Understanding Cells and Cell Functions

1. Cells

2. Why are cells so tiny? • Larger cells do not function as efficiently • The surface is the only way cells interact with the environment • Surface-area-to-volume ratio • As cell size increases, volume grows much more rapidly

3. Cell Theory • Schleiden and Schwann • Three principles • All living things are composed of cells • Cells are the smallest living things (Functional units of the body) • Cells come from pre-existing cells

4. Cell Types • Prokaryotes • Lack a nucleus and membrane bound organelles • MUCH smaller than eukaryotes • Bacteria • Eukaryotes • Have a nucleus and organelles • Much bigger than prokaryotes

5. Cell Organelles • Cell membrane • Semi-permeable • Cytoplasm— “cell blood” • Fluid matrix surrounding nucleus • Surrounded by a cell membrane • Nucleus— “cell brain” • Contains chromatin (loosely coiled DNA)

6. Endoplasmic reticulum • Interconnected membranes forming canals and flattened sac-like spaces • Functions: • Communications system • Rough ER: studded with ribosomes • Involved in protein synthesis • Smooth ER: has no ribosomes • Involved in synthesizing lipid

7. Ribosomes • Composed of protein and RNA • May be free in the cytoplasm or attached to ER • Function: • Involved in protein synthesis

8. Golgi apparatus • Stack of flattened membranes • Function: • Package and transports proteins from the cell

9. Mitochondria • “Cell powerhouse” • Contains its own DNA • Capable of self-reproduction • Composed of 2 membranes • Contains enzymes used in cell respiration • Function: • Produce ATP for cellular energy (cell respiration)

10. Lysosomes • Small sacs from the Golgi apparatus • Contains enzymes capable of breaking down breaking down nutrients or toxins • Function: • Digestion

11. Centriole • Twin hollow cylinders (centrioles) • Function: • Involved in cell division

12. Vesicles • Tiny sacs formed by the cell membrane folding in and pinching off • Function: • Intake or excretion of large materials (endocytosis and exocytosis)

13. Microfilaments and Microtubules • Tiny rods usually arranged in meshes or bundles • Function: • Involved in cell movement • Provides structure to the cell

14. Cillia and Flagella • Fine, long, threadlike organelles protruding from the cell surface • Function: • Cell movement

15. centrosome Golgi apparatus lysosome vesicles nucleus mitochondria flagella smooth ER rough ER

16. Cell Membrane • Selectively permeable (semi-permeable) • Allows some substances in, excludes others • Composed of phospholipid bilayer (containing cholesterol) and protein inclusions • Fat soluble molecules pass through the lipid part • Water soluble molecules must move through protein component • Pores, channels or receptors

18. Passive Transport • Movement of a material into or out of a cell without the use of energy. • Diffusion • Osmosis • Facilitated diffusion • *** NO ENERGY REQUIRED***

19. Diffusion • The process by which molecules move down a concentration gradient • Move from area where there is moreconcentration to areas that are less concentrated • Rate limited by concentration

20. Facilitated Diffusion • Diffusion using special carrier molecules to allow usually non-permeable molecules to pass through a selectively permeable membrane • Example: Insulin facilitates glucose movement • Rate of passage is limited by the number of carrier molecules and concentration

21. Osmosis • The diffusion of water through a selectively permeable membrane which may not allow dissolved substances to pass • May result in changing volumes on either side of the membrane • Osmotic pressure • The amount of pressure needed to stop osmosis

22. Concentration Types • Hypertonic • A solution which has a greater concentration of solute particles than a given cell or solution • Hypotonic • A solution which has a lesser concentration solute particles than a given cell or solution • Isotonic • A solution which has an identical concentration of solute particles to a given cell or solution

23. Filtration • The forcing of permeable molecules through a membrane by hydrostatic pressure • Example: Blood pressure

24. Active Transport • The movement of molecules against a concentration gradient using cellular energy and carrier molecules • Proton pump • Sodium-potassium pump ***ENERGY REQUIRED***

25. Bulk Passage • Endocytosis • The inward movement of molecules through a membrane by infolding and pinching off vesicles • Pinocytosis: taking in tiny droplets of liquid • Phagocytosis: taking in solid material • Receptor Mediated: molecule bonds with receptor protein • Exocytosis

26. Cell division • Prokaryotes • Binary fision • DNA replicated in parent • Parent divides • Fast • Eukaryotes • Mitosis • Complicated • Lots of DNA • Form chromosomes (compact structures, composed of DNA and histone proteins, that can be manipulated easily during cell division

27. Cell cycle • Interphase • Period “Inbetween” cell division • Majority of cell’s life • Cell growth • Protein synthesis

28. Mitosis • Cell division that Is Mighty Common • Makes all cells EXCEPT gametes (reproductive cells) • DNA is doubled then • Cells divide once

29. Prophase • Cells Prepares to divide • Chromatin condenses into chromosomes • Nuclear membrane disappears

30. Metaphase • Chromosomes line up in the Middle • Spindle Apparatus stretches from pole to pole

31. Anaphase • Sister chromatids move Awayto opposite poles

32. Telophase • Cell “Tears” in two • Nuclear membrane reforms • Chromosomes disperse into chromatin • Cytokinesis (cytoplasmic division) (separate phase?) • Produces 2 identical “daughter cells”

33. Cell differentiation • Process by which cells develop different characteristics in structure and function • Differences in outcome • Directed by cell’s DNA • Determined by cell’s position in the body and its chemical environment