Unit 3 Cells and Tissues

1. Unit 3Cells and Tissues

2. Objectives • Identify and discuss the basic structure and function of the three major components of a cell. • List and briefly discuss the functions of the primary cellular organelles. • Compare the major passive and active transport processes that act to move substances through cell membranes.

3. Objectives • Compare and discuss DNA and RNA and their function in protein synthesis. • Discuss the stages of mitosis and explain the importance of cellular reproduction. • Explain how epithelial tissue can be grouped according to shape and arrangement of cells. • List and briefly discuss the major types of connective tissue and muscle tissue. • List the three structural components of a neuron.

4. What is a Cell? • Describe a cell • What makes a cell different from an atom or a molecule? • Are all cells the same?

5. Cells • Size and shape • Human cells vary considerably in size • All are microscopic • Cells differ notably in shape

6. Cells • Composition • Cytoplasm containing specialized organelles surrounded by a plasma membrane • Organization of cytoplasmic substances important for life

7. Cells • Composition • Structural parts • Plasma Membrane or Cytoplasmic Membrane • Forms outer boundary of cell • Thin, two-layered membrane of phospholipids containing proteins • Is selectively permeable

9. Cells • Composition • Structural parts • Cytoplasm • Organelles • Ribosomes - May attach to rough ER or lie free in cytoplasm - Manufacture proteins - Often called protein factories

11. Cells • Composition • Structural parts • Cytoplasm • Organelles • Endoplasmic reticulum (ER) - Network of connecting sacs and canals - Carry substances through cytoplasm - Types are rough and smooth - Rough ER collects and transports proteins made by ribosomes - Smooth ER synthesizes chemicals; makes new membrane

12. Cells • Composition • Structural parts • Cytoplasm • Organelles • Golgi apparatus - Group of flattened sacs near nucleus -Collect chemicals that move from the smooth ER in vesicles - Called the chemical processing and packaging center

13. Cells • Composition • Structural parts • Cytoplasm • Organelles • Mitochondria - Composed of inner and outer membranes - Involved with energy-releasing chemical reactions - Often called power plants of the cell - Contains one DNA molecule

14. Cells • Composition • Structural parts • Cytoplasm • Organelles • Lysosomes - Membranous-walled organelles - Contain digestive enzymes - Have protective function (eat microbes) - Formerly thought to be responsible for apoptosis (programmed cell death)

15. Cells • Composition • Structural parts • Cytoplasm • Organelles • Centrioles - Paired organelles - Lie at right angles to each other near nucleus - Function in cell reproduction

16. Cells • Composition • Structural parts • Cytoplasm • Organelles • Microvilli - Small, fingerlike extensions of the plasma membrane - Increase absorptive surface area of the cell

17. Cells • Composition • Structural parts • Cytoplasm • Organelles • Cilia - Fine, hairlike extensions found on free or exposed surfaces of some cells - Capable of moving in unison in a wavelike fashion

18. Cells • Composition • Structural parts • Cytoplasm • Organelles • Flagella - Single projections extending from cell surfaces - Much larger than cilia - “Tails” of sperm cells only example of flagella in humans

19. Cells • Composition • Nucleus • Controls cell because it contains the genetic code—instructions for making proteins, which in turn determine cell structure and function • Component structures include nuclear envelope, nucleoplasm, nucleolus, and chromatin granules • 46 chromosomes contain DNA, which contains the genetic code

20. Relationship of Cell Structure and Function • Regulation of life processes • Survival of species through reproduction of the individual

21. Relationship of Cell Structure and Function • Relationship of structure to function apparent in number and type of organelles seen in different cells • Heart muscle cells contain many mitochondria required to produce adequate energy needed for continued contractions • Flagellum of sperm cell gives motility, allowing movement of sperm through female reproductive tract, thus increasing chances for fertilization

22. Movements of Substances Through Cell Membranes • Passive transport processes do not require added energy and result in movement “down a concentration gradient”

23. Movements of Substances Through Cell Membranes • Diffusion • Substances scatter themselves evenly throughout an available space • It is unnecessary to add energy to the system • Movement is from high to low concentration

24. Movements of Substances Through Cell Membranes • Diffusion • Osmosis and dialysis are specialized examples of diffusion across a selectively permeable membrane • Osmosis is diffusion of water (when some solutes cannot cross the membrane) • Dialysis is diffusion of solutes

26. Osmosis

27. What are examples of diffusion and osmosis in everyday life?

28. What is this an example of ?

29. Movements of Substances Through Cell Membranes • Filtration • Movement of water and solutes caused by hydrostatic pressure on one side of membrane • Responsible for urine formation • What are examples of filtration in everyday life?

30. Filtration

31. Movements of Substances Through Cell Membranes • Active transport processes occur only in living cells; movement of substances is “up the concentration gradient”; requires energy from ATP • Where does the ATP come from?

32. Movements of Substances Through Cell Membranes • Ion pumps • An ion pump is protein complex in cell membrane • Ion pumps use energy from ATP to move substances across cell membranes against their concentration gradients • Examples: sodium-potassium pump; calcium pump • Some ion pumps work with other carriers so that glucose or amino acids are transported along with ions • http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/ion_pump/ionpump.html

33. Movements of Substances Through Cell Membranes • Phagocytosis and pinocytosis • Both are active transport mechanisms because they require cell energy • Phagocytosis is a protective mechanism often used to destroy bacteria • Pinocytosis is used to incorporate fluids or dissolved substances into cells

34. Movements of Substances Through Cell Membranes • Several severe diseases result from damage to cell transport processes

35. Movements of Substances Through Cell Membranes • Cystic fibrosis, characterized by abnormally thick secretions in the airways and digestive ducts, results from improper Cl– transport • Cholera is a bacterial infection that causes Cl– and water to leak from cells lining the intestines, resulting in severe diarrhea and water loss

36. Cell Reproduction • DNA structure—large molecule shaped like a spiral staircase; sugar (deoxyribose), and phosphate units compose sides of the molecule; base pairs (adenine-thymine or guanine-cytosine) compose “steps”; base pairs always the same but sequence of base pairs differs in different DNA molecules; a gene is a specific sequence of base pairs within a DNA molecule; genes dictate formation of enzymes and other proteins by ribosomes, thereby indirectly determining a cell’s structure and functions; in short, genes are heredity determinants

38. Cell Reproduction • Genetic information—stored in base-pair sequences on genes—expressed through protein synthesis • RNA molecules and protein synthesis • DNA—contained in cell nucleus • Protein synthesis—occurs in cytoplasm, thus genetic information must pass from the nucleus to the cytoplasm • Process of transferring genetic information from nucleus to cytoplasm where proteins are produced requires completion of transcription and translation

39. Cell Reproduction • Transcription • Double-stranded DNA separates to form messenger RNA (mRNA) • Each strand of mRNA duplicates a particular gene (base-pair sequence) from a segment of DNA • mRNA molecules pass from the nucleus to the cytoplasm, where they direct protein synthesis in ribosomes and ER

40. Cell Reproduction • Abnormal DNA that is inherited, or that results from damage from viruses or other factors, is often the basis of disease • Cell division—reproduction of cell involving division of the nucleus (mitosis) and the cytoplasm;

42. Cell Reproduction • Stages of mitosis • Prophase—first stage • Chromatin granules become organized • Chromosomes (pairs of linked chromatids) appear • Centrioles move away from nucleus • Nuclear envelope disappears, freeing genetic material • Spindle fibers appear

43. Cell Reproduction • Stages of mitosis • Metaphase—second stage • Chromosomes align across center of cell • Spindle fibers attach themselves to each chromatid

44. Cell Reproduction • Stages of mitosis • Anaphase—third stage • Centromeres break apart • Separated chromatids now called chromosomes • Chromosomes are pulled to opposite ends of cell • Cleavage furrow develops at end of anaphase

45. Cell Reproduction • Stages of mitosis • Telophase—fourth stage • Cell division is completed • Nuclei appear in daughter cells • Nuclear envelope and nucleoli appear • Cytoplasm is divided (cytokinesis) • Daughter cells become fully functional

46. Stages of mitosis • . interphase prophase metaphase anaphase telophase Two identical cells www.bbc.co.uk/schools

47. Cell Reproduction • Changes in cell growth and reproduction • Changes in growth of individual cells • What is hypertrophy? • What is atrophy?

48. Answer • Hypertrophy—increase in size of individual cells, increasing size of tissue • Atrophy—decrease in size of individual cells, decreasing size of tissue

49. Cell Reproduction • Changes in cell growth and reproduction • Changes in cell reproduction • What is Hyperplasia? • What is Anaplasia? • What causes a tumor?

50. Answer • Hyperplasia—increase in cell reproduction, increasing size of tissue • Anaplasia—production of abnormal, undifferentiated cells • Uncontrolled cell reproduction results in formation of a benign or malignant neoplasm (tumor)