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The History of Cells & the
Cell Theory
Discovery of Cells
1665 - English Scientist, Robert Hooke, discovered cells while looking at a thin slice of cork. He described the cells as tiny boxes or a honeycomb He thought that cells only existed in plants and fungi
Anton van Leuwenhoek
1673 - Used a handmade microscope to observe pond scum & discovered single-celled organisms He called them “animalcules” He also observed blood cells from fish, birds, frogs, dogs, and humans Therefore, it was known that cells are found in animals as well as plants
150 - 200 Year Gap???
Between the Hooke/Leuwenhoek discoveries and the mid 19th^ century, very few cell theory advancements were made. This is probably due to the widely accepted, traditional belief in Spontaneous Generation. Examples:
- Mice from dirty clothes/corn husks
- Maggots from rotting meat
19 th^ Century Advancement
Much doubt existed around Spontaneous Generation Conclusively disproved by Louis Pasteur Pasteur: Ummm, I don’t think so!!!
Development of Cell Theory
1838 - English Botanist, Matthias Schleiden, concluded that all plant parts are made of cells 1839 - German physiologist, Theodor Schwann, who was a close friend of Schleiden, stated that all animal tissues are composed of cells.
Development of Cell Theory
1858 - Rudolf Virchow, Russian physician, after extensive study of cellular pathology, concluded that cells must arise from preexisting cells.
3 Basic Components of
the Cell Theory
1. All organisms are composed of one or more cells. (Schleiden & Schwann)(1838-39) 2. The cell is the basic unit of life in all living things. (Schleiden & Schwann)(1838-39) 3. All cells are produced by the division of preexisting cells. (Virchow)(1858)
Theory
A set of statements or principles
devised to explain a group of
facts or phenomena, especially
one that has been repeatedly
tested or is widely accepted and
can be used to make predictions
about natural phenomena.
Modern Cell Theory
Modern Cell Theory consists of the 3 basic components of cell theory, plus 4 additional statements: 4. The cell pass information from cell to cell during cell division using DNA. 5. All cells have basically the same chemical composition and metabolic activities. 6. All cells have basically the same chemical & physiological functions.(movement, digestion, etc) 7. Cell activity depends on the activities of structures within the cell. (organelles, nucleus, plasma membrane)
How Has The Cell Theory Been Used?
The previously discovered truths about cells listed in the Cell Theory are the basis for things such as: Disease/Health/Medical Research and Cures(AIDS, Cancer, Vaccines, Cloning, Stem Cell Research, etc.)
Characteristics of Cells
All Cells have common
structures
Cell Membrane
Ribosomes
Cytoplasm
Cells contain DNA
Found in the nucleus
Cells are independent
units of life
Eukaryotic cells
Components Cytosol Nucleus Mitochondria Chloroplast Ribosomes Rough ER Smooth ER Golgi body Vacuoles Lysosomes Cytoskeleton Centriole Cilium and Flagellum Cell membrane Cell Wall
has a nucleus
can be single or multicellular
have many organelles,
performing complex functions
specialized to perform
specific functions
larger than prokaryotic cells
Animals, plants, fungi and
protists are made of
eukaryotic cells
Characteristics of Eukaryotes
Summary of Differences
Prokaryotic Cells Eukaryotic cells small cells (< 5 mm) larger cells (> 10 mm) always unicellular often multicellular no nucleus or any membrane-bound organelles always have nucleus and other membrane-bound organelles DNA is circular, without proteins DNA is linear and associated with proteins to form chromatin ribosomes are small (70S) ribosomes are large (80S) no cytoskeleton always has a cytoskeleton cell division is by binary fission cell division is by mitosis or meiosis reproduction is always asexual reproduction is asexual or sexual
Animal and Plant Cells
Both Have:
A nucleus
Ribosomes that make protein
Rough and smooth endoplasmic
reticulum
Golgi bodies
Mitochondria
Cytoplasm
Vacuoles that store food, water
and waste products.
Animal Cells
Can not make their own food
Have many lysosomes
Are more round shaped
Have centrioles
Use mitochondria to release energy
Have many Golgi bodies
Have more extensive cytoskeleton than
plant cells
Animal cells cont.
Do not have a cell wall
Do not have a large vacuole
Do not have chloroplasts
© 2013 Pearson Education, Inc. Figure 3.2 Structure of the generalized cell. Chromatin Nucleolus Smooth endoplasmic reticulum Cytosol Mitochon drion - Lysosome Centrioles Centro some- matrix Cytoskeletal elements
- Microtubule • Intermediate filaments Nuclear envelope Nucleus Plasma membrane Rough endoplasmic reticulum Ribosomes Golgi apparatus Secretion being released from cell by exocytosis Peroxisome
Animal Cell Diversity
Section 7- 2 Figure 7-5 Plant and Animal Cells Go to Section:
Animal Cell
Nucleus Nucleolus Rough Endoplasmic Reticulum Smooth Endoplasmic Reticulum Ribosomes Golgi Bodies Cell Membrane Cytoplasm
Eukaryotic Cell Organelles and
Function
1. Nucleus
Nickname: “The Control Center” Function: holds the DNA Parts:
- Nucleolus: dark spot in the middle of the nucleus that helps make ribosomes Nucleus – largest organelle; control center of the cell; consists of:
Nuclear envelope – double membrane
structure containing pores
Nucleoli – synthesize ribosomes
Chromatin – threadlike material composed
of DNA (genes) & proteins Note: during cell division, chromatin condenses to form chromosomes Figure 3.28a
Cytoskeleton – network of rods that support the cell
Microtubules – thick rods composed of
tubulin
form cilia, flagella & centrioles
Microfilaments – thin filaments composed of
actin
involved in muscle contraction form cleavage furrow during cell division
Intermediate filaments – tough protein
fibers attached to desmosomes Centrioles – paired cylindrical bodies composed of microtubules Organize spindle apparatus (cell division)
Cellular extensions
Microvilli : fingerlike projections of the plasma membrane; increase surface area for absorption
Cilia: short hair-like
projections; propel substances over surface of cell
Flagella: long hair-like
projections; propel the cell
Endoplasmic Reticulum (ER)
Nickname: “Roads” Function: The internal delivery system of the cell
Endoplasmic Reticulum
2 Types:
- Rough ER:
- Rough appearance because it has ribosomes
- Function: helps make proteins, that’s why it has ribosomes
- Smooth ER:
- NO ribosomes
- Function: makes fats or lipids
Endoplasmic reticulum (ER) – extensive membrane system Functions
- Synthesis of proteins, carbohydrates, and lipids
- Storage of synthesized molecules and materials
- Transport of materials within the ER
- Detoxification of drugs or toxins
Rough ER – studded with ribosomes; abundant in
secretory cells
Smooth ER – free of ribosomes
Synthesizes lipids and steroids Detoxifies drugs/poisons (liver cells) Stores calcium ions (muscle cells) Figure 3. Figure 3.
Golgi Apparutus
AKA Golgi Body or Golgi complex Nickname: The shippers Function: packages, modifies, and transports materials to different location inside/outside of the cell Appearance: stack of pancakes Golgi apparatus – stack of flattened membranous sacs Packages proteins for secretion from the cell (exocytosis) Packages proteins for incorporation into plasma membrane Forms lysosomes Figure 3.
Chloroplasts
Function: traps energy from the sun to produce food for the plant cell Green in color because of chlorophyll, which is a green pigment
Chloroplasts
Cell Wall
Function: provides support and protection to the cell membrane Found outside the cell membrane in plant cells
