2. Cell Theory (3-1) Four basic concepts of the cell theory
Cells are the building blocks of all plants and animals.
Cells are the smallest functioning units of life.
Cells are produced through division of preexisting cells.
Each cell maintains homeostasis.

3. Cells in the Human Body (3-1)
Trillions of cells in the human body
Homeostasis of body maintained by coordinated action of cells
Cells come in variety of shapes and sizes
Figure 3-1 The Diversity of Cells in the Human Body.

4. The Study of Cells (3-1) Cytology Studied using microscopes
Study of the structure and function of cells
Studied using microscopes
Light microscopy (LM)
Electron microscopy (EM)
Transmission electron microscopy (TEM)
Allows to see through a specimen
Scanning electron microscopy (SEM)
Allows to see the external structures of a specimen

5. Overview of Cell Anatomy (3-1)
Wide variety of cell anatomy
All cells have a plasma membrane, or cell membrane
Separates cell contents (cytoplasm) from surrounding environment (extracellular fluid)
Figure 3-2.

6. The Plasma Membrane Functions (3-2)
Four key functions
Provides cell with physical isolation from extracellular fluid
Regulation of exchange with the environment
Allows for sensitivity to the environment
Provides for structural support

7. The Plasma Membrane Structure (3-2)
Extremely thin (6 nm–10 nm)
Components
Lipids
Phospholipids
Cholesterol
Proteins
Carbohydrates
Figure 3-3 The Plasma Membrane.

8. Figure 3-3 The Plasma Membrane.

9. Membrane Lipids (3-2)
Phospholipids are major component of plasma membrane
Cholesterol gives “stiffness” to plasma membrane
Makes it less fluid and less permeable
Lipid-soluble (non-polar) materials cross membrane easily
Ions and water-soluble (polar) compounds do not cross lipid portion

10. Phospholipid Bilayer (3-2)
Chemical properties of phospholipids results in formation of phospholipid bilayer
Hydrophilic non-lipid “head” in each layer faces watery environment (extracellular fluid on outside or intracellular fluid on inside of cell)
Hydrophobic “tails” of phospholipids move away from watery environment and face each other
Figure 3-3 The Plasma Membrane.

11. Membrane Proteins (3-2)
Most common are transmembrane proteins that span width of membrane
Proteins can “drift” within membrane or remain in specific position
Membrane composition can change over time

12. Membrane Protein Functions (3-2)
Six major functions
Table 3.1

13. Membrane Carbohydrates (3-2)
Join with proteins and lipids to form complex molecules on outer surface of membrane
Combine with lipids to form glycolipids
Combine with proteins to form glycoproteins
Function as lubricants and adhesives, receptors, and part of immune system “self” recognition

14. Permeability (3-3) Ease with which substances can cross a membrane
Impermeable membrane = nothing can cross
Freely permeable membrane = anything can cross
Selectively permeable membrane = some things can cross; others cannot
Describes plasma membranes
Lipid-soluble (non-polar) materials cross membrane easily
Ions and water-soluble (polar) compounds do not cross lipid portion

15. Movement across the Membrane (3-3)
Passive processes
Require no energy
Examples: diffusion, osmosis, facilitated diffusion
Active processes
Require energy, usually from ATP
Examples: active transport, vesicular transport

16. Diffusion (3-3) Molecules are in constant motion
Random collisions spread out molecules
This movement from area of high concentration to area of low concentration called diffusion
Difference between concentrations called concentration gradient
Diffusion proceeds “down concentration gradient”
Molecules eventually uniformly distributed

17. Figure 3-4 Diffusion.

18. Diffusion across Plasma Membranes (3-3)
Plasma membrane selectively restricts diffusion
Diffusion possible through:
Crossing lipid portion of membrane
Lipid-soluble drugs, alcohol, fatty acids, steroids, and dissolved gases (e.g., oxygen and carbon dioxide)
Passing through channel proteins
Small water-soluble compounds, water, ions
Large water-soluble molecules will require a protein carrier

19. Figure 3-5 Diffusion across the Plasma Membrane.
EXTRACELLULAR FLUID
Figure 3-5 Diffusion across the Plasma Membrane.

20. Characteristics of Osmosis (3-3)
Three characteristics of osmosis
Diffusion of water molecules across a selectively permeable membrane
Occurs across a selectively permeable membrane that is freely permeable to water but not freely permeable to solutes (dissolved materials)
Water flows from low solute concentration to high solute concentration

21. Osmotic Pressure (3-3) Osmotic pressure
Indication of the force of the water movement into a solution as a result of solute concentration
Increase in solute concentration = increase in osmotic pressure
Can be measured as amount of hydrostatic pressure required to oppose flow of water
Water moves toward the higher concentration of solutes, until equilibrium is reached

22. Figure 3-6 Osmosis.

23. Tonicity (3-3)
The effect of solute concentrations on the shape or tension of the cell membrane
Isotonic solution
Does not cause net movement of water into or out of cell
Water molecules move in and out at equal rate
Cell retains normal appearance

24. Hypotonic and Hypertonic Solutions (3-3)
Hypotonic solution
Net flow of water into the cell
Causes cell to swell and perhaps burst (lyse)
In red blood cells, this is called hemolysis
Hypertonic solution
Net flow of water out of the cell
Causes cell to shrivel and dehydrate
In red blood cells, shrinking is called crenation

25. Figure 3-7 Osmotic Flow across a Plasma Membrane.

26. Carrier-Mediated Transport (3-4)
Process using membrane proteins to move specific ions or organic substrates across plasma membrane
Can be passive (no ATP required) or active (ATP dependent)
Carrier proteins
Are specific to a substrate (e.g., glucose carrier will not carry other simple sugars)
Can be used repeatedly

27. Types of Carrier-Mediated Transport (3-4)
Cotransport
Carrier moves two substances in same direction
Countertransport
Carrier moves two substances in opposite directions
Examples of carrier-mediated transport
Facilitated diffusion
Active transport

28. Facilitated Diffusion (3-4)
Uses carrier proteins to passively move larger compounds down concentration gradient
Compound binds to receptor site on carrier protein
Protein changes shape and moves compound across membrane
Limited number of carriers prevents diffusion rate from indefinite increase
No further increase in rate once all carriers are bound

29. Figure 3-8 Facilitated Diffusion.

30. Active Transport (3-4) Requires energy from ATP
Can move substances against concentration gradient
Ion pump transports essential ions across plasma membranes
Exchange pump is an ATP-driven countertransport mechanism
Best example is sodium–potassium exchange pump

31. Figure 3-9 The Sodium-Potassium Exchange Pump.

32. Vesicular Transport (3-4)
Moves materials into or out of cell in small membrane-enclosed sacs called vesicles
Vesicles fuse with plasma membrane
Two major categories
Endocytosis
Exocytosis

33. Endocytosis (3-4)
Packages extracellular materials in vesicles at cell surface and moves them into the cell
Active process that requires energy
Three major types
Receptor-mediated endocytosis
Pinocytosis
Phagocytosis

34. Receptor-Mediated Endocytosis (3-4)
Begins when receptors on plasma membrane surface bind to specific target molecules (ligands)
In-pouching of plasma membrane forms coated vesicle
Ligands are removed from the vesicle
Receptors recycled to be used again

35. Figure 3-10 Receptor-Mediated Endocytosis.

36. Pinocytosis (3-4) Pinocytosis or “cell drinking”
Pocket forms in plasma membrane
Forms small vesicles filled with extracellular fluid
No receptors involved
Process common to most cells

37. Phagocytosis (3-4) Phagocytosis or “cell eating”
Produces vesicles containing solid objects
Cytoplasmic extensions (pseudopodia) surround an object outside the cell
Membrane fuses to form vesicle around object
Vesicle fuses with lysosomes inside the cell and contents are digested
Process unique to specialized cells that protect tissues

38. Exocytosis (3-4) Reverse of endocytosis
Vesicle created inside the cell
Vesicle fuses with plasma membrane
Contents discharged to extracellular environment

39. Figure 3-11 Phagocytosis.

40. Inside the Cell (3-5) Cytoplasm
General term for material between plasma membrane and membrane surrounding nucleus
Contains cytosol (intracellular fluid) and organelles

41. The Cytosol (3-5)
Contains dissolved nutrients, ions, proteins, and waste products
Differs from extracellular fluid (ECF) in that cytosol:
Contains higher K+ and lower Na+ concentrations than ECF
Contains higher concentration of dissolved proteins than ECF
Gives cytosol a thicker, more viscous consistency
Usually contains small reserves of amino acids and lipids along with carbohydrates

42. The Organelles (3-5)
Internal structures that perform specific functions
Membranous (membrane-enclosed) organelles are isolated from the cytosol
Allow storage and manufacture of substances
Nonmembranous organelles are in direct contact with cytosol

43. The Cytoskeleton (3-5) Internal protein framework
Threadlike filaments and hollow tubules give strength and flexibility
Most important cytoskeletal elements in most cells
Microfilaments
Intermediate filaments
Microtubules

44. Microfilaments and Intermediate Filaments (3-5)
Thinnest strands of the cytoskeleton
Usually composed of actin
Attach plasma membrane to underlying cytoplasm
Intermediate filaments
Intermediate in size
Varying protein composition
Strengthen and stabilize the cell

45. Microtubules (3-5) Microtubules Largest component of cytoskeleton
Hollow tubes built from globular protein tubulin
Give cell strength and rigidity
Anchor organelles
Form spindle apparatus during cell division

46. Microvilli (3-5)
Small, finger-shaped projections of the plasma membrane on exposed surface of some cells
Have internal core of microfilaments for support
Provide additional surface area of membrane
Found on cells that are absorbing lots of materials from the extracellular fluid
Figure 3-12 The Cytoskeleton.

47. Centrioles (3-5) Centrioles Cylindrical in shape
Composed of triplets of microtubules
Move DNA strands during cell division

48. Cilia and Flagella (3-5) Cilia Flagella
Relatively long, slender extensions of plasma membrane
Formed by microtubules arranged in pairs
Multiple motile cilia use ATP to move substances across cell surface
Single, nonmotile primary cilium acts as signal sensor
Flagella
Look like long cilia, but are used to move the cell through its environment

49. Ribosomes and Proteasomes (3-5)
Manufacture proteins
Consist of small and large subunits
Two major types
Free ribosomes that are spread throughout cytosol
Fixed ribosomes attached to endoplasmic reticulum (ER)
Proteasomes
Organelles containing protein-breaking (proteolytic) enzymes, or proteases
Remove and recycle damaged proteins from cytoplasm

50. Endoplasmic Reticulum (3-5)
Network of intracellular membranes
Continuous with nuclear envelope
Forms hollow tubes, flattened sheets, and chambers (cisternae)
Two types
Smooth endoplasmic reticulum (SER)
Rough endoplasmic reticulum (RER)

51. Endoplasmic Reticulum Functions (3-5)
Four key functions
Synthesis of proteins, carbohydrates, and lipids
Storage of materials, isolating them from the cytosol
Transport of materials through the cell
Detoxification of drugs or toxins

52. Smooth Endoplasmic Reticulum (3-5)
Smooth endoplasmic reticulum (SER)
Has no ribosomes
Synthesizes lipids and carbohydrates, such as:
Phospholipids and cholesterol for membranes
Steroid hormones
Glycerides (especially triglyceride)
Glycogen in skeletal muscles and liver cells

53. Rough Endoplasmic Reticulum (3-5)
Rough endoplasmic reticulum (RER)
Has fixed ribosomes on the membrane
Location of protein synthesis
Some proteins packaged into membrane-bound sacs
Sacs (transport vesicles) pinch off from tips of ER and deliver proteins to Golgi apparatus

54. Figure 3-13 The Endoplasmic Reticulum.

55. Golgi Apparatus (3-5)
Made of flattened membranous discs called cisternae
Three major functions
Modifies and packages secretions for release
Renews or modifies plasma membrane
Packages enzymes within vesicles (lysosomes)

56. Figure 3-14 The Golgi Apparatus.

57. Figure 3-15 Protein Synthesis, Processing, and Packaging

58. Lysosomes (3-5) Vesicles filled with digestive enzymes Functions
Cleanup and recycling of materials within the cell
Example: removing damaged organelles
Defense against disease
Fuse with vesicles containing pathogens and breaks them down
Autolysis, or self-destruction, of damaged cells

59. Peroxisomes (3-5) Formed from existing peroxisomes
Most abundant in metabolically active cells (e.g., liver cells)
Carry different group of enzymes than lysosomes
Enzymes absorb and break down fatty acids and other organic compounds
By-product is hydrogen peroxide (H2O2), a free radical that is highly reactive and can be destructive to cells
Free radicals = ions or molecules that contain unpaired electrons

60. Mitochondria (3-5) Provides 95% of energy for the cell
Have a double membrane
The outer surrounds the organelle
The inner is folded to form the cristae
Cristae increase surface area exposed to fluid matrix
Enzymes in this matrix catalyze energy-producing reactions

61. Mitochondrial Energy Production (3-5)
First step of breaking down glucose (glycolysis) occurs in cytosol
Remaining steps of aerobic cellular respiration, occur in the mitochondria

62. The Nucleus (3-6) Control center of the cell Nuclear envelope
Dictates cell function and structure by controlling protein synthesis
Nuclear envelope
Double membrane that surrounds the nucleus
Separates nucleoplasm from cytosol
Nuclear pores
Allow movement of substances into and out of the nucleus

63. Nuclear Structure and Contents (3-6)
Nucleoli
Synthesize ribosomal RNA (rRNA)
Assemble small and large ribosomal subunits
Chromosomes
Contain DNA, which stores instructions for protein synthesis
Human body cells contain 23 pairs of chromosomes
Chromatin
Loosely coiled DNA found in cells that are not dividing

64. Figure 3-17 The Nucleus.

65. Information Storage in the Nucleus (3-6)
Genetic code
Chemical “language” of the cell
Contains information for protein synthesis in form of nitrogenous base sequence on DNA
Arranged in sequence of three bases each representing a single amino acid
Gene
The functional unit of heredity
Each protein-coding gene contains all the triplets needed to produce a specific protein

66. DNA Control of Cell Function (3-7)
Genes are normally tightly coiled with histones, keeping them inactive
To activate, enzymes must break bonds and remove histone, revealing the promoter segment
Protein synthesis occurs in two stages
Transcription
Translation

67. Transcription (3-7)
Production of single strand of messenger RNA (mRNA) from single strand of DNA
Process required to get DNA blueprint for protein synthesis from the nucleus out to the cytosol

68. Three Steps of Transcription (3-7)
Two DNA strands separate, and RNA polymerase binds to promoter gene
New mRNA strand is formed using complementary RNA nucleotides
Uracil in RNA strand is paired with adenine in DNA strand
Sequence of three nitrogenous bases in RNA represents a codon (complementary to DNA triplet)
At DNA “stop” signal, RNA polymerase and mRNA detach, and the original DNA strands reattach

69. Figure 3-19 Transcription.

70. Translation (3-7)
Uses new mRNA codons to signal the assembly of specific amino acids in series to synthesize a protein
mRNA leaves the nucleus and binds to a ribosome in cytoplasm
Transfer RNA (tRNA) delivers amino acids to ribosomes
Each tRNA has a complement to the codon called an anticodon

71. Table 3.3

72. Translation Process (3-7)
Three phases of translation
Initiation
Elongation
Termination

73. Initiation of Translation (3-7)
“Start” codon of mRNA combines with small ribosomal subunit and first tRNA
Coding for methionine with the base sequence AUG
Small and large ribosomal subunits enclose the mRNA

74. Figure 3-20a-b Translation.

75. Elongation in Translation (3-7)
2nd tRNA brings another amino acid
Its anticodon binds to 2nd codon of mRNA
Ribosomal enzymes remove 1st amino acid and attach it to the 2nd with a peptide bond
Ribosome moves along the codons repeating these steps

76. Figure 3-20a-b Translation.

77. Termination of Translation (3-7)
Amino acids continue to be added until ribosome reaches the “stop” codon at end of mRNA
Ribosome detaches leaving the strand of mRNA and a newly completed polypeptide
Figure 3-20c-e Translation.

78. Stages of a Cell’s Life Cycle (3-8)
Stages include interphase, mitosis, and cytokinesis
Cell division
Form of cellular reproduction
Increases numbers of cells
Replaces old and damaged cells
Requires duplication of genetic material (DNA replication)

79. Types of Cell Division (3-8)
Mitosis
Nuclear division of somatic (body) cells
Cells differ in frequency of mitosis
Stem cells divide rapidly
Some cells programmed to self-destruct
Apoptosis is genetically controlled death of cells
Meiosis
The production of sex cells—the sperm and ova

80. Interphase (3-8) The period of time between cell divisions
Cell spends majority of life here, performing normal functions
G1 phase is when the cell duplicates organelles and adds cytosol
S phase is when DNA is replicated in the nucleus
G2 phase is when centrioles are replicated and protein synthesis continues

81. Figure 3-21 Stages of a Cell’s Life Cycle.
INTERPHASE S
DNA
replication,
synthesis of
histones G1 G2
Normal
Protein
synthesis
cell functions
plus cell growth,
THE
CELL
CYCLE
duplication of
organelles,
protein
synthesis
MITOSIS AND
CYTOKINESIS
(see Fig. 3-23)
Figure 3-21 Stages of a Cell’s Life Cycle.

82. Figure 3-22 DNA Replication.

83. Mitosis (3-8)
Process that separates duplicated chromosomes into two new nuclei
Occurs in four stages
Prophase
Metaphase
Anaphase
Telophase

84. Prophase (3-8) Chromosomes become visible under light microscope
Each of two copies of DNA is called a chromatid
Chromatids are connected to each other at a point called the centromere
Nucleoli disappear
Two pairs of centrioles move to opposite poles
Spindle fibers appear
Nuclear envelope disappears
Chromatids attach to spindle fibers

85. Figure 3-23a Interphase, Mitosis, and Cytokinesis.1b
INTERPHASE
STAGE
EARLY PROPHASE
STAGE
LATE PROPHASE
Nucleus
(contains replicated DNA)
Spindle
fibers
Centriole
Chromosome
with two sister
chromatids
MITOSIS BEGINS
Centrioles
(two pairs)
Centromeres
Figure 3-23a Interphase, Mitosis, and Cytokinesis.

86. Metaphase (3-8)
Chromatids move to narrow central zone called metaphase plate
Paired chromatids line up along the plate

87. Anaphase (3-8)
Centromere of each chromatid splits creating daughter chromosomes
Daughter chromosomes are pulled apart and move toward the centrioles

88. Telophase (3-8) New nuclear membranes form Nucleoli reappear
DNA uncoils
Cell is preparing to enter interphase again

89. Cytokinesis (3-8) Cytoplasmic division that forms two daughter cells
Usually begins in late anaphase
Continues throughout telophase
Is usually completed after a nuclear membrane has re-formed around each daughter nucleus

90. Figure 3-23b Interphase, Mitosis, and Cytokinesis.4
STAGE
METAPHASE
STAGE
ANAPHASE
STAGE
TELOPHASE
INTERPHASE
Daughter
chromosomes
Daughter
cells
Cleavage
furrow
CYTOKINESIS
Metaphase
plate

91. Tumors (3-9)
Tumor or neoplasm is mass produced by abnormal cell growth and division
Benign tumors
Usually encapsulated and rarely life threatening
Malignant tumors
Spread from original location or primary tumor through a process called invasion
May also spread to distant tissues forming secondary tumors
Migration called metastasis

92. Cancer (3-9)
Characterized by gene mutations leading to malignant cells and metastasis
Form extremely active secondary tumors
Stimulates additional blood vessel growth into area
Additional nutrients to cancer cells accelerate tumor growth and metastasis
Cancer cells take nutrients and energy away from healthy tissues

93. Cellular Differentiation (3-10)
All somatic cells in the body have the same chromosomes and genes
Yet develop to form a wide variety of cell types
Differentiation
Occurs when specific genes are turned off, leaving the cell with limited capabilities
A collection of cells with specific functions is called a tissue