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Are All Cells Alike?All living things are made up of cells. Some organisms are composed of only one cell. Other organisms are made up of many cells.
1. What are the advantages of a one-celled organism?
2. What are the advantages of an organism that is made up of many cells?
Section 7-1
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7–1 Life Is CellularA. The Discovery of the Cell
1. Microscopes2. The Cell Theory
B. Exploring the CellC. Prokaryotes and Eukaryotes
1. Prokaryotes2. Eukaryotes
Section 7-1
Section Outline
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Discovery of the Cell
1. Robert Hooke – 1665 – named cell
2. Leeuwenhoek – 1674 – observed living microorganisms
3. Schleiden – 1838 – all plants made of cells
4. Schwann – 1839 – all animals made of cells
5. Virchow – 1855 - all cells come from cells
Section 7-1
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Exploring the Cell
Microscopy
- the history of cytology is tied to the development of the microscope.
1. Light microscopes - pass light through the specimen
- can magnify up to about 1200x
- easy to prepare specimens and can look at living specimens.
Section 7-1
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2. Transmission Electron Microscope
- send a beam of electrons through the specimen
- focused with magnets
- resolving power up to 100,000(+)x
- specimens have to be prepared and can’t be alive
Section 7-1
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3. Scanning Electron Microscope
- bounce electrons off the surface of the specimen
- gives detailed three-dimensional images of the surface of the specimen
Section 7-1
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Cell TheoryCells are the basic structural and functional units of life
Under the conditions present on Earth today all cells come from other cells.
All living things are composed of cells
Section 7-1
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Prokaryotes-cells that have genetic material that is not contained in the nucleus. Generally smaller and more simple than eukaryotes.
Bacteria are prokaryotes.
Eukaryotes-contains a nucleus in which their genetic material is separated from the rest of the cell. Plants, animals, fungi, and protists are Eukaryotes.
Section 7-1
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Prokaryotic Cell
Cell membrane
Cell membrane
Cytoplasm
Cytoplasm
Nucleus
Organelles
Eukaryotic Cell
Section 7-1
Prokaryotic and Eukaryotic Cells
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Section 7-1
Prokaryotes Eukaryotes
Cell membraneContain DNA
NucleusEndoplasmic reticulum
Golgi apparatusLysosomesVacuoles
MitochondriaCytoskeleton
Venn Diagram
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Division of Labor
A cell is made up of many parts with different functions that work together. Similarly, the parts of a computer work together to carry out different functions.
Working with a partner, answer the following questions.
1. What are some of the different parts of a computer? What are the functions of these computer parts?
2. How do the functions of these computer parts correspond to the functions of certain cell parts?
Section 7-2
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7–2 Eukaryotic Cell StructureA. Comparing the Cell to a FactoryB. NucleusC. RibosomesD. Endoplasmic ReticulumE. Golgi ApparatusF. LysosomesG. VacuolesH. Mitochondria and Chloroplasts
1. Mitochondria2. Chloroplasts
3. Organelle DNAI. Cytoskeleton
Section 7-2
Section Outline
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Section 7-2
Nucleus“control center” of the cellContains the chromosomes on which the genes are located
Fine threads called chromatin in nondividing cellsCondense into visible chromosomes during cell division
Nuclear membrane has two parallel membranes with nuclear pores penetrating themNuclear pores allow mRNA to leave the nucleus to go to the cytoplasmAlso contains the nucleolus where ribosomal subunits are produced
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Section 7-2
Ribosomes
- sites of protein synthesis – where amino acids are joined
- many are attached to Rough ER; others are free in the cytoplasm
- composed of RNA and protein
- attached ribosomes make proteins for export
- free ribosomes make proteins for intracellular use
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Section 7-2
Endoplasmic Reticulum
- membranous-walled canals and flat sacs that extend from the plasma membrane to the nucleus
- important in the synthesis, modification, and movement of materials within the cell
A. Rough Endoplasmic Reticulum
- has ribosomes attached to its’ surface
- ribosomes make proteins which move into the cisternae of the ER and are transported toward the Golgi apparatus
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Section 7-2
B. Smooth Endoplasmic Reticulum
- lacks ribosomes
- transports, synthesizes, and chemically modifies small molecules
- synthesizes certain lipids and carbohydrates and creates membranes for use throughout the cell
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Section 7-2
Golgi Apparatus- series of flattened membranous sacs that modify protein products of the rough endoplasmic reticulum- final products are packaged in vesicles which can then be moved to the cell membrane for export- some of these vesicles remain in the cell as lysosomes - can also give rise to new membrane structures for the cell
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Section 7-2
Lysosomes- digestive system of the cell- membranous sacs which pinch off the Golgi apparatus- contain hydrolytic enzymes which digest particles or large molecules that enter them- also responsible for digesting unneeded or unhealthy cells and cell parts
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Section 7-2
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Section 7-2
Vacuoles- saclike structures used for storage within the cell- stores water, salts, proteins, and carbohydrates- discerning feature in many plant cells that is large and liquid filled
makes possible for plants to support heavystructures such as leaves and flowers
- in many cases the vacuole is controls the water content of the cell which maintains homeostasis
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Section 7-2
Mitochondria- “power plants” of cells- double membraned organelle with fluid between the membranes- lots of enzymes attached to both membranes- enzymes catalyze oxidation reactions of cellular respiration and capture the energy of sugars in the bonds of ATP- provide 95% of the cell’s energy- contain their own ribosomes and DNA and can replicate themselves
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Section 7-2
Chloroplasts- capture the energy of the sunlight and convert it into the chemical energy of sugar in a process called photosynthesis- double membraned organelle like mitochondria- also contain their own DNA- contain large stacks of membranes containing chlorophyll
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Section 7-2
CytoskeletonInternal support framework made up of rigid,
rodlike proteins that support the cell and allow movement and mechanisms that can move the cell or its partsActs as both muscle and skeleton for cell
Cell Fibers- form a three-dimensional support framework- support endoplasmic reticulum, mitochondria,
and free ribosomes
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Section 7-2
1. Microfilaments – smallest fibers- cellular muscles that provide for movement
2. Intermediate filaments – form much of the support network of the cell3. Microtubules – maintain cell shape and move things within the cell made up of proteins known as tublin
4. Tubulin is also used to make structures in animal cells known as the centrioles. These aid
in organization during cell division
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Cell membrane
Endoplasmicreticulum
Microtubule
Microfilament
Ribosomes Mitochondrion
Section 7-2
Figure 7-11 Cytoskeleton
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Plant Cell
Nuclearenvelope
Ribosome(attached)
Ribosome(free)
Smooth endoplasmicreticulum
Nucleus
Rough endoplasmic reticulum
Nucleolus
Golgi apparatus
Mitochondrion
Cell wall
CellMembrane
Chloroplast
Vacuole
Section 7-2
Figure 7-5 Plant and Animal Cells
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Animal Cell
Centrioles
NucleolusNucleus
Nuclearenvelope
Rough endoplasmic reticulum
Golgi apparatus
Smooth endoplasmicreticulum
Mitochondrion
CellMembrane
Ribosome(free)
Ribosome(attached)
Section 7-2
Figure 7-5 Plant and Animal Cells
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Animal Cells Plant Cells
Centrioles
Cell membraneRibosomes
NucleusEndoplasmic reticulum
Golgi apparatusLysosomesVacuoles
MitochondriaCytoskeleton
Cell WallChloroplasts
Section 7-2
Venn Diagram
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In or Out?How is a window screen similar to a cell membrane? Read on to find out.
1. What are some things that can pass through a window screen?
2. What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen?
3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?
Section 7-3
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7–3 Cell BoundariesA. Cell Membrane
B. Cell Walls
C.Diffusion Through Cell Boundaries
1. Measuring Concentration
2. Diffusion
D.Osmosis
1. How Osmosis Works
2. Osmotic Pressure
E. Facilitated Diffusion
F. Active Transport
1. Molecular Transport
2. Endocytosis and Exocytosis
Section 7-3
Section Outline
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Cell MembraneAll of the membranes of the cell have similar structure.
Plasma Membrane
-Fluid Mosaic Model – developed by Singer and Nicolson
-Molecules are arranged in a sheet
-Molecules are held together by chemical attractions between them and their interactions with water.
-Primary structure is a double layer of phospholipid molecules
Phosphate heads are hydrophilic; tails are hydrophobic
Section 7-3
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Cell Membrane-cont.
Section 7-3
-Cholesterol molecules within the membrane help it function at body temperatures.-Because the hydrophobic tails make-up most of the membrane,
water soluble materials can’t pass through the membrane.-Channel proteins which are embedded in the membrane help control movement of materials into and out of the cell-Glycoproteins have carbohydrates attached and serve as cell surface identifiers-Receptor proteins react to specific chemicals and cause changes
within the cell.-Overall, the plasma membrane is selectively permeable.
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Outsideof cell
Insideof cell(cytoplasm)
Cellmembrane
Proteins
Proteinchannel Lipid bilayer
Carbohydratechains
Section 7-3
Figure 7-12 The Structure of the Cell Membrane
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Cell Walls
Section 7-3
-Provide support and protection for the cell.-Most are composed of fibers of carbohydrate and protein-Plant cell walls are mostly cellulose
Passive and Active Transport
Section 7-3
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Movement Through the Cell Boundaries
Section 7-3
Passive Transport Processes-Do not require energy expenditure by the cell-Second Law of ThermodynamicsDiffusion
- movement of particles from an area of high concentration to an area of low concentration down a concentration gradient.
- continues until equilibrium is reached- membrane channels are pores through which
specific ions or small water-soluble molecules can pass- gases also move by diffusion
Diffusion and Osmosis Video
Section 7-3
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Section 7-3
Passive Transport Processes cont.Osmosis
- diffusion of water through a selectively permeable membrane
- water moves down it’s concentration gradient – this often means it is moving toward higher salt concentrations
- Osmotic Pressure – water pressure that develops as a result of osmosis
- healthy cells are normally in an environment where the net movement of water is 0.
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Section 7-3
Passive Transport Processes cont.Osmosis cont.
- Tonicity – ability of a solution to move water in/out of a cell and change its shape
a. Isotonic – osmotic pressure is = inside and outside
b. Hypertonic – osmotic pressure is greater than within the cell – water moves out of cell causing crenation
c. Hypotonic – osmotic pressure is less than within the cell – water moves into the cell causing lysis.
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Section 7-3
Figure 7-15 Osmosis
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Section 7-3
Figure Osmosis
Osmosis Video
Section 7-3
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HighConcentration
LowConcentration
CellMembrane
Glucosemolecules
Proteinchannel
Section 7-3
Facilitated Diffusion
Facilitated Diffusion- movement through carrier proteins along the concentration gradient
- rate is dependent on concentration gradient and availability of carrier molecules
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Molecule tobe carried
Moleculebeing carried
Energy
Active TransportSection 7-3
-cell uses metabolic energy to move materials 1. Molecular Transport
- carrier-mediated process that moves substances against their concentration gradients
- opposite of diffusion- substances are moved by
pumps which use ATP to change shape and move their cargos
- carrier proteins bind to cargo, change shape, and release the cargo
Active Transport
Section 7-3
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Active Transport (cont.)
Section 7-3
2. Endocytosis and Exocytosis- allow things to enter and leave a cell without
actually passing through the plasma membrane.A. Endocytosis – plasma membrane traps some
extracellular material and moves it to the interior in a vesicle.
- Phagocytosis – large particles are engulfed within a vesicle that then fuses with lysosomes to digest particles
- Pinocytosis – fluid and the substances dissolved in it enter the cell
Endocytosis and Exocytosis
Section 7-3
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From Simple to More Complex
Many multicellular organisms have structures called organs that have a specific function and work with other organs. Working together, these organs carry out the life processes of the entire organism.
Section 7-4
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1. Some activities cannot be performed by only one person, but need a team of people. What type of activity requires a team of people to work together in order to complete a task?
2. What do you think are some characteristics of a successful team?
3. How is a multicellular organism similar to a successful team?
Section 7-4
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7–4The Diversity of Cellular LifeA.Unicellular Organisms
B.Multicellular Organisms
1. Specialized Animal Cells
2. Specialized Plant Cells
C. Levels of Organization
1. Tissues
2. Organs
3. Organ Systems
Section 7-4
Section Outline
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Unicellular Organisms
Single-celled organisms that grow, respond to the environment, transform energy, and reproduce
Multicellular Organisms
Organisms that are made up of many cells that are developed for different tasks through a process called cell specialization
Section 7-4
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Muscle cell Smooth muscle tissue Stomach Digestive system
Section 7-4
Levels of Organization
Levels of Organization
1. Cells
2. Tissues
3. Organs
4. Organ Systems
Interest Grabber Answers
1. What are the advantages of a one-celled organism?
A one-celled organism has simpler needs and can respond immediately to its environment because its entire cell is immersed in its environment.
2. What are the advantages of an organism that is made up of many cells?
In a multicellular organism, different jobs are divided among different groups of cells that work together. Also, a multicellular organism can continue to survive even if it loses some of its cells.
Interest Grabber Answers
Working with a partner, answer the following questions.
1. What are some of the different parts of a computer? What are the functions of these computer parts?
Answers may include: monitor (interfaces with the computer’s environment), software (instructions for how to carry out different jobs), CPU (directs the computer's activities), recycle bin or trash can (storage area for wastes), and so on.
2. How do the functions of these computer parts correspond to the functions of certain cell parts?
Students should try to link the functions they described in question 1 to the functions of the different cell structures. The cell needs a way to interface with its environment (cell membrane), instructions for carrying out different jobs (DNA), and a CPU to direct the cell’s activities (nucleus).
Interest Grabber Answers
1. What are some things that can pass through a window screen?
Answers may include air, fine dust, and rainwater.
2. What are some things that cannot pass through a window screen? Why is it important to keep these things from moving through the screen?
Insects, leaves, and other matter that may fall from trees. The screen keeps out annoying insects and objects that may bring dirt into the home.
3. The cell is surrounded by a cell membrane, which regulates what enters and leaves the cell. Why is it important to regulate what moves into and out of a cell?
Materials such as oxygen and food that are needed by the cell have to be able to get inside the cell. At the same time, excess materials have to leave the cell.
Interest Grabber Answers
1. Some activities cannot be performed by only one person, but need a team of people. What type of activity requires a team of people to work together in order to complete a task?
Answers might include building a human pyramid or constructing an arch out of blocks.
2. What do you think are some characteristics of a successful team?
Divide up jobs and cooperate well with one another.
3. How is a multicellular organism similar to a successful team?
The functions of the organism are divided up among its parts (organs and organ systems). All the parts cooperate to carry out all the functions of the whole organism.
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