MCD Past Paper Questions Flashcards

1
Q

Explain the acute phase response

A

Systemic inflammatory response to tissue injury/inflammation leading to the production of cytokines and mediate leucocytosis and an increase in body temperature cause by IL-2.
Production of many acute phase proteins from liver e.g. C-reactive protein, serum amyloid protein, mannose binding lectin which activate complement to lyse pathogens

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2
Q

Define basement membrane and state where it is found and state its major constituents

A

Thin flexible mat of ECM which acts as highly selective filter for macromolecules
Underlies epithelial cells and tubes and separates epithelial cells from connective tissue
Type 4 collagen, laminins and perlecan

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3
Q

Explain how the 7-methylguanylate cap is formed and its function

A

Initially the 5’ end of the mRNA chain is dephosphorylated from the triphosphate to a diphosphate, which reacts with the alpha phosphate of a GTP forming 5’-5’ phosphate linkage. The guanyl is then methylated at the 7th carbon position.
Protects mRNA and enhances translation

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4
Q

Explain how azt works

A

Nucleoside reverse transcriptase inhibitor
Used to treat HIV as part of HAART
Inhibits reverse transcriptase and prevents the formation of cDNA from viral RNA so no new genetic material can be made and no new HIV viruses are formed in infected cells, therefore helping to treat person

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5
Q

Name some anti-flu drugs and state their targets

A

Oseltamivir: competitively inhibits neuraminidase which normally cleaves silica acid, allowing new virus particles from leaving the cell so it prevents the spread of the virus between cells
Ribavirin: blocks RNA polymerase required to produce new virus particles
Zanamivir: prevents vessel from detaching from cell preventing new viruses from spreading from cell to cell

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6
Q

How are MCV, MCH and MCHC calculated?

A

MCV=Hct/(RBCx1000)
MCH=(Hbx10)/RBC
MCHC=HB/Hb

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7
Q

Distinguish between pathogenic and non-pathogenic bacteria

A

Pathogenic bacteria produce toxins, are opportunistic, antagonize host immune response, spread, translocate cell membranes and usurp normal cell function

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8
Q

Name the different components of two types of steroid hormone receptor

A
  • Steroid hormone receptor is an intracellular receptor
  • Type 1: in cytosol. When hormone binds, hsp dissociates so receptor translocates to nucleus to bind to DNA
  • Type 2: in nucleus. Hormone binds to receptor to regulate transcription
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9
Q

Name 4 types of membrane proteins

A

Receptors, transport channels, cell adhesion molecules, membrane enzymes

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10
Q

Explain how ETC poisons work

A

Cyanide/Azide: bind to Fe3+ form of haem group in cytochrome oxidase complex, blocking flow of electrons and hence ATP production
Malonate: closely resembles succinate, competitively inhibiting succinate dehydrogenase, slowing down electron flow from succinate to ubiquinone by reducing oxidation of succinate to fumarate
Rotenone: found in roots/seeds, inhibits electron flow from complex one to ubiquinone
Oligomycin: antibiotic produced by streptomyces that binds to ATP synthase stalk, blocking flow of protons through stalk
Dinitrophenol: proton ionophore which can shuttle protons across inner mito membrane, giving another pathway to enter matrix, limiting ATP synthase - can be used to induce weight loss by decoupling oxphos from ATP production, leading to markedly increased metabolic rate and body temperature yet very fatal - DANGEROUS

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11
Q

How is HbS formed and how does this cause sickling?

A

Mutation at position 6 - valine instead of glutamate
Hydrophobic valine residue of HbS forms hydrophobic interactions with residues on beta chain of another haemoglobin molecule
Interactions give rise to polymers/aggregates of HbS which tend to precipitate/crystallise and distort the erythrocyte

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12
Q

Name 4 processes in HIV replication which effect drugs target

A

Viral nucleic acid binding/entry
Reverse transcription of HIV mRNA into DNA
Integration transcription
Virion assembly

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13
Q

Explain how a tyrosine kinase receptor works

A
  1. Ligand binds to receptor
  2. Activates receptor and causes more receptors to move to surface of cell, leading to receptor clustering
  3. Receptor clustering leads to activation of tyrosine kinase enzyme
  4. Tyrosine kinase phosphorylates receptor causing a signal protein to bind to the cytoplasmic domain
  5. Signal protein recruits other signal proteins so signal is generated
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14
Q

What is the function of a heat shock protein?

A

Chaperone molecule to guide receptor bound to ligand to DNA

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15
Q

What are the differences in pathogen specificity between the innate and acquired/adaptive immune response?

A

Innate immune response is characterized by its reliance upon preformed molecules with no specificity. It has limited specificity due to it recognizing PAMPs.
The adaptive immune response is based on clonal selection (growth of cells and molecules for antigen specificity). It is characterized by its diversity, specificity and memory via the production of antibodies that label target pathogens.

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16
Q

Explain how the polyA tail is formed

A

Cleavage stimulation factor (CstF) and Cleavage polyadenylation specificity factor (CPSF) are 2 RNA binding proteins that recognize the end of the genome to be transcribed. They bind to specific nucleotide sequences. Poly A Polymerase (PAP) enzyme adds around 200 A nucleotides to the end of the RNA sequence.

17
Q

How does acyclovir function?

A

Has similar structure to guanosine but doesn’t have 3’OH group
Treats HSV
Virus produces viral thymidine kinase which acyclovir has a high affinity for so is converted into acycloGMP which is phosphorylated by cellular kinase to acycloGTP. This then binds to the growing chain instead of guanosine and due to no 3’OH it prevents the formation of the subsequent phosphodiester bond resulting in the chain no longer growing, leading to viral replication being stopped early so the virus no longer can replicate and increase in number.

18
Q

Define ‘epigenetic’

A

Study of hereditary changes in genome that do not affect the primary DNA sequence. Disorders are different despite the gene mutation being the same.