1. Cells
Chapter 3
Lisa Ochs RN, MSN 2011

2. Cells
The cell is the structural and functional unit of all living matter
Cells vary in size, shape and function, but share many of the same characteristics
Cell structure is closely related to function (sound familiar?)
Cyto- means cell

3. Structures of the Cell Cell Membrane Also called the plasma membrane
Separates the intracellular (inside the cell) and extracellular (outside the cell) contents
Allows substances to enter or leave the cell- semipermeable also called selectively permeable

5. Cell Membrane Composed of phospholipids and proteins Phospholipids
Phosphate and lipid (fat) molecules
Arranged in 2 layers
Proteins
Provide structural support
Poke holes through the phospholipids to create pores (channels) in the membrane

6. Cell Membrane Substances move across the semipermeable membrane by
Dissolving in the lipid portion of the membrane; lipid soluble
Oxygen (O2) and carbon dioxide (CO2)
Passing through the protein pores; water soluble
Sodium (Na+) and chloride (Cl-)
Substances larger than the pores cannot pass through

8. Inside the Cell
Nucleus
Cytoplasm
Cytoplasmic Organelles

9. Nucleus The control center of the cell
Contains genetic information and controls protein synthesis
Surrounded by a nuclear membrane
Filled with nucleoplasm
Contains nucleolus (“little nucleus”) and chromatin (contains genes)

10. Nucleus Contains nucleolus (“little nucleus”)
Synthesizes RNA and ribosomes
Chromatin
In non-dividing cell, threadlike structures that contain DNA
In dividing cell, threads form chromosomes (DNA containing structures)

11. Cytoplasm Found inside the cell, surrounding the nucleus
Contains cytosol- intracellular fluid composed of water, electrolytes, proteins and nutrients
Cytosol contains organelles (little organs) and inclusion bodies (temporary structures that appear and disappear)

12. Figure 3-2 A typical cell.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

13. Organelles Mitochondria Shaped like a kidney bean
Called the “powerhouse” of the cell
Inner layer has many folds called cristae
Cristae hold enzymes responsible for ATP production- provides energy used by the body

14. applegate

15. Figure 3-4 Mitochondria are the power plants of the cells.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

16. Organelles Ribosomes Involved in protein synthesis
Free floating or attached to the endoplasmic reticulum (ER)
Free ribosomes produce proteins to be used inside the cell; ribosomes attached to the rough ER produce proteins to be shipped out of the cell

17. Organelles Endoplasmic Reticulum (ER)
Network of long, folded membranes that forms channels through the cytoplasm; substances are able to move along these channels
Rough ER (RER) has ribosomes; involved in protein synthesis and transporting proteins to the Golgi apparatus for finishing
Smooth ER (SER) has no ribosomes; involved in synthesis of lipids, steroids and carbohydrates

18. Ribosome (composed of two subunits- RNA and amino acids)
From: and
Ribosome (composed of two subunits- RNA and amino acids)
Rough and smooth ER

19. Organelles Golgi Apparatus Series of flattened membrane sacs
Modifies, packages and distributes proteins and lipids made by the rough and smooth ER
Finishes protein synthesis and transports substances out of the cell in secretory vesicles (“packages” the proteins); may attach carbohydrates or lipids to proteins to concentrate and form lipoproteins before releasing them into the cell

20. Organelles
Lysosomes
Contain powerful enzymes; “digestive organelles”; can breakdown and destroy proteins, polysacharides & lipids
Breakdown intracellular waste and debris
Certain white blood cells have many lysosomes

21. Organelles Peroxisomes
Vesicles smaller than lysosomes; generate hydrogen peroxide (H2O2) which detoxifies harmful molecules like alcohol
Hydrogen peroxide can be toxic in large amounts, so peroxisomes also contain an de-activating enzyme
Cells active in detoxification (liver, kidneys) have many peroxisomes

22. Figure 3-5 The Golgi apparatus.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

23. Organelles Cytoskeleton Centrioles
Composed of microfilaments and microtubules
Maintains the shape of the cell, holds organelles in place and assists in cellular movement
Centrioles
Microtubule pairs that form the spindle apparatus in dividing cells
Help to separate chromosomes during cellular division

24. http://images. google. com/imgres. imgurl=http://www. immediart
Fibroblasts showing cytoskeleton (microfilaments- yellow, microtubules- blue) and nucleus (purple)

26. On the Cell Membrane Cilia Flagella Microvilli
Short, hair-like projections
Create a wavelike motion to move substances across the surface of the cell
Flagella
Thicker, longer projections (fewer in number)
Help to move the cell with whip motion
Microvilli
Folds in the membrane that increase surface area

27. Cell covered with cilia
From and
Cell covered with cilia
Cell with single flagellum

28. Structure of a typical cell.
From Crowley
Structure of a typical cell.

29. Movement Across Cell Membrane

30. Movement across cell membrane
Substances that are important for cellular function must be able to enter the cell
Oxygen, glucose, amino acids (protein)
Waste products of metabolism must be able to be removed from the cell
This process is accomplished by 2 mechanisms
Passive Transport, Active Transport

31. Passive Transport Requires no additional energy (in the form of ATP)
Includes
Diffusion
Facilitated Diffusion
Osmosis
Filtration

32. Active Transport Requires energy from ATP Includes
Active transport pumps
Endocytosis (phagocytosis, pinocytosis)
Exocytosis

33. Passive Transport Simple Diffusion
Movement of a substance from an area of high concentration to an area of low concentration
Most common transport mechanism
Equilibrium is the point where no further diffusion occurs
Ex. Diffusion moves oxygen into the blood and carbon dioxide out of the blood in the lungs

34. Diffusion

35. Diffusion

36. Passive Transport Facilitated Diffusion
Similar to diffusion- substances move from higher concentration to lower concentration, but they are “helped” across cell membranes by a molecule in the membrane.
The “helper” molecule increases the rate of diffusion

37. Facilitated Diffusion

38. Passive Transport Osmosis Special type of diffusion
Diffusion of water through a semi-permeable membrane
Some substances are allowed through while others are not

39. More Osmosis
When dissolved substances (esp. glucose & protein) are confined by a semi-permeable membrane, they pull water in by osmosis
The strength of the osmotic pull is directly related to the concentration of solution
This pulling is known as osmotic pressure

40. Figure 3-9 Osmosis. The glass is sectioned into sides A and B by a membrane that is permeable only to water. The water moves from side A to side B, thereby creating unequal volumes.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

41. Osmosis
Because osmotic pressure pulls water into a compartment, it can cause swelling
When tissues are injured, proteins are released into the tissue spaces- the confined proteins attract water (create osmotic pressure)
This accumulation of water in the tissues is known as edema

42. Pitting Edema

43. Tonicity
The ability of a solution to affect the volume and pressure within a cell.
Isotonic (iso- means the same)
Hypotonic
Hypertonic

44. Isotonic
An isotonic solution has the same concentration of the intracellular fluid
No net movement of water across the cell membrane
The cell neither gains nor loses water

45. Isotonic

46. Hypotonic
A hypotonic solution has a more dilute concentration than the inside of the cell (the intracellular space is more concentrated)
Water moves from the solution into the cell and can cause the cell to burst, or lyse

47. Hypotonic

48. Hypertonic
A hypertonic solution is more concentrated than the inside of the cell
Water moves from the inside of the cell to the outside, causing the cell to shrink, or crenate

49. Hypertonic

51. In practice…
Are most IV solutions administered to patients isotonic, hypotonic or hypertonic? Why?

52. Passive Transport Filtration
Water and dissolved substances move across a membrane in response to pressure (not concentration); pressure pushes substances across the membrane

53. Figure 3-11 Filtration. A, Water is forced through the needle
Figure 3-11 Filtration. A, Water is forced through the needle. B, Water is forced through the holes in the barrel of the syringe. C, H2O is forced out of capillary.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

54. Active Transport Active Transport Pumps
Require addition energy in the form of ATP
Used to move additional substances into a cell when there is already a large number there.
Moving substances from an area of low concentration to high concentration (“uphill”)

55. Image from “The Virtual Cell” website
Active Transport Pump
The red ball is ATP; the yellow diamonds are Na+ and the red squares are K+

56. Active Transport Endocytosis
Intake of food or fluid by the cell membrane; particles are too large to cross the membrane by diffusion
Cell membrane surrounds the substance and engulfs it
Phagocytosis (cell eating)
Pinocytosis (cell drinking)

57. Endocytosis

58. Phagocytosis
A white blood cell engulfing and “eating” a piece of cellular debris

59. Active Transport Exocytosis
Moves substances out of the cell, both those produced by the cell and waste products
Substance is wrapped in a membrane, moves toward the cell membrane, fuses with the membrane, then exits the cell

60. Exocytosis

61. Membrane wrapped particles are moved to the outside of the cell
Exocytosis
Membrane wrapped particles are moved to the outside of the cell

62. Cell Division

63. Cell Division (Reproduction)
Necessary for body growth and repair
Frequency of cell division various between cell types
RBCs and cells in digestive tract replicate quickly, brain and spinal nerves do not replicate at all
Meiosis (only applies to sex cells)
Mitosis

64. Mitosis
Splitting of one “mother” cell into two identical “daughter” cells
Exact genetic copies- contain the same genetic information

65. Cell Cycle Sequence of events from one mitotic division to the next
Interphase
Cell prepares for mitosis through growth and DNA replication
Divided into 3 phases: First gap phase (G1), S phase, Second gap phase (G2)
Mitosis
M phase; cell divides into 2 cells so that each has the exact same genetic information

66. Mitosis
Four Phases:
Prophase
Metaphase
Anaphase
Telophase
Chromosomes line up and are pulled apart, separating into 2 sets. The cell spits into 2 identical cells

67. Mitosis Animation click here
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68. Figure 3-13 Mitosis. A, Mother and two identical daughters
Figure 3-13 Mitosis. A, Mother and two identical daughters. B, The arrangement of chromosomes during mitosis.
Elsevier items and derived items © 2007, 2003, 2000 by Saunders, an imprint of Elsevier Inc.

69. Cell Differentiation

70. Cell Differentiation
During embryonic development, cells that were once identical to the original single cell start to specialize and form the various cells in the body

71. Stem Cells
Stem cells remain undifferentiated or unspecialized; when they divide, one cell specializes and the other prepares for further stem cell division
Research implications- possibility of replacing damaged tissue and growing new organs
Induced pluripotent stem cells (iPS cells)- undifferentiated cells

72. Stem Cells
Induced pluripotent stem cells (iPS cells)- adult cells which have regressed to embryonic state; these undifferentiated cells can then be pushed into a desired cell type (bone, muscle, nerve, etc)
May eliminate ethical dilemma posed by using embryos as stem cell donors and hasten stem cell research

73. Order, Disorder & Death Cell division should be orderly
Uncontrolled and disorganized cell reproduction results in tumors
Tumors can be classified as
Benign (non-cancerous)
Malignant (cancerous)
Metastasis refers to the spreading of cancer cells throughout the body

74. Order, Disorder & Death
Apoptosis- programmed sequence of events that leads to cell death
Helps rid the body of old, unnecessary and unhealthy cells
Severely injured cells will necrose, or die (necrosis means death)

75. Cell Growth Disorders Atrophy (decrease size of the cell)
Dysplasia (alteration in size, shape or organization)
Hyperplasia (increased number of cells)
Metaplasia (transformation from one cell type into another)
Necrosis (death of cell or group of cells)
Neoplasm (abnormal new growth, tumor)