Biol 155 Human Physiology

1. Biol 155Human Physiology Instructor: Dr. Robert Harris Office: 1354 Biological Sciences Phone: 822-5709 Email: harris@zoology.ubc.ca

2. Course requirements • Text: Fundamentals of Anatomy and Physiology 6th ed. Frederic H. Martini • Exams: Two midterms (30% each) and a final (40%) • Read course synopsis. Failure to read it, or failure to listen to what I say does not constitute an excuse • Lecture Notes and synopsis are posted at: http://www.science.ubc.ca/~biomania/biol153/lecture/main01.htm

3. Atomic structure and elements • An element is a substance that retains its chemical and physical characteristics even when it is broken down into its smallest units. • The smallest practical unit, for our purposes is the atom.

4. The chemical characteristics are determined by the number of protons • These are the three forms of hydrogen • All three have one electron • All three have one proton

5. Electron orbits • Number of electrons generally equals number of protons. • There are specific orbits (or shells), that contain a specific maximum number of electrons

6. Charged atoms • Atoms are most stable when there are 8 electrons in the outermost shell. • In order for the outermost shell to be filled, atoms will either take in or give off electrons. When this happens there is a change in net charge. • Charged atoms (ions) can be electrically attracted (opposite charges attract) • This is known as ionic bonding • Ionic bonds are fairly weak

7. Covalent bonds • Another way atoms can fill their outer shell is to share electrons with another atom • The electrons orbit around BOTH nuclei • This is known as a covalent bond • Covalent bonds are much stronger than ionic bonds

8. Molecular dipoles • When covalent bonds are formed, the electrons may not be shared equally between the atoms • This unequal sharing can result in an uneven distribution of electrical charges on the molecule • This is known as a partial charge, or a dipole

9. Hydrogen bonding • Water molecules interact with each other electrically • The partial negative charge around the oxygen is attracted to the partial positive charge around the hydrogen • These very weak electrical attractions are called hydrogen bonds

10. Ions in aqueous solution • Water molecules can form hydrogen bonds with ions • Ions in solution have a layer of tightly bound water molecules around them • This layer of water molecules is known as the hydration sphere • Water can form hydrogen bonds with uncharged molecules as well (providing there is a partial charge)

11. pH is the negative log (the small p) of the hydrogen concentration (the large H) In pure water, some of the H2O molecules will dissociate into H+ and OH- The H+ concentration in pure water is 0.1 mM, or 1x10-7 moles/L (hence pH 7)

12. Molecular Representations • There are several ways or representing molecular structures • Here are three representations of glucose • Linear model • Structural model • Space-filling model

13. Synthetic and Lytic Reactions • Smaller organic molecules can be linked together • Often this involves the production of H2O • Larger organic molecules can be broken down into subunits • This often consumes H2O, hence the term “Hydrolysis”

14. Energetics of chemical reactions • In order for chemicals to react, they must first overcome an energy barrier • This is known as the activation energy • Some bonds are easily reorganized, resulting in a lower activation energy

15. Enzyme catalyzed reactions • Enzyme has binding sites for the reactants • The active region will attack the bonds in the precursors • Once bonds have been reorganized, product is released

16. Polymers in organic systems • A polymer is a chain made up of repeating subunits • Useful compounds are often stored in the form of a polymer • For example, glycogen is a branched polymer of glucose • Glycogen molecules can have different numbers of glucose subunits • Proteins are also polymers

17. Fatty acids and lipids

18. Phospholipids in aqueous solutions • Phospholipids and glycolipids are amphipathic • Meaning they have a hydrophillic region and a hydrophobic region • When they are in solution, they form micelles

19. Fluid Mosaic Model

20. Cell Membrane Structure

21. Transportation Across Cell Membranes • Simple Channels • Gated Channels • Protein Channels • Ion Channels

22. Leak and Gated Channels

23. Transport of solutes through cell membranes • Cell membranes are made up of phospholipids arranged in a bilayer. • The centre of the bilayer is hydrophobic, which means that hydrophilic molecules cant penetrate. • Hydrophobic and lipid-soluble molecules can penetrate cell membranes. • In order for hydrophilic molecules to be taken up, a transport mechanism is needed. • These transport mechanisms are integral membrane proteins.

25. Integral Proteins

26. Peripheral Proteins

27. Anchoring Proteins

28. Recognition Proteins and Enzymes

29. Receptor and Carrier Proteins

30. Ion channels • Ions are fairly small molecules. • Specialized proteins in the membrane form aqueous pores, which allow ions through. • The driving force is the chemical gradient • These pores can be quite selective. • Most of these pores are regulated • Example: CFTR

31. Forces Involved in Movement Through Membranes

32. Diffusion

34. Effect of osmotic concentration on cells • Cell membranes are semipermeable, and thus subject to osmotic forces. • Animal cell membranes are flexible, and allow for inflation and deflation depending on the movement of water

35. Facilitated diffusion • Molecules that are slightly larger need more help in getting into or out of cells. • Rather than a pore, molecules are actually bound to carrier protein, which translocates molecule. • Driving force is still the chemical gradient

36. Active transport • In order to move ions against a concentration gradient, energy must be used. • Energy is supplied by the hydrolysis of the terminal high-energy bond of ATP. • Example: Na-K-ATPase

37. Active secondary transport • ATPases only pump ions, nothing bigger. • Larger molecules are transported by coupling them to movement of an ion down its concentration gradient. • Ions can also be transported in this way. • Example: Na-coupled glucose uptake.

38. Membrane transport and cycling • Molecules can bind to cell surface receptors and then be internalized. • This same mechanism can be used to recycle membrane.

39. Phagocytosis • Phagocytosis also involves membrane invagination. • This process does not involve clathrin. • Pseudopods extend around a particle, forming a phagosome. • Phagosome will fuse with a lysosome, containing digestive enzymes. • There are smaller transport mechanisms in the wall of the secondary lysosome.

40. Cellular organelles • Most intracellular organelles are membrane-bound. • Since membranes are barriers to diffusion of aqueous solutes, they allow for partitioning of cellular components • Such partitioning allows for the generation of gradients and/or the segregation of specific compounds inside the cell, a process that is essential for life.

41. Nucleus • Nucleus also has two membranes. • Nucleus protects the DNA and maintains a specific environment for the DNA. • Nuclear pores allow for transport into and out of nucleus.

42. Nucleus

43. Ribosomes • Ribosomes are enzymes made up of two subunits. • Ribosomes are the enzyme that synthesize proteins, based on an mRNA template • Some ribosomes are attached to the ER and some a free in the cytoplasm.

44. Mitochondria • Mitochondria actually have two membranes, separated by a small space. • Mitochondria also have their own DNA. • Mitochondria are essential for oxidative phosphorylation and creating ATP

45. Adenosine triphosphate (ATP) • Adenosine backbone • Three phosphate groups attached in a chain • Last two have high energy bonds

46. Endoplasmic reticulum • The endoplasmic reticulum consists of a series of interconnected membrane-bound tubes and lamina that are all continuous. • It is essential in the production of membrane proteins. • It also serves as a Ca2+ storage organelle.

47. Golgi apparatus • The Golgi apparatus is a contiguous system of lamellae and cisternae. • It is responsible for post-translation modifications of proteins, formation of secretory vesicles and membrane formation and trafficking.

48. Membrane flow • Transport vesicles bud off the ER and are transported to the forming face of the Golgi. • Membrane-bound proteins and secretory proteins then move through the Golgi, where they are modified, usually by glycosylation. • The proteins and membranes are then packaged into specific vesicles, which are targeted.

49. Cell cycle

50. DNA and RNA structure