UNITY OF LIFE A STUDY OF CELLS
Dec 25, 2015
Despite vast differences in appearance and ways of life, all living things have a unity of life. They are all composed of cells that are similar in structure and function. Some organisms such as Paramecuim and Euglena, are made of only one cell. In more complex, multicellular organisms, the cells may perform more specialized functions, but all have certain features in common.
Before we begin our study of cells. It is necessary to discuss the instrument that allowed people to see cells in the first place!
This discovery lead to our modern Cell Theory
MICROSCOPES
• 1590- The first microscope is built by Zacharias Janssen
• 1670’s Anton von Leeuwenhoek built a simple microscope that could magnify objects 270X.
Compound light microscope
• The compound light microscope is widely used in science. The term light refers to the method by which light transmits the image to your eye. Compound deals with the microscope having more than one lens. Microscope is the combination of two words; "micro" meaning small and "scope" meaning view.
Stereomicroscope
• Also called dissecting scope
• Has two eyepieces (binocular)
• Objects are seen in 3-D
• Does not have high power, use to observe relatively large objects such as insects or crystals
Phase-contrast microscope
• Allows observer to distinguish different structures within a cell, without staining, using light waves.
Electron microscope
• Uses a beam of electrons instead of light rays
• Can provide magnifications of 200,000X
• Tissues must be thinly sliced, dry and in a vacuum chamber, therefore electron microscopes cannot be used to view living specimens
Cell Theory
• 1665- Robert Hooke looked at cork with his compound light microscope and saw walled compartments, he called “CELLS”
1831- Robert Brown ( Scottish botanist)
• Discovers the nucleus of the cell.
• 1838- Matthias Schleiden ( German botanist) concluded “All plants are made of cells”
• 1839- Theodor Schwann (German zoologist) said “All animals are composed of cells”
• 1839- Johannes Purkinje- (Czech physiologist) discovered cytoplasm.
• 1858- Rudolph Virchow (German biologist) said “Cells arise from other cells by cell reproduction”
CELL THEORY
• 1. Cells are the basic unit of life
• ( How else could we express this idea?)
• 2. Cells come from pre-existing cells.
• (How else could this idea be expressed?)
CELLS
• There are two basic types of cells• Prokaryotic and Eukaryotic
• Prokaryotic cells- (also called prokaryotes) belong to the kingdoms Eubacteria & Archaebacteria, are very small, 1-10 micrometers, have no nucleus and few organelles. They are primitive cells. Bacteria are prokaryotic cells.
Eukaryotic cells (also called eukaryotes)
• Larger than prokaryotes, 10-100micrometers
• Have nucleus
• Have organelles
• Complex cells
• Protists, Fungi, Plants and Animals all have eukaryotic cells
Cell Organelles
• Tiny structures within a cell that perform various, specialized functions , such as transporting materials, building important biological substances, secreting products, releasing energy from food molecules, etc.
Cell Organelles
• Cell (plasma) membrane- separates the cell from its environment.
• Consists of a double layer of phospholipids with embedded proteins.
• Called fluid-mosaic model
• Selectively permeable membrane
Endoplasmic reticulum (ER)
• Network of tubes found throughout cytoplasm
• Transports materials around the cell
GOLGI COMPLEX
•Look like flattened sacs
•Function in the secretion of products produced in the cell.
•Act like the “packaging and shipping department “
MITOCHONDRIA
• Look like short rods or tiny spheres
• Site of cellular respiration, (chemical reactions that release energy from food molecules)
• “powerhouse of the cell”
Lysosomes
• Small, oval organelles
• Contain digestive enzymes
• Digest food molecules
• Destroy old cells
CENTRIOLES
• Found in the cytoplasm of animal cells
• Cylinder of tiny tubes
• Important in cell division
CILIA & FLAGELLA
• Cilia are tiny hair-like structures on outside of cell
• Flagella are long projections from cell membrane
• Aid in movement of cell and in movement of materials
CHLOROPLAST
• Found in photosynthetic organisms- plants, algae, some bacteria
• Site of photosynthesis• Contain chlorophyll
CELL WALL
• Found in plant cells, fungi and bacterial cells
• Surrounds and protects the cell
• Composed of cellulose
• Supports the cell
DIFFERENCES BETWEEN PLANT & ANIMAL CELLS
• Plant cell• Cell wall• Chloroplasts• Large vacuole
• Animal cell • Centrioles• Small vacuoles
Spontaneous Generation•The idea that organisms originate directly from nonliving matter.
•"life from nonlife"
•abiogenesis - (a-not bio-life genesis-origin)
These Scientist ran experiments to prove or disprove the theory of spontaneous generation. Review their experiments and attempt to answer the questions on the end.
Listen to this story
One of the first to disprove spontaneous generation. An Italian doctor who proved maggots came from flies. (Italian 1668)
Lazzaro Spallanzani - One of the first to disprove spontaneous generation. An Italian scientist who proved microorganisms could be killed by boiling. (Italian 1767)
Louis Pasteur - One of the first to disprove spontaneous generation. A French scientist who proved that micro organisms were carried by dust not air. (French 1864)
Fancesco Redi
Redi's ProblemWhere do maggots come from? Hypothesis: Maggots come from flies.Redi put meat into three separate jars.Jar 1 was left open Jar 2 was covered with nettingJar 3 was sealed from the outside
Redi's Experiment Step 1
Jar-1Left open Maggots developedFlies were observed laying eggs on the meat in the open jar
Redi's Experiment Step 2
Jar-2Covered with netting Maggots appeared on the nettingFlies were observed laying eggs on the netting
Redi's Experiment Step 3
Jar-3
Sealed
No maggots developed
Spallanzani's Problem
What causes microbes to form in decaying broth?
Hypothesis: Microbes come from the air. Boiling will kill microorganisms.
Spallanzani put broth into four flasks
Flask 1 was left open
Flask 2 was sealed
Flask 3 was boiled and then left open
Flask 4 was boiled and then sealed
Spallanzani's Experiment Step 1
Flask-1Left Open Turned cloudyMicrobes were found
Spallanzani's Experiment Step 2
Flask-2Sealed Turned cloudyMicrobes were found
Spallanzani's Experiment Step 3
Flask-3Boiled and left open Turned cloudyMicrobes were found
Spallanzani's Experiment Step 4
Flask-4Boiled and sealed Did not turn cloudyMicrobes not found
Pasteur's ProblemWhere do the microbes come from to cause broth to decay .
Hypothesis: Microbes come from cells of organisms on dust particles in the air; not the air itself.Pasteur put broth into several special S-shaped flasksEach flask was boiled and placed at various locations
Pasteur's Experiment Step 1
S-shaped FlaskFilled with broth The special shaped was intended to trap any dust particles coming in.
Pasteur's Experiment Step 3
Flask Left OutNotice the dust that collected in the neck of the flask
Pasteur's Experiment ResultsWhat did Pasteur's experiment show? Was his hypothesis correct or incorrect?
Questions: If you can answer the following questions you indicate a good understanding of this material.
Why did early people believe in spontaneous generation?
In Redi's experiment why did the flies lay their eggs on the netting?
What important process in canning did Spallanzani teach us?
How has the information from these scientists been used to protect our food from going bad? (application of information-technology)
What process was named after Pasteur?
Approximately how many years apart were the experiments of these three famous scientists?
What does the phrase "Life From Life" Mean?
Is the theory of spontaneous generation considered to be correct or incorrect? Why?
CELL DIVISION
• For life to continue, cells must replicate (make copies) of themselves.
• New cells must have the exact same genetic info as the parent (original) cell
• The number and types of chromosomes must be exactly the same.
Stages of the Cell Cycle
• Interphase- the cell spends most of its life in this phases
• Mitosis- The period in a cell’s life when the cell divides to form two new cells. This includes the division of genetic information.
INTERPHASE
• the period in a cell’s life when the cell performs its function and grows
• At the end of interphase , the cell replicates (makes a copy) of its chromosomes.