Cells are the basic unit of life. Robert Hooke first observed cells in 1665 using a microscope he invented. The cell theory states that all living things are made of cells and cells are the fundamental unit of life. Key structures of cells include the nucleus, which contains DNA; organelles like mitochondria and chloroplasts; and a cell membrane that encloses the cell. Organelles perform specialized functions like carrying out photosynthesis in chloroplasts or producing energy in mitochondria.

1. Cell Biology

2. Cells
• Cell – Smallest unit of life that can function
independently
– Discovered by Robert Hooke – 1660
– Antony van Leeuwenhoek – improved lenses,
made observing cells easier
• Cell Theory – Schleiden, Schwann
– All organisms are made of one or two cells
– Cell fundamental unit of all life

3. History of Cell Biology
• Robert Hooke 1635-1703 – invented
compound microscope
– Allowed us to “see” cells

4. History of Cell Biology
• Anton von
Leeuwenhoek 1673-
1723 – used higher
magnification lenses
to see microbes

5. Microscopy
Why do we need
microscopes?

6. Microscopes
• Microscope uses an energy source (light, electrons,
ect.) to view objects under magnification
– Can view things that you cannon view with the naked eye
– Light Microscopes – uses light to view things in real color,
item must be thin enough to get light through
• Compound – uses 2 or more lenses to focus visible light through a
specimen, magnify 1600 times
• Confocal – focus white or laser light through a lens to the object.
– Electron Microscopes – uses electrons, MUCH higher
magnification
• Transmission – Sends beam of electrons through a sample
• Scanning – Sends beam of electrons over the surface of object

7. Dark Field
Cross PolarizedBright Field
Phase Contrast

8. Electron Microscopy
Scanning Electron Microscopy (SEM)
Advantage: shows details of cell surfaces

9. Electron Microscopy
Transmission Electron Microscopy (TEM)
Advantage: shows detail of internal cell structures

10. Cell Structures
• All cells have these structures:
– DNA
– RNA
– Ribosomes – make proteins
– Proteins
– Cytoplasm – fluid filling of the cell
– Cell Membrane – makes a boundary between
inside and outside of cell

11. Types of Cells – Prokaryotic
• Lack a true nucleus and membrane bound
organelles
• Domains Bacteria and Archaea
• Structures:
– Nucleoid – contains cells DNA, NOT bound by a
membrane
– Cell Wall – rigid, outside of cell membrane, gives
cell its shape (rod-shaped, round, spiral)
– Flagella – whip-like tail for movement

12. Types of Cells - Eukaryotic
• All other cells except for bacteria, archaea
– Plants, animals, protists, fungi
• Domain – Eukarya
• Have MEMBRANE BOUND organelles, larger
than prokaryotic
• 2 basic types of eukaryotic cells
– Animal
– Plant

15. Cell Membrane
• Function:
– Separate cell from environment
– Transport substances in and out of cell
– Receive and respond to stimuli
• Properties
– Hydrophobic and hydrophilic
– Selectively permeable
• Structure:
– Phospholipid bi-layer
– Fluid mosaic of phospholipids, sterols, proteins

16. • Transport Proteins
• Enzymes
• Recognition Proteins
• Adhesion Proteins
• Receptor Proteins
Membrane Proteins
Animal cell membrane

17. • Maintain structure
• Maintain internal pressure
Cell Wall

18. Nucleus
• Function:
– “Brain” of the cell
– Contains DNA, mRNA
• Structure
– Nucleolus – assemble ribosomes
– Nuclear envelope – separates nucleus from
cytoplasm
– Nuclear pores – holes in envelop with channels for
mRNA to leave nucleus

19. Nucleus
Nuclear envelope
Nucleolus
Nuclear pore
1) Nuclear envelope
2) Outer ring
3) Spokes
4) Plug

20. Endoplasmic Reticulum and
Ribosomes
• Rough Endoplasmic Reticulum (ER)
– Function: Help make cell membrane and secretory
proteins for various bodily functions
• In pancreas, insulin; leukocytes, antibodies
– Structure: Connected to nuclear envelop and cell
membrane with ribosomes on outside
• Smooth ER
– Function: Make and store proteins, carbohydrates, lipids
• In liver, enzymes for detox; muscle, proteins for contraction
– Structure: Same as smooth ER – ribosomes
• Ribosomes
– Function: Assemble proteins for the cell
– Structure: Large and small subunits

21. Endoplasmic Reticulum and Ribosomes

22. Golgi Apparatus
• Function:
– Process and complete protein production
– Sorts and packages proteins to send to cell
membrane and out or as membrane proteins
• Structure:
– Stack of flat membrane enclosed sacs

23. Golgi Apparatus

24. Lysosomes
• Function:
– Digestion
– Enzymes to break down and recycle food, bacteria, old
organelles
• Structure:
– Made by Golgi Apparatus
– Fuse with vesicles that have things that need to be
digested
• Number of lysosomes depends on type of cell
– White blood cells, liver cells - lots

25. Peroxisomes
• Function:
– Dispose of toxic
substances
– Protect cells from
toxic byproducts
• Structure:
– DIFFERENT from
lysosomes that
originate from ER NOT
Golgi body
Peroxisomes (green)

26. Vacuoles
• Function:
– Same as lysosomes
– Replace lysosomes in plant cells
– Growth
– Maintain pressure
– Holds pigments
– Contractile vacuole – protists (pump water, digest)
• Structure:
– Contains water solution of enzymes, sugars, salts,
weak acids

27. Vacuoles
• Various Functions http://www.youtube.com/watch?v=iG6Dd3
COug4
Contractile vacuole
Central vacuole

28. Cytoskeleton
• Function:
– Transportation within the cell
– Support
– Cell division
– Connectivity
– Movement – Cilia and flagella
• Structure:
– Network of protein tubules and tracks
• Microfilaments
• Intermediate filaments
• Microtubules – organized by centrosomes

29. The Cytoskeleton
• Microfilaments
• Functions
– Structure
– Cell motility (muscles)

30. The Cytoskeleton
• Intermediate Filaments
– Functions:
• Cell shape
• Anchor organelles
Keratin intermediate filaments (red)

31. The Cytoskeleton
• Microtubules
– Functions:
• Support
• Tracks
• Cell division

32. Cilia and Flagella
http://www.youtube.com/watch?v=QGAm6hMysTA
http://www.youtube.com/watch?v=7kM_kRPrcrk
http://www.youtube.com/watch?v=09kLIsNfaO8&NR=1
Cilia Flagella

33. Cytoplasm
• Cytoplasm - intracellular fluid that surrounds
organelles
– ~55% cell volume
– 70-90% water + ions, glucose, amino acids, fatty
acids, proteins, lipids, ATP, waste products, some
cells have large macromolecules for storage

34. Endosymbiotic Theory

35. Chloroplast
• Function:
– Site of photosynthesis
– Only 1 type of plastid – all have different pigments
• Structure
– Double membrane
– Stroma – inner fluid
– Thylakoid – stacked disks with grana
• Have photosynthetic pigments (chlorophyll)
– Have OWN DNA and ribosomes

36. Plastid

37. Mitochondria
• Function:
– Powerhouse of the cell
– Carries out cellular respiration
• Structure:
– Double membrane
– Matrix – inner “goo”
– Crtistae – folds in inner membrane w/ enzymes for
cellular respiration
– Have OWN DNA

39. Cell Junctions
Type Function Example Location
Plasmodesmata enable direct, regulated, symplastic intercellular
transport of substances between cells
plant cell walls
Tight Junctions hold cells together; help to maintain the polarity of
cells; prevent the passage of molecules and ions
through the space between plasma membranes of
adjacent cells
the kidney and liver
Anchoring
(adhering)
Junctions
serve as a bridge connecting the actin cytoskeleton
of neighboring cells through direct interaction
epithelial and
endothelial tissues
Gap Junctions connects the cytoplasm of two cells, which allows
various molecules, ions, and electrical impluses to
directly pass through a regulated gate between cells
nerves

40. Tight Junctions

41. Anchoring (Adhering) Junction

42. Gap Junctions

43. Organelles Summary
Organelle Structure Function
Plant
Cells?
Animal
Cells?
Nucleus contains DNA and RNA provides a segregated site for genetic
transcription, allowing levels of gene regulation
that are not available to prokaryotes
Yes Yes
Ribosome highly complex; made up of dozens of
distinct proteins
serves as the primary site of biological protein
synthesis (translation)
Yes Yes
Rough Endoplasmic
Reticulum
membrane studded with ribosomes manufacture of secreted proteins; manufacture
of lysosomal enzymes
Yes Yes
Smooth Endoplasmic
Reticulum
membrane (smooth) synthesizes lipids, phospholipids, and steroids Yes Yes
Golgi Apparatus large stacks of membrane-bound
structures
packages proteins inside the cell before they
are sent to their destination
Yes Yes
Lysosome spherical vesicles containing enzymes break down proteins, nucleic acids,
carbohydrates, lipids, and cellular debris
Rarely Yes
Central Vacuole enclosed compartments filled with water isolates materials that might be harmful or a
threat to the cell; contains waste products
Yes No
Peroxisome lipid bilayer membrane; crystalloid core
(not always present)
breakdown very long chain fatty acids; detoxify
various toxic substances that enter the blood
Yes Yes
Chloroplast outer and inner membrane surrounding
thylakoid system
conduct photosynthesis Yes No
Mitochondrion Membrane surrounding cristae and
matrix (containing mitochondrial DNA)
generate most of the cell's supply of ATP, used
as a source of chemical energy
Yes Yes
Cytoskeleton network of fibers composed of proteins;
dynamic
allows cells to migrate; stabilizes tissues Yes Yes
Cell Wall tough, flexible layer surrounding cells protection and filtering Yes No