1. A Tour of the Cell

2. History of the Cell
 Cells were first discovered in 1665 by Robert Hooke
From Micrographia
 The accumulation of scientific evidence led to the ‘cell theory’
(1) All living things are composed of cells
(2) All cells form from previously existing cells

3. Cells are the building blocks of all life forms
Organisms are either:
 Single-celled, such as most bacteria and protists
 Multicelled, such as plants, animals, and most fungi

4. Cells are made up of MACROMOLECULES:
Nucleic Acids
(2) Proteins
(3) Lipids
(4) Carbohydrates

5. The Two Major Categories of Cells
Prokaryotic cells
 Eukaryotic cells

6. Prokaryotes Vs. Eukaryotes
Prokaryotic cell
Nucleoid region
Eukaryotic cell
Nucleus
Organelles
Figure 4.4

7. Prokaryotic cells: Are much smaller than eukaryotic cells
Lack internal structures surrounded by membranes
 Lack a nucleus

8. A Detailed View of Prokaryotic Cells
flagella
Nucleoid region (DNA)
Plasma
membrane
Ribosomes
Cell wall
Capsule
Pili
Figure 4.5

9. A Detailed View of Eukaryotic Cells
 An idealized animal cell
Centriole
Ribosomes
Lysosome
Not in most
plant cells
Flagellum
Cytoskeleton
Plasma
membrane
Mitochondrion
Nucleus
Rough
endoplasmic
reticulum (ER)
Smooth
endoplasmic
reticulum (ER)
Golgi
apparatus
Figure 4.6A

10. A Detailed View of Eukaryotic Cells
 An idealized plant cell
Not in animal cells
Cytoskeleton
Mitochondrion
Central
vacuole
Nucleus
Cell wall
Rough endoplamsic reticulum (ER)
Chloroplast
Ribosomes
Plasma
membrane
Smooth
endoplasmic
reticulum (ER)
Plasmodesmata
Golgi apparatus
Figure 4.6B

11. Antony van Leeuwenhoek (1632-1723):
Microscope Maker
 Identified and termed ‘animalcules’

12. Microscopes as Windows to Cells
 The light microscope is used by many scientists
(1) Light passes through the specimen
(2) Lenses enlarge, or magnify, the image
(a) Light micrograph (LM) of a white blood cell (stained purple) surrounded by red blood cells
Figure 4.2A

13. Microscope Terminology
Magnification: An increase in the specimen’s apparent size
Resolving power: The ability of an optical instrument to show two objects as separate

14. The Electron Microscope:
 Uses a beam of electrons instead of light
Has a higher resolving power than light microscopes
(can magnify up to 100,000X)
 The power of electron microscopy reveals many details of cellular components

15. Scanning Electron Microscopy
(b) Scanning electron micrograph (SEM) of a white blood cell
Figure 4.2B
 for studying external cellular structures

16. Transmission Electron Microscopy
(c) Transmission electron micrograph (TEM) of a white blood cell
Figure 4.2C
 for studying internal cellular structures

17. Power and Scale of Microscopy
Human height
Length of some
nerve and
muscle cells
Chicken
egg
Unaided eye
Frog
eggs
Plant and
animal
cells
Light microscope
Nucleus
Most bacteria
Mitochondrion
Smallest bacteria
Electron microscope
Viruses
Ribosomes
Proteins
Lipids
Small
molecules
Atoms
Figure 4.3

18. MEMBRANE STRUCTURE AND FUNCTION
The plasma membrane separates the living cell from its nonliving surroundings and regulates what goes in and out.
Organelles are surrounded by membranes to separate them as distinct compartments of the cell with specialized functions.

19. The Fluid Mosaic Model of Membranes:
 Membranes are composed of lipids AND proteins and are highly dynamic (fluid)
 Membranes of the cell have selective permeability (04-07a-MembraneStructure.mov):
(1) They allow some substances to cross more easily than others
(2) They block passage of some substances altogether
(3) The traffic of some substances can only occur through transport proteins (like glucose)

20. The LIPID Component
 The lipids belong to a special category called phospholipids
 Phospholipids form a two-layered membrane, the phospholipid bilayer
Outside cell
Hydrophilic
head
Hydrophobic
tail
Cytoplasm
(inside cell)
(a) Phospholipid bilayer of membrane
Figure 4.7A

21. Phospholipids in Membranes

22. The PROTEIN Component
 Most membranes have specific proteins embedded in the phospholipid bilayer
Hydrophilic
region of
protein
Phospholipid
bilayer
Hydrophobic
region of protein
(b) Fluid mosaic model of membrane
Figure 4.7B

23. FUNCTIONS of Membrane Proteins
Cytoplasm
Fibers of
extracellular
matrix c
Enzymatic activity b
Cell signaling a
Attachment to
cytoskeleton and
extracellular
matrix e
Intercellular
joining f
Cell-cell
recognition d
Transport
Cytoplasm
Cytoskeleton
Figure 4.8
04-08-ReceptorProtAnim.mov

24. EVOLUTION CONNECTION: The Origin of Membranes
 Phospholipids were probably among the organic molecules on the early Earth
 When mixed with water, phospholipids spontaneously form membranes

25. THE NUCLEUS: GENETIC CONTROL OF THE CELL
 The nucleus is the ‘manager’ of the cell
Genes in the nucleus store the information necessary to produce proteins, which perform cellular functions

26. Structure and Function of the Nucleus
 The nucleus is bordered by a double membrane called the nuclear envelope
The nucleus contains chromatin and
the nucleolus

27. Nuclear
envelope
Ribosomes
Chromatic
Nucleolus
Pore
Figure 4.9

28. How DNA Controls the Cell
 Genes encoded by DNA are copied to another molecule, mRNA
DNA 1
Synthesis of
mRNA in the
nucleus
mRNA
mRNA molecules representing genes are exported from the nucleus into the cytoplasm
Nucleus
Cytoplasm 2
Movement of
mRNA into
cytoplasm via
nuclear pore
mRNA
 Ribosomes in the cytoplasm ‘read’ the mRNA and use the info to make a protein
Ribosome 3
Synthesis of
protein in the
cytoplasm
Protein
Figure 4.10

29. The Central Dogma of Molecular Biology
DNA
RNA
Protein  
Transcription
Translation

30. Exceptions to the Central Dogma
DNA
RNA
Protein  
Retroviruses

31. Chloroplasts and Mitochondria: Energy Conversion
 Cells require a constant energy supply to do all the work of life

32. Chloroplasts
Inner and outer
membranes of
envelope
 Chloroplasts are the sites of photosynthesis: the conversion of light energy to chemical energy
Space between
membranes
Granum
Stroma (fluid in
chloroplast)
Figure 4.17

33. Mitochondria
 Mitochondria are the sites of cellular respiration, the process of producing ATP from food molecules
Outer
membrane
Inner
membrane
Cristae
Matrix
Space between
membranes
Figure 4.18

34. EVOLUTION CONNECTION: The Origin of Organelles
 The Endosymbiont Theory: eukaryotic organelles evolved from prokaryotes that were engulfed by other cells

35. The Cytoskeleton: Cell Shape and Movement
 The cytoskeleton is an infrastructure of the cell consisting of a network of fibers:
(1) Actin Fibers (structure & movement OF the cell)
(2) Microtubules (structure & movement WITHIN the cell)

36. Functions of the Cytoskeleton:
 Provide mechanical support and structure to the cell to give it shape
Figure 4.19A

37. Functions of the Cytoskeleton:
 The cytoskeleton can change the shape of a cell for movement
Figure 4.19B

38. Motile Appendages  Flagella propel the cell in a whiplike motion
 Cilia move in a coordinated back-and-forth motion
Figure 4.20A, B

39. Non-moving cells have cilia and flagella, too
 The human windpipe is lined with cilia
Figure 4.20C

40. The universal architecture of eukaryotic cilia
(a) Paramecium
(b) Cells from
fallopian
tube
(c) Cross section of cilium
Figure 1.9

41. CELL SURFACES: Protection, Support, and Cell-Cell Interactions
 Most cells secrete materials that are external to the plasma membrane (except those that have cell walls!)

42. Plant Cell Walls and Cell Junctions
 Plant cells are encased by cell walls
Walls of two adjacent
plant cells
Vacuole
Plasmodesmata
(channels between cells)
Figure 4.21

43. Animal Cell Surfaces and Cell Junctions
 Animal cells lack cell walls:
They secrete a sticky covering called the extracellular matrix
(2) This layer helps hold cells together to form tissues and organs and so on.

44. Connections Between Animal Cells:
Extracellular matrix
(a) Tight junctions
(b) Anchoring
junctions
(c) Communicating
junctions
Plasma membranes
of adjacent cells
Extracellular matrix
Figure 4.22

45. The Secretory System: Manufacturing and Distributing Cellular Products
 Many of the membranous organelles in the cell belong to the secretory, or endomembrane, system

46. The Endoplasmic Reticulum
 The endoplasmic reticulum (ER):
Nuclear
envelope
Produces an enormous variety of molecules
(2) Is composed of smooth and rough ER
Ribosomes
Rough ER
Smooth ER
Figure 4.11

47. Rough ER
 The “roughness” of the rough ER is due to ribosomes that stud the outside of the ER membrane
 The functions of the rough ER include:
(1) Producing proteins
(2) Producing new membrane

48. After the rough ER synthesizes a molecule it packages the molecule into transport vesicles4
Transport vesicle
buds off
Secretory
protein inside
transport
vesicle
Ribosome 3
Protein 1
Rough ER 2
Polypeptide
Figure 4.12

49. Smooth ER
 The smooth ER lacks the surface ribosomes of ER and produces lipids, including steroids

50. The Golgi Apparatus  Works in partnership with the ER
 Refines, stores, and distributes the products of cells
Transport
vesicle
from ER
“Receiving” side of
Golgi apparatus
Golgi apparatus
New vesicle forming
Transport vesicle
from the Golgi
“Shipping” side of
Golgi apparatus
Plasma membrane
Figure 4.13

51. Lysosomes  A lysosome is a membrane-enclosed sac:
It contains digestive enzymes
(2) The enzymes break down macromolecules

52. Digestive Functions of the lysosome:
To fuse with food vacuoles to digest the food
Lysosome
Digestive enzymes
Plasma
membrane
Digestion
Food
Food vacuole
(a) Lysosome digesting food
Figure 4.14a

53. Digestive Functions of the lysosome:
To break down damaged organelles
Lysosome
Digestion
Damaged
organelle
(b) Lysosome breaking down damaged organelle
Figure 4.14b

54. Vacuoles: Membranous Sacs
 Two types are the contractile vacuoles of protists and the central vacuoles of plants
Central
vacuole
Contractile
vacuoles
(a) Contractile vacuoles in a protist
(b) Central vacuole in a plant cell
Figure 4.15

55. Summary of the Endomembrane System
Rough ER
Transport
vesicle from ER
Golgi
apparatus
Secretory
vesicle from Golgi
Secretory
protein
Vacuole
Lysosome
Plasma membrane
Figure 4.16
04-16-EndomembraneSysAnim.mov

56. BIOLOGY AND SOCIETY: Drugs That Target CELLS
 Antibiotics are one of the great marvels of modern medicine:
(1)Treatment with these drugs will kill invading bacteria
(2)The drugs don’t harm the human cells of the host
Figure 4.1

57. BIOLOGY AND SOCIETY: Drugs That Target CELLS
 Chemotherapy and Cancer:
Targets cells that are growing rapidly
(2) The drugs don’t affect most human cells, but…