BMSC 220

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BMSC 220
2013-10-16 02:00:36
BMSC 220 Lect

Lecture 3- Molecular Composition
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  1. Water
    • -70% of wet weight in cells
    • -oxygen is slightly negative in water
    • -hydrogen is slightly positive in water
  2. Hydrogen Bond
    • -electromagnetic bond between H and an electronegative atom
    • -water can form H bonds (especially with itself)
  3. Macromolecules contribute what percentage of dry weight of most cells?
    • -80-90%
    • -proteins, nucleic acids and carbs=macromolecules
  4. Carbohydrates
    • -major source of nutrients in the cell
    • -form plant cell walls
    • -role in signalling and recognition(blood typing)
  5. Monosaccharides
    • -simple sugars with form (CH2O)n
    • -glycosidic bonds link monosaccharides together
  6. Disaccharides
    • -molecule made of two monosaccharides linked through glycosidic bond
    • -ex. lactose, sucrose
  7. Oligosaccharide
    -made up of 3-20 monosaccharides
  8. Polysaccharide
    • -100's-1000's of monosaccharides linked together
    • -ex. glycogen or starch
  9. Glycosidic Bond
    -dehydration reaction joining two monosaccharides
  10. Glycogen
    • -branched α glucose polymer
    • -major energy storage polysaccharide in animals
  11. Starch
    • -branched or unbranched α glucose polymer
    • -major energy storage polysaccharide in plants
  12. Cellulose
    • -unbranched polymer of β glucose molecules
    • -principal structural component of plant cell walls
  13. Lipid Composition
    • -basic fatty acid chain is simplest lipid, long non-polar hydrocarbon chain attached to a polar head group (carboxyl)
    • -variations can include cis and trans conformations when double bonds introduced
  14. Lipid Basic Functions
    • -long term energy storage
    • -major components of cell membranes
    • -role in cell signalling and cell recognition
  15. Triacylglycerols
    • -store fatty acids 
    • -consist of three fatty acids linked to a glycerol molecule
  16. Phospholipids
    • -principle components of cell membranes
    • -two fatty acids joined to a polar head group
    • -amphipathic molecules
  17. Glycolipids
    • -consist of carbohydrate linked to a lipid
    • -also part of cell membrane
  18. Steroid Hormones
    • -ex. estrogen, testosterone
    • -cholesterol derivative 
    • -signalling molecules 
    • -amphipathic (polar OH group)
  19. DNA Constituents
    • -adenine(purine)
    • -guanine(purine)
    • -cytosine(pyrimidine)
    • -thymine(pyrimidine)
  20. RNA Constituents
    • -adenine(purine)
    • -guanine(purine)
    • -cytosine(pyrimidine)
    • -uracil(pyrimidine)
  21. _ is the sugar for DNA, and _ is the sugar for RNA?
    • -deoxyribose for DNA
    • -ribose for RNA
    • -difference is on the 2 carbon
  22. Nucleoside vs Nucleotide
    -nucleoside lacks phosphate group
  23. Nucleotide Composition
    • -nitrogenous base attached to the 1 carbon 
    • -ribose/deoxyribose 5 C sugar
    • -phosphate group on carbon 5 of sugar
    • -form chains through 5' phosphate group to 3' hydroxyl group to form phosphodiester bonds
  24. Nucleotide Base Pairing
    • -A with T (DNA)
    • -A with U (RNA)
    • -C with G
  25. Other Uses of Nucleotides
    • -ATP as primary energy source
    • -signalling molecules ex. cAMP or cGMP for signalling
  26. Fundamental Property of Proteins
    -ability to act as enzymes which catalyze nearly all chemical reactions in biological systems
  27. Basic Structure of Amino Acids
    • -all 20 AA have same basic structure
    • -amino group NH3+
    • -carboxyl group COO-
    • -H group 
    • -side chain group
  28. Four Categories of Proteins
    • -based on side chains
    • -nonpolar sidechains
    • -polar sidechains
    • -basic (positively charged sidechains)
    • -acidic (negatively charged sidechains)
  29. 4 Levels of Protein Structure
    • -primary (AA sequence)
    • -secondary (formation of either α helices or β sheets)
    • -tertiary (folding of polypeptide chain. stabilized by hydrophobic, hydrophilic and disulfide bonds between cysteine residues)
    • -quaternary(composition of final protein from more than one polypeptide chain ex. hemoglobin)
  30. Definition of Cell Membrane
    -bilayer of amphipathic phospholipids with associated proteins and other specialized lipids
  31. Lipids Constitute _% of the mass of most cell Membranes? What constitutes most of the rest?
    • -50%
    • -rest is mostly proteins
  32. Freedom of Movement in Cell Membranes is in what Direction?
    -free to rotate and move in lateral directions
  33. Fluid Mosaic Model
    • -coined by Jonathan Singer and Garth Nicolson
    • -used to describe the cell membrane when they observed that proteins are inserted into lipid bilayer
  34. Integral Membrane Proteins
    -embedded directly within the lipid bilayer
  35. Membrane Permeability
    • -allows small uncharged molecules to pass freely
    • -stops large polar molecules and ions from passing
    • -hydrophobic molecules can also readily pass through the membrane
  36. Channel Proteins
    -form open pores through the membrane, allows free passage of any molecule of the appropriate size and structure
  37. Carrier Proteins
    -selectively bind and transport small molecules such as glucose
  38. Passive Transport
    -process where molecules are transported by channels or carriers across the membrane in the energetically favourable direction (ex. down a concentration gradient)
  39. Active Transport
    • -process where molecules are transported in energetically unfavourable direction (ex. against concentration gradient)
    • -usually coupled to ATP as a source of energy
  40. Proteomics
    • -large scale analysis of proteins contained in a cell
    • -proteome is all the proteins expressed in a given cell
    • -important because we can now see where and somewhat how proteins interact with each other and the cell