Cell Structure & Function Chapters 6, 7 & 12 Hershey High School Biology Mr. Barber

1. Cell Structure & FunctionChapters 6, 7 & 12Hershey HighSchool BiologyMr. Barber

2. Types of Cells http://www-class.unl.edu/bios201a/spring97/group6

3. Animal Cells

4. The Cell Nucleus • Why have nuclear pores at all? • What materials can pass through the nuclear envelope? What materials are retained? • What is in the nucleolus? • What molecules are in chromatin?

5. Plasma Membrane Structure • Understand the structures and properties of the plasma membrane. • Chapter 7

6. Endoplasmic Reticulum • What are the two types of ER? • How does the role of each type differ? • What kind of cells would have a lot of rough ER? Smooth ER?

7. Golgi Apparatus • Courtesy of Camillo Golgi, Italian cytologist, 1890. • What is the function of Golgi? • Each flattened sac is a __________. • How is the Golgi apparatus oriented within the cell?

8. Lysosomes • How many membranes? • Where are lysosomes formed? • Contain what? • Describe the internal environment of a lysosome. • List three major functions. • What is the relationship between Tay Sachs disease and lysosomes?

9. Mitochondrion • How many membranes? Why? • What cells would have high numbers of mitochondria? • What do mito. have to do with cloning? • What is the current theory on mito. origin?

10. Ribosomes • Non-membrane bound! • Composed of ______ and ________. • Sites to synthesize __________. • How are prokaryotic ribosomes different from eukaryotic ribosomes? • Antibiotics, including tetracycline and streptomycin, paralyze prokaryotic ribosomes. Why don’t these drugs harm eukaryotic ribosomes?

11. Centrioles • Only in animal cells. • Microtubule-producing center. • How are they usually arranged within the cell? • During cell division, centrioles organize the spindle. What is the spindle? • If plants cells lack centrioles, do they form a spindle?

12. Cytoskeleton • Enables a cell to change shape • Anchors organelles and cytoplasmic enzymes • Basically just non-membrane bound organelles that can self-assemble. • If the cytoskeleton organelles do not require the nuclear input, then from where are these structures inherited? • Cytoskeleton contains: • Microtubules • Microfilaments (actin fibrils) • Intermediate fibrils

13. Microtubules • Hollow tubes of globular proteins called tubulins. • Extend outward from organizing center, _________. • Can be broken down, and rebuilt elsewhere. Come up with a good analogy for microtubules. • List three functions of microtubules.

14. Microfilaments • Solid rods of the protein actin. Where else do we find a lot of actin? • What are the functions of microfilaments?

15. Cilia and Flagella • Structure of cilia and flagella is the same. What separates these terms? • Note the basal body in the lower left. What is a basal body?

16. Cooked Meat • What type of tissue is this. • What is different about the cell membranes in this picture? • Can you spot the nuclei?

17. Mouse Intestines • The thick, dark areas in the bottom of the picture do not represent thickened cell membranes or cell walls (obviously). • What is this space called? • Why is it important to intestine cells?

18. Frog Blood • What are the cells shown in this picture? • What organelles can you see? Are you sure?

19. Plant cells

20. Plant Cell Organelles • The following organelles are shared by both plant cells and animal cells: • Mitochondria • Golgi • ER (both types) • Nucleus (and nucleolus) • Plasma membranes • Peroxisomes • Ribosomes The organelles specific to plants cells are described in the following slides.

21. Vacuole • What materials can be found in the plant vacuole? • Contractile vacuoles are found in Protists.

22. Plant Cell Wall • Comprised of ___________. • What are the properties of the plant cell wall? • What would the role of the cell wall be during times of drought or excessive rainfall? • Tree trunk vs. sapling?

23. Plasmodesmata • What are the functions of plasmodesmata? • What kind of molecules can pass and what molecules are restricted?

24. Plastids • Became integrated in the same manner as mitochondria – some eukaryotic cells acquired bacteria. • Added photosynthetic powers to cells. • Three types of plastids: • Amyloplasts white in color, stores starch, found in roots & tubers (i.e. potatoes) • Chromoplasts many colors, important in Ps • Chloroplasts this is one will will investigate (see next slide)

25. Chloroplasts • How many membranes? • What color? Why? • Found in leaves and stems. • Be sure to understand the internal structure of a chloroplast.

26. Potato Cells • What are the circles inside the cells?

27. Onion Cells • Note the heavily stained circle in the center. • What are they?

28. Tracheids – Woody Stem • Note the rows of box-like cells. • What are tracheids? • Why is the bottom half stained differently than the top half?

29. Diatom • What is a diatom? • What elements are you most likely viewing? • This image is contrasted with darkfield microscopy.

30. Prokaryotic Cell

31. Prokaryote Characteristics • Four main shapes • Bacillus (pl. bacilli): rod shaped • More surface area than cocci • Why would this be important to a free-living organism? • Coccus (pl. cocci): sphere shaped • Less distortion • Spirillium: spiral shaped • Spirochetes: Spiral shaped with flagella • Very Motile

32. Prokaryote Characteristics (cont.) • DNA Loop • Naked loop (not associated w/ proteins) • Mainly housed in nucleoid region • Plasmids • Small, circular loops of extrachromosomal DNA • Ribosomes • Free floating

33. Prokaryote Characteristics (cont.) • Cell wall • Why does a cell wall benefit a free-living organism? • Gram Positive: Thick PG layer w/ no outer layer • Gram Negative: Multi-layered & complex cell wall. Thin PG layer surrounded by a lipopolysaccharide membrane. **Penicillin inhibits the development of peptidoglycan. Which bacterial type is more affected by penicillin? ** Tears, mucous, and saliva contain ______ that dissolve bacterial cell walls away.

34. Prokaryote Characteristics (cont.) • Capsule: Some bacteria develop a jelly-like coating surrounding the cell wall. • Four functions: • Prevents the cell from drying out • Helps the cells to stick to surfaces • Helps prokaryotes to slide on surfaces • Keep bacteria form being destroyed by host organism

35. Prokaryote Characteristics (cont.) • Flagella • Used for motility • Spin like propellers • Structurally different than eukaryotic flagella • What is the difference? • Pili • Short, bristle appendages with two functions • Attach bacteria to surfaces • Assist in transfer of DNA during conjugation

36. Paramecium • This is a single-celled protist. • What organelles can you identify?

37. Plasma Membrane: Fluid Mosaic Model • 1 • 2 • 3 • 4 • 5 • 6 • 7 • 8 • 9

38. Fluidity • Membrane must be fluid to work properly • Cholesterol (in eukaryotic membranes) controls the fluidity in two ways: • In warmer temperatures, it decreases fluidity by restraining phospholipid movement • In colder temperatures it increases fluidity by preventing the close packing of phospholipids

39. Mosaic • A mosaic of proteins is imbedded and dispersed in the phospholipid bylayer. • Two protein types (depending on their location) 1) Integral Proteins: Inserted so the hydrophobic region of the protein is surrounded by the hydrocarbon portion of the phospholipid • Unilateral: reach only partway across the membrane • Transmembrane: completely span the membrane (Chemically, how do you think these proteins are arranged?) 2) Peripheral Proteins: Not imbedded, but attached to the surface • May be attached to integral proteins • May be held by filaments

40. Movement of Substances • Cell membrane must act as a selectively permeable barrier • This prevents passive movement of most molecules • There are seven ways a substance can get into a cell: • Bulk Flow • Diffusion • Osmosis • Facilitated Diffusion • Active Transport • Vesicle-Mediated Transport • Cell-Cell Junction http://www.biointeractive.org

41. Bulk Flow • Molecules move all together in the same direction • Hydrostatic pressure forces molecules through the plasma membrane • Where in our bodies can you find high hydrostatic pressure acting on molecules? • Note the hydrostatic pressure acting on the basement wall.

42. Diffusion • Movement of molecules from high to low concentra-tion • Requires no energy • Only very small molecules can diffuse through the membrane.Which ones?

43. Diffusion Rates…..Determined by Several Factors • Distance • The ________ the distance the _______ the rate of diffusion. • Gradient Size • The ___________ the concentration gradient the __________ the rate of diffusion. • Molecule Size • The _________ the ion or molecule the _________ the rate of diffusion. • Temperature • The __________ the temperature the ________ the rate of diffusion. • Electrical Forces • Electrochemical _______ exists whereby ___ are attracted by an opposite charge and the rate of diffusion is _________.

44. Osmosis • Movement of water through a semipermiable membrane from an area of high water potential to an area of low water potential until equilibrium is reached. • Does not require energy

45. Osmotic Environments • Isotonic Environment Aqueous environment has same solute concentration as cell. Water flows in & out equally. • Hypertonic Environment area outside cell has higher solute concentration. Water moves out of the cell. When the cell collapses and dies, this is known as _____. • Hypotonic Environment environment has lower solute than the cell. Water moves into cell.When a cell bursts, this in known as cell _________. What happens in plant cells?

46. Facilitated Diffusion • Since lipid layer is amphipathic, most polar molecules cannot pass through the nonpolar region. • Most organic molecules are polar • Ex: Glucose & amino acids enter a cell via facilitated diffusion, rather than simple diffusion. • Does not require energy • Transport into cell depends upon integral membrane proteins • These proteins are highly selective – called permeases.

47. Types of Transport Proteins • Uniport carries a single molecule across a membrane • Ex: Glucose enters a cell • Symport moves two different molecules at the same time in the same direction. Both must bind to protein • Ex: Na+ and Glucose enter a cell • Antiport two molecules move in opposite directions • Ex: Na+ and K+ move through a membrane • These proteins can be inhibited by molecules that mimic the normally transported molecules.

48. Active Transport • Requires energy & membrane proteins • Substance moved AGAINST its concentration gradient

49. Vesicle Mediated Transport • Vesicles or vacuoles can fuse with the cell membrane

50. Exocytosis • Exocytosis: Vesicles form inside the cell, move outward, fuse with the cell membrane, and expel their contents.