Cell Biology Flashcards by Arhanth Prema

Site of RNA splicing ??

Nucleus
Pre-messenger RNA (m-RNA) ==> Mature mRNA
- Introns are removed & Exons (protein coding part) are joined

How well did you know this?

Not at all

Perfectly

Give some eg. of diseases caused by Splicing errors

Famial Parkinson’s (Chr 17)
Fronto-Temporal Dementia

How well did you know this?

Not at all

Perfectly

What pharmacokinetic property is a/w highest level of clearance by Dialysis ??

High water solubility (drugs are removed by Counter-Current Flow across Semi-permeable memb.
Compound should be in Plasma at high conc.
Low protein bound compound
Molecular size < 10 kDa

How well did you know this?

Not at all

Perfectly

What does drug with high lipid solubility indicate ??

High lipid solubility => Increased Tissue binding

How well did you know this?

Not at all

Perfectly

In which part of the cell is Insulin receptor is located ??

Cell membrane (a Transmemb. receptor)
- It is a Tyrosine Kinase receptor

How well did you know this?

Not at all

Perfectly

Give eg. of a Cytoplasmic receptor

Androgen receptor

How well did you know this?

Not at all

Perfectly

Hallmark of Nuclear receptor ??

These regulate Gene expression
- eg.- Peroxisome proliferator-activated receptors, Retinoids & Vit. D receptors

How well did you know this?

Not at all

Perfectly

What is the primary function of microRNAs ??

Silencing of mRNA
- microRNAs target particular segments of mRNA to silence them, preventing ribosomal binding to mRNA & protein translation

How well did you know this?

Not at all

Perfectly

How is gene transcription regulated ??

by Repressors & Activators
- Repressor binds to the operator region on DNA => impedes RNA polymerase progress on DNA
- Activators increase the attraction of RNA polymerase for a promoter region of DNA, increasing Transcriptional activity

How well did you know this?

Not at all

Perfectly

How is mitochondrial func. regulated ??

Nutritional status (fasting & Glucagon production stimulation improves Mitochondrial’s energy production
PPAR-Alpha & PPAR-Gamma activity

How well did you know this?

Not at all

Perfectly

How is protein degradation regulated ??

Recognition by Ubiquitin molecules & subsequent digestion by 26S proteosome

How well did you know this?

Not at all

Perfectly

What is Protein Phosphorylation ??

Driven by KINASES
MC & important Post-translational modifications; in this, Phosphate groups are added to the polar group R of various amino acids, which can lead to gain/loss of function by inducing a conformational change in protein structure

How well did you know this?

Not at all

Perfectly

What is the function of Peroxisome ??

Oxidation of Very Long-Chain FAs to liberate energy

How well did you know this?

Not at all

Perfectly

What is Refsum’s disease ??

A R
Impaired Beta oxidation of VLC FAs
Causes build up of Phytanic acid & its derivatives in plasma & tissues
Progressive visual loss, impaired night vision due to R pigmentosa

How well did you know this?

Not at all

Perfectly

Which HIV peptide plays a role in initial step for HIV entry into cells ??

GP-41
- GP 120 fuses to the CD4 receptor, which then allows GP-41 to penetrate the cell memb.

How well did you know this?

Not at all

Perfectly

Features of Vit B12 ??

aka Cobalamin; Essential water-soluble vit.
Source: Meat, fish, eggs & dairy
Produced by certain Bacteria in the gut

How well did you know this?

Not at all

Perfectly

How is Cobalamin absorbed, transported in the body ??

Binds to [IF] produced in the stomach => forms a complex => absorbed in the SI
Once absorbed, Vit.B12 binds to Transcobalamin II (TC II) for transport in the blood stream
TC II - B12 complex delivers B12 to cells
Enters cells through Receptor-mediated Endocytosis

How well did you know this?

Not at all

Perfectly

What happens to Vit B12 inside the cells ??

After entering the cell, B12 undergoes conversion to its active coenzyme forms- Methylcobalamin & Adenosylcobalamin
- M Cobalamin: participates in Methionine synthesis (key step in DNA synthesis)
- A Cobalamin: needed for conversion of Methylmalonyl-CoA ==> Succinyl-CoA (a process of Energy metabolism)

How well did you know this?

Not at all

Perfectly

Role of B12 in
- DNA synthesis ??
- Energy metabolism ??

M Cobalamin donates ‘Methyl’ grp. for conversion of Homocysteine ==> Methionine- needed for DNA methylation
A Cobalamin facilitates breakdown of certain Fatty A & Amino A
It is a cofactor for enzyme Methylmalonyl-CoA mutase, prevents the accumulation of toxic metabolites

How well did you know this?

Not at all

Perfectly

What is the main pathology of the following
- Methylmalonic Acidemia (MMA) ??
- Homocystinuria ??

Build up of Methylmalonic acid due to impaired B12 function
Elevated levels of Homocysteine due to impaired B12 metabolism

How well did you know this?

Not at all

Perfectly

What are the active forms of B12 (Cobalamin) ??

Methyl-B12 & Adenosyl-B12

Features of Folate ??

Vit. B9, a water soluble vitamin
Sources: Leafy green, legumes, fruits & fortified grains
Essential for normal growth & devt., specially during pregnancy

How is B9 absorbed, & processed intracellularly ??

Absorbed in Jejunum; converted to its active forms- Dihydrofolate & Tetrahydrofolate
Active forms are utilized in 1-carbon transfer reactions, critical for syn. of Nucleotides, Amino A & other cellular components
DHF-reductase converts DHF ===> THF; a crucial step in regeneration of active folate forms

What is the use of Folate in
- DNA synthesis ??
- Amino Acid synthesis ??
- Methylation reaction ??

Significance of Folate Metabolism ??

Megaloblastic anaemia Neural tube defect Elevated Homocysteine levels, a/w Folate deficiency, may contribute to CVS disease

Which drug does the following to Folate - Interfere with metabolism ?? - Reduce absorption ??

- Trimethoprim, MTX, Pyrimethamine - Phenytoin

Manifestations of Vit. C deficiency ??

Scurvy: leads to defective synthesis of collagen resulting in capillary fragility (bleeding tendency) & poor wound healing Features - Gingivitis, Loose teeth - Poor wound healing - Bleeding from gums, Haematuria, Epistaxis - General malaise

What are the functions of Vit. C ??

Water soluble vitamin - Antioxidant - Collagen synthesis: acts as a co-factor for enzymes that are required for hydroxylation of Proline & Lysine in collagen synthesis - Co-factor of Norepinephrine synthesis

What is sources of Ascorbic acid ??

Source: Citrus fruits, Tomatoes, potatoes, Brussel sprouts, cauliflower, broccoli, cabbage & spinach

What is Scurvy ??

Vit C deficiency => impaired Collagen synthesis & disordered connective tissue as it is a cofactor for enzymes used in Proline & Lysine production => Capillary fragility => Bleeding tendency - Follicular Hyperkeratosis & Perifollicular Haemorrhage - Ecchymosis, easy bruising - Poor wound healing - Gingivitis, bleeding & receding gums - Sjogren's. - Arthralgia. - Oedema. - Impaired wound healing - Generalized weakness, malaise, anorexia & depression

What is Vit. D and their sources ??

Fat soluble vitamin that plays key role in Ca2+ & PO4- metabolism - Vit D ==Liver==> Calcifediol (prohormone) aka Cholecalcidol ==Kidney==> CALCITRIOL (Vit D active form) Source: - D2 (Ergocalciferol): Plants - D3 (Cholecalciferol): Dairy products, can be synthesized by SKIN under sunlight

Features of vit D deficiency ??

RICKETS : in Children OSTEOMALACIA : in Adults

What is Vit. D resistant rickets ??

X-linked Dominant condition; presents in Infancy with FTThrive - Due to IMPAIRED PO4- Reabsorption in renal tubules C/F- - FTT - Normal Ca2+, Low PO4-, High ALP - X-ray: Cupped Metaphyses + Widening of Epiphyses

How to Dx. & Rx of Vit. D Resistant Rickets ??

By demonstrating HIGH Urinary PO4- Rx.- - High dose Vit. D supplements - Oral PO4- supplements

Features of Vit. K ??

Fat soluble vitamin which acts as a cofactor in Carboxylation of Clotting Factors (2, 7, 9, 10) - Used to reverse Warfarinization - Takes >= 4hrs to see a change in INR Deficiency - Seen in conditions affecting Fat absorption - Due to prolonged use of Broad-spectrum Abx. by killing Gut flora

What are the indications for Nutritional support ??

- BMI < 18.5 - 10% body wt. loss unintentionally in the past 3 to 6 months - BMI < 20 + > 5% unintentional wt. loss in the past 3 to 6 months

Lose.... I don't lose, I WIN, I WIN.... That's my job & That's what i do

What is DIC ??

Simultaneous Coagulation & Haemorrhage caused by the initial formation of thrombi => consumes clotting factors (5, 8) & platelets => leading to Bleeding - Bleeding is a dominant feature, bruising, ischaemia & organ failure

Blood profile of DIC ??

Prolonged Clotting times Thrombocytopenia Decreased Fibrinogen Increased F degradation product

What are the metabolism products of Arachidonic acid ??

Phospholipids ==Phospholipase A2===> Arachidonic acid- produces 2 substrates - AA ==COX1,COX2==> Endoperoxides - AA ==(Lipooxygenase)==> HPETSs ==> LB4 & Leukotrienes

What are produced by Endoperoxidase matabolism ??

Prostacyclin (PGI2) - Vasodilation - Decreases Plt. aggregation - Decrease Uterine tone Prostaglandin (PGE2) - Increase Pain, Temp., Uterine tone, Gastric mucosa THROMBOXANES (TXA2) - Vasoconstriction - Increases Plt. aggregation

What are the functions of LB4 & Leukotrienes ??

Both are the products of HPETEs metabolism LTB4: Increases Neutrophil Chemotaxis Leukotrienes: - A4, C4, D4 & E4: ALL constricts lungs (Bronchoconstriction)