module 2.1.3 - nucleotides and nucleic acids Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

what are the 3 components of a nucleotides

A

a phosphate group, a pentose sugar and an organic nitrogenous base

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what are the purine bases (2 rings) in RNA and DNA

A

adenine and guanine for both RNA and DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the pyrimidine bases (1 ring) in RNA and DNA

A

cytosine and uracil in RNA
cytosine and thymine in DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what are the pentose sugars in RNA and DNA

A

ribose in RNA and deoxyribose in DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the 3 types of RNA

A

messenger RNA, transfer RNA and ribosomal RNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what does mRNA do

A

it carries the copy of the gene out of the nucleus and transfers it to the ribosomes where the code is for protein synthesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what does tRNA do

A

it transports amino acids to the ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what does rRNA do

A

it make up the ribosomes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is the structure of RNA

A

it is a polynucleotide, non - helical, usually single stranded and much shorter than DNA
bases are complementary: adenine to uracil (2 H bonds), cytosine to guanine ( 3 H bonds)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what is the structure of DNA

A

it is found in the nucleus. the 2 polynucleotide strands lies in opposite directions (anti-parallel) and are joined together to form double helix. each purine is paired to a pyrimidine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is the structure of ATP and ADP

A

they both contain a pentose sugar (ribose), a nitrogenous base (adenine)
ADP has 2 phosphate groups but ATP has 3 phosphate groups

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is a polynucleotide and how is it formed

A

formed when nucleotides bind together in a long chain
- the bonds are formed by condensation and are called phosphodiester bonds. they can be broken by hydrolysis
- these bonds form between the sugar of one nucleotide and the phosphate group of another, making a sugar–phosphate ‘backbone’
- leaves the organic base of each nucleotide sticking out to the side of the chain

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

explain the process of semi conservative replication

A
  1. one double-stranded molecule untwists and the hydrogen bonds between the base pairs break —-> catalysed by the enzyme helicase
  2. the two polynucleotide chains separate, exposing the bases
  3. each strand is then used as a template to make two new double strands
  4. new nucleotides pair to the exposed bases on both strands, using their complementary shapes to pair correctly
    5 each new chain of nucleotides is bonded together by the enzyme DNA polymerase to form the second half of each DNA molecule
  5. the enzyme also checks that the pairing of the bases is correct
  6. each new molecule then twists to form its double helix
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is a mutation

A

when an incorrect base may be bonded into place

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the pattern of mutation

A

random and spontaneous

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what are 3 consecutive bases called and what does it code for

A

triplet and codes for 1 amino acid

17
Q

what is a degenerate codon

A

amino acids that coded for by more than 1 triplet

18
Q

how many possible triplet codes are there

A

64

19
Q

from this point, what is the process of protein production

A

a sequence of amino acids forms one polypeptide
- the length of DNA that codes for one polypeptide is called a gene
- one gene codes for one polypeptide. This may form a protein
- if the protein contains more than one polypeptide (i.e. it has a quaternary structure), there will be more than one gene used to code for the protein

20
Q

what are the 2 stages of polypeptide synthesis

A

transcription and translation

21
Q

what happens in the first one (not description, definition)

A

reading the code and producing a messenger molecule to carry the code out to the cytoplasm

22
Q

what happens in the second (not description, definition)

A

converting the code to a sequence of amino acids

23
Q

describe what happens during transcription

A

The genetic code is held in the nucleus. The DNA molecule is too large to leave the nucleus, so a smaller messenger molecule is made called messenger RNA (mRNA). The double-stranded DNA molecule is unwound and split by the action of the enzyme RNA polymerase, which breaks the hydrogen bonds holding the two strands together. This exposes the sequence of bases in the gene. The coding strand carries the genetic code and the complementary strand is a non-coding strand sometimes called the antisense strand or the template strand, which is used to build a copy of the coding strand called messenger RNA (mRNA). It has an identical sequence of bases to the coding strand of the gene, except that the thymine is replaced by uracil. Each triplet of bases on the mRNA is called a codon. The enzyme RNA polymerase joins the bases of the RNA to produce a complete single-stranded molecule. The base pairing is given in the table.

The molecule of mRNA detaches from the DNA template and the DNA strands can rejoin to remake the double helix. The mRNA leaves the nucleus via the nuclear pores and enters the cytoplasm

24
Q

describe what happens during translation

A

translation is the conversion of the genetic code to a sequence of amino acids. the mRNA joins on to a ribosome in the cytoplasm (ribosomes consist of ribosomal RNA associated with enzymes). the ribosome contains enough space for two codons at a time. the mRNA slides through the groove between the two components of the ribosome. as each codon enters the ribosome, it is used to position the next amino acid. amino acids must be activated — they are combined with a specific molecule of transfer RNA (tRNA) that has a specific base triplet called the anticodon. the anticodon of the tRNA is complementary to a codon on the mRNA. ATP is used in this activation process. the amino acids attached to tRNA molecules are aligned with the correct part of the mRNA by the complementary pairing of the bases in the codon and anticodon. enzymes bind the amino acids together in a chain by condensation reactions to create a growing polypeptide chain. the tRNA molecule is then released to be reused. when the ribosome reaches the end of the mRNA, the complete polypeptide chain is released and folds to form the secondary and tertiary structure of the protein. some proteins need to be activated by cyclic AMP (cAMP), which interacts with the new protein to alter its three-dimensional shape. this makes the protein a better shape to fit their complementary molecules