3 Cellular Level of Organization

1. 3 Cellular Level of Organization

2. Section 1: An Introduction to Cells Learning Outcomes 3.1 Describe the cell and its organelles, including the composition and function of each. 3.2 Describe the chief structural features of the plasma membrane. 3.3 Differentiate among the structures and functions of the cytoskeleton. 3.4 Describe the ribosome and indicate its specific functions.

3. Section 1: An Introduction to Cells Learning Outcomes 3.5 Describe the Golgi apparatus and indicate its specific functions. 3.6 Describe mitochondria, indicate their functions, and explain their significance to cellular function.

4. Section 1: An Introduction to Cells Typical cell Smallest living unit in the body ~0.1 mm in diameter Could not be examined until invention of microscope in 17th century Animation: Your Cells

5. Section 1: An Introduction to Cells Cell theory Cells are building blocks of all plants and animals All new cells come from division of preexisting cells Cells are smallest unit that perform all vital physiological functions

6. Figure 3 Section 1 Cells are the smallest units that perform all vital physiological functions. Cells are the building blocks of all plants and animals. All new cells come from the division of pre-existing cells. Nutrients O2 Division CO2 Wastes Cell Growth New cells The cell theory Epithelial tissue Connective tissue Muscle tissue The differentiation of the four tissue types from a single cell: the fertilized ovum Neural tissue

7. Section 1: An Introduction to Cells Each cell maintains homeostasis Coordinated activities of cells allow homeostasis at higher organizational levels

8. Section 1: An Introduction to Cells Cells vary in structure and function but all descend from a single fertilized ovum Fertilized ovum contains genetic potential to become any cell Cell divisions occur creating smaller, different parcels of cytoplasm Cytoplasmic differences turn off/on specific genes in DNA and daughter cells become specialized = Differentiation Differentiated cells are responsible for all body functions

9. Section 1: An Introduction to Cells Extracellular fluid Watery medium surrounding cells Called interstitial fluid (interstitium, something standing between) in most tissues

10. Module 3.1: Smallest living units of life Cell components Plasma membrane (cell membrane) Separates cell contents from extracellular fluid Cytoplasm Material between cell membrane and nuclear membrane Colloid containing many proteins Two subdivisions Cytosol Intracellular fluid Organelles (“little organs”) Intracellular structures with specific functions

11. Module 3.1: Smallest living units of life Organelles Nonmembranous Not completely enclosed by membranes In direct contact with cytosol Examples: Cytoskeleton Microvilli Centrioles Cilia Ribosomes

12. Module 3.1: Smallest living units of life Organelles Membranous Enclosed in a phospholipid membrane Isolated from cytosol Examples: Mitochondria Nucleus Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes

13. Module 3.1: Smallest living units of life Organelles Microvilli STRUCTURE: membrane extensions containing microfilaments FUNCTION: increase surface area for absorption Cytoskeleton STRUCTURE: fine protein filaments or tubes Centrosome Organizing center containing pair of centrioles FUNCTION: Strength and support Intracellular movement of structures and materials

14. Module 3.1: Smallest living units of life Organelles Ribosomes STRUCTURE: RNA and proteins Fixed: attached to endoplasmic reticulum Free: scattered in cytoplasm

15. Module 3.1: Smallest living units of life Organelles Peroxisome STRUCTURE: vesicles containing degradative enzymes FUNCTION: Catabolism of fats/other organic compounds Neutralization of toxic compounds Lysosome STRUCTURE: vesicles containing digestive enzymes FUNCTION: Removal of damaged organelles or pathogens

16. Module 3.1: Smallest living units of life Organelles Golgi apparatus STRUCTURE: stacks of flattened membranes (cisternae) containing chambers FUNCTION: storage, alteration, and packaging of synthesized products Mitochondria STRUCTURE: Double membrane Inner membrane contains metabolic enzymes FUNCTION: production of 95% of cellular ATP

17. Module 3.1: Smallest living units of life Organelles Nucleus STRUCTURE: Fluid nucleoplasm containing enzymes, proteins, DNA, and nucleotides Surrounded by double membrane FUNCTION: Control of metabolism Storage/processing of genetic information Control of protein synthesis Animation: Nucleus

18. Module 3.1: Smallest living units of life Organelles Endoplasmic reticulum (ER) STRUCTURE: membranous sheets and channels FUNCTION: synthesis of secretory products, storage, and transport Smooth ER No attached ribosomes Synthesizes lipids and carbohydrates Rough ER Attached ribosomes Modifies/packages newly synthesized proteins

19. Module 3.1 Review a.Distinguish between the cytoplasm and cytosol. b.Describe the functions of the cytoskeleton. c.Identify the membranous organelles and describe their functions.

20. Module 3.2: Plasma membrane Plasma membrane Selectively permeable membrane that controls: Entry of ions and nutrients Elimination of wastes Release of secretions

21. Module 3.2: Plasma membrane Plasma membrane components Glycocalyx Superficial membrane carbohydrates Components of complex molecules Proteoglycans (carbohydrates with protein attached) Glycoproteins (protein with carbohydrates attached) Glycolipids (lipids with carbohydrates attached) Functions Cell recognition Binding to extracellular structures Lubrication of cell surface

22. Module 3.2: Plasma membrane Plasma membrane components (continued) Integral proteins Part of cell membrane Cannot be removed without damaging cell Often span entire cell membrane = Transmembrane proteins Can transport water or solutes Peripheral proteins Attached to cell membrane surface Removable Fewer than integral proteins

23. Figure 3.2 1 Structure of the plasma membrane EXTRACELLULAR FLUID Glycocalyx (extracellular carbohydrates) Integral protein with channel Glycolipid Integral glycoproteins = 2 nm CYTOPLASM Cytoskeleton (microfilaments) Peripheral proteins Integral (transmembrane) proteins

24. Module 3.2: Plasma membrane Plasma membrane structure Thin (6–10 nm) and delicate Phospholipid bilayer Mostly comprised of phospholipid molecules in two layers Hydrophilic heads at membrane surface Hydrophobic tails on the inside Isolates cytoplasm from extracellular fluid Animation: Cell Membrane Barrier

25. Figure 3.2 2 The phospholipid bilayer that forms the plasma membrane Hydrophilic heads Hydrophobic tails Cholesterol

26. Module 3.2: Plasma membrane Plasma membrane functions Physical isolation Regulation of exchange with external environment Sensitivity to environment Structural support Lipid bilayer provides isolation Proteins perform most other functions

27. Figure 3.2 3

28. Figure 3.2 3

29. Module 3.2 Review a.List the general functions of the plasma membrane. b.Which structural component of the plasma membrane is mostly responsible for its ability to isolate a cell from its external environment? c.Which type of integral protein allows water and small ions to pass through the plasma membrane?

30. Module 3.3: Cytoskeleton Cytoskeleton (cellular framework) components Microfilaments <6 nm in diameter Typically composed of actin Commonly at periphery of cell Microvilli Finger-shaped extensions of cell membrane Has core of microfilaments to stiffen and anchor Enhance surface area of cell for absorption Terminal web (layer inside plasma membrane in cells forming a layer or lining)

31. Module 3.3: Cytoskeleton Cytoskeleton (cellular framework) components (continued) Intermediate filaments 7–11 nm in diameter Strongest and most durable cytoskeletal elements Microtubules ~25 nm in diameter Largest components of cytoskeleton Extend outward from centrosome (near nucleus)

32. Figure 3.3 1 Structures of the cytoskeleton Microvilli Microfilaments Plasma membrane Terminal web Microvilli SEM X 30,000 Intermediate filaments Microtubule Secretory vesicle Mitochondrion Endoplasmic reticulum

33. Module 3.3: Cytoskeleton Centrioles Cylindrical structures Composed of microtubules (9 groups of triplets) Two in each centrosome Control movement of DNA strands during cell division Cells without centrioles cannot divide Red blood cells Skeletal muscle cells

34. Figure 3.3 3 The structure of centrioles Microtubules in centriole

35. Module 3.3: Cytoskeleton Cilia Long, slender plasma membrane extensions Common in respiratory and reproductive tracts Also composed of microtubules Nine groups of pairs surrounding a central pair Anchored to cell surface with basal body Beat rhythmically to move fluids or secretions across cell

36. Figure 3.3 4 The structure of cilium Plasma membrane Microtubules Basal body

37. Figure 3.3 5 The action of a beating cilium Power stroke Return stroke

38. Module 3.3 Review a.List the three basic components of the cytoskeleton. b.Which cytoskeletal component is common to both centrioles and cilia? c.What is the function of cilia?

39. Module 3.4: Ribosomes Ribosomes Protein synthesis Two subunits (1 large, 1 small) containing special proteins and ribosomal RNA (rRNA) Must join together before synthesis begins Free ribosomes Throughout cytoplasm Manufactured proteins enter cytosol

40. Figure 3.4 1 Small ribosomal subunit Large ribosomal subunit The two subunits of a functional ribosome

41. Module 3.4: Ribosomes Endoplasmic reticulum (ER) Network of intracellular membranes attached to nucleus Forms hollow tubes, sheets, and chambers (cisternae, singular, cisterna, reservoir for water)

42. Module 3.4: Ribosomes Endoplasmic reticulum (ER) Two types Smooth (SER) Lacks ribosomes Tubular cisternae Rough (RER) Has attached (fixed) ribosomes Modification of newly synthesized proteins Export to Golgi apparatus Proportion of SER to RER depends on the cell and its functions

43. Figure 3.4 2 – 3 The structure of the endoplasmic reticulum (ER) Nuclear envelope Tubular cisternae Cisternae Smooth endoplastic reticulum (SER)

44. Figure 3.4 3

45. Module 3.4: Ribosomes Functions of SER Synthesis of phospholipids and cholesterol Synthesis of steroid hormones Synthesis and storage of glycerides in liver and fat cells Synthesis and storage of glycogen in skeletal and liver cells

46. Figure 3.4 4 The structure and function of rough endoplasmic reticulum (RER) Fixed ribosomes mRNA strand Ribosome Transport vesicles Enzyme Growing polypeptide Protein Glycoprotein As a polypeptide is synthesized on a ribosome, the growing chain enters the cisterna of the RER. Glycoproteins, proteins, and enzymes are packaged in transport vesicles. The polypeptide assumes its secondary and tertiary structure. The complete protein may become an enzyme or a glycoprotein. Transport vesicles deliver proteins, enzymes, and glycoproteins to the Golgi apparatus.

47. Module 3.4: Ribosomes Function of RER Polypeptide synthesized on attached ribosome Growing chain enters cisterna Polypeptide assumes secondary/tertiary structures Completed protein may become enzyme or glycoprotein Products not destined for RER are packaged into transport vesicles Deliver products to Golgi apparatus

48. Module 3.4 Review a.Describe the immediate cellular destinations of newly synthesized proteins from free ribosomes and fixed ribosomes. b.Describe the structure of smooth endoplasmic reticulum. c.Why do certain cells in the ovaries and testes contain large amounts of smooth endoplasmic reticulum (SER)?

49. Module 3.5: Golgi apparatus Golgi apparatus Functions Renews or modifies plasma membrane Modifies or packages secretions for release from cell (exocytosis) Packages special enzymes within vesicles for use in cytosol Typically consist of 5–6 flattened discs (cisternae) May be more than one in a cell Situated near nucleus Animation: Golgi Apparatus

50. Module 3.5: Golgi apparatus Golgi apparatus Steps of function Products from RER arrive at the forming face in transport vesicles Transport vesicles fuse with Golgi apparatus and empty contents into cisternae Enzymes modify products New vesicles move material between cisternae Product arrives at maturing face