1. NOTES: 7.2 – CELL STRUCTURES & FUNCTIONS

2. Comparing the cell to a factory:
● each cell part (“organelle”) can be compared to a specialized machine in a factory; ● each part performs a specific “job” or function towards the functioning of the cell as a whole…

4. Cell Organization:
● each eukaryotic cell can be divided into 2 major parts: 1) Cytoplasm 2) Nucleus

5. CYTOPLASM:
● CYTOPLASM: the portion of the cell outside the nucleus; mostly water; all other organelles suspended in cytoplasm

6. NUCLEUS:
● NUCLEUS: contains nearly all of the cell’s DNA (the coded instructions for making all of the cell’s proteins); ● considered the “control center” of the cell; ● nucleus is surrounded by a nuclear envelope

8. NUCLEAR ENVELOPE ● double membrane which encloses the nucleus;
● includes many nuclear pores (holes) which allow material to move in and out of the nucleus

9. CHROMATIN
● threadlike complex of DNA bound to proteins; it makes up chromosomes in eukaryotic cells

10. CHROMOSOMES ● compacted, coiled up chromatin;
● human cells have 46 chromosomes (23 pairs)

11. NUCLEOLUS ● dense, spherical region in the nucleus
-ribosome assembly begins here

13. Organelles that Store, Clean Up, and Support:
● vacuoles & vesicles ● lysosomes ● cytoskeleton

14. VACUOLE: ● used for storage (of water, salts, proteins, carbs);
● in animal cells, vacuoles are smaller than in plant cells

15. PLANT VACUOLES…
● may contain soluble pigments in some cells (red and blue pigments in flowers);

17. PLANT VACUOLES…
● help protect from predators by storing waste products that may also be poisonous compounds
● contractile vacuole:
specialized vacuole that
pumps excess water
out of cell.

18. VESICLES:
● VESICLES: small, membrane-enclosed structures that store and move materials between cell organelles, or to and from cell surface

19. LYSOSOMES: ● the cell’s “clean-up crew”!
● contain digestive enzymes that break down macromolecules into smaller subunits;
● recycle the cell’s own organic material;
● can destroy cells by breaking open all at once and digesting the cell from within

21. CYTOSKELETON:
● CYTOSKELETON: provides shape & internal organization; also involved in transport of materials within the cell, as well as whole-cell movement ● includes protein filaments: -microfilaments -microtubules

22. Cytoskeleton

23. MICROTUBULES & MICROFILAMENTS
● make up the cytoskeleton
● structural support to cell; maintain shape
● involved in cell movement

24. Microfilaments: ● threadlike structures; ● made up of protein: ACTIN
● stabilize cell shape
● microfilament assembly & disassembly allow amoebas & other cells to “crawl” along surfaces
Yellow: nucleus
Green: microfilaments throughout cytoplasm

25. Microtubules: ● thin, hollow cylinders made of protein: TUBULIN
● maintain cell shape;
● can serve as “tracks” to
guide organelle movement;
● involved in separation of chromosomes in cell division; make up SPINDLE FIBERS / CENTRIOLES (in animal cells)

26. Microtubules (cont.)…
● responsible for movement of flagella & cilia

27. FLAGELLA and CILIA:
● FLAGELLA: longer usually single extensions; used to propel a cell
● CILIA: shorter and more numerous than flagella; wavelike motion used to sweep extracellular material over/away from cell

28. Organelles that Build, Modify, and Transport Proteins:
● ribosomes ● endoplasmic reticulum ● Golgi Apparatus

29. RIBOSOMES: ● site of protein synthesis
-small particles of RNA & protein
-follow coded instructions from DNA
-made in the nucleolus
-cells especially active in protein synthesis often contain large #s of ribosomes
-may be free (in cytoplasm) or attached to the ER

30. ENDOPLASMIC RETICULUM (ER):
● extensive network of internal membranes
● used to transport and/or modify proteins;
● can be ROUGH (ribosomes) or SMOOTH (no ribosomes)

31. Rough ER: ● rough appearance due to ribosomes on outer surface;
● newly made proteins leave the ribosomes and are “dropped off” into the rough ER;
● modifies and transports proteins;

32. Smooth ER: ● synthesizes lipids, phospholipids, steroids
● detoxifies drugs and poisons

33. GOLGI APPARATUS: ● stacked, flattened membranes
● finishes, sorts, packages and ships many cell products (a.k.a. the “post office” of the cell)

35. Organelles that Capture and Release Energy:
● chloroplasts ● mitochondria

36. CHLOROPLASTS: (“the organelles that feed the world”)
● contain chlorophyll;
● site of photosynthesis (convert light energy into “food”, or chemical energy)

37. MITOCHONDRIA: ● sites of cellular respiration
● convert the chemical energy stored in food into usable energy packets for the cell
● the # in cells varies and is related to the cell’s metabolic activity (i.e. if a cell uses more energy, it will have more mitochondria!)

38. Cellular Boundaries:
● cell wall ● cell membrane

39. Cellular Boundaries: ● CELL WALL:
- semi-rigid structure outside of cell membrane
of PLANT CELLS & most prokaryotes;
- in plants, consists of CELLULOSE fibers;
provides support, limits cell’s volume, and protects against fungi and/or microorganism infection;
most cell walls are porous enough to allow water, oxygen, carbon dioxide, etc. to pass through.

40. CELL WALL:

41. CELL MEMBRANE:

42. What must a membrane do? ● let some things leave / enter cell
● keep stuff inside or outside of cell
● be flexible as cell changes shape

43. ● cell membranes form a LIPID BILAYER that is flexible & can regulate what enters & exits the cell;
● The cell membrane is composed of molecules called PHOSPHOLIPIDS.

44. PHOSPHOLIPIDS:
-one end is strongly nonpolar (hydrophobic);
-one end is extremely polar (hydrophilic)

45. ● the nonpolar lipid “tails” are repelled by polar water molecules; the polar “heads” of the molecules form hydrogen bonds with water molecules.

46. ● So, every phospholipid molecule orients so that its polar “head” faces water and its nonpolar “tails” face away... two layers are formed with the tails facing each other...the result is called a LIPID BILAYER.

47. Lipid bilayer membranes are:
● PERMEABLE to:
lipids
nonpolar molecules: O2, CO2
small polar molecules: H2O
● IMPERMEABLE to:
ions (Na+, K+, Cl-)
large polar molecules: sugars, proteins

48. 3 Main Types of Cell Membrane PROTEINS…
1) Channels
2) Receptor proteins
3) Cell surface markers

49. 1. CHANNELS:
● a channel will transport only certain kinds of molecules...which gives the cell membrane its selectively permeable nature
                      

50. 2. RECEPTOR PROTEINS:
● collect & transmit information from the cell’s environment

52. 3. CELL SURFACE MARKERS:
● identify your body‘s cells as belonging to you (useful in cell-cell recognition)