Molecules, Genes & Disease Flashcards
0
Q
Lysosome function?
A
Cellular Digestion
1
Q
Function of cytoplasm?
A
Fatty acid synthesis, metabolism if carbohydrates, aa, nucleotides
2
Q
Golgi Complex function?
A
Export of proteins, detoxification reactions
3
Q
Endoplasmic reticulum function?
A
Lipid + steroid synthesis, protein synthesis, membrane synthesis! export of proteins, detoxification reactions
4
Q
Nucleus function?
A
RNA & DNA synthesis, DNA repair,
5
Q
Nucleolus function?
A
RNA processing and assembly
6
Q
Plasma membrane function?
A
Cell morphology + movement, transport of ions and small molecules
7
Q
What is an amphipathic molecule?
A
Molecule has both polar (hydrophilic) and non polar (hydrophobic) ends
8
Q
What is a buffer? And an example?
A
Consists of a weak acid and a small amount of conjugate base, allowing the solution to resist small changes in pH e.g. Blood H2CO3 —> HCO3- + H+
9
Q
What are the classifications of amino acids?
A
Non polar (hydrophobic), polar uncharged (hydrophilic), polar uncharged (hydrophilic)
10
Q
Define Isoelectric Point, Pi?
A
The pH at which a protein has no overall net charge
11
Q
What is a peptide bond? And it’s properties?
A
A covalent bond that joins amino acid together, found in the primary structure of proteins.
1) all atoms in bond are in the same plane 2) no rotation around peptide bond (due to double bond characteristics) 3) carbonyl O and amide H are in trans orientation
12
Q
What is the primary structure? bonds?
A
Linear aa sequence of the polypeptide chain
- peptide bonds
13
Q
What is the secondary structure? bonds? Examples?
A
Local spatial arrangement of the polypeptide
- hydrogen bond
E.g. Alpha helix, beta sheet (adopted if angles remain the same throughout a section of the poly peptide)
Atoms on either side of peptide bond can rotate freely
14
Q
What is the tertiary structure? Bonds?
A
Three dimensional arrangement of all the atoms in a polypeptide
- secondary structure folds so that amino acids far away in the primary structure can interact
- hydrogen bonds, van der waals, hydrophobic interactions, ionic interactions, covalent (disulphide bonds)
15
Q
Quaternary Structure? Bonds?
A
Three dimensional arrangement of a multi sub unit protein
- hydrogen bonds, van der waals, hydrophobic interactions, ionic interactions, covalent (disulphide) bonds
16
Q
What is a homomeric protein?
What is a heteromeric protein?
A
- contains identical polypeptide chains
- contains different polypeptide chains
17
Q
What is a domain?
A
Region of a protein that folds into a distinct globular unit and has a particular role.
18
Q
What is a chaperone?
A
Proteins that assist in the folding/unfolding or assembly or disassembly of proteins
19
Q
Example of a misfolding of a protein
A
Amyloid fibres
20
Q
Describe an Alpha Helix
A
- right handed helix - alanine = builder
- 36aa in one turn - proline = breaker
- 0.54nm per pitch
- R groups point outwards
- maximise H bonding, form every 4th aa, parallel to helix
21
Q
Describe a Beta Helix?
A
- less compact, double space between residues
- 0.35nm between adjacent aa
- R groups alternate between opposite sides of chain
- H bonds perpendicular to pp backbone
- parallel C—>N x2 and anti-parallel C—>N x1 N<—C
22
Q
What are the two types of protein? Give examples?
A
Globular (several types of secondary structure, up to quaternary, tend to be soluble) haemoglobin, enzymes, regulatory proteins
Fibrous (primary and secondary structure only, provides structure support, protection) collagen and keratin
23
Q
Acidic proteins contain……
A
Many negatively charged aa
- low Pi
24
Basic Proteins contain.....
Contain many positively charged aa
| High Pi
25
Isoelectric protein & pH & pKa
Less than Pi = protonated
Higher than Pi = de protonated
pH>pKa = deprotonated
pH
26
Explain T & R states in haemoglobin?
See notes
27
Structure of an adult haemoglobin...
4 haem groups, 4 sub units
| 2 Beta and 2 Alpha forming an tetramer
28
Effect of 2,3-bisphosphateglycerate...
Increases amounts of BPG decreases the affinity of Hb for oxygen so shifts curve to right I.e. Enhances Low affinity T state
Is an allosteric inhibitor, is negatively charged + binds to histine or Lysine in beta sub unit preventing Hb from changing conformation
High altitude increases release so more O2 delivered to tissues
29
Effect of CO2 and H+......
Binds to haemoglobin molecule lowering affinity for O2, curve shifts to right gives up oxygen to tissues so delivery meets demand
Allosteric inhibitor
Bohr effect
30
What is the Bohr effect?
Is the name given to the effect that pH and CO2 have on binding and release for O2 by Hb referring specifically to oxygen released from Hb when the pH falls
31
Effect of carbon monoxide on haemoglobin.....
Increases affinity for O2, curve shifts to left, enhancing high affinity R state, little O2 released to tissues
Binds 250x greater than Oxygen
[HbCO3] > 50%
Allosteric activator
32
What is the mutation in sickle cell anaemia?
Glutamate ---> valine
GAG ---> GTG
In Beta Globin
33
What is thalassemias?
A group of haemoglobinmyopathys that are caused by mutations in globin genes resulting in an inbalance between globin proteins.
Beta thalassemias, decreased/absent Beta globin production, symptoms only after birth
Alpha thalassemias, decreased/absent alpha chain production, several versions of severity as multiple copies of alpha chains and beta chains can form stable tetramers
34
What are enzymes? And name some of their properties?
Are biological catalyst that increase the rate of reaction by lowering the activation energy, facilitate the formation of the transition state and increase the local concentration of substrates
- proteins - highly specific for a substrate and a reaction - left unchanged after reaction - may require present of additional chemical components e.g. co enzymes, co factors, prosthetic group (covalently linked to enzyme)
35
What is the lock and key hypothesis?
Only molecules with a complementary shape will be able to bind
36
What is the induced fit hypothesis?
Binding of substrate results in a change to the shape of the confirmation of the enzyme enhancing binding
37
What is Vmax? And what type of inhibitor it is effected by?
The maximum velocity of an enzyme catalysed reaction, when all active sites are filled with a substrate
- effected by reversible non competitive, lowers Vmax
38
What is Km? And what inhibitor is it effected by?
Km is the substrate concentration that gives half the maximal rate
- effected by a reversible competitor inhibitor (active site), increases Km so decreases affinity of enzyme for substrate
39
What does a high Km mean?
That the enzymes has a low affinity for its substrate
40
What does a low Km mean?
That an enzyme has a high affinity for its substrate
41
What do the x intercept, y intercept and gradient mean on a line weaver Burke plot?
X: 1/Vmax
Y: -1/Km
Gradient: Km/Vmax
42
What is the international unit of enzyme activity?
Amount of enzyme that catalyses the conversion of 1 um of substance per minute under standard conditions
- normally expressed as per litre of serum or per gram of tissue
43
What is competitive inhibition?
The inhibitor competes with the substrate for binding at the active site, it is characterised by a increase in Km for the substrate but Vmax remains unchanged
- can be overcome by increasing the substrate concentration
44
What is non competitive inhibition?
Where the inhibitor binds at a site other than the active site, s is characterised by a decrease in Vmax but Km remains unchanged
- cannot be over some by increasing the substrate concentration
45
Name the two types of short term regulation
Substrate and product concentration e.g. Glucose 6 phosphate inhibits the activity of hexokinase
Changes in enzyme confirmation
46
What can short term regulation be broken down into
Allosteric activation - binding of 1 substrate at one site of a multi sub unit protein that influences subsequent binding of other substrates to other sub units
Covalent modification - the addition of a chemical group to a protein e.g. A phosphate group by phosphorylation to tyrosine, threonine, serine (protein kinase)
Proteolytic activation - specific proteolysis removing a few amino acids from a pp chain activating the enzyme
47
What is a zymogen?
The inactive precursor of a proteolytic enzyme
48
What is the enzyme example of allosteric regulation?
Phosphofructokinase
- activators: AMP, fructose-2,6-bisphosphate
- inhibitors: ATP, citrate, H+
49
What are the two types of long term regulation of protein activity?
Regulation of enzyme synthesis: increasing/decreasing transcription forming mRNA
Regulation of protein degradation: proteins can be tagged for destruction by ubiquitin, in ubiquitin proteosome pathway (ubiquitinissation target cells for apoptosis)
50
What are the type of regulation seen in metabolic pathways?
Feedback inhibition: end products inhibit own synthesis by inhibiting enzyme which are alert of reaction pathway
Feedback activation: initial amount of initial substrate increase first step in pathway
Counter regulation: catabolic pathway inhibits the anabolic one and vice versa e.g. Glycogenesis and glycogenolysis
51
What are isoenzymes?
Different forms of the same enzyme they just have slightly different kinetic properties e.g. Hero kinase found in muscle and glucokinase found in liver both catalyse the conversion of glucose to glucose-6-phosphate but glucokinase has a lower affinity for glucose so it's activity varies substantially depending on the glucose concentration
52
Define the phenotype
All observable characteristics of an individual or the observable trait as a result of the genetic make up of one or more specific genetic locus/loci
53
Define the genotype
The genetic make up of an individual (either as a whole or specific gene locus)
54
What is a chromosome?
A structure in the cell nucleus containing are double stranded DNA molecule or two identical double stranded DNA molecules after replication
55
What is a chromatid?
One of the two identical components of a duplicated chromosome each containing a single identical double stranded DNA molecule. Can get sister chromatids and non sister chromatids
56
What is a chiasma?
The point where two non siter chromatids exchange genetic information during crossing over in metaphase 1 in meiosis.
Plural = chiasmata
57
Define an allele
An alternative form of a gene
- each individual has two alleles for each gene one from each parent they can be the same or different
- there are many alleles within a population
58
Define a gene
A length if DNA on a chromosome that contains the code for a protein (or RNA) as well as sequences necessary for its expression e.g. Promoter, introns, termination sequences, unit of heredity
59
Define a locus
A specific position in a chromosome
60
What are the environmental factors in genetics?
Radiation, mutagens, chemical that affect cell growth, diet, lifestyle
61
What does homozygous mean?
Having two identical alleles for a specific genetic locus
62
What does heterozygote mean?
Having two different alleles for a specific genetic locus
63
What does hemizygous mean?
Only 1 allele of a gene on the X chromosome (only occurs in males as have Y chromosome and it is shorter than X chromosome)
64
Dominant?
A phenotypic trait is dominant when it occurs in both homozygous and heterozygote and it determines the phenotype in the heterozygote
65
Recessive?
A phenotypic trait is recessive when it occurs in homozygous condition only
66
What is an autosomes?
A chromosome other than the sex chromosome
| Humans chromosomes: 1-22
67
Autosomal recessive?
- heterozygote unaffected
- affects males and females equally
- can skip a generation (diseased an come out of no where)
- gene located on a autosome
68
Examples of autosomal recessive?
Cystic fibrosis, sickle cell anaemia, Tay sacs disease (disease that causes progressive damage to the nervous system)
69
Autosomal dominant?
- heterozygote effects
- males and females equally effected
- does not skip a generation an affected individual will have an affected parent
- rarely found in homozygous state as this is often lethal
70
Examples of autosomal dominant conditions
Huntington's disease, Gilbert's disease (people experience occasional episodes of jaundice)
71
X-linked recessive
- hemizygous makes and homozygous females equally effected
- disease more common in males
- heterozygous female carrier has 50% chance of having an affected son
- affected male cannot give trait to son
- affected daughter = carrier mum & affected father
- daughter of effected males are heterozygote
72
Examples of X-linked recessive
Haemophilia A
Haemophilia B/Christmas disease
Duchenne Muscular Dystrophy
73
X-linked dominant
- Allele responsible is located X-chromosome and is dominant
E.g. Rett syndrome
74
Y-linked
Only passed from father to son
Rare: Y chromosome does not contain many genes
E.g. Frequent genetic cause of make infertility
75
Co dominance?
Where both alleles are expressed in the phenotype in the heterozygous condition
76
Example of co-dominance?
- human ABO Blood groups
Allele B and A dominant over O
Alleles A and B are expressed together so get blood type AB
77
Complementation?
Where more than one gene is involved in producing a phenotype
Substrate -----------> intermediate ------------> product
Enzyme 1 Enzyme 2
Gene 1 Gene 2
78
Example of complementation?
Albinism
| - albino parents can birth to a child of normal pigmentation
79
Why was is the polarity in a DNA molecule?
From the 5' to 3'
| I.e. phosphate group on 5' and OH group on 3'
80
Name the two purines and what they pair with?
Adenine pairs with thymine (DNA) uracil (RNA) 2 H bonds
Guanine pair with cytosine 3 H bonds
Are 2 ring structures
81
What are the key features of a DNA helix?
Right handed double, helix
10 base pairs in 1 helical turn
Major and minor grooves
Hydrophobic bases on inside and hydrophilic phosphate groups on outside
Nucleotides are planar to stack tightly with van der waals bonds
82
What is euchromatin?
Bead on a string:
formed by each double stranded DNA molecule wrapping around a histone forming nucleosomes which make up beads on a string
Active chromatin
Histone acylated, DNA de methylated
83
What is heterochromatin?
```
Solenoid structures:
Tightly packed nucleosomes
Inactive chromatin
Dark under microscope
DNA methylated, histone de acylated
```
84
How do you form chromosomes?
Solenoid fibres co lacy into several hierarchies loops creating highly condensed structures called chromosomes, occurs in mitosis and meiosis and are visible under a light microscope
85
Which direction is DNA replication chain growth?
From 5' to 3'
| Extends from 3'end
86
What occurs during initiation of DNA replication?
- recognition of origin of replication
- DNA helicase unwinds double helix
- requires specific proteins for recruitment of DNA polymerase
- primate makes small amount of DNA that acts as a primer (removed later)
87
What occurs during elongation of DNA replication?
```
Leading stand (3 prime strand, 5'--->3') is replicated
Lagging strand (5 prime strand 3') is replicated discontinuously forming Okazaki fragments which are joined by DNA ligase forming a continuous sugar phosphate backbone
```
88
What occurs during termination of DNA replication?
Replication forks meet and DNA ligase joins the fragments together
89
Describe the cell cycle
Mitosis to cytokinesis to G1 to S to G2
90
What is G0?
Stage where cell has left the cell cycle it's not preparing for division or is dividing as it doesn't receive signals to enter the cell cycle. This exists if the cell is fully differentiate.
So could be temporary phase or a final/mature stage (nerve cells and heart muscle) Idea that regulation of growth is one of its main purposes.
91
What occurs during the S phase?
DNA replication
92
What occurs during the G1 and G2 phases?
Organelle replication/ replication of cell contents
| Checks replicated DNA for errors and repairs them
93
Describe mitosis?
Definition: cell division of somatic cells
| Prophase, pro metaphase, metaphase, anaphase, telophase
94
Describe meiosis?
Definition: process of cell division in which gametes are produced
Meiosis 1 and meiosis 2
95
What are the differences between spermatogenesis and oogenesis?
Spermatogenesis produces 4 gametes (sperm), takes 48 days
| Oogenesis produced 1 egg and 3 polar bodies, takes 12 to 50 years
96
What are linked genes?
Are genes that are on the same chromosome and do not show independent assortment during meiosis
97
What are recombinant progeny?
an offspring that shows non parental combination if the alleles
98
How do you calculate recombinant frequency?
= recombinant progeny/total number of informative progeny
99
How do you calculate the number of possible combinations from independent assortment?
2^n
| Where n = number of chromosomes
100
Describe transcription?
Initiation
Elongation
Termination
See notes
Direction 5 to 3
Requires RNA polymerase ll
101
What are the three post transcriptional modifications?
Capping: addition of methylated guanine to 5'
Polyadenylation: addition of up to 200 adenine molecules through use of poly A polymerase to 3'
Splicing: removes introns so exons spliced together using endonuclease
102
Describe translation
Initiation
Elongation
Termination
```
Start: AUG
Stop: UAA, UAG, UGA
P and A sites
Read from 5 to 3 direction
N to C chain growth
Peptidyl transferase
```
103
What are the differences between gene expression in mammalian and bacterial cells?
- single promoter
- different transcription factors
- single RNA polymerase
- coupled transcription & translation as no nucleus
- short lived mRNA as no post transcriptional modification therefore no protection against degradation.
- 70s ribosomes (50s and 30s) (humans = 80s: 40s and 60s
104
Mutation effects, what can we predict?
Is similar aa then probably little effect (think hydrophilic, hydrophobic, charge, size)
If premature stop codon = truncated
If delayed stop codon = elongated
If outside of coding region can still have an effect gene expression if located in promoter region, where transcription factors bind
105
What are the three types of RNA?
rRNA: many copies of each, few/4 kinds, RNA polymerase l
mRNA: few copies of each, 100000/ many kinds, RNA polymerase ll
tRNA: very many copies of each, 100 kinds, RNA polymerase lll
106
Define preproprotein
A protein containing both a signal peptide and a pro peptide
107
What is the name of the enzyme that cleaves a signal peptide?
Signal peptidase
| Found in ER
108
What is a signal peptide?
A short N-terminal hydrophobic sequence of aa that directs newly formed secretory or membrane proteins into the ER
109
What is a pro protein?
An inactive precursor of a protein
| To encode fully active it must undergo limited proteolysis to remember the pro peptide
110
Define protein targeting
Mechanism involved in directing proteins to their correct site of action inside or outside of the cell
111
What is tropocollagen?
Collagen triple helices formed extra cellularly where the N and C terminal regions have been removed
112
What is required for nuclear targeting?
- nuclear localisation sequence (NLS) (basic aa) contained in primary sequence
- requires importin, ran GTP
- signal retained
- requires hydrolysis by GTP
- folded during transfer
113
What is required for lysosomal targeting?
Signal: mannose-6-phosphate linked to N-linked oligosaccrides
Location: signal patch to distinguish lysosomal proteins from other mannose labelled ones
Folded -> delivered in a vesicle
Phosphate removed by phosphatase
- lysosome pH causes dissociation of receptor and protein
- receptor returns to Golgi
- requires energy -> phosphotransferase enzyme add M6P
-m6P receptors in trans Golgi
114
What is required for mitochondrial targeting?
- Transported unfolded
- amphipathic N-terminal sequence which is removed by mitochondria processing peptidase
- TOM proteins recognise signal sequence, outer mitochondrial membrane
- TIM proteins transport it across the inner mitochondrial membrane
- chaperones -> HSP70 family
- protein folds into conformation via ATP dependant process
Signal cleaved
- ATP hydrolysis drives translocation into lumen
115
What is required for retention on proteins in ER?
Possible for proteins in the ER to be lost when vesicles are pinched off and transported to the Golgi.
- ER proteins have KDEL sequence near C-terminus
- if transported to Golgi interact with KDEL receptors helps acidic
- proteins bound to receptors are returned to the ER in transport vesicles
- ER proteins dissociate from the receptor in neutral conditions of ER
- KDEL receptor transported back to the Golgi
- no energy needed directly but budding vesicles requires GTP hydrolysis
- signal retained
116
What is a numerical chromosomal abnormality?
Disturbances in distribution of chromosomes or chromatids during cell division
Not 46 chromosomes in a cell
117
What are the types of numerical chromosomal abnormality?
1. Polyploidy, no of chromosomes that is a multiple of haploid but not diploid
2. Aneuploidy, abnormal no of chromosomes that it's not a multiple of haploid -> monosomy, trisomy
118
What is a monosomy?
Loss of one homologous chromosome
| E.g. Turners syndrome: 45 X
119
What is trisomy?
Gain of 1 homologous chromosome
| E.g. Down's syndrome, 47,XX/XY,+21
120
What is a structural chromosomal abnormality?
Physical changes of one or more chromosomes
121
If a structural chromosomal abnormality is balanced what does this mean?
Does not result in missing or extra genetic information
122
If a structural chromosomal abnormality is unbalanced what does this mean?
Causing misses or extra genetic information
123
What is a deletion?
Loss of genetic material
| Unbalanced
124
What is a duplication?
Same genetic material is doubled, unbalanced
125
What is an inversion?
Rearrangement of genetic material in that chromosome
| Balanced, unbalanced
126
What is a ring chromosome?
Loss of telomeres on ends of both arms of the chromosome resulting in the formation of a ring structure
Unbalanced
127
What is an isochromosone?
Creation of 2 non identical chromosomes: one is a combination of the p arms and the other a combination of the q arms
128
What is translocation?
No loss of genetic material but a rearrangement of genetic material to a non homologous chromosome
Balanced/unbalanced
- risk of passing phenotype to offspring resulting in disease
- person has full compliment of genes
129
What is a reciprocal translocation?
No loss of genetic material but an exchange of genetic material between two non homologous chromosomes
130
What is robertsonian translocation
Rearrangement of genetic material between two chromosomes:
- the q arms of two acrocentric chromosomes (G-13,14,15 and D-21, 22 groups) combine to from a super chromosome with the loss of the p arms
- inappropriate recombination between satellites at tips of p arms between RNA genes --> head to head chromosome translocation and loss of small portion of genetic material of both chromosomes
131
What patients get referred to karyotyping? And what are the benefits of this?
```
Pre natal screening
Birth defects
Abnormal sexual development
Infertility
Recurrent foetal losses
Leukaemia
Accurate diagnosis, better management if pt, future reproductive risk if carrier, pre natal diagnosis/termination
```
132
What are the two causes of aneuploidy?
- Non disjunction at cell division: failure of homologous chromosomes or sister chromatids to separate
- Anaphase lag
133
What is a transition mutation?
Purine to purine
| Pyrimidine to pyrimidine
134
What are the three types of pout mutations in the coding region?
Silent mutation - does not alter aa specified
Missense mutation - alters aa specified
Nosence mutation - changes aa to stop codon
135
What can point mutations in the coding region cause?
Change transcription factors binding sites, promoter sequences, splice sites, polyadenylation
136
What are the three main types of mutations?
Point mutation
Rearrangement of sequences
Deletion/insertation
137
What is a frame shift mutation?
Addition/deletion of bases not multiples of 3
| - often get nonsense mediated decay so the mRNA is degraded so little protein produced
138
What is a change in the aa code mutation?
The addition or deletion of bases in multiples of 3
139
What are the two causes of mutations?
1. Spontaneous
- tautomeric shift: gives altered base pairing properties C-A, T-G
- DNA strand slippage during replication, 1 base in loop not coded
2. Induced
- chemicals, direct alteration of DNA bases, disruption of DNA base stacking
- radiation, x rays, UV light, environmental, nuclear power plant, solar radiation
140
What are examples of agents that's cause induced mutations?
- alkalyting agents = remove bases
- acridine agents = add/remove base
- nitrous acid = replaces amino group with keto giving different base aspiring properties
- ethyl methane sulphonate = removal of purine rings giving apurinic sites which can pair with any base in DNA replication
- IQ, forces DNA bases further apart on DNA strand = misreading by DNA polymerase so get single base deletions
- ethidium bromide, inserts itself between strands of DNA disgorging it
141
What is a balanced chromosomal abnormality?
No loss of genetic information or genetic material.
| But maybe separated in cell
142
What is an unbalanced chromosomal abnormality?
Loss of genetic information but may still have all the genetic material e.g. If translocation break occurs in the middle of a gene
143
What does UV light cause?
Thymidine dimers where adjacent thy mines base pair with each other normally resolved by photo re activation spontaneously
144
What are the three type is of DNA repair?
Proof reading: by DNA polymerase detecting mispaired 3 base
Mismatch repair: enzymes detect mismatched DNA bases in newly synthesised strand and replaces them
Excision repair: damaged DNA removed by excision and replaced by DNA polymerase -> base excision or nucleotide excision repair
145
What is mismatch repair?
enzymes detect mismatched DNA bases in newly synthesised strand and replaces them
146
What are the two types of excision repair?
Base excision, replaces 1-5 bases oxidative
| Nucleotide excision repair, UV damage/carcinogens replaces up to 30 bases
147
What are oncogenes?
Are genes that have the potential to cause cancer. They are often mutated and are expressed at high levels in tumours.
If normal called protooncogenes
148
What is the name of the protein used to cause apoptosis is there is too much damage to DNA?
P53
149
Protein modifications that occur in the Golgi?
O-linked glycosylation
Modification of n-linked oligosaccrides
Phosphorylation of oligosaccrides on lysosomal proteins
150
Protein modifications that occur in the Golgi?
Specific proteolytic cleavage
Hydroxylation of specific Lysine and proline residues
Formation of disulphide bonds
N-linked glycosylation
151
Role of proteolytic pathway
Yield different products in different amounts
Endo protease and exo proteases are used
Gives rise to small products that cannot be synthesised otherwise or those that would be too destructive to synthesise in the cell
Can get multi biologically active products from 1 pp
152
What is required for proteins going to ER?
- hydrophobic signal on n terminal
- recognised by SRP, signal recognition protein
- unfolded (as synthesised through membrane)
- signal cleaved by signal peptidase
- hydrolysis of GTP
- also requires SRP receptors
153
What are the 5 main ways in which cells can become resiatnt to a antibiotic or drug?
- higher rate of division
- decreased influx
- increased efflux
- increasing transcription of target
- altering the target
154
How do antibiotics work that inhibit bacterial cell wall synthesis?
They inhibit transpeptidase which prevents cross links in cell walls peptioglycan cannot be maintained so osmotic pressure increase resulting in cell lysis or death. Work as mammalian cells do not have a cell wall
E.g. Flucloxacillin
155
How do antibiotics work that inhibit bacterial protein synthesis?
Bins to a beta subunit where it sterically blocks synthesis of 2nd/3rd phosphodiester bond. So RNA polymerase dissociates from DNA so mRNA breaks down
E.g. Rifampicin
156
How do antibiotics work that inhibit bacterial protein synthesis?
Are a translation inhibitor so binds to 30s subunit of ribosome, blocking access of amino acyl tRNA to A-site of ribosome complex. Preventing the introduction of new amino acids
Works because mammalian cells do not actively pump tetracycline into cytoplasm and we have 40s and 60s sub unit ribosomes
E.g. Tetracycline
157
How do antifolates work in chemotherapy?
Eh competively inhibit the enzymes, DHFR, which prevents the formation of tetrahydrofolate. So no formation on dNTPs and no synthesis there of DNA and RNA. But as folate sexist in both but is more effective in s phase since cancer cells divide more they are effected more, and lack of thymine production due to drug so malignant cells cannot divide.
158
Define DNA sequencing?
Determination of the order in which individual nucleotides are linked together to form a DNA molecule
159
What does restriction endonuclease do?
It is a enzyme that recognises and cuts specific DNA sequences at specific sites called restriction sites producing sticky ends. Mostly the ends are palladrone.
160
What is the stain used in gel/DNA electrophoresis?
Ethidium bromide
161
What does gel/DNA electrophoresis separate DNA fragments by?
Size and charge
162
Describe the process of the polymerase chain reaction, PCR?
- requires primers that anneal to coding strand and bind to specific known sequences of DNA
1. Denaturation, separating strands of template, 95 C
2. Hybridisation, sequence specific primers anneal to DNA, 55 C
3. DNA synthesis, using themostable DNA polymerase 5->3, 72
And repeat........
163
What increase in DNA does PCR give?
Exponential, so 2^n
164
How is RT-PCR different to PCR?
RNA is used instead of DNA as a template, so the enzyme reverse transcriptase is used to give cDNA, a complementary copy of the RNA
165
Define southern blotting and hybridisation?
Process where following DNA gel electrophoresis the separated DNA molecules can be transferred to a membrane and specific DNA fragments can be detected via the hybridisation of a labelled probe.
166
What are the advantages of Southern blotting?
- Allows investigation of individual gene in a background of other genes.
- can analyse larger sequences of DNA, within and around a gene
167
Define northern blotting?
Technique in which RNA separated by electrophoresis is transferred to a membrane filter and is detected by the hybridisation of a labelled probe
168
Snow drop?
Southern DNA
Northern RNA
O O
Western Protein
169
What is karyotyping?
Picture of a full set of stained metaphase chromosomes of an individual, labelled and organised by chromosome number.
170
What is fluorescence in situ hybridisation (FISH)?
Specific DNA sequences on chromosomes inside cells are detected by the hybridisation of a fluorescent labelled probe.
Is specific to a gene or several genes.
And can see presence or absence of specific DNA sequences.
171
What is chromosome painting?
Each chromosome is visualised using a different coloured fluorescent probe p.
172
What is microarray technology?
Is the simultaneous investigation of many DNA or RNA fragments, the DNA fragments are orang used into arrays are hybridised to labelled DNA from two different sources.
Array comparative genomic hybridisation compares normal DNA and DNA from the patient they are raised in equal quantised and hybridised to probe array. And different hybridisation signals are detected and compared. So if signal of control DNA exceeds that id patients the patient will have a delegation in the chromosomal region where that probe was derived from.
173
What is SDS-page?
Is where proteins are separated on the basis of molecular weight. A detergent SDS is used to denature the proteins, it has a large negative charge hence why molecular weight, as wipes out intrinsic charge on the protein.
174
What is the stain used in SDS-page?
Coomassise blue
175
What is isoelectric focusing?
Is where proteins are separated in the basis of isoelectric point, Pi.
176
What is the method used in isoelectric focusing?
- a stable pH gradient is established in the gel
- proteins will migrate until they reach a pH that matches their Pi
- at this point the protein has no net charge so will stop migrating
177
What is 2D-page?
Is the separation if complex molecules if proteins by combining isoelectric focusing and SDS-page. Just simply rotate by 90 degrees!
178
What is the advantage to 2D-page?
It's allows the separation of proteins with the same molecular weight but different isoelectric points and vice versa
179
What are the two types of immunological techniques?
Western blotting
| Enzyme linked immunoabsorbent assays, ELISA
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What is a polyclonal Ab used for?
For multiple epitopes
181
What is a monoclonal Ab used for?
1 epiptopes
182
Describe how ELISA works?
1. Primary Ab specific to protein is immobilised on a solid support
2. Solution to be assayed is applied to antibody coated surface
3. Second antibody conjugated with an enzyme binds to 2nd antibody antigen complex
3. Binding of the second antibody is measured by an enzyme assay.
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What is ELISA used for?
To determine the concentration if a protein by analysing the binding of a corresponding antibody
184
What are the conditions used in enzyme assays?
- optimum pH, temperature, ionic strength
- ions or cofactors needed are included
- high concentration of the substrate
185
What is measured in enzyme assays?
The production of product or disappearance of substrate.
186
What is ALT and AST looking for?
Liver damage or liver disease
187
What are the enzyme assays used to indicate pancreatitis?
Amylase and lipase
188
What do the enzymes Creatine kinase and lactate dehydrogenase indicate?
Myocardial infarction
189
What does gamma glutamyl trans peptidase, GGT indicate?
Liver damage, increased by alcohol
190
What is the marker for bone disorder?
Alkaline phosphatase, ALP
191
What does acid phosphatase, ACP indicate?
Prostate cancer
192
What does plasma cholinesterase indicate?
Is decreased in liver disease.
193
What enzyme is inhibited in organophosphate poisoning?
Plasma cholinesterase
