferase catalyses formation of peptide bonds between adjacent amino acids continues until it reaches a stop codon

Question 33

what processes is ATP used in?

Answer 33

- synthesis - transport - movement

Question 34

why is ATP the universal energy currency?

Answer 34

- present in all organisms - releases energy in small, manageable quantities

Question 35

how are two polynucleotide chains held together?

Answer 35

- hydrogen bonds between complementary base pairs - phosphodiester bonds in the backbone - purines pair with pyramidines

Question 36

what are two enzymes in replication (not ligase) and their functions?

Answer 36

- DNA helicase unwinds and unzips DNA strand - DNA polymerase forms phosphodiester bonds between adjacent nucleotides