Biomolecules 1

• What are the 4 major biomolecules?

  carbohydrates, proteins, lipids & nucleic acids
• Major functions of lipids:

  • Separate aqueous environments (bilayer)
  • Form anhydrous energy stores & provide insulation (adipose fat tissues)
  • hormones & vitamins
  • H2O repellent (coats duck feathers)
  • sebaceous gland produce sebum (protects skin & coats hair)
  • tear film (meibum enables tears)
• What do fatty acids make?


  Triglycerides & phospholipids
• Structure of triacylglycerol (TAG):

  3 fatty acids & a glycerol backbone, joined via ester bonds.

  Stored in white fat (vacuoles)(primarily adipocytes) & reduced during fasting or intense exercise.
• What do polyunsaturated fatty acids in the diet maintain?


  protective skin layer (e.g, omega 3 & 6)
• What property do lipids have that make them a good energy source?

  Hydrophobic

  1g fat stores 6x much energy as 1g hydrated glycogen carbohydrate
• When are fatty acids released?

  In negative energy states, by TAG hydrolysis. Catalysed by Hormone-Sensitive Lipase (HSL). E.g, may lose weight when stressed
• What is HSL regulated by?


  Adrenaline & Cortisol
• What are the 2 types of obesity?

  1. Visceral fat (around internal organs)
  2. Subcutaneous fat (in hypodermis)
• What is steatosis?


  When fat is stored in liver cells (bad)
• What is Cirrhosis?


  Scarring of the liver
• What is non-alcoholic fatty liver disease caused by?

  Diet
• What are steroid hormones formed from?


  Cholesterol
• Examples of steroid hormones:

  • Sex Hormones (testosterone & oestrogen)
  • Stress Hormones (Cortisol & Aldosterone)
• What form does the body store cholesterol?

  Ester
• Where does the body store cholesterol?


  Sex glands or adrenal cortex/gland (hormones made here)
• What are the 5 main classes of steroid hormones?

  Androgens, oestrogens, progestogens, glucocorticoids & mineralocorticoids.
• What are prostaglandins & leukotrienes (local hormones) made from?


  Arachidonic acid (AA Breakdown)
• What class are local hormones?

  Eicosanoids
• What type of receptors do local hormones use?


  extracellular
• What type of hormone is prostaglandin?


  Inflammatory
• Drugs like aspirin block...


  Cox enzyme, to prevent prostaglandin production.
• What are the other bioactive lipids?


  Lipid-soluble vitamins:

  Vitamin A- Retinol

  Vitamin D3- cholecalciferol

  Vitamin E- tocopherols

  Vitamin K- blood clotting (found in leafy greens)
• What forms bilayers?

  Glycerophospholipids- due to their amphipathic nature (polar & hydrophobic ends)
• Phospholipid structure:

  • 2 fatty acid chains
  • glycerol backbone
  • polar head (phosphate + choline)
• Lipid bilayer membranes contain:

  • proteins with variable functions (e.g, hormone receptors)
  • glycolipids (structurally stabilise membrane)
  • cholesterol (stabilises temperature- buffer at high & low temperatures)
  • sphingolipids (form myelin)
  • glycerophospholipids
• Roles of steroid hormones:


  Electrolyte balance, metabolism & reproduction
• What are steroid hormones?


  Potent, cholesterol derived & use intracellular receptors
• What is mucopolysaccharidosis?


  Genetic disorder (autosomal recessive) of skeleton, connective tissues & organs.

  Insufficient enzymes produced to breakdown sugar chains, causing accumulation of GAGs.
• Fatty acid structure:


  Carboxyl group followed by hydrocarbon chain

  End of chain is called 'omega' & has a terminal methyl group
• Why are they called omega-3 & 6 fatty acids?


  First double bond is on the 3rd/6th carbon from the omega end of hydrocarbon tail
• Essential fatty acid supplementation may be beneficial in...


  • animals with scaly skin (seborrhea)
  • allergic skin disease (atopic dermatitis)
• Where can you find polyunsaturated fats?

  • Omega 3: Fish
  • Omega 6: Plant-based oils (e.g, sunflower, corn & soya)
• Where to find monounsaturated fats?


  Avocados, nuts, olive oil.
• Phosphatidylethanolamine:


  Phospholipid in cell membrane- maintains fluidity
• Phosphatidylinositol:


  In cell membrane: cell-signalling