chapter 7 cellular structure and function. cells!
TRANSCRIPT
Chapter 7
Cellular Structure and Function
CELLS!
Chapter 7.1Cell Discovery and Theory
Robert Hooke observes the structures of cork (oak bark) and calls the units cells.
History of Cell Theory
What did Anton Van Leeuwenhoek see through his microscope? He was surprised to find what looked like tiny animals.
He named these animals “animalcules”.
How do you develop a theory?
Cell Theory
1. All living organisms are composed of one or more cells.
2. Cells are the basic unit of structure and organization of all living organisms.
3. Cells arise only from previously existing cells, with cells passing copies of their genetic material on to their daughter cells.
Microscopes
Review Figure 7.1 on page 182-183,Microscopes in Focus
Why were there long periods between significant discoveries about cells?
How Big? http://www.cellsalive.com/howbig.htm
Types of Microscopes
1. Compound Light Microscopes2. Electron Microscopes
a. Transmission Electron Microscopeb. Scanning Electron Microscopec. Scanning Tunneling Electron Microscope
Based on the names of these microscopes, how do you think each type magnifies objects?
Compound Light Microscope
• Uses series of glass lenses and visible light to produce a magnified image
• Specimens must be thin• Specimens can be alive
or dead• Maximum
magnification is 1000x
Compound Light Microscope
Calculating Total Magnification
• Compound light microscopes use a series of lenses to magnify; each lens magnifies the image
• For example, if eyepiece lens magnifies at 10x and the objective lens magnifies at 10x, the total magnification is 100x (10 X 10)
What would the total magnification be if the eyepiece magnified at 10x and the objective lens magnified at 4x?
Answer = 40 x = 10 X 4
Helpful Hints:
• Diaphragm Usage• Course Adjustor v. Fine Adjustor– Location and purpose– Movement of stage
• Lowest power to highest power!– DON’T USE COURSE ADJUSTOR IN HIGH POWER!
Compound Light MicroscopeMicroscope Part Function
Ocular (eyepiece)
Nosepiece
High Power Objective Lens
Low Power Objective Lens
Stage and Stage Clips
Diaphragm
Fine Adjustment
Course Adjustment
Base/Arm
Compound Light MicroscopeMicroscope Part Function
Ocular (eyepiece) Used for viewing object; hold lens with 10x magnification
Nosepiece Holds objective lens
High Power Objective Lens Lenses with magnification of 10x, 40x, 100x, or more
Low Power Objective Lens Lens with magnification of 4x
Stage and Stage Clips Hold microscope slide in place
Diaphragm Controls the light entering the field of view
Fine Adjustment Brings object into sharp focus
Course Adjustment Brings object into focus
Base/Arm Support for the microscope
Electron Microscopes – Uses beams of electrons to magnify images
Transmission Electron Microscope (TEM)
Scanning Electron Microscope (SEM)
Scanning Tunneling Electron Microscope (STM)
• Aim a beam of electrons at a thin slice of cells• Electrons are passed through a specimen to a screen• Thick parts of the specimen absorb more electrons than thin parts forming a black-and-white shaded image of specimen• Can magnify up to 500,000x• Specimen must be dead, sliced thin, and stained
• Directs electrons over the surface of the specimen• produces a three dimensional image• Specimen must be nonliving
• Brings a charged tip of a probe extremely close to the specimen so that the electrons “tunnel” through the small gap between• Creates a three-dimensional image• Can use live specimens
Transmission Electron Microscope (TEM)
Scanning Electron Microscope (SEM)
Scanning Tunneling Electron Microscope (STM)
Transmission Electron Microscope
Bacteriophages (viruses that infect bacteria)
Scanning Electron Microscope
Human atrial (heart) muscle
Scanning Electron Microscopy
Stainless Steel Screen
Scanning Electron Miscroscopy
Table Salt
Scanning Electron Miscroscopy
Insect on the leg of a daddy long-leg spider
Scanning Electron Miscroscopy
Eye of an Ant
Scanning Electron Miscroscopy
Spider
Scanning Tunneling Microscope
STM of DNA molecule
Quiz Tomorrow
• History of Cell Theory– Hooke and Van Leeuwenhoek
• Cell Theory• Types of Microscopes– Electron Microscopes– Compound Light Microscopes
• Parts• Functions• Calculating total magnification
• (NOT Basic Cell Types)
Basic Cell Types
• What do all cells have in common?– Plasma Membrane (barrier controls what moves in and out of
cell)– Genetic material
Basic Cell TypesProkaryotic Cells Eukaryotic Cells
• Smaller • Larger
• Contain no organelles • Contain membrane-bound organelles – specialized structures that carry out specific cell functions
• No nucleus • Contain nucleus to hold genetic material
• Bacteria • Protists, Fungi, Plants, and Animals
Prokaryotic Cells
Eukaryotic Cells
• http://www.arsmachina.com/hooke.htm• http://www.nndb.com/people/356/00008709
5/• http://www.kidsbiology.com/biology_basics/c
ells_tissues_organs/cell_history_discovery4.php
• http://nzforu.com/tag/a-transmission-electron-microscope-tem/
Function of Plasma Membrane• Thin, flexible boundary between the cell and
its environment• Maintains homeostasis by controlling what
enters and exits the cell– Allows nutrients to enter– Allows waste and other products to leave
Selective Permeability• The plasma membrane allows some
substances to pass through while keeping others out
• Controls how, when, and how much of these substances enter and leave a cell
Structure of the Plasma Membrane
• Most molecules in the membrane are lipids–Phospholipids containing• Glycerol• 2 fatty acids• Phosphate group
Phospholipids
Structure of Plasma Membrane
Structure of the Membrane• “Phospholipid bilayer”– TWO layers of
phospholipids– Interior is hydrophobic
(water fearing)• Non-polar fatty acid tails
– Exterior is hydrophilic (water loving), polar• Polar phosphate groups
Phospholipids are arranged in a bilayer.hydrophilic (polar) heads are on the
outsidehydrophobic (nonpolar) tails are on the
inside
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Structure of the Plasma Membrane
Proteins are imbedded in the membrane. Transmit signals to the inside of the cell. Anchor the membrane to the internal support structure of the
cell. Transport proteins act as tunnels for substances to enter and
leave the cell.
Other Components of the Plasma Membrane
Cholesterol prevents fatty acid tails from sticking together.
Carbohydrates attach to the proteins.
Identify the cell Identify chemical signals in
the cell’s environment.
© Glencoe Biology 2007
The Fluid Mosaic Model
“Fluid Mosaic Model”• Phospholipids move sideways• Other molecules float in the
phospholipids like apples bobbing in a barrel of water
Chapter 7.3
Cell Structures and Organelles
Cell OrganellesCell Part Function
Cytoplasm Semfluid material that surrounds the organelles and provides a place for chemical reactions to take place.
Cytoskeleton A network of long, thin protein fibers that form a framework and support system for the cell; anchors all the organelles
Nucleus Control center of the cell; contains the cell’s DNA; surrounded by nuclear membrane (envelope)
Ribosomes Produces proteins
Nucleolus Produces ribosomes
Endoplasmic reticulum Folded membrane system that is the site for protein and lipid production
Smooth ER Area with no ribosomes attached; place where many carbohydrates and lipids are produced
Rough ER Ribosomes are attached and produce proteins
Cell OrganellesCell Part Function
Golgi Apparatus Flattened membranes that modified, sorts, and packages proteins
Vacuoles Temporary storage for the cell; used to store food, enzymes, and other materials needed for the cell
Lysosomes Structure containing enzymes used to digest waste
Centrioles Used in cell reproduction
Mitochondria Produce energy by breaking down sugars
Chloroplasts Capture light energy and convert it to chemical energy (food); found in plant cells
Cell wall Thick, rigid fibers that surround the plasma membrane and protects the cell
Cilia and Flagella Used for cell movement in some eukaryotic cells
Chapter 7 Test
• History of Cell Theory– Hooke– Leeuwenhoek– Cell theory
• Microscopes– Light microscopes– Electron microscopes
• Prokaryotic & eukaryotic cells• Plasma membrane
– Selective permeability– Phospholipid bilayer
• Cell Organelles Function