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MGD Flashcards

1
Q

Explain allosteric regulation of enzymes

A

The binding of a substance to a point other than the active site to stimulate or depress the activity of the enzyme

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2
Q

What substances increase and decrease PFK activity?

A

Increase - AMP

Decrease - Citrate and ATP

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3
Q

Generally, explain the action of kinase and phosphorylase enzymes

A

Kinase enzymes add phosphate to make a chemical more reactive whereas phosphorylase enzymes take off a phosphate

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4
Q

What are endogenous inhibitors?

A

These are substances produced by the body to competitively inhibit an enzyme to regulate its activity

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5
Q

What are the three stages of transcription?

A

Initiation - TATA box is found at -30
Elongation - reading the DNA from 5’ to 3’ and making the sequence from 3’ to 5’
Termination - creation of a 5’ cap and a polyA tail at 3’ end

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6
Q

What is the coding and template strand of DNA?

A

Terminology used in transcription process
Coding - has the same code as the mRNA created
Template - has the opposite bases to the mRNA because of base pairing

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7
Q

Give the substrate for translation

A

Amino acids

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8
Q

Give the substrate for transcription

A

Deoxynucleotide triphosphates (dNTPs)

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9
Q

Give the enzyme for transcription

A

RNA polymerase

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10
Q

Give the enzyme for translation

A

Ribosomes

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11
Q

Give the function of tRNA

A

Has an anticodon to the mRNA bases and is bound to the specific amino acid that the mRNA codon codes for

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12
Q

What enzyme binds tRNA to an amino acid?

A

tRNA synthetase

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13
Q

What amino acid is always found at the start of a protein sequence?

A

Methionine

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14
Q

Give the function of peptidyl transferase

A

In translation, this enzyme elongates the peptide sequence by bringing the next tRNA to the mRNA codon

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15
Q

What is euchromatin?

A

The genetic material within the nucleus that can be accessed and expressed. Stains a light colour

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16
Q

What is heterochromatin?

A

The densely packed genetic material that cannot be expressed

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17
Q

Explain the basis of the ‘beads on a string’ formation

A

The negatively charged sugar phosphate backbone is coiled round a series of positively charged histone proteins

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18
Q

What is a solenoid fibre?

A

The coiling of the ‘beads on a string’ into one continuous, 70nm fibre

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19
Q

What base does adenine bind to?

A

Thymine - “a tea for two” meaning by two hydrogen bonds

Cytosine and guanine bind by three hydrogen bonds

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20
Q

Give the purine and pyramidine bases

A

Purine - adenine and guanine “pure silver”

Pyramidine - cytosine and thymine

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21
Q

What creates the polarity of the sugar phosphate backbone?

A

Phosphate at the 5’ end and hydroxyl at the 3’ end

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22
Q

Outline the PCR process

A

Existing DNA heated to 95°C to break hydrogen bonds
DNA primers added to line up to exposed strands
Cooled again to allow primers to bind
Taq polymerase then elongates the primer to create a new DNA strand

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23
Q

What is blotting?

A

Electrophoresis + fluorescent probe to highlight the divisions created by the electrophoresis process. Southern blotting for DNA, Northern for RNA and Western for proteins

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24
Q

What is protein gel electrophoresis?

A

Filtering of proteins based on size, shape and charge. Proteins applied to a porous gel and a charge is set up. Proteins migrate toward their opposite charge but the gel restricts movement of the large proteins

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25
What is SDS-PAGE?
Extension of the protein electrophoresis process except addition of a solution breaks all disulphides bridges and makes all proteins negatively charged so filtering is based only on size
26
Explain isoelectric focusing
Separation of proteins based on isoelectric point. Proteins will stop at their isoelectric point
27
What is the conglomeration of isoelectric focusing and SDS PAGE called?
2D PAGE. A system to better separate proteins
28
Explain the process of ELISA
Determining the concentration of a specific antibody. Antigen lines container Unknown antibody quantity is added (solution washed) Enzyme-linked antibody added (solution washed) Substrate added and conversion rate measured (Production rate is directly proportional to unknown antibody conc)
29
Define aneuploidy
Where the DNA from one chromosome is added to another so that one is deficient and another has excess. No overall change in genetic material
30
Define polyploidy
More than two chromosomes present as in trisomy 21 (down's)
31
Give the function of helicase
Unwinding the DNA strand during replication
32
Give the function of DNA polymerase
This creates the new strands from the templates when replicating DNA. Reads in the 5' to 3' and creates the new strand from 3' to 5'
33
What are Okazaki fragments?
The strands in DNA replication are read from 5' to 3' but one strand is at 3' to 5' so DNA polymerase does this strands in short sections, known as Okazaki fragments
34
Give the function of ligase enzyme
Ligase joins together the Okazaki fragments on the lagging strand in DNA replication to give a continuous strand
35
What happens at prophase?
Dissolution of the nucleolus and formation of two poles in the cell
36
What happens in metaphase?
Formation of spindle fibres from the poles which attach to the centromeres of the chromosomes
37
What happens in anaphase?
Pulling apart of the chromosomes to either pole so that it is now divided into two daughter chromosomes
38
What happens in telophase?
The formation of the new nucleolus followed by separation of the cytoplasms (cytokinesis) into two distinct cells.
39
How is diversity created in meiosis?
Random assortment of chromosomes in metaphase I | Crossing over of material at the chiasmata at prometaphase I
40
Define Vmax
The maximum rate at which product is produced by an enzyme
41
What is Km?
The substrate concentration that gives half of the Vmax. This is a measure of affinity of the enzyme to its substrate
42
How are Km and Vmax affected in competitive inhibition?
Km increases (affinity decreases) and Vmax is unaffected
43
How are Vmax and Km affected in non-competitive inhibition?
Km is unaffected but Vmax will decrease
44
Explain how amino acids show stereoisomerism
The central carbon atom can have two different formations for the four bonds that connect to it. This is optical isomerism or enantiomers
45
Define pK
The pH at which a substance becomes protonated. Strong acids will need a very low pH to become protonated because they have a strong tendency to donate a proton
46
Define isoelectric point
The pH at which a chemical has no overall net charge
47
Describe the primary structure of proteins
A string of amino acids in sequence held together by peptide bonds
48
Describe the secondary structure of proteins
The creation of beta pleated sheets and alpha helices with hydrogen bonding and the original peptide bonds
49
Describe the structure of alpha helices
Right handed turn structure with 3.6 amino acids per turn | Pitch of 0.54nm - rise in height per full turn
50
Describe the tertiary structure of proteins
3D folding of the secondary structure | Bonding is peptide, hydrogen, ionic, van der Waals forces and disulphide bridges
51
Describe the quaternary structure of proteins
Association of more than one tertiary protein to create a large protein e.g. Haemoglobin (globular) and collagen (fibrous)
52
Give the difference between adult and foetal haemoglobin
Foetal has two alpha subunits and two gamma subunits as opposed to two alpha and two beta in adults
53
Give the basis for the sigmoid curve for oxygen uptake by haemoglobin
This is due to co-operative binding of haemoglobin, whereby it is more likely to take up subsequent oxygen molecules once it has taken up the first
54
Describe the dissociation pattern of myoglobin
Hyperbolic curve to give oxygen as a dump at low partial pressures
55
Describe the difference between beta and alpha thalassaemia
Beta thalassaemia is a defect in the beta subunits of haemoglobin and will present after birth. Fatal. Alpha is a defect of the alpha subunits and will be present before birth but have a higher affinity for oxygen and so breathlessness and stunted growth are common
56
Give the pathophysiology of sickle cell anaemia
Mutation of glutamate to valine in the beta subunit of haemoglobin. Valine is hydrophobic and so creates a sticky pocket which is susceptible to lysis
57
Give a description of complementation in inheritance patterns
More than one gene codes for the same phenotype as in albinism
58
Give and describe the two forms of single nucleotide polymorphism (SNPs)
Transitions - purine to purine or pyramidine to pyramidine | Transversions - purine to pyramidine or vice versa
59
What is the commonest cause for single nucleotide polymorphism (SNPs)?
Radiation
60
Give the four types of mutation that a single nucleotide polymorphism (SNPs) can cause
Missense - different amino acid coded for Nonsense - creation of a stop codon Silent - no change to amino acid sequence
61
Explain the basis for frameshift mutations
The open reading frame is changed due to insertion or deletion of nucleotides. Most commonly caused by slippage, where a base loops out of the template strand.
62
What is tautomeric shift?
Where a proton transiently moves so that the wrong base pair is made by DNA polymerase e.g. cytosine binds to adenine
63
Give the two types of genetic repair
Mismatch - removal of one base and replacement with correct one Excision - removal of a defective strand of DNA and insertion of the correct one

ESA 1 (4 decks)

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