Cell Biology

1. Cell Biology Ch. 4 1

2. Cell Theory • Every organism is made of on or more cells. • Cell is the smallest unit of life. • Continuity of life depends on the growth and division of single cells. 2

3. Basic Components of a Cell: • Plasma membrane • Nucleus or nucleoid • Cytoplasm 3

4. Cell Membrane • Lipid bilayer – two sheets of lipid molecules. Hydrophilic Head Hydrophobic Tail 4

5. Cell Size • If a cell keeps growing the volume will increase more rapidly than its surface area will. • Problem: a cell needs surface area to take in material and excrete material. surface-to-volume ratio • If volume is too large then materials cannot be transported easily across the cell. 5

6. Nucleus • Directs cell activities. • Separated from cytoplasm by nuclear membrane. • Contains genetic material – DNA • DNA stores information to make proteins, enzymes that are needed for cellular functions. 6

7. Nucleus • Nuclear envelope- double-membrane system, 2 lipid bilayers. • Proteins are embedded in the innermost layer. • These are used to anchor the molecules of DNA to the envelope and help keep them organized. • On the surface of the nuclear envelope are ribosomes where proteins are built. 7

8. Nucleolus • Inside nucleus • Protein and RNA molecules are being constructed here. • Needed to synthesis proteins. 8

9. Chromosomes • Tightly bundled DNA. 9

10. Cytomembrane System • System in cytoplasm that assembles, modifies, packages and ships proteins and lipids. • Some polypeptide chains enter the space inside rough ER, where they are shaped into proteins. • In smooth ER, lipids are assembled. • Vesicles bud from the ER membrane and then transport unfinished proteins and lipids to a golgi body. 10

11. Proteins and lipids take on their final form in the space inside the golgi body. There they are sorted out and shipped to their proper destinations. • Vesicles budding from the golgi membrane transport finished products to the plasma membrane. 11

12. Endoplasmic Reticulum ER • Rough – ribosomes attached. • Smooth – ribosome free, lipids are assembled here. • Polypeptide chains are synthesized on ribosomes. 12

13. Golgi Bodies • Enzymes in here put the finishing touches on proteins and lipids. • Sorts them. • Package them inside vesicles for shipment. 13

14. Vesicles • Tiny sacs that move through the cytoplasm. • Common type: Lysosome- buds from golgi membranes. • Lysosomes contain digestive enzymes that breakdown proteins, carbs, nucleic acids, and some lipids. 14

15. Vesicles • Peroxisomes – another type of vesicle that break down fatty acids and amino acids. • Hydrogen peroxide is formed during these reactions. 15

16. Mitochondria • Where ATP is formed. • Organic compounds are broken down to carbon dioxide and water. • Has a double membrane system. • Crista – inner fold. 16

17. Membrane System of Mitochondria • Enzymes and other proteins stockpile hydrogen ions in the outer compartment of the cristae. • Electrons transfer through the folds which drive the stockpiling. • This electron transfer forms ATP. 17

18. Chloroplasts • Only in photosynthetic cells. • Convert sunlight energy into ATP which is used to make sugars and other organic compounds from CO2 and Water. CentralVacuole -stores amino acids, sugars, ions, and toxic wastes. • x 18

19. Cytoskeleton • Internal organization • Shape • Capacity to move Cytoskeletal Elements: -microtubules -microfilaments -intermediate filaments (give strength to cells) 19

20. Microtubules • Long, hollow cylinder, largest • Tubulin – protein • Polar – so that the microtubules can line up in the same direction. • Used in cell division to split chromosomes apart. 20

21. Microfilaments • Thinnest of cytoskeletal elements • Helix shape • Polar • Myosine and actin – protein that attaches to microtubules and microfilaments to cause cell movement. 21

22. Cell Cortex • 3d network of microfilaments and other proteins. • Just beneath the plasma membrane. • Reinforces the cell surface. • Facilitates movements.

23. Movement • Pseudopods • Microfilaments and microtubules • Cilia • flagella

24. 4.11 Prokaryotic Cells • All bacteria cells are prokaryotic. • Simplest kind of cells. • Some have flagella. • pilli

25. Class Jump Assignment Homework pg.77 • Review Questions: 1 – 15 • Self-Quiz: 1 - 6

26. Sec. 5 – Membrane FluidMosaicModel: • Mixture of phospholipids, glycolipids, sterols, and proteins. • Glycolipids have more than one sugar than phospholipids on their heads. • Membrane is fluid, drift sideways, short or kinked hydrophobic tails contribute to the membrane fluidity because phospholipid bonds are weak.

27. Proteins in Membrane X • Transportprotein – span the bilayer and allow water-soluble substances to move through their interior. Bind to molecules on one side of the membrane then release them on the other side.

28. ReceptorProteins – bind extracellular substances, like hormones, that trigger changes in cell activities. RecognitionProteins – oligosaccharide chains identify other cells. Ex. WBC AdhesionProteins – help locate like cells and adhere to them.

29. Selective Permeability • Membrane permits some substances but not others to cross it in certain ways, at certain times. • Large polar molecules such as glucose almost never move freely across the bilayer, nor ions.

30. Concentration Gradients and Diffusion Concentration – number of molecules or ions of a substance in a specified region. Gradient – the number in one region is not the same as it is in another. Concentrationgradient – a difference in the number of molecules or ions of a given substance between adjoining regions.

31. Diffusion • Molecules moving from high concentration to lower concentration. Ex. Drop of dye in water or spraying perfume. Faster at higher temp. When concentration is equal – dynamic equilibrium http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_diffusion_works.html

32. Electric Gradient • Difference in electric charges of adjoining regions. Ex. Fluid around a membrane may have many dissolved ions. --- so the fluid having the more negative charge tends to exert the greatest pull on positively charged substances such as sodium ions.

33. Pressure Gradient • Difference in the pressure being exerted in adjoining regions. • High pressure to low pressure

34. Facilitateddiffusion – transport protein diffuses substances into cell, no energy required. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_facilitated_diffusion_works.html ActiveTransport – solutes are pumped through interior by transport proteins, energy required.

35. Active Transport System-against concentration gradient • Calciumpump – helps keep the calcium concentration in a cell at least a thousand times lower than outside. • Sodium-potassiumpump – moves potassium ions across the plasma membrane. This protein also facilitates binding of a sodium ion on one side of a cell membrane and released on the other side. Its release facilitates the binding of K+ at a different binding site on the protein, which reverts to its original shape after K+ is delivered to the other side.

36. http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.htmlhttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_sodium_potassium_pump_works.html

37. Osmosis • Bulkflow – mass movement of one or more substances in response to pressure, gravity, or some other external force. • Osmosis – diffusion of water molecules in response to a water concentration gradient between two regions separated by a selectively permeable membrane. • http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_osmosis_works.html

38. Isotonic – the amount of solute in a water solution is equal on both sides of membrane. • Hypotonic – one side has less solute than the other side of membrane.

39. Hypertonic – one side has more solute than the other side of the membrane.

40. Bulk Transport Across Membrane • Exocytosis – exocytic fuses with plasma membrane and release its contents outside the cell. • Endocytosis – substance is taken up by cell. • Receptor mediated: membrane receptors recognize specific substances and bind with them. Ex. Vitamins, lipoproteins, iron, hormones..

41. Bulk-phase: endocytic vesicle forms around a small volume of extracellular fluid regardless of what kinds of substances happen to be dissolved in it. • Phagocytosis: cell engulfs microorganisms, large particles, and cellular debris. “cell eating” http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__phagocytosis.html

42. Review • Prokaryotes • Pro = before; karyon = nucleus • lack membrane-bound organelles • earliest cell type • Eukaryotes • Eu = true; karyon = nucleus • contain membrane-bound organelles • Evolved from prokaryotes

44. Cytoskeleton Answer: • Scaffold of microfilaments, intermediate filaments, microtubules that maintain cell shape, support, anchor organelles, movement, intracellular transport…

45. Answer: Nucleus • Contains DNA

46. Rough ER Answer: • Contains ribosomes and is involved in protein synthesis.

47. Smooth ER Answer: • Lacks ribosomes and is involved in membrane lipid synthesis.

48. Golgi Apparatus Answer: • Flattened vesicles that receive protein from ER. • Refine protein and sort it and send it out in either vacuoles or lysosomes.

49. Lysosome Answer: • Contain enzymes for use in hydrolytic breakdown of macromolecules.

50. Ribosomes Answer: • Involved in protein synthesis. • Free or bound to ER.