Unit 2: Cytology

1. Unit 2: Cytology

2. §2.1 Nucleus and Nucleolus The nucleus has been called a cell’s “control center” The nuclearmembrane (or nuclear envelope) encloses it The nuclear membrane has pores in it that make the fluid of the nucleus (nucleoplasm) somewhat continuous with the fluid of the cell (cytoplasm) These pores allow relatively large molecules to pass between the nucleus and the cytoplasm

4. The genetic material known as chromatin is suspended in the nucleoplasm Chromatin is made out of DNA and protein It is known as chromosomes when it is coiled up and ready for cell division In its unraveled form, segments of the chromatin produce RNA for the manufacture of proteins in the cytoplasm RNA is an example of a nuclear product that leaves the nucleus through nuclear pores

6. The production of RNA (transcription) requires enzymes Enzymes enter the nucleus through the nuclear pores The nucleolus is a visible region within the nucleoplasm It is here that RNA and specific proteins are combined to form the sub-units of the non membranous structures called ribosomes

7. Ribosomes A complete ribosome is made out of two unequal-sized sub-units, which leave the nucleus through the pores and get assembled into ribosomes in the cytoplasm Some ribosomes in eukaryotic cells become embedded in the membranes of the endoplasmicreticulum (ER) where others remain free in the cytoplasm or become loosely clustered together to form polysomes Ribosomes are the site of protein synthesis

9. It is on the ribosomes surface that the amino acids are put into a sequence to form the long helical protein molecules Proteins produced by free ribosomes in the cytoplasm are generally used within the cell Those produced by ribosomes embedded in the ER are often secreted from the cell

11. Intramembranous Structures ER Golgi Bodies Mitochondria and Chloroplasts

12. §2.2 ER • The ER of a cell is a set of membranous channels that wind throughout the cytoplasm • Two types: • Roughendoplasmicreticulum(RER), have ribosomes embedded in its membranes • Smoothendoplasmicreticulum(SER), which lack ribosomes

13. SER The interior contains enzymes that enable a variety of specific cellular functions Cells that produce steroids have abundant SER

14. Illustrations of SER and RER • Discrete organelles • Interconnects, which is most likely, as the functions of SER require enzymes • An interconnection with RER would provide the communication link and route for the movement of the proteins to the SER • The ER is connected to the nuclear membrane, which could facilitate the movement of RNA and ribosomal sub-units out of the nucleus

15. Both types of ER serve a transportation function in the cell by facilitating the movement of molecules from one area to another Both accumulate molecular products in their interiors Where SER accumulates the steroids they produce, the RER accumulates the proteins produced by the ribosomes that are embedded in them

16. Sections of ER thus filled with these products then break free in a process described as “blebbing” or “budding” to produce small membrane bound sacs called vesicles containing the biochemicals These products are often destined for secretion from the cell The vesicles are called transition (or transport) vesicles

17. Review Cells lacking RER would NOT likely be able to produce vesicles any proteins steroid hormones enzymes for secretion

18. Cells lacking RER would NOT likely be able to produce vesicles any proteins steroid hormones enzymes for secretion

19. Which of these BEST describes a function of SER? Protein storage Communication Energy distribution Intracellular transport

20. Which of these BEST describes a function of SER? Protein storage Communication Energy distribution Intracellular transport

21. Which BEST describes traffic through a nuclear pore? Enzymes in; nucleic acids in Enzymes out; nucleic acids in Enzymes in; nucleic acids out Enzymes out; nucleic acids out

22. Which BEST describes traffic through a nuclear pore? Enzymes in; nucleic acids in Enzymes out; nucleic acids in Enzymes in; nucleic acids out Enzymes out; nucleic acids out

23. Where in a cell are steroids produced? Nucleus Cytoplasm RER SER

24. Where in a cell are steroids produced? Nucleus Cytoplasm RER SER

25. Which is least likely a role of the RER? Producing vesicles Intracellular transport Detoxification of cytoplasm Synthesis of membrane phospholipids

26. Which is least likely a role of the RER? Producing vesicles Intracellular transport Detoxification of cytoplasm Synthesis of membrane phospholipids

27. Which of the following is synthesized by the structure V? ATP Proteins Vesicles ribosomes

28. Which of the following is synthesized by the structure V? ATP Proteins Vesicles ribosomes

29. §2.3 Golgi Bodies The functions of the ER are related to that of the Golgi apparatus or Golgibodies They are comprised of a set of several discrete (flattened but curved) saccules usually located between ER and the cell membrane

30. Functions Golgi bodies receive transition vesicles from the ER They concentrate the molecular contents of the vesicles, and chemically adjust some of the secretion New vesicles form by blebbing from the Golgi apparatus These vesicles are called secretoryvesicles and they contain the biochemicals that have been modified by the Golgi apparatus

31. Secretory vesicles move to and join with the cell membrane in such a way that there contents are expelled from the cell This process is called exoctyosis This sequence of functional interrelationships among organelles is called the secretorypathway A specific example of a reaction that occurs in the Golgi bodies is the addition of carbohydrate chains to proteins thus making molecules called glycoproteins, which become components of cell membranes

33. Lysosomes The Golgi bodies also produce vesicle- like structures called lysosomes, which contain hydrolyticenzymes used for the hydrolysis (digestion) of molecules in cells Typically have a double outer membrane for protection against enzymes becoming free (which could potentially destroy a cell) in the cytoplasm Unicellular organisms use lysosomes to digest food particles they ingest by endocytosis

34. Functions Food particles become enveloped by a section of the membrane and form a structure known as a food vacuole The food vacuole fuses with the lysosome and digestion follows; this process is known as intracellulardigestion

35. The result is the production of simple molecules, which then leave the lysosome and enter the cytoplasm where they are used by the cell Through a process called autodigestion, multicellular organisms use lysosomes to digest unwanted cells and cell parts such as those in a tadpole’s tail as it undergoes metamorphosis to become a frog

36. §2.4 Mitochondria and Chloroplasts Mitochondria and chloroplasts are related both structurally and functionally Both are fluid-filled and have complex internal membranes Energy-related chemical reactions occur in their interiors as well as in their internal membranous structures

37. Mitochondria • Mitochondria exist in almost all cells • Their inner membrane loops back and forth in the innermost fluid (matrix) increasing its surface area and producing shelf-like structures called cristae • The mitochondria conduct cellular respiration by oxidizing parts of carbohydrates from the cytoplasm and capturing the energy from the chemical bonds that get broken • They save this energy as the high-energy bonds of ATP • Making the mitochondria the powerhouse of the cell

38. C6H12O6 + 6O2 6CO2 + 6H2O + 38ATP

39. Chloroplasts • Organelles that exist only in some plant cells • Contain pigment molecules like chlorophyll, which enable them to capture sunlight energy and use it to build sugar molecules • This is the process of photosynthesis

40. 6CO2 +6H2O  C6H12O6 + 6O2

41. Take a second look at the chemical reactions taking place What did you notice?

42. Relationship The reactants of one are the products of the other Photosynthesis makes glucose, which cellular respiration oxidizes for energy Plant cells have mitochondria so the sugars they make never get very far Other sugar molecules that are consumed by animals foraging on leaves, are converted to starch for storage in the plant tissues or cellulose in cell walls as the plant grows

43. Review Inhibitors that prevent ATP production in cells would MOST likely affect the ribosomes mitochondria golgi apparatus RER

44. Inhibitors that prevent ATP production in cells would MOST likely affect the ribosomes mitochondria golgi apparatus RER

45. Which organelles give off oxygen and use up carbon dioxide? Lysosomes Chloroplasts Mitochondria ER

46. Which organelles give off oxygen and use up carbon dioxide? Lysosomes Chloroplasts Mitochondria ER

47. Which BEST describes the function of the Golgi apparatus? Phagocytosis Protein synthesis Intracellular digestion Modifying cellular products for secretion

48. Which BEST describes the function of the Golgi apparatus? Phagocytosis Protein synthesis Intracellular digestion Modifying cellular products for secretion

49. Lysosomes are produced by the Nucleus Cell membrane Golgi apparatus ER

50. Lysosomes are produced by the Nucleus Cell membrane Golgi apparatus ER