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A Level Biology > Module 2.1.3 Nucleotides & Nucleic Acids > Flashcards

Module 2.1.3 Nucleotides & Nucleic Acids Flashcards

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1
Q

What are the 2 types of nucleic acid?

A

DNA (deoxyribonucleic acid) & RNA (ribonucleic acid)

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2
Q

Why are nucleic acids vital molecules?

A

They carry the genetic code for all living things

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3
Q

What elements do nucleic acids contain?

A

Carbon, hydrogen, oxygen, nitrogen & phosphorus (CHONP)

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4
Q

What is a polynucleotide?

A

A molecule made of many nucleotide monomers joined by covalent bonds

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5
Q

What is a nucleotide?

A

A biological molecule that participates in nearly all biochemical processes.
They form the monomers of nucleic acids (DNA & RNA) & they help regulate metabolic pathways

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6
Q

What does it mean when a nucleotide becomes phosphorylated?

A

When a nucleotide contains more than 1 phosphate group (ADP & ATP)

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7
Q

What is the structure of a nucleotide?

A

A pentose sugar molecule (either ribose/deoxyribose)
An organic nitrogenous base (Adenine, Cytosine, Thymine, Guanine & Uracil)
A phosphate group

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8
Q

What is an organic nitrogenous base?

A

A nitrogen-containing organic compound that is a constituent of nucleotides (there’s 5)

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9
Q

What is the difference between a ribose & deoxyribose pentose sugar?

A

Ribose has 2 OH molecules
Deoxyribose has 1 OH molecule

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10
Q

Which bases are present in DNA nucleotides?

A

Adenine
Thymine
Cytosine
Guanine

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11
Q

Which bases are present in RNA nucleotides?

A

Adenine
Uracil
Cytosine
Guanine

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12
Q

What is a pyrimidine?

A

A smaller base that contains a single carbon ring structure

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13
Q

Which bases are pyrimidines?

A

Thymine, Uracil & Cytosine

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14
Q

What is a purine?

A

A larger base that contains a double carbon ring structure

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15
Q

Which bases are purines?

A

Adenine & Guanine

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16
Q

Why do we need energy?

A

Synthesis -> to build large complex molecules from smaller ones
Transport -> active transport
Movement -> protein muscle fibres in muscle cells require energy to contract

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17
Q

What is ATP?

A

Adenosine Triphosphate
A compound that transfers energy within cells
A RNA nucleotide that contains 3 phosphate groups

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18
Q

How does ATP release energy?

A

Energy is needed to break the bonds & is released when bonds are formed
A small amount of energy is needed to break the weak bond holding out the last phosphate group in ATP
A large amount of energy is released when this phosphate is involved with other reactions with bond formation

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19
Q

What is the equation for ATP releasing energy?

A

ATP + H20 -> ADP + Pi + Energy

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20
Q

What is the word equation for ATP releasing energy?

A

Adenosine Triphosphate + Water -> Adenosine Diphosphate + Inorganic Phosphate + 30.5kjmol-1

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21
Q

Why can ATP not be stored easily long term?

A

It is a relatively unstable molecule

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22
Q

How is energy stored in the body?

A

As fats & carbohydrates

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23
Q

How is ATP made during cellular respiration?

A

Fats & carbohydrates are broken down to release ATP

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24
Q

What are the properties of ATP?

A

Small -> can easily move in & out of cells
Water soluble -> energy requiring reactions can happen in aqueous environments
Contains a bond between phosphates with intermediate energy -> large enough to be used in cellular reactions, not large enough to be wasted as heat
Easily regenerated -> can be recharged with energy

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25
Q

What is DNA?

A

Deoxyribonucleic acid -> a double-stranded polynucleotide which carries the information for protein synthesis (contains the pentose sugar deoxyribose)

26
Q

How does DNA form?

A

Nucleotides are joined in condensation reactions to form a polynucleotide chain. This happens as the phosphate group of one joins to the sugar molecule of the next which makes the sugar-phosphate backbone of the DNA molecule. This creates a single chain of DNA with the bases projecting out of the chain.

27
Q

What is the structure of DNA?

A

The nucleic acid forms when the 2 polypeptide chains join together by hydrogen bonds between the nitrogenous bases, to form a double stranded molecule.

28
Q

What is complementary base pairing?

A

Adenine & Guanine (purines) always pair up with Thymine & Cytosine (pyrimidines) as this is the only way the hydrogen bonds can form between the bases in DNA

29
Q

How many hydrogen bonds does adenine form with thymine in DNA?

A

2

30
Q

How many hydrogen bonds does guanine form with cytosine in DNA?

A

3

31
Q

Why is complementary base pairing important?

A

So the molecule is stable and consistent in width

32
Q

Do both DNA strands run parallel or antiparallel?

A

Anti-parallel

33
Q

Are bases on nucleotides hydrophobic or hydrophillic?

A

Hydrophobic

34
Q

How are polynucleotides synthesised?

A

Formation of phosphodiester bonds between nucleotides

35
Q

Why does DNA need to replicate?

A

Each new cell has the full amount of DNA before cell division
Making new cells for growth & repair
Reproduction
Must form 2 sister chromatids so it has to be accurate

36
Q

What is DNA replication controlled by?

A

Enzymes

37
Q

What is Helicase?

A

An enzyme that catalyses the breaking of hydrogen bonds between the nitrogenous pairs of bases in a DNA molecule

38
Q

When helicase breaks a DNA molecule, what are the products?

A

2 single strands of DNA with exposed nucleotide bases

39
Q

What is DNA polymerase?

A

An enzyme that catalyses the formation of DNA from activated deoxyribose nucleotides using single stranded DNA as a template & forms phosphodiester bonds between the nucleotides

40
Q

Which direction do the nucleotide bases add?

A

5’ to 3’

41
Q

What is the function of DNA ligase?

A

Joins together short sections of the lagging strand

42
Q

What is the function of the single strand binding protein?

A

Keeps the separated DNA strands apart during replication

43
Q

How does DNA replicate?

A

DNA helicase causes hydrogen bonds to break which separates the 2 strands & DNA unwinds. Free nucleotides then join to the complementary unpaired bases. Hydrogen bonds then reform between the bases & DNA polymerase catalyses the formation of phosphodiester bonds between the nucleotides

44
Q

What is semi-conservative DNA replication?

A

Half the DNA molecule is old DNA & half is made of new DNA

45
Q

Is the plasmid DNA in prokaryotes semi-conservatively replicated?

A

Yes

46
Q

How does DNA undergo continuous replication?

A

DNA polymerase always moves along the template strand in the same direction & can only bind to the 3 prime end so travels in the 3 to 5 prime direction. DNA polymerase has to replicate each of the template strands in opposite directions. the strand that is unzipped from the 3 prime end is continuously replicated & is the leading strand that undergoes continuous replication.

47
Q

How does DNA undergo discontinuous replication?

A

The other strand is unzipped from the 5 prime end so DNA polymerase has to wait until a section of the strand has been unzipped & then work back along. This results in DNA being produced in okazaki fragments which then have to be joined. This strand is the lagging strand & undergoes discontinuous replication

48
Q

Describe the stages of DNA replication?

A

1) DNA twists by the action of DNA helicase
2) Hydrogen bonds between base pairs break
3) Both strands act as a template
4) Free nucleotides align to the DNA & complementary base pair
5) Hydrogen bonds reform between the base pairs
6) The sugar-phosphate backbone forms, joining by a phosphodiester bond
7) This is catalysed by DNA polymerase
8) Two new DNA molecules form, semi-conservatively replicated

49
Q

Why is is important that DNA is accurately replicated?

A

To make sure that genetic information is conserved each time DNA in a cell is replicated

50
Q

What is a mutation?

A

A change to the DNA base sequence which may affect the phenotype of the organism

51
Q

What is a transition mutation?

A

A type of substitution mutation where 1 pyrimidine is swapped for a different pyrimidine/1 purine swapped for a different purine

52
Q

What is a transversion mutation?

A

Where a pyrimidine is swapped for a purine/ a purine swapped for a pyrimidine

53
Q

Is a transition mutation more or less common than a transversion mutation?

A

More common

54
Q

What are the 3 different types of substitution mutation where it occurs in a region of the gene that is involved in coding?

A

Silent
Missense
Nonsense

55
Q

What is a Silent mutation?

A

The triplet codes for the same amino acid

56
Q

What is a Missense mutation?

A

The triplet codes for a different amino acid (if it’s chemically similar it may have no noticeable effect -> neutral mutation)

57
Q

What is a Nonsense mutation?

A

The triplet codon codes for a stop codon

58
Q

What are frameshift mutations?

A

Mutations that alter the ‘reading frame’ of the gene downstream of the mutation which affects the structure of the protein

59
Q

What are 2 examples of frameshift mutations?

A

Insertion & deletion mutations

60
Q
A

A Level Biology (18 decks)

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