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Yr 1 Medicine > Principles Of Medicine > Flashcards

Principles Of Medicine Flashcards

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1
Q

Evidence for endosymbiotic theory

A

Mitochondria contain separate DNA with No associated histones

Mitochondria can only be formed from other mitochondria

Mitochondria contain their own protein synthesising complexes with many similarities to prokaryotic machinery

First amino acid of mitochondrial transcript fMET as is the case in bacteria and not MET as in eukaryotes

A number of antibiotics such as streptomycin will also block protein synthesis is mitochondria, but not in cytoplasm of eukaryotes.

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2
Q

Describe the steps of glycolysis including the types of each reaction

A

Glucose phosphorylated by hexokinase enzyme at carbon 6

  • requires ATP investment
  • Group transfer

Phosphoglucose Isomerise enzyme converts 5C ring to 4C, creating an extra side branch and molecular symmetry

  • isomerization
  • glucose 6 phosphate —> fructose 6 phosphate

Fructose-6-phosphate phosphorylated to fructose 1,6 bisphosphate by phosphofructokinase

  • Requires ATP investment
  • group transfer

Fructose 1,6 bisphosphate hydrolysed by aldolase to 2 3 carbon molecules including glyceraldehyde 3 phosphate
-hydrolysis

Other 3C molecule converted to glyceraldehyde 3 phosphate by TPI
-Isomerization

Inorganic phosphate added to each G3P to form 2x 1,3 bisphophoglycerate

  • NAD+ reduced by dehydrogenase enzyme
  • Group transfer

1 phosphate group removed by phosphoglycerate kinase enzyme
-ATP generated

Phosphate group moved from position 3->2 by isomerise enzyme (phosphoglycerate mutase)
-isomerization

Water eliminated to form double bond by enolase enzyme
-group removal

ATP generated by removal of final phosphate group by Pyruvate kinase
-group transfers

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3
Q

Describe formation of Lactate from pyruvate under anaerobic conditions

A

Catalysed by pyruvate dehydrogenase

NADH oxidised

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4
Q

What is the importance of lactate production in anaerobic conditions

A

Allow NAD+ to be regenerated so that glycolysis can continue as NAD+ is required for dehydration of gkyceraldehyde-3-phosphate

When rate of NADH formation in glycolysis greater than its rate of oxidation in NADH dehydrogenase complex

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5
Q

Describe the role of Creatine phosphate as a buffer

A

Acts as buffer for storage of ATP

Creatine phosphate + ADP + H+ creatinine + ATP

Catalysed by creatine kinase

Sustain supply first 4s intense exercise

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6
Q

Describe the platelet plug formation

A

Platelet binds to Von Willebrand factor or to Glpla receptor

ADP and thromboxane released

Thromboxane causes vasoconstriction

Positive feedback mechanism present

Conformational change In GP11b/111a

Opens fibrinogen binding sites

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7
Q

Mechanism of action of aspirin

A

Inihibits production of thromboxane A2.

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8
Q

Describe formation of a stable haemostatic plug (secondary haemostats)

A

FVII bind to TF in extravascular environment

Causes activation of fx->Xa and IX->IXa

Cleaves some prothrombin to thrombin

Causes activation of other cofactors which cleave more fX and IXa

Rapid, sustained generation of thrombin

Thrombin catalyses cleavage of fibrinogen to fibrin

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9
Q

Describe the action of protein C

A

Thrombin binds to thrombomodulin

Causes conformational change of protein C to APc (activates protein C)

Protein C binds and inhibits fVa and VIIIa in presence of protein S

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10
Q

Describe action of antithrombin

A

Inhibit thrombin and fxa

Potentiated by heparin

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11
Q

Describe the mechanism of action of heparin

A

Potentiates antithrombin inhibition of thrombin and fXa

IV drip

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12
Q

Mechanism of action of clopidogrel on platelets

A

Inhibits ADP binding site (P2Y12) on platelet cell membrane.

Lasts 7 days till new platelets produced

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13
Q

What Is the role of calcium ions in the thrombotic cascade

A

Help bind activated clotting factors to phospholipid surface of platelets

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14
Q

Mechanism of action of Warfarin

A

Vitamin K antagonist

Reduces synthesis of clotting cofactors
F(2,3,9,10)

Need to monitor

Several days to take effect

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15
Q

Mechanism of action of direct oral amticoagulants (DOACs)

A

Inhibit thrombin or fXa

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16
Q

Describe fibrinolysis

A

Plasminogen activated to plasmin by tPA when bound to lysine residues of fibrin

Plasmin catalyse degradation of fibrin clot

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17
Q

Mechanism of action of transexamic acid

A

Prevents plasminogen binding to lysine residues of fibrin

Prevents fibrinolysis

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18
Q

Describe how prothrombin time (PT) is measured

A

Blood collected

Sodium citrate added (prevents Ca2+ activating blood clotting)

Sample centrifuged, plasma taken

TF and phospholipid added

Calcium added and timer started

(Can use thromboplastin recombinant instead of phsopholipid and TF)

INR generated- normalised ratio

Pt patient/ Pt average

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19
Q

Describe how activated thromboplastin test is carried out (APTT)

A

Contact activator such as glass added to phospholipid after addition of sodium citrate and centrifugation

Ca2+ added and time to clot measured

(fXII activated by surface contact)

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20
Q

Describe three causes of bleeding

A

Reduction in platelet number

Reduction in platelet function

Reduction in coagulation factors

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21
Q

Describe 3 causes of thrombosis

A

Reduced anticoagulant proteins

Increased levels clotting factors

Increased platelet levels

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22
Q

What is mitochondrial uncoupling?

A

Any process which disrupts the proton concentration gradient between the intermembrane space and the mitochondrial matrix. Rate of NADH And FADH2 oxidation not linked to rate of ATP synthesis

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23
Q

Action of cyanide on mitochondria

A

Block cytochrome oxidase complex

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24
Q

Action of Malonate on mitochondria

A

Competitive inhibitor of succinate dehydrogenase

Slows flow of electrons to Co enzyme Q

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25
Action of Rotenone on mitochondria
Inhibits transfer of electrons from complex 1 to ubiquinone
26
Action of oligomycin on mitochondria
Block flow of protons in F0F1 ATP synthase complex
27
Action of dinitrophenol on mitochondria
Introduce micropores in inner membrane Causes mitochondrial uncoupling Decreases proton gradient
28
Describe formation of a granulocyte from a HSC
Multipotent Hemopoeitc stem cell divides and differentiates to form a common myeloid progenitor. In presence of G-CSF myeloblast formed Further differentiate to Basophils, neutrophils and eosinophils
29
Function of neutrophils
Defence against infection Phagocytosis Neutrophil migration associated with infection
30
Function of eosinophils
Defence against parasitic infection
31
Function of basophils
Involved in regulation of immune responses | Stores of histamine and heparin and proteolytic enzymes
32
Function of monocytes
Present antigens to lympohoid cells | Migrate to tissues where they develop into tissue macrophages
33
Function of tissue macrophages
Phagocytic and scavenging function | Storage and release of iron
34
Describe formation of a natural killer (NK) cell
HSC differentiates to common lymphoid progenitor via mitosis | CLP further differentiates to NK cell
35
Function of natural killer (NK) cell
Kill tumour cells Kill virus infected cells secrete cytotoxic granules
36
What is leucocytosis?
An increase in the number of lymphocytes in the blood above the reference range ``` Different names depending on cell type affected e.g. monocytosis eoisinophilia basophilia lymphocytosis neutrophilia ```
37
What is leucopenia?
An decrease in the number of lymphocytes in the blood below the reference range e.g. neutropenia
38
Causes of neutrophilia
Infection, inflammation infarction chronic myeloid leukaemia Pregnancy Exercise Corticosteroids
39
What is left shift in regards to neutrophilia?
Increase in non-segmented neutrophils or neutrophil precursors in the blood
40
Causes of neutropenia
``` Chemotherapy/radiotherapy Autoimmune disorders (Produce antibodies against own neutrophils) Severe bacterial infections Viral infections drugs-e.g. anti-pscycotics ``` Benign ethnic neutropenia -African or Afro-Caribbean ancestry
41
Causes of neutrophil hypersegmentation
Lack of vitamin B12 Folic acid deficiency (Megaloblastic anaemia)
42
Causes of lymphocytosis
``` Viral infection (transient) e.g. whooping cough Leukaemia (persistent) ```
43
Histological presentation of lymphocytosis
Atypical lymphocytes Basophilic cytoplasm 'Hugging' of red blood cells
44
Causes of lymphopenia
HIV Chemotherapy Radiotherapy Corticosteroids
45
Causes of monocytosis
Infection (chronic) | Chronic inflammation
46
Histological features of eoisinophils
Granular cytoplasm | lobed nuclei
47
Histological features of basophils
Purple/blue cytoplasm | granular
48
Histological features of monocyte
Lobular nucleus | Clear cytoplasm
49
Histological features of neutrophil
``` lobed nucleus (5-7) Clear cytoplasm ```
50
Histological features of lymphocyte
Blob of cytoplasm with inner blob (purple)
51
Causes of Eosinophilia
Allergy Parasitic infection leukaemia
52
Causes of Basophilia
leukaemia (uncommon finding)
53
Describe normal inflammatory pathway after vascular tear.
1. Inflammatory signals: Non apoptotic cell death releases molecular signals (DAMPS) 2. Vasodilators released: Histamine Nitric oxide 3. Vascular changes Increased permeability reduced flow Plasma leakage 4. Immune cell recruitment Chemokines released causes leukocyte migration to chemokine source 5. Cytokines causes up regulation of adhesion molecules such as selectins. Chemokines promote low to high affinity switch in integrins. Neutrophils bind to selectins Cytoskeletal rearrangement and extension of pseudopodia causes neutrophil 'rolling'
54
Neutrophil function at site of inflammation
Pathogen recognition and clearance (TLR4) Cytokine secretion promoting recruitment and activation of other immune cells Phagocytosis -Destruction by reactive oxygen species (ROS)
55
Resolution of acute inflammation
Pathogen recognition Neutrophils have short half life Macrophages clear apoptotic cells Repair/wound healing
56
Pros vs cons of macrophage residency in chronic inflammation
Good: Phagocytic Cytotoxic Anti-inlfmmatory Bad: Cytotoxic Inflammatory Pro-fibrotic
57
Consequences of chronic inflammation
Fibrosis- collagen deposition loss of function scarring excessive tissue damage
58
Describe the structure of collagen I, II and III
3 alpha chains: type I- heterotrimer (2 genes) Type II/III- homotrimer (1 gene) Triple helix
59
Describe the primary sequence of collagen.
Characteristic glycine X-Y repeat Glycine only amino acid small enough to fit in helix X-Y normally hydroxyproline/proline
60
What does post translational modification of proline lead to?
Hydroxylation of proline allows formation of hydrogen bonds
61
How does vitamin C deficiency lead to scurvy?
Vitamin C required co factor in enzyme required for collagen cross linking Unhydroxylated collagens cause tissue weekness
62
Describe collagen biosynthesis from a secreted protein | Fibril associated collagen
Procollagen converted to tropocollagen after cleavage of end terminals tropocollagens form collagen fibrils with hydrogen bonds between each
63
What are non fibril associated collagens
Arrange head to tail or laterally Form 'web/grid' Collagen IV in basement membrane
64
What is Ehlers-Danlos syndromes (EDS)
Inherited connective tissue disorder resulting in stretchy skin and loose joints Mutation in collagen gene
65
Components of a basement membrane:
Collagens Glycoproteins Proteoglycans
66
Consequence of diabetic nephropathy
Accumulation of extracellular matrix- highly thickened basement membrane -restricts renal function
67
Cause and effects of Alport syndrome
``` Mutation in collagen IV Abnormally split and laminated GBM -progressive loss kidney function -proteinuria (proteins in urine) -hearing loss ```
68
Describe the structure of elastic fibres
Elastin core | Microfibrils surround which are rich in fibrillin protein
69
Consequences of Marfan's syndrome
Predisposition to aortic ruptures | Spider like fingers
70
Describe the structure and function of laminins
heterotrimic proteins alpha, beta, gamma chain in cross shape Multi adhesive proteins -interact cell surface receptors (integrins, dystroglycan) Interact with basement matrix components (collagen, proteoglycans)
71
What disease is caused by an absence of the alpha 2 chain in laminin 2?
Congenital muscular dystrophy
72
Describe the structure and function of fibronectin
glycoprotein derived from single gene- alternate splicing mRNA gives rise to different types Multi adhesive protein
73
Describe formation of a collagen fibril
Pro alpha chains undergo covalent modifications and 3 form triple helixed procollagen molecule Procollagen cleaved to collagen Forms fibrils in parallel direction
74
What is paracrine signalling?
Hormone acts on an adjacent cell | I.E. Nitric Oxide
75
What is signalling between membrane proteins?
Plasma proteins on adjacent cells interacting | - Bacterial cell wall components with toll like receptors on haemopoetic cells
76
What is autocrine signalling?
signalling molecule acts on same cell | - acetylcholine-presynaptic receptors
77
List and describe the four types of cell signalling receptors
Ionotrophic receptor- Ligand binding opens ion channel which traverses membrane G-Protein coupled receptors ligand binding activates intracellular G-protein complex and GDP is converted to GTP Enzyme-linked receptor Ligand binding to receptor activates internal enzymes Intracellular receptor Membrane permeable ligand binds to a receptor inside a cell
78
Describe action of an ionotrophic receptor
Ligand binds to receptor Conformational change opens pore Ions can move in or out of cells depending on conc gradient
79
Describe mechanism of a G-protein coupled receptor activating target protein.
Heterotrimic G-protein and receptor are inactive extracellular ligand binding changes conformation of receptor Unassociated G-protein can now bind with receptor (receptor increased affinity) GDP-GTP G protein dissociates into alpha and a beta-gamma subunit binds to target protein
80
Describe the mechanism of a G-protein coupled receptor disassociating from a target protein
Internal GTP-ase dephosphorylates GTP-GDP alpha subunit dissociates from target protein and rebinds to beta/gamma subunit Receptor remains active as long as ligand bound and can activate further G-proteins
81
3 categories of G-protein alpha subunits
G-alpha S (Stimulate) G-alpha I (inhibitory) G-alpha q (activates system e.g. muscle contraction)
82
Describe mechanism of an enzyme-linked receptor
Ligand binding causes receptors to cluster Receptor clustering activates enzyme activity within cytoplasm Enzymes phosphorylate receptor phosphorylation causes binding of signalling proteins to cytoplasmic domain signalling proteins recruit other signalling proteins autocrine signalling
83
Describe mechanism of a type 1 intracellular receptor
Ligand/hormone binds to receptor Causes Heat Shock Protein (HSP) to dissociate 2 receptors bind together forming homodimer and travel to nucleus Bind to DNA and cause DNA changes or affect transcription
84
Describe mechanism of a type 2 intracellular receptor
Hormone/ligand binds to receptor which is bound to DNA within the nucleus causes changes to DNA/ transcription
85
Describe the structure of collagen
3 alpha chains, can be homo or heterotrimer Triple helix ``` Glycine- X-Y repeat (x-proline) (Y-hydroxyproline) Hydrogen bond cross links (hydroxylated Proline-proline) ((-PTM)) ```
86
How many chain types does type I collagen have? | How many chain types does type II/III collagen have?
2 chain types, 2 genes, heterotrimer | 1 chain type, 1 gene, homotrimer
87
Consequences of vitamin C deficiency on collagen structure
Results in unhydroxylated collagens, vitamin C required co-factor for enzymes involved
88
Describe formation of a collagen fibril
Pro alpha chains undergo covalent modifications and 3 form triple helixed procollagen molecule Procollagen cleaved to collagen Forms fibrils in parallel direction (troop

Yr 1 Medicine (2 decks)

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