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A Level Biology Paper 1 > Protein Synthesis > Flashcards

Protein Synthesis Flashcards

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1
Q

What does a nucleotide consist of

A

A phosphate group
A pentose sugar
An organic base (ATCG)

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2
Q

What is DNA

A

Deoxyribose nucleic acid
A polymer of DNA nucleotides
A double helix consisting of two polynucleotide strands
Held together by hydrogen bonds
Between complementary base pairs (A and T/C and G)

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3
Q

Explain base pairing

A

A with T
-Purine Adenine always pairs with pyrimidine Thymine, forming two hydrogen bonds
C with G
-Purine Guanine always pairs with Pyrimidine Cytosine, forming three hydrogen bonds

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4
Q

Contrast eukaryotic and prokaryotic DNA

A

E is linear/P is circular
E is associated with histones/P is not
E contains introns/P does not
E is membrane bound (in nucleus)/P is free floating in the cytoplasm (not membrane bound)
E has no plasmids/P has plasmids
E is replicated in the nucleus/P is replicated in the cytoplasm

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5
Q

Similarities between eukaryotic and prokaryotic DNA

A

Contain exons
Phosphodiester bonds
Hydrogen bonds
Polymer of nucleotides

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6
Q

Structure of an RNA nucleotide

A

1 phosphate group
1 ribose sugar
1 organic/nitrogenous base
4 bases are Adenine, Uracil, Cytosine, Guanine

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7
Q

4 categories of RNA

A

mRNA; messenger, formed during transcription
tRNA; transfer, involved in translation
rRNA; ribosomal
RNAi; interfering, inhibits translation

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8
Q

What is mRNA

A

Messenger RNA
Single stranded polynucleotide chain
A complementary copy of a single gene from the template strand of DNA
Length depends on the number of bases that make up gene
Sequence of bases on mRNA are complementary to the sequence of bases on the gene its copying

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9
Q

What is a codon

A

3 bases on an mRNA strand
Complementary to a triplet of DNA strands
Codes for a specific amino acid
Stop codons tell RNA polymerase to stop transcription
Start codons tell RNA polymerase to start transcription

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10
Q

Stop codon

A

Tell RNA polymerase to stop transcription

Tell ribosome to detatch from mRNA

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11
Q

Start codon

A

Tell RNA polymerase to start transcription

Tell ribosome to initiate translation

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12
Q

Anticodon

A

Region of 3 bases on a tRNA molecule
Complementary to the codons on mRNA
Specific to the amino acid it carries

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13
Q

What is a triplet

A

Region of 3 bases on DNA
Coding for one specific amino acid
In a protein

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14
Q

What is transcription

A

Making a copy of the base sequence of a gene (DNA)
Onto the base sequence of an mRNA molecule
Beginning in the nucleus for Eukaryotes

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15
Q

What is translation

A

Conversion of the base sequence of mRNA
Into a specific sequence of amino acids
In a polypeptide chain (primary sturcture)
At a ribosome

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16
Q

Where does transcription occur in eukaryotes

A

Nucleus

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17
Q

Where does transcription occur in prokaryotes

A

Cytoplasm

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18
Q

What is an exon

A

Coding sequences within a gene of DNA

Code for amino acids in the sequence of a polypeptide (protein)

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19
Q

What is an intron

A

Non coding sequences of DNA found in a gene
Do not code for amino acids In the polypeptide chain of a protein
Spliced out in transcription
Not found in prokaryotes

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20
Q

Explain transcription

A

DNA helicase attaches to and unwinds DNA double helix
Hydrogen bonds broken by DNA helicase
Separating strands
One strand of DNA acts as template
Complementary free RNA nucleotides associate with exposed DNA bases on template strand via complementary base pairing
Adenine with Uracil and Cytosine with Guanine
RNA polymerase joins adjacent nucleotides by phospodiester bonds via condensation reactions
Pre mRNA spliced to remove introns
Forming mature mRNA
Exons spliced back together to form mRNA
Passes out of nucleus via nuclear pore to ribosome

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21
Q

Differences between DNA and mRNA

A

DNA double stranded/mRNA single stranded
DNA longer/mRNA shorter
DNA has thymine and no uracil/mRNA has uracil and no thymine
DNA is deoxyribose/mRNA is ribose
DNA has hydrogen bonding/mRNA has no hydrogen bonding
DNA has introns/mRNA does not

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22
Q

Similarities between DNA and mRNA

A

Both polymers of nucleotides

Both contain phosphodiester bonds between adjacent nucleotides

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23
Q

What is tRNA

A

Transfer RNA
Molecule that carries a specific amino acid into a ribosome so protein synthesis (translation) can occur
Has anticodons

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24
Q

Structure of tRNA

A

One polynucleotode chain of around 75 nucleotides
Clover leaf structure held together by hydrogen bonds
Amino acid attachment site where only a specific amino acid binds
Region of 3 bases called anticodons complementary to mRNA codon

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25
Q

Similarities between tRNA and mRNA

A

Both single stranded
Both contain uracil, ribose sugar and a phosphate group
Both polymers of RNA nucleotides
Both contain phosphodiester bonds between adjacent nucleotides

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26
Q

Differences between tRNA and mRNA

A

mRNA has codons and no anticodons/tRNA has no codons and anticodons
mRNA is linear/tRNA is clover leaf shape
mRNA has no hydrogen bonds/tRNA has hydrogen bonds
mRNA is longer/tRNA is shorter
mRNA has varying lengths depending on the gene/tRNA is always the same length

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27
Q

Genome

A

Complete base sequence of all the DNA from a cell of an organism

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28
Q

Proteome

A

Full range of proteins that a cell is able to produce

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29
Q

Loci

A

Position of a gene within a chromosome

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30
Q

Explain translation

A

mRNA binds/associates with ribosome
Ribosome moves along mRNA to find the start codon
tRNA carrying a specific amino acid binds to binding site on mRNA via base pairing with its anticodon
Complementary codons and anticodons ensure correct amino acid sequence to form the specific protein primary structure
Ribosome catalyses the formation of peptide bonds between amino acids using energy from ATP
tRNA releases as ribosome moves along mRNA to next codon
Ribosome releases polypeptide into RER when reaches the stop codon
mRNA can associate with another Ribosome to begin translation again

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31
Q

How many ribosomes can translate a molecule of mRNA at oncd

A

Multiple
Resulting in many polypeptides being formed at once
Or the same mRNA molecule being reused until silenced by RNAi

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32
Q

Explain universal in terms of the genetic code

A

Same three bases on mRNA/DNA (codon/triplet) code for the same amino acid in all organisms

Same for prokaryotes and eukaryotes

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33
Q

Explain non overlapping in terms of the genetic code

A

Each base part of only one triplet/codon

During translation each codon is read only once by ribosome

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34
Q

Explain degenerate in terms of genetic code

A

More than one triplet codes for the same amino acid

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35
Q

Why three bases

A

There are 20 amino acids

1 base: 4¹ = 4 combinations = 4 amino acids isn’t enough
2 bases: 4² = 16 combinations = 16 amino acids isn’t enough
3 bases: 4³ = 64 combinations = 64 amino acids is enough

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36
Q

Why is the amino acid table in mRNA codons

A

It is the mRNA that codes for/determines amino acids

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37
Q

What is a mutation

A

Any change to the DNA base sequence

Occurring randomly and spontaneously

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38
Q

6 types of mutation

A 
Substitution
Deletion
Addition
Translation
Inversion
Duplication
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39
Q

Explain substitution mutation

A

One or more bases in a triplet change
Could be a silent mutation in which the amino acid coded for doesn’t change due to the degenerate nature of the genetic code, hence no effect on the polypeptide
If it does alter the amino acid coded for then it will alter the sequence of amino acids In the polypeptide, changing the primary structure
This may change the tertiary structure
Changing the proteins shape and function
Non functional protein

40
Q

Explain a deletion mutation

A

A loss of a base in a region of DNA coding for a gene
Alters the triplets from the mutation onwards
Causing a frame shift to the left
If it occurs early in a sequence coding for a gene then likely all triplets will be altered, so all amino acids may change
Lesser effect towards the end since less triplets affected and less alters to amino acid sequence
Can change the primary structure and hence change tertiary structure
May lead to a non functional protein

41
Q

Explain addition mutation

A

A gain of a base in a region of DNA coding for a gene
Alters the triplets from the mutation onwards
Causing a frame shift to the right
If it occurs early in a sequence coding for a gene then likely all triplets will be altered, so all amino acids may change
Lesser effect towards the end since less triplets affected and less alters to amino acid sequence
Can change the primary structure and hence change tertiary structure
May lead to a non functional protein

42
Q

Explain duplication

A

Duplication of part of a chromosome, the whole chromosome or the whole genome

43
Q

Explain inversion

A

Segment of bases is reverses end to end

44
Q

Explain translocation mutation

A

When groups of base pairs relocate from one area of the genome to another
Usually between non homologous chromosomes
Essentially an addition or deletion

45
Q

Explain chromosomal mutations in metaphase 1 of meiosis

A

During metaphase 1 of meiosis
When homologous chromosomes do not separate after associating
Remaining as a bivalent
Called chromosome non disjunction of homologous chromosomes
Gametes: 2(n+1) 2(n-1)

46
Q

Explain chromosomal mutations in metaphase 2 of meiosis

A

During metaphase 2 of meiosis
When sister chromatids do not separate and remain attached via centromere
Called chromosome non disjunction of sister chromatids
Gametes: 2(n) 1(n+1) 1(n-1)

47
Q

Explain two types of chromosomal mutations

A

Metaphase 1 and metaphase 2 of meiosis

48
Q

How can a mutation have a positive result

A

Change to the DNA base sequence in which a different amino acid sequence coded for
Changing primary structure and therefore tertiary structure
Which is beneficial to the individual
Allows for variation, leading to natural selection and passing on the positive mutation so population is better adapted
Properties of polypeptide change

E.g antibody that makes immune to certain diseases so likely they will survive, thrive and reproduce

E.g enzyme fits substrate better so faster rate of reaction

49
Q

How can a mutation have no effect

A

Silent mutation
Base changing has no effect on polypeptide
Since sake amino acid coded for
Due to degenerate nature of genetic code

Mutation occurring in intron
So spliced out in transcription.

May change the primary structure by changing the amino acid sequence
But may not change the tertiary structure if it folds the same due to similar properties of changed amino acid and bonds forming in same place

50
Q

How can a mutation have a negative effect

A

Frame shift
All amino acids after mutation change
Give a completely different primary and tertiary structure
Bonds form in different places
So function changes and non functional
If it changes the start/stop codons either no translation or uncontrolled translation
Change of properties of protein (soluble to insoluble)

51
Q

3 mutagenic agents

A

High energy ionising radiation
DNA reactive chemicals
Biological agents

52
Q

Explain high energy ionising radiation

A 
Damage DNA molecule (bases) and chemicals
That alter DNA structure
Or interfere with DNA replication
X rays
Gamma
Alpha particles
Beta particles
53
Q

Explain DNA reactive chemicals

A

Can convert DNA bases
Benzene, bromine, hydrogen peroxide
Nitrous acid can remove the NH2 on cytosine and convert it to uracil

54
Q

Explain DNA reactive chemicals

A

Can convert DNA bases
Benzene, bromine, hydrogen peroxide
Nitrous acid can remove the NH2 on cytosine and convert it to uracil

55
Q

Explain DNA reactive chemicals

A

Can convert DNA bases
Benzene, bromine, hydrogen peroxide
Nitrous acid can remove the NH2 on cytosine and convert it to uracil

56
Q

Explain biological agents

A

Viruses and bacteria

Can integrate their genetic code into ours

57
Q

Occurance of mutations

A 
Spontaneously during DNA replication
Natural and random events
Causing permebant changes to DNA
Which get passed on to generations 
Occur at a set rate that is different for each species
58
Q

What are mutagenic agents

A

Increase the rate of spontaneous mutations

59
Q

Natural selection

A

Process by which organisms better adapted to their environment survive and reproduce in greater numbers
Resulting in the increase of the frequency of the advantageous allele within the population
Over generations

60
Q

Explain natural selection

A

Variation due to a mutation
Better adapted individuals more likely to survive and reproduce (differential survival)
These more likely to pass on their advantageous alleles to offspring
Less well adapted fail to survive and reproduce
These less likely to pass on their alleles
Organisms subject to selection pressure in environment
Selection pressure determines the spred of alleles within a gene pool
Can be biotic or abiotic

61
Q

What is a biotic factor

A

Living factor
That can act as a selection pressure on a population
Normally have a bigger impact on smaller population

62
Q

Examples of biotic factors

A 
Predators
Prey
Diseases
Competition
Viruses
Presence of a mate
63
Q

What is an abiotic factor

A

Non living factor
Can act as a selection pressure on a population
Same impact regardless of population size

64
Q

Examples of abiotic factors

A 
Temperature
pH (salinity)
Humidity (water potential)
Terrain
Light intensity
Weather
65
Q

Where does stabilising selection occur

A

All populations where environment is stable

66
Q

Stabilising selection

A

Occurs in all populations where environment is stable
Selection pressure at both ends of the distribution
Favours the average
Those with favoured optimum mean phenotype more likely to survive, thrive, reproduce and pass on advantageous alleles
Differential survival occurs
Those without die out
Over time the mean allele becomes more frequent in the population
Tends to eliminate extremes
Reduces variability (size of range in population)
Reduces opportunity for evolutionary change

67
Q

Example of stabilising selection

A

Birth mass

Really heavy/really light babies show higher neonatal mortality rates than medium mass
Over time, selection operates to reduce heavy/light numbers

68
Q

Directional selection

A

Environmental change may produce new selection pressure that favours an extremem phenotype
Those with favoured optimum extreme phenotype more likely to survive, thrive, reproduce and pass on advantageous alleles
Differential survival occurs
Those without favoured optimum extreme phenotype die out
Over time the extreme allele becomes more frequent in the population
New mean phenotype that’s shifted along with the normal distribution curve

69
Q

Example of directional selection

A

Antibiotic resistance

Speckled moths
Sooty environment meant dark moths more camouflaged so more likely to survive

70
Q

Explain disruptive selection

A

Environment has two selection pressures that favour 2 extreme phenotype
Least common but most important for evolution
Those with favoured optimum extreme phenotype more likely to survive, thrive, reproduce and pass on advantageous alleles
Differential survival occurs
Those without favoured optimum extreme phenotype die out
Over time the extreme alleles becomes more frequent in the population

71
Q

Example of disruptive selection

A 
Mice at beach
Light coloured mice blend with sand
Dark blend with grass
Medium don't camouflage
Susceptible to predators
72
Q

2 types of antibiotic

A

Narrow spectrum

Broad spectrum

73
Q

Explain narrow spectrum antibiotics

A

Antibiotics that act against limited group of bacteria

74
Q

Explain broad spectrum antibiotics

A

Antibiotics that zct against a larger group of bacteria

75
Q

How do antibiotics work

A

Stop binary fission:
Stop cell wall forming
Stop nucleic acid synthesis

Penicillin/RNA polymerase inhibitor/Cell membrane puncturing

76
Q

Mechanisms of antibiotic resistance

A

Plasmids: Contain genes for antibiotic resistance, passed between eachother

Impermeabilty: Modified cell wall that won’t let antibiotic in

Modification: Modified drug target no longer complementary to drug

Pumping it out: Removes drug using ATP

Inactivation: Add a phosphate group to antibiotics to reduce its ability to bind to bacterial ribosomes

77
Q

Why don’t antibiotics affect human cells

A

We don’t have cell walls in our cells
Antibiotics prevent cell wall formation

Target bacterial cells replicating by binary fission but human cells don’t replicate by binary fission (mitosis and meiosis)

78
Q

What is a spectrophotometer

A

Shines light through bacteria culture
Amount of light that passes through measured
Correlates to amount of bacterial cells (more light passing through means less cells)
Written as a percentage

79
Q

Issues with spectrophotometer to count cells

A

Glass tube affects the amount of light passing through
Shouldn’t matter if constant for all readings

Cells sink to the bottom so isn’t accurate

Percentage of light passing through isn’t equal to the number of cells

80
Q

Total count

A

Includes living and dead cells

81
Q

Viable count

A

Only includes living cells

82
Q

Turbidity

A

Cloudiness of a culture

83
Q

Colony

A

A cluster of cells
Arise from a single bacterium
By asexual reproduction

84
Q

What is a serial dilution

A

Step by step dilutions of a substance to create a range of different concentrations

Can be a method of counting individuals of a large population by obtaining a population density per unit of a culture

85
Q

Differences between chloroplast DNA and nuclear DNA

A

Chloroplast is circular/Nuclear is linear
Chloroplast is not associated with histones/Nuclear is associated with histones
Chloroplast is shorter/Nuclear is longer

86
Q

How do you perform a 1 in 10 serial dilution

A

Add 9 parts distilled water to 1 part sample solution
Mix

Very important to mix

87
Q

How do you make a 1 in 100 serial dilution

A

1 part solution to 99 parts distilled water
Mix

Or

1/10th of a 1 in 10 dilution to 9 parts distilled water
Mix

88
Q

How do you make a 1 in 1000 serial dilution

A

1 part sample solution to 999 distilled water
Mix

Or

1/10th of a 1 in 100 dilution to 9 parts distilled water
Mix

Or

1/10th of a 1 in 10 dilution to 99 parts distilled water
Mix

89
Q

Steps for counting cells via serial dilution

A

Add x part stock solution to x parts distilled water
Mix
Work aseptically
Sterilise any equipment
Total viable cell count = number of colonies counted × dilution factor

90
Q

What can splicing produce

A

Different lengths of mRNA

With different exon arrangements

91
Q

Function of ribosomes in protein synthesis

A

Attached to mRNA
Catalyse peptide bonds
Between amino acids of polypeptide chain being synthesised
In translation

92
Q

Gene pool

A

Number of different alleles of genes in a population

93
Q

What is an organisms characteristics determined by

A

Phenotype
Is determined by the genotype
And it’s interactions with tbe environment

94
Q

Purine

A

Adenine
Guanine
Consist of a six-membered and a five-membered nitrogen-containing ring fused together

95
Q

Pyrimidine

A

Thymine
Cytosine
Uracil
Consist of only a six-membered nitrogen-containing ring

A Level Biology Paper 1 (16 decks)

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