Cell Structure and Function Part 1: Cell intro and the plasma membrane

1. Cell Structure and Function Part 1:Cell intro and the plasma membrane

2. 75-100 trillion per body 75,000,000,000,000 200+ different types Each is structurally and functionally different 7µm – 120µm in size 7/10,000th – 12/1000th of a cm 7/125,000 -120/125,000ths of an inch Cell Factoids (not on test)

3. Cell Theory (for AP150) • All known living things are made up of one or more cells • Cells are the fundamental structural and functional unit of the body. • Cells are responsible for the fundamental structure of the human body • Cells are responsible for the fundamental functions of the human body • The structure (and function) of higher levels of organization (e.g., tissues, organs) reflects the activities and structures of cells • The activity of an organism/the whole body depends on the total activity of independent cells. • Cells contain DNA which is passed from cell to cell during division • Energy processing and most chemical reactions occurs in cells • Cells only come from other, pre-existing cells.

4. Things Cells Do: • Obtain nutrients and O2 from its environment • Perform chemical reactions and process nutrients to release energy (metabolism) • Eliminate cell waste • Regulate their internal environment • Move (external or internal) • Sensitive to and responds to surroundings • Grow • Reproduce

5. A Prototypical/Generic Cell

6. The generic (composite) cell • There are 200+ types of specialized cells in the human body. • Different types of cells have different functions which result in cells having a variety of shapes, sizes, and composition of parts. • We study a “generic” cell that has representative parts found in most human cells

7. Parts/Components of cell Cell = Plasma Membrane + Cytoplasm + Nucleus Cytosol + organelles + inclusions

8. The Generic Cell The major parts of the cell include • Plasma membrane — the outer boundary of the cell • Cytoplasm — within PM, performs most cell activities • Nucleus— contains protects DNA Plasma Membrane Cytoplasm Nucleus

9. Body/Fluid Compartments • intracellular v. extracellular compartments • Intracellular = inside cells • Extracellular = outside cells • Plasma Membrane separates A. intracellular B. extracellular 1-45

10. Body/Fluid Compartments • Extracellular : • blood plasma • interstitial fluid or tissue fluid 1-45

11. The extracellular and intracellular environments can be very different • Example is extracellular v. intracellular Na+ and K+ concentration

12. Functions of the Plasma Membrane (PM)those from text in blue Forms a physical barrier (that separates): separates inside of cell from outside (forms a compartment). Selectively Permeable allows some things through but not others regulation of movement Actively regulates or influences what can enter/exit cell Connection(Attachment) connects cells to other cells and/or surrounding structures connects to internal cell parts Communication regulation/coordination allows cell-cell communication/signalling for coordination of activity Chemical reactions chemical reactions take place on the PM Cell recognition The PM “labels”/identifies the cell *italicized words represent the four functions the book describes, I have elaborated and reworded

13. The Plasma Membrane • The plasma membrane creates a boundary between the cells internal environment and its external environment. • It makes the cell a compartment that is separated from other areas/compartments of the body. • It creates a selectively permeability barrier that some substances can pass through and others can’t • Because of this: • There is a difference in the composition of the intracellular (inside cell) and extracellular (outside cell) environment. • The cells internal environment can be regulated

14. PM Structure:Composition of the PM • Three types of molecules make up the PM • Lipids—about 42% of PM (by mass/weight), more by surface area • 5-10% of lipids have carbohydrates attached • Proteins—about 55% of PM (by mass) • Includes glycoproteins The PM is mostly Lipids and Proteins and these two molecules exist in relatively equal proportions. * Carbs make up about 3%of overall PM by weight/mass

15. Membrane Lipids 2 primary types of Membrane Lipids • Phospholipids—Most abundant (~70-75%), • One factor that creates selective permeability -- prevents the movement of most substances across the PM -- Especially fluids: Prevents intracellular fluids from escaping and extracellular fluids from entering • Cholesterol—less abundant (~20%), effects membrane fluidity/ stabilizes at high temperatures (i.e., prevents it from becoming too fluid) keeps membrane from being too rigid • Glycolipids—5-10% of lipids the sugar portion located on cells exterior and helps form glycocalyx

16. Phospholipids have 2 regions • Head—hydrophilic, attracted to water • Tails—hydrophobic, repelled by water Phospholipid Head Tails

17. Cholesterol Spans hydrophobic and hydrophilic regions. Doesn’t pass through both sides of PM Extracellular (outside cell) Non-polar tail region: Impermeable to ions and polar molecules Except Water Lipid bilayer Intracellular (inside cell)

18. Functional Consequences of phospholipids • Because the center of the phospholipid bilayer is hydrophobic (and non-polar): • Most polar/water soluble substances and ions cannot pass through the lipid portion of membrane. • Only non-polar (lipid soluble) can substances can pass directly through the lipids of the membrane. Thus: the lipid bilayer creates selective permeability and influences what can pass into and out of a cell (contributing to the difference between the intracellular and extracellular environments).

19. 19

20. structural classifications Integral proteins deeply embedded extend from both inner and outer surfaces Peripheral proteins only attached to a single side of PM Glycoproteins Sugar+protein 90% of membrane carbs Glycocalyx Functional Classifications Transport Into/out of cell Connection Intercellular Intracellular—to cytoskeleton Enzymes Chemical rxns Recognition Receptors (signal transduction) Two different ways to describe membrane proteins

21. structure

22. Transport Proteins • Move substances that cannot pass through phosolipid bilayer • Ions • Polar molecules Examples:

23. Transport Proteins • Allow ions and polar molecules to pass through membrane. • Selective permeability proteins CELL

24. Transport Protein Composition • Types of transport proteins influences permeability Na+ Na+ Na+ K+ Na+ Na+ K+ K+ Na+ K+ K+ K+ Na+ Na+ Na+ Na+ K+ Na+ Na+ K+ K+ K+ Na+ Na+ K+ Na+ K+ A B C

25. Ion Channels • Temperature • Ligands/chemical • Voltage • Mechanical distortion • Protein based tubes • Allow ions to pass through membranes • Can be ion and direction specific • Types A) Non-gated/leak channels: always open B) Gated: open and close under specific conditions A B

26. Ligand Gated Channels Closed open

27. Carriers • Carriers (facilitated diffusion) • Ions pumps (also a type of carrier) ATP ATP Ion pump

28. Characteristics of Carriers • Can transport ions and polar molecules • Specific • Due to shape • Can be Direction specific • Some require/use ATP • Can be activated and deactivated

29. or channel

30. Transport Proteins • Channel and carrier proteins are specific to certain substances (i.e., different molecules move through different transport proteins). • Which types of transport proteins and how many of each type is a very important aspect of what is able to move into and out of a cell. • The transport proteins of individuals cells are the major influence on what is able to move into and out of different types of cells under different conditions.

31. Attachment Proteins • Holds/attaches the PM to surrounding structures • E.g., Hold a cell to an extracellular structure • E.g., Connects plasma membrane to cytoskeleton Cell A Cell B

32. Connection/Anchoring/Attachment • Often contain a carbohydrate component (glycoproteins) • Cell to Cell connections • Cell to extracellular material • Cell to intracellular material

33. Recognition/Marker Proteins • Identify the cell • E.g., “self”, to prevent immune response on cell • Often have carb component (glycoproteins) • Glycoproteins • Part of glycocalyx

34. Marker Proteins can indicate cell type I’m a kidney cell I’m a bone cell I’m a liver cell Cell A Cell B Cell C A

35. Receptor Proteins • Binding sites for specific chemical messengers/signals (i.e., ligands): • Typically polar messengers/signallers • Specificity based on: • Shape • Enables cellular communication/coordination and responsiveness to environment

36. Possible Actions of Receptor Proteins • Opening/activating transport proteins • Activate enzymes • Activate DNA/proteins synthesis • Activate movement of vesicles to the PM Alters activity/behavior of receiving cell

37. Receptors and endocrine signaling I’ll stop secreting I’ll work faster Now, I’ll uptake nutrients OK, I’ll start making proteins D C A B

38. Nervous & endocrine system signaling, both rely on membrane receptors to work • Nervous system: receptors for neurotransmitters on post-synaptic cell • Endocrine system: hormone receptors on target cells

39. Enzymes • Perform chemical reaction on PM surface • Breakdown molecules • Create molecules • Extracellular • intracellular

40. Membrane Carbohydrates: make the glycocalyx • outermost/most external part of the cell’s membrane. • Made of carbs bound to lipids (glycolipids) and proteins (glycoproteins) • Functions in: • cell identification (its type and in self/non-self) • attachment of the cell to other cells/structures

41. Relationship between membrane components and cell function

42. Cell Transport

43. Types/Modes of Cell Transport • Passive Transport • Diffusion • Osmosis • Filtration • Active Transport • Ion pumps • Exocytosis • endocytosis

44. Solution = solvent + solutes non-water materials water

45. Diffusion

46. Diffusion

47. Diffusion subtypes and classes of molecules transported • Simple Diffusion Through lipids: • nonpolar molecules—O2, CO2, fatty acids, steroid hormones • Water • Facilitated diffusion Through channel proteins: • ions • water (through aquaporins) • Facilitated Diffusion through carrier protiens: • e.g., glucose, amino acids

48. Example of Simple Diffusion through membrane lipids

49. Osmosis • Water moves toward area with more solutes

50. Diffusion Times Time it takes the “average” molecule to diffuse a given distance. size range of “typical” cells and typical distance from a blood vessel too slow; if a substance had to diffuse this distance the cell would die waiting for needed materials ųm = 1/1000 of a millimeter msec = 1/1000 of a second MOST CELLS ARE WITHIN 125 ųm OF A BLOOD VESSEL