1. Unit II: The Cell
All organisms are made of cells, the organism’s basic unit of
structure and function.

2. Size range of cells

3. How We Study Cells Microscopes - light microscope
- electron microscope (TEM/SEM)

5. A Panoramic View of the Cell
Prokaryotic Eukaryotic
+only in bacteria/archaebacteria Protists, Fungi, Plantae, Animalia
+no true nucleus/nuclear envelope true membrane-bound nucleus
+genetic material in nucleoid region genetic material in nucleus
+no organelles many organelles

6. Animal vs. Plant Cell Unique to Plant Cells: - cell wall
- large central vacuole
Chloroplasts
Plasmodesmata
Unique to Animal Cells:
Centrioles
Lysosomes
- flagella and/or cilia

11. How organelles are fractionated (isolated)

12. The Nucleus and Ribosomes
- enclosed by nuclear envelope
- contains most of the genes that
control the entire cell
+ DNA organized with
proteins into chromatin
- nucleolus
Nuclear lamina – protein filaments
that give structure to the inner
nuclear membrane

13. The Nucleus and Ribosomes (con’t)
- build proteins
- RNA/protein
complexes
- free/bound

14. The Endomembrane System
Includes:
nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane*

15. Endomembrane System (con’t)
Endoplasmic reticulum
manufactures membranes
two distinct regions
+ smooth ER
- synthesis of lipids
- carbohydrate metabolism
- detoxify drugs/poisons
- stores calcium ions
+ rough ER
- manufacture proteins for
secretion
- membrane production

16. Endomembrane System (con’t)
Golgi apparatus
finishes, sorts, and ships cell products
two poles
+ cis face
+ trans face
Enzymes in the Golgi modify products of the ER in stages
as they move through the Golgi stack from cis to trans face.

19. Endomembrane System (con’t)
Lysosomes – contain hydrolytic enzymes
digestive compartments
+ intracellular digestion
+ recycle cell material
+ program cell destruction (apoptosis)

21. Apoptosis – programmed cell death

22. Endomembrane System (con’t)
Vacuoles
function in cell maintenance
+ food vacuole
+ contractile vacuole
+ central vacuole (pictured)
- tonoplast

23. Endomembrane System Summary

24. Other Membranous Organelles
Peroxisomes
consume oxygen for
metabolism
+ contain specialized
teams of enzymes
- peroxide-producing
oxidases and catalase
RH2 + O2 -oxidase-> R + H2O2
2H2O2 -catalase-> 2H2O + O2

25. Mitochondria and Chloroplasts
energy transformers of cells
+ double membranes
+ contain ribosomes/DNA
Mitochondrial DNA is only passed on
by mom

28. The Cytoskeleton Cytoskeleton provides structural support
for motility and regulation
+ network of fibers
- microtubules
- microfilaments
- intermediate filaments

30. Cytoskeleton (con’t)

31. Centrosomes Found in animal & plant cells Produce microtubules
during cell reproduction
Animal cells contain
centrioles which
contain 9 sets of 3
microtubules

32. F L A G E C I L
I A

33. Flagellum Structure

34. Cell Surfaces and Junctions
Cell Walls (1° & 2°)
cellulose fibers
Plasmodesmata
Middle lamella
Made of pectin
(sticky polysaccharide)
Pectin holds cell walls
together like concrete

35. Cell Surfaces and Junctions
ECM (Extra Cellular Matrix)
meshwork of macromolecules outside plasma membrane
+ mostly glycoproteins (Collagen & proteoglycan)
+ support/anchorage (Fibronectin & integrin)

36. Cell Surfaces and Junctions
Tight junctions – prevent fluid from moving between cell layers in a tissue
Desmosomes – anchor adjacent cells
Gap junctions – allows the movement of cytoplasm, ions, sugars, amino acids from one cell to the next

37. Tight Junctions

38. Desmosomes

39. Gap junctions

41. Membrane Structure and Function
Collagen
proteoglycan
Fibronectin

42. Membrane Structure and Function (con’t)
Plasma Membrane
boundary that separates living cell from
its non-living surroundings
+ 8 nm thick
+ selectively permeable
+ unique structure relates to function

43. Phospholipid Glycerol Fatty Acid Chains
Amphipathic molecule – has hydrophilic & hydrophobic regions

44. Hydrophilic vs Hydrophobic

47. Membrane Structure and Function (con’t)
Fluid Mosaic Model
The Fluid Quality of Membranes
+ held together by hydrophobic interactions
- lipids/proteins drift about laterally
+ unsaturated hydrocarbon tails
- maintain fluidity at low temperatures
+ cholesterol
- stabilizes the membrane
restrains movement at high temp.
hinders close packing at low temp.

48. Membrane Structure and Function (con’t)
Fluid Mosaic Model
Membranes as Mosaics
+ membrane is collage of proteins
- integral proteins
transmembrane
- peripheral proteins
appendages

49. Plasma membrane synthesis

50. Membrane Structure and Function (con’t)
Functions of Membrane Proteins
Transport
Enzymatic Activity
Signal Transduction
Intercellular joining
Cell-cell recognition
Attachment to the cytoskeleton and ECM

51. Signal Transduction with G proteins

52. Types of Membrane Proteins

55. Voltage Gated Ion Channels

56. Glycoprotein

57. Glycolipid

58. Cholesterol
Reduces membrane fluidity by reducing phospholipid movement
Hinders solidification at low temperatures

59. Cholesterol is a steroid

62. Traffic Across Membranes
Selective Permeability
hydrophobic, small, lipid molecules pass easily across the membrane
hydrophilic, large, charged (polar) molecules cannot pass easily
How do cells get the materials they need inside?

63. Traffic Across Membranes (con’t)
Passive Transport
Diffusion
+ the tendency for molecules of any
substance to spread out into the
available space
- concentration gradient

64. Passive Transport Requires no energy
Occurs due to natural concentration gradient
Molecules move from high concentration to low concentration (DOWN the gradient)
3 Types
Diffusion
Osmosis
Facilitated Diffusion

66. Diffusion

67. Diffusion
A.K.A. simple diffusion
Movement of small molecules across a selectively permeable membrane from an area of HIGH concentration to an area of LOW concentration w/o the use of energy (DOWN the concentration gradient)
e.g. O2, CO2, urea, & alcohol

68. Traffic Across Membranes (con’t)
Passive Transport
Osmosis
+ the diffusion of water
- hypotonic,hypertonic, isotonic
Tonicity – the ability of a solution to cause a cell to gain or lose water
Osmoregulation – the control of water balance e.g. contractile vacuole in paramecium

69. Osmosis The diffusion of WATER across a selectively permeable membrane
OSMOTIC PRESSURE
The pressure exerted on plasma membranes in solution
Isotonic solution
Hypertonic solution
Hypotonic solution

70. Water Potential
The physical property predicting the direction in which water will flow, controlled by the solute concentration

71. Water potential (ψ) = pressure potential (ψp ) + solute potential (ψs )

72. (ψ) = Greek letter psi
Water potentials (ψ) are a way of measuring the free-energy of water. Water will flow spontaneously from a high potential to a low potential, like a ball rolling down a hill.

73. Physical pressure due to air & the container

74. Water Potential
“Water potential" (Ψ) is a measure of the free energy of water;  pure water  (which has a high amount of free energy) is arbitrarily assigned a water potential of zero; units pressure: MPa; can be positive or negative
Factors that determine plant water potential:  1) amount of solutes- increasing concentrations will lower  the free energy (water potential); termed osmotic potential (ψs)
2)  turgor pressure (ψp) in plant cell- positive pressure inside plant cells; increases free energy; loss of turgor = wilting

77. Cells in Isotonic Solution
If the concentration of solute (salt) is = on both sides, there will be no net movement of water
"ISO" means the same

78. Cells in Hypertonic Solution

79. Hypertonic Solutions
More solute (salt) molecules outside the cell, which causes water to be sucked out of the cell.
In plant cells, the central vacuole loses water and the cells shrink, causing plasmolysis resulting in the plant wilting.
In animal cells, the cells also shrink.
In both cases, the cell may die.
This is why it is dangerous to drink sea water

80. Plasmolysis
A phenomenon in plant cells in which the cytoplasm shrivels and the plasma membrane pulls away from the cell wall when the cell loses water to a hypertonic environment.

81. Cells in Hypotonic Solution

82. Hypotonic Solutions
There are less solute (salt) molecules outside the cell, since salt sucks, water will move into the cell.
The cell will gain water and grow larger. In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the cell wall keeps the plant from bursting
In animal cells, the cell may be in danger of bursting, organelles called CONTRACTILE VACUOLES will pump water out of the cell to prevent this.

84. Osmotic Potential
The tendency of water to move across a selectively permeable membrane into a solution
Determined by measuring the pressure required to stop the osmotic movement of water into the solution.

88. Osmosis Review

89. Traffic Across Membranes (con’t)
Passive Transport
Facilitated Diffusion
+ diffusion with the help
of transport proteins
- gated channels

90. Facilitated Diffusion Protein Channel or Pore

91. Facilitated Diffusion Protein Carrier

94. Traffic Across Membranes (con’t)
Active Transport
energy-requiring process
+ ATP
pumps molecules against
concentration gradient
+ Na+/K+ pump

95. Active Transport
Requires cell energy (ATP) to move molecules AGAINST the concentration gradient; from an area of LOW concentration to an area of HIGH concentration
Sodium–Potassium pump (Exchange 3 sodium ions for 2 potassium ions)
Hydrogen ion, or proton pump (Pump hydrogen ion against the concentration gradient)

96. Phosphorylation
The addition of a phosphate (PO4) group (From ATP) to a protein or a small molecule
This changes the protein shape

98. Active Transport (Uniport)

99. Active Transport Na-K Pump

100. Na-K Pump Antiport

102. Glucose-Sodium Symport

104. Traffic Across Membranes (con’t)
Membrane Potential
electrogenic pump
+ proton pumps (H+)
electrochemical gradient
+ cotransport

106. Traffic Across Membranes (con’t)

107. Bulk Media Transport
Endocytosis – Vesicle is created from the invagination of the plasma membrane, which pinches off, bringing large molecules into the cell
Pinocytosis – Cell drinking (endocytosis)
Phagocytosis – Cell eating (endocytosis)
Receptor Mediated Endocytosis – Substrate binds to receptor found on the plasma membrane to be brought into the cell
Exocytosis – Vesicle binds to the plasma membrane releasing the contents outside of the cell

108. Endocytosis

109. Pinocytosis

110. Phagocytosis

111. Receptor Mediated Endocytosis
Ligand – molecule that binds specifically to a receptor site of another molecule
LDL uses receptors to enter cells (hypercholesterolemia is due to receptor defect)

112. Exocytosis

113. Traffic Across Membranes (con’t)
Transport of Large Molecules
Exocytosis
+ the cell exports macromolecules
using vesicles from Golgi apparatus
Endocytosis
+ the cell takes in macromolecules
by forming new vesicles from membrane
- phagocytosis (“cellular eating”)
- pinocytosis (“cellular drinking”)
- receptor-mediated endocytosis
+ ligands