INI CET Bio Chemistry Flashcards

24 sample cards from the Bio Chemistry deck

Sampled from the end of the deck, so these are different cards from the ones shown on the syllabus page.

1. How are fatty acids activated and transported into the mitochondria for beta-oxidation?

   Fatty acids are activated to fatty acyl-CoA, then carried across the inner mitochondrial membrane by the carnitine shuttle (carnitine palmitoyltransferase I and II).

2. What does each round of fatty acid beta-oxidation produce?

   Each cycle removes a 2-carbon acetyl-CoA and yields 1 FADH2 and 1 NADH, shortening the fatty acid chain by two carbons.

3. What is the structure of a triacylglycerol and the rate-limiting enzyme of its breakdown?

   A glycerol backbone esterified to three fatty acids; hormone-sensitive lipase is the rate-limiting enzyme of lipolysis (stimulated by glucagon/epinephrine).

4. What are the major lipoprotein classes ranked by density, and what do chylomicrons and LDL carry?

   Chylomicrons < VLDL < IDL < LDL < HDL (increasing density). Chylomicrons carry dietary triglycerides; LDL carries cholesterol to tissues ('bad'); HDL returns cholesterol to liver ('good').

5. What are ketone bodies, where are they made, and when are they produced?

   Acetoacetate, beta-hydroxybutyrate, and acetone, synthesized in the liver mitochondria (ketogenesis) during prolonged fasting/starvation or uncontrolled diabetes; the liver cannot use them (lacks thiophorase).

6. How is the amino group removed from amino acids before their carbon skeletons are metabolized?

   By transamination (transferring the amino group to alpha-ketoglutarate forming glutamate) followed by oxidative deamination of glutamate by glutamate dehydrogenase, releasing ammonia.

7. What enzyme defect causes phenylketonuria (PKU) and what is the consequence?

   Deficiency of phenylalanine hydroxylase (or its BH4 cofactor) prevents conversion of phenylalanine to tyrosine, causing phenylalanine accumulation and intellectual disability if untreated.

8. What is one-carbon metabolism and which vitamins/carrier are central to it?

   Transfer of single-carbon units (methyl, methylene, formyl) for synthesis of purines, thymidylate, and methionine; it relies on tetrahydrofolate (from folate) and vitamin B12, with SAM as the major methyl donor.

9. Where do the electrons from NADH and FADH2 enter the electron transport chain, and what is the final electron acceptor?

   NADH enters at Complex I and FADH2 at Complex II; oxygen (O2) is the final electron acceptor, being reduced to water.

10. Explain the chemiosmotic theory of ATP synthesis.

    Electron transport pumps protons into the intermembrane space, creating an electrochemical gradient; protons flow back through ATP synthase (Complex V), driving phosphorylation of ADP to ATP.

11. How do uncouplers like 2,4-dinitrophenol affect oxidative phosphorylation?

    They dissipate the proton gradient by carrying protons across the inner membrane, so electron transport continues but ATP synthesis stops and energy is released as heat.

12. Why are mitochondrial disorders often multisystem and maternally inherited?

    Mitochondrial DNA is inherited from the mother, and tissues with high energy demand (brain, muscle, heart) are most affected; defects impair oxidative phosphorylation (e.g., MELAS, LHON, Leigh syndrome).

13. What is meant by integration of metabolism in the fed (absorptive) state?

    High insulin promotes glucose uptake, glycogen synthesis, lipogenesis, and protein synthesis, while inhibiting gluconeogenesis and lipolysis, storing fuel.

14. How is metabolism integrated during fasting/starvation?

    Glucagon dominates: glycogenolysis then gluconeogenesis maintain blood glucose, lipolysis and beta-oxidation supply energy, and ketone bodies fuel the brain to spare glucose and protein.

15. How are hormones classified by chemical structure?

    Peptide/protein hormones (e.g., insulin), steroid hormones (e.g., cortisol), and amino-acid derivatives (e.g., thyroxine, epinephrine).

16. How do steroid hormones differ from peptide hormones in their mechanism of signaling?

    Lipophilic steroid hormones cross the membrane and bind intracellular/nuclear receptors to alter gene transcription; hydrophilic peptide hormones bind cell-surface receptors and act via second messengers.

17. What is the cAMP second messenger signal transduction pathway?

    Hormone binds a GPCR, activating Gs protein, which stimulates adenylate cyclase to produce cAMP, which activates protein kinase A (PKA) to phosphorylate target proteins.

18. What are the major classes of essential nutrients the body cannot synthesize adequately?

    Essential amino acids, essential fatty acids (linoleic and alpha-linolenic acid), vitamins, minerals, and water (plus dietary energy from carbohydrates/fats).

19. Which deficiencies cause scurvy, beriberi, and pellagra?

    Scurvy from vitamin C deficiency; beriberi from vitamin B1 (thiamine) deficiency; pellagra from vitamin B3 (niacin) deficiency (the 3 Ds: dermatitis, diarrhea, dementia).

20. Which vitamin deficiency causes night blindness, and which causes rickets/osteomalacia?

    Vitamin A deficiency causes night blindness (xerophthalmia); vitamin D deficiency causes rickets in children and osteomalacia in adults.

21. What does vitamin B12 (cobalamin) deficiency cause, and what is its main dietary source?

    Megaloblastic (pernicious) anemia with subacute combined degeneration of the spinal cord; sourced from animal products and requires intrinsic factor for absorption.

22. What is the principle of electrophoresis as a biochemical technique?

    Charged molecules (proteins, nucleic acids) migrate through a gel in an electric field; separation is based on charge, size, and shape (e.g., SDS-PAGE separates proteins mainly by molecular weight).

23. What is the principle behind ELISA?

    Enzyme-Linked Immunosorbent Assay uses antigen-antibody specificity with an enzyme-linked antibody that produces a measurable color change, used to detect and quantify proteins/antigens or antibodies.

24. What does the Lambert-Beer law describe in spectrophotometry?

    Absorbance is directly proportional to the concentration of the absorbing substance and the path length (A = epsilon x c x l), allowing quantification of solutes by light absorption.

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