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Chapter 2 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See separate FlexArt PowerPoint.

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Presentation on theme: "Chapter 2 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See separate FlexArt PowerPoint."— Presentation transcript:

1 Chapter 2 *Lecture Outline Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. *See separate FlexArt PowerPoint slides for all figures and tables pre-inserted into PowerPoint without notes.

2 Chapter 2 Outline The Study of Cells A Prototypical Cell Plasma Membrane Cytoplasm Nucleus Life Cycle of the Cell Aging and the Cell

3 The Study of Cells The study of cells: cytology –only visible by microscopy –measured in micrometers (µm) 1 cm = 10,000 µm –sizes vary from 7µm (RBC) to 120µm (oocyte) –shapes vary flat, cylindrical, oval, and irregular in shape

4 Figure 2.1

5 Types of Microscopy Light Microscopy (LM) –visible light passes through the cell Transmission Electron Microscopy (TEM) –a beam of electrons passes through the cell –can magnify about 100X greater than LM Scanning Electron Microscopy (SEM) –beam of electrons bounces off surface of the cell to provide a 3D study of the cell surface

6 Comparison of the Three Types of Microscopy Figure 2.2

7 Cellular Functions Covering Lining Storage Movement Connection Defense Communication Reproduction

8 Cellular Functions Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Produce new individual Produce new blood cells Send information between regions of the brain Produce antibodies to target antigens or invading cells Form ligaments that attach bone to bone Movement Lining Storage Covering Epithelial cells in small intestineLymphocytes Epidermal cells in skin Regulate nutrient movement into body tissues Defense Protect outer surface of body Connection (attachment) Collagen (protein) fibers from fibroblasts Nerve cells CommunicationFat cells Liver cells Store lipid reserves Muscle cells of heart Skeletal muscle cells Bone marrow stem cells Sperm and oocyte cells ReproductionPump blood Move skeleton Functional Category ExampleSpecific Functions Functional Category ExampleSpecific Functions Store carbohydrate nutrients as glycogen Selected Common Types of Cells and Their Functions Table 2.1 (left-1): © Ed Reschke/ Peter Arnold; (left-2-4): © The McGraw-Hill Companies, Inc./ Photo by Dr. Alvin Telser; (right-1): © Ed Reschke/ Peter Arnold; (right-2): © The McGraw Hill Companies, Inc./Photo by Dr. Alvin Telser; (right-3): © Carolina Biological Supply Company/Phototake; (right-4): © Jason Burns/ Phototake

9 A Prototypical Cell A generalized cell (not a real cell in the body) Combines features from many different cells for teaching purposes Most human cells have three basic parts: Plasma (cell) membrane Cytoplasm Nucleus

10 A Prototypical Cell Figure 2.3

11 Plasma (Cell) Membrane An extremely thin outer border on cell Serves as a selective physical and chemical barrier deciding what comes into and leaves the cell It is the “gatekeeper” that regulates the passage of gases, nutrients, and wastes between the internal and external environments of the cell

12 Composition and Structure of Membranes The plasma membrane and membranes within the cell have two molecular components: Lipids Proteins

13 Structure of Membranes Figure 2.4

14 Membrane Lipids Two layers: outer and inner Insoluble in water... prevents cells from dissolving in water 3 types of lipids in membranes: Phospholipids Cholesterol Glycolipids

15 Phospholipids The majority of lipids in cell membranes Each has a polar (charged) region and nonpolar (uncharged) region When exposed to aqueous (water) environment, they form a phospholipid bilayer –polar regions face outside and inside of the cell –nonpolar regions face each other (form internal core of the membrane)

16 Other Lipids Cholesterol about 20% of all membrane lipids strengthens and stabilizes membrane against extreme temperature Glycolipids about 5–10% of all membrane lipids have carbohydrate (sugar) molecules attached facing out and forming the glycocaylx

17 Membrane Proteins Lipids are majority of structure but proteins give membrane functions Proteins: complex molecules made of amino acids chains 2 types of membrane proteins: Integral Peripheral

18 Membrane Proteins Figure 2.4

19 Integral Membrane Proteins Embedded in phospholipid bilayer Span the entire thickness of the membrane Exposed to the outside and inside of the cell Also termed transmembrane proteins Can have carbohydrates (sugars) attached to outer surface = glycoproteins The glycoproteins and the glycolipids form the glycocalyx on the external surface of the plasma membrane Have many varied functions

20 Peripheral Proteins Not embedded in the lipid bilayer Loosely attached to the external or internal surface of the plasma membrane Have many varied functions

21 General Functions of the Plasma (Cell) Membrane Communication Intercellular connection Physical barrier Selective permeability

22 Protein-Specific Functions of the Plasma (Cell) Membrane Transport Intercellular connection Anchorage for the cytoskeleton Enzyme activity Cell–cell recognition Signal transduction

23 Crossing the Membrane 2 general types of membrane transport: Passive: –does not require energy from the cell –materials move from area of higher concentration “down” to area of lower concentration = diffusion Active: –requires energy from the cell –materials are moved up or against concentration gradient

24 Passive Transport All involve diffusion None require energy from the cell 4 types of diffusion: Simple diffusion Osmosis Facilitated diffusion Bulk filtration

25 Types of Diffusion Simple diffusion small and/or nonpolar (uncharged) molecules –examples movement of O 2 out of lungs (higher concentration) into blood (lower concentration) movement of CO 2 from blood (higher concentration) into lungs (lower concentration)

26 Types of Diffusion Osmosis applies only to movement of H 2 O –same principle as simple diffusion –H 2 O moves from region of higher concentration to region of lower concentration

27 Types of Diffusion Facilitated diffusion for large and/or polar (charged) molecules requires a specific transport protein (integral membrane protein) that will bind to the molecule being transported Bulk Filtration diffusion of both liquids (solvents) and dissolved molecules (solutes)

28 Active Transport Movement of a molecule against the concentration gradient –opposite of passive transport Requires energy from the cell May involve a transport protein –example is an ion pump –Na + and K + are moved in opposite directions against their concentration gradients

29 Active Transport by Ion Pump Na + is pumped out of cell and K + is pumped into cell Requires energy Figure 2.5

30 Bulk Transport Moves large molecules or bulk structures across the plasma membrane Requires energy from the cell Can go in either direction: 1.Exocytosis: out of the cell 2.Endocytosis: into the cell

31 Bulk Transport Exocytosis materials to be secreted out of cell and are packaged into vesicles vesicles fuse with plasma membrane and materials are released Endocytosis opposite of exocytosis materials are taken into the cell packaged into vesicles

32 Exocytosis Endocytosis Figure 2.6

33 Types of Endocytosis Phagocytosis nonspecific uptake of particles by formation of membrane extensions (pseodopodia) that surround particles to be engulfed Figure 2.7

34 Types of Endocytosis Pinocytosis nonspecific uptake of extracellular fluid Figure 2.7

35 Types of Endocytosis Receptor-mediated endocytosis engulfing of specific molecules bound to receptors on the surface of the plasma membrane Figure 2.7

36 Cytoplasm All materials (solid and liquid) between plasma membrane and nucleus ̶ Cytosol ̶ Inclusions ̶ Organelles

37 Figure 2.8

38 Cytosol A viscous, syruplike fluid containing many different dissolved substances such as: –Ions –Nutrients –Proteins –Carbohydrates –Amino acids

39 Inclusions Large storage aggregates of complex molecules found in the cytosol Examples: Melanin: brown pigment in skin cells Glycogen: long chains of sugars in the liver and skeletal muscles

40 Organelles Means “little organs” Many types, each perform different function –A type of division of labor –The type and number of organelles within a cell is a reflection of the cell’s function Organelles can be classified in two types: Membrane-bound Non-membrane-bound

41 Membrane-Bound Organelles Biochemical activity in organelle is isolated from cytosol and other organelles Examples are: Endoplasmic reticulum Golgi apparatus Lysosomes Peroxisomes Mitochondria

42 Endoplasmic Reticulum (ER) A network of intracellular membrane-bound tunnels ̶ enclosed spaces are called cisternae 2 types of ER: ̶ Smooth endoplasmic reticulum (SER) ̶ Rough endoplasmic reticulum (RER)

43 Endoplasmic Reticulum Figure 2.8 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Nucleus Cisternae Ribosomes Smooth ERRibosomesRough ER TEM 12,510x Functions of Endoplasmic Reticulum 4. Detoxification: Smooth ER detoxifies both drugs and alcohol 3. Storage: Stores newly synthesized molecules 1. Synthesis: provides a place for chemical reactions a. Smooth ER is the site of lipid synthesis and carbohydrate metabolism b. Rough ER synthesizes proteins for secretion, incorporation into the plasma membrane, and as enzymes within lysosomes 2. Transport: Move molecules through cisternal space from one part of the cell to another; sequestered away from the cytoplasm (bottom): © Dennis Kunkel/ Phototake

44 Smooth Endoplasmic Reticulum Walls have a smooth appearance Continuous with RER Functions include: 1.Synthesis, transport, and storage of lipids including steroid hormones 2.Metabolism of carbohydrates 3.Detoxification of drugs, alcohol, and poisons

45 Rough Endoplasmic Reticulum Walls appear rough due to attachment of ribosomes on outside of the RER membrane –ribosomes synthesize proteins The RER functions to synthesize, transport, or store proteins for: 1.Secretion by the cell 2.Incorporation into the plasma membrane 3.Creation of lysosomes

46 Golgi Apparatus Stacked cisternae whose lateral edges bulge, pinch off, and give rise to small transport and secretory vesicles Function to receive proteins and lipids from the RER for modification, sorting, and packaging –Receiving region is the cis-face –Shipping region is the trans-face

47 Golgi Apparatus Figure 2.9 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. 12 3 4 5 5 5 1 2 3 4 5 6 (b) Movement of materials through the Golgi apparatuss 6b (a) Cisternae Vesicles become either (a) lysosomes, (b) secretory vesicles that undergo exocytosis, or (c) plasma membrane Modified proteins are packaged in shipping region Proteins are modified as they move through Golgi apparatus Vesicle fuses with Golgi apparatus receiving region RER proteins in transport vesicle Vesicle from RER moves to Golgi apparatus Transport vesicle Secretory vesicles Functions of Golgi Apparatus 1. Modification: Modifies new proteins destined for lysosomes, secretion, and plasma membrane 2. Packaging: Packages enzymes for lysosomes and proteins for secretion 3. Sorting: Sorts all materials for lysosomes, secretion, and incorporation into the plasma membrane Vacuole Shipping region Vacuole Shipping region Lumen of cisterna filled with secretory product TEM17,770x Transport vesicle Receiving region Protein incorporation in plasma membrane Extracellular fluid Plasma membrane Cytoplasm Transport vesicles Receiving region Golgi apparatus Rough endoplasmic reticulum Transport vesicle Exocytosis Membrane protein transport vesicles 6c Secretory vesicles Lysosomes 6a Shipping region Transport vesicle a: © DennisKunkel/ Phototake

48 Protein Flow through the Golgi Apparatus 1.Proteins synthesized in RER get packaged into transport vesicles. 2.Transport vesicles pinch off from RER and fuse with the receiving cis-face of the Golgi apparatus. 3.The proteins move between and are modified in the cisternae of the Golgi apparatus. 4.Modified proteins are packaged in secretory vesicles. 5.Secretory vesicles either participate in exocytosis or become lysosomes in the cel.l

49 Protein Flow through the Golgi Apparatus Figure 2.9

50 Lysosomes Vesicles generated by the Golgi apparatus Contain enzymes used to digest and remove waste products and damaged organelles within the cell (autophagy) When a cell is dying it releases lysosomal enzymes that digest the cell (autolysis)

51 Lysosomes Figure 2.10 Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Lysosomes Lysosome TEM 16,000x Functions of Lysosomes 3. Self-destruction: Digest the remains (autolysis) after cellular death 2. Removal: Remove worn-out or damaged organelles and cellular components (autophagy); recycle small molecules for resynthesis 1. Digestion: Digest all materials that enter cell by endocytosis (top left): © David M. Phillips/ Visuals Unlimited

52 Peroxisomes Vesicles smaller than lysosomes Use O 2 and an enzyme (catalase) to detoxify harmful molecules taken into the cell

53 Peroxisomes Figure 2.11

54 Mitochondria Bean-shaped organelles with double membrane –inner membrane folded into shelf-like cristae –internal fluid: matrix Function to produce a high energy containing molecule called ATP on the cristae Cells that require more energy have more mitochondria than cells requiring less energy

55 Mitochondrion Figure 2.12

56 Non-Membrane-Bound Organelles In direct contact with the cytosol Examples are: Ribosomes Cytoskeleton Centrosomes and centrioles Cilia and flagella Microvilli

57 Ribosomes Comprised of a large and small subunit Responsible for protein synthesis Free ribosomes float unattached within the cytosol Fixed ribosomes are attached to the outer surface of RER

58 Ribosomes Figure 2.13

59 Cytoskeleton Proteins organized in the cytosol as solid filaments or hollow tubes 3 main protein types: Microfilaments Intermediate filaments Microtubules

60 Microfilaments 7 nm (nanometer) thick filaments 1,000 nanometers = 1 micron (µm) Maintain and change cell shape Participate in muscle contraction and cell division

61 Intermediate Filaments 8−12 nm thick filaments Provide structural support and stabilize junctions between apposed cells

62 Microtubules 25 nm thick hollow tubes Radiate from centrosome Fix organelles in place Maintain cell shape and rigidity Direct movement of organelles in the cell Allow cell motility (in cilia and flagella)

63 Cytoskeleton Figure 2.14

64 Centrosome and Centrioles Centrosome: a pair of centrioles at right angles to each other Centriole: nine sets of microtubule triplets –involved in organizing microtubules –attached to chromosomes during cell division causing chromosomal migration

65 Centrosome and Centrioles Figure 2.15

66 Cilia and Flagella Projections of the cell containing cytoplasm and microtubules capable of movement Cilia: grouped on cells that move objects across their surface (i.e., cells of the respiratory tree and oviduct) Flagella: longer, usually singular, to propel a cell (e.g., sperm)

67 Cilia and Flagella Figure 2.16

68 Microvilli Extensions of cell, not capable of motion –much smaller than cilia Increase the surface area to increase absorption of food –found on surface of cells of the small intestine

69 Nucleus Control center for cellular activity Contains DNA (deoxyribonucleic acid), a complex molecule containing –when not dividing, nuclear DNA is unwound into fine filaments called chromatin –during cell division chromatin coils tightly to form chromosomes

70 Chromatin and Chromosomes Figure 2.17Figure 2.18

71 The Nuclear Envelope Double membrane structure Controls entry and exit of molecules from nucleus and cytoplasm Outer membrane is continuous with endoplasmic reticulum Nuclear pores are selectively permeable channels that allow some molecules in or out of the nucleus

72 Nucleoli Dark staining bodies within the nucleus Responsible for making the components of the small and large units of the ribosome Figure 2.17

73 Life Cycle of the Cell Cells are always in one of two states: Interphase: maintenance (resting) phase between cell divisions where the following activities occur: normal activities prep for cell division cells spend the majority of life in this Mitotic phase: when the cell divides

74 Interphase and Mitosis Figure 2.20

75 Interphase Stages G 1 Phase Cells grow, replicate organelles, produce proteins for replication, and centrioles just prior to cell division S Phase “Synthesis” phase where DNA replicates in preparation for cell division G 2 Phase Centriole replication is complete Other organelle production continues Enzymes needed for cell division are synthesized

76 Interphase Stages Figure 2.19

77 Mitotic Phase Mitotic cell division is the process by which two daughter cells are produced that are genetically identical to the original (mother) cell 2 distinct events occur in this phase: −Mitosis: duplication of DNA and division of the nucleus –Cytokinesis: division of the cytoplasm and the mother cell

78 Stages of Mitosis Mitosis has 4 consecutive stages –takes less than two hours to complete all 4 1.Prophase 2.Metaphase 3.Anaphase 4.Telophase

79 Stages of Mitosis Figure 2.19

80 Prophase Chromatin supercoils forming chromosomes. Duplicate, identical sister chromatids are conjoined at a region called the centromere. Elongated microtubules called spindle fibers begin to grow from each centriole. The end of prophase is marked by the dissolution of the nuclear envelope.

81 Metaphase Chromosomes line up along the equatorial plate. Spindle fibers attach to the centromere of sister chromatids and form an oval structure array called the mitotic spindle. Figure 2.20

82 Anaphase Spindle fibers pull sister chromatids apart to opposite ends of the dividing cell. Figure 2.20

83 Telophase The nuclear envelope forms around each set of chromosomes. Chromosomes begin to uncoil and the mitotic spindle disappears. A pinched area, the cleavage furrow, appears that will complete the physical division of the daughter cells. Figure 2.20

84

85 Aging and the Cell Aging is a normal and continuous process –indicated by changes in number of organelles or chromatin structure Cells can die in two general ways: 1.Harmful agents or mechanical damage 2.Programmed cell death or apoptosis


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