1. Chapter 4 Lecture Outline See PowerPoint Image Slides
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2. The Cell Theory All living things are made of cells. A cell
The basic unit of all living things.
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3. The Historical Context of the Cell Theory
Robert Hooke coined the term “cell.”
Look at cork cells under a simple microscope.
Anton van Leeuwenhoek
Made better microscopes
Used them to look at a variety of substances and identified animalcules
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4. The Historical Context of the Cell Theory
Mathias Jakob Schleiden
Concluded that all plants were made of cells
Theodor Schwann
Concluded that all animals were made of cells
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5. Initial Observations of Cells
Cell wall
Outer non-living part of plant cells
Protoplasm
Interior living portion of the cell
Nucleus
Contains the genetic information of the cell
Cytoplasm
Fluid part of the protoplasm
Organelles
“Little organs” within the protoplasm
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6. Different Kinds of Cells
Prokaryotic
Structurally simple cells
Lack a nucleus
Lack most other organelles
Bacteria
Eukaryotic cells
More complex
Have a nucleus
Have a variety of organelles
Plants, animals, fungi, protozoa and algae
Typically much larger than prokaryotic cells
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7. Major Cell Types
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8. Cell Size Prokaryotic cells Eukaryotic cells
1-2 micrometers in diameter
Eukaryotic cells
micrometers in diameter
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9. Surface Area-to-Volume Ratio
Cell size is limited.
Cells must get all of their nutrients from their environment through their cell membranes.
Volume increases more quickly than surface area.
Surface area-to-volume ratio must remain small.
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10. The Structure of Cell Membranes
Thin sheets composed of phospholipids and proteins
Fluid-mosaic model
Two layers of phospholipids
Fluid
Has an oily consistency
Things can move laterally within the bilayer.
Mosaic
Proteins embedded within the phospholipid bilayer
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11. The Phospholipid Bilayer
Phospholipid structure
Hydrophobic tails
Hydrophilic heads
Bilayer
Hydrophobic tails of each layer associate with each other.
Hydrophilic heads on the surface of the bilayer
Cholesterol
Hydrophobic
Found within the hydrophobic tails
Keeps the membrane flexible
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12. Membrane Proteins Some are on the surface Some are partially embedded.
Protrude from one side
Some are completely embedded.
Protrude from both sides
Functions
Transport molecules across the membrane
Attachment points for other cells
Identity tags for cells
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13. Organelles Composed of Membranes
Plasma membrane (cell membrane)
Different cellular membranous structures serve different functions
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Peroxisomes
Vacuoles and vesicles
Nuclear membrane
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14. The Plasma Membrane Composed of a phospholipid bilayer
Separates the contents of the cell from the external environment
Important features
Metabolic activities
Moving molecules across the membrane
Structurally different inside and outside
Identification: Self vs. nonself
Attachment sites
Signal transduction
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15. The Endoplasmic Reticulum
Consists of folded membranes and tubes throughout the cell
Provides a large surface area for important chemical reactions
Because it is folded, it fits into a small space.
Two types of ER
Rough
Has ribosomes on its surface
Sites of protein synthesis
Smooth
Lacks ribosomes
Metabolizes fats
Detoxifies damaging chemicals
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16. The Golgi Apparatus Stacks of flattened membrane sacs Functions
Modifies molecules that were made in other places
Manufactures some polysaccharides and lipids
Packages and ships molecules
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17. Traffic Through the Golgi
Vesicles bring molecules from the ER that contain proteins.
Vesicles fuse with the Golgi apparatus.
The Golgi finishes the molecules and ships them out in other vesicles.
Some are transported to other membrane structures.
Some are transported to the plasma membrane.
Some vesicles become lysosomes.
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18. Lysosomes Vesicles containing enzymes that digest macromolecules
Carbohydrates
Proteins
Lipids
Nucleic acids
Interior contains low pH
These enzymes only work at pH=5.
The cytoplasm is pH=7.
If the lysosome breaks open, these enzymes will inactivate and will not damage the cell.
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19. Functions of Lysosomes
Digestion
Of food taken into the cell
Destruction
Disease-causing organisms
Old organelles
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20. Peroxisomes Not formed from golgi membrane, but from ER membrane
Contain the enzyme catalase
Breaks down hydrogen peroxide
Breaks down long-chain fatty acids
Synthesizes cholesterol and bile salts
Synthesizes some lipids
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21. Vacuoles and Vesicles Membrane-enclosed sacs Vacuoles Vesicles
Larger sacs
Contractile vacuoles found in many protozoa
Forcefully expel excess water from the cytoplasm
Vesicles
Smaller vesicles
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22. Vacuoles and Vesicles
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23. The Nuclear Membrane
Separates the genetic material from the rest of the cell
Filled with nucleoplasm
Composed of two bilayers
Contains holes called nuclear pore complexes
Allow large molecules like RNA to pass through the membrane into the cytoplasm
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24. The Endomembrane System ̶ Interconversion of Membranes
Membranes are converted from one membranous organelle to another.
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25. Energy Converting Organelles
Mitochondrion
A small bag with a large bag stuffed inside
Larger internal bag is folded into cristae
Cristae contain proteins for cellular respiration.
Releases the energy from food
Requires oxygen
Uses the energy to make ATP
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26. Energy Converting Organelles
Chloroplasts
Sac-like organelle
Contain chlorophyll
Perform photosynthesis
Uses the energy in light to make sugar
Contain folded membranes called thylakoids
Thylakoids stacked into grana
Thylakoids contain chlorophyll and other photosynthetic proteins.
Thylakoids surrounded by stroma
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27. Nonmembranous Organelles
Ribosomes
Cytoskeleton
Centrioles
Cilia flagella
Inclusions
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28. Ribosomes Made of RNA and proteins Composed of two subunits
Large
Small
Are the sites of protein production
Found in two places
Free floating in the cytoplasm
Attached to endoplasmic reticulum
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29. Cytoskeleton Provides shape, support and movement Made up of
Microtubules
Microfilaments (actin filaments)
Intermediate filaments
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30. Centrioles
Two sets of microtubules arranged at right angles to each other
Located in a region called the centrosome
Microtubule-organizing center near nucleus
Organize microtubules into spindles used in cell division
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31. Cilia and Flagella Hair-like projections extending from the cell
Composed of microtubules covered by plasma membrane
Flagella
Long and few in number
Move with an undulating whip-like motion
Cilia
Small and numerous
Move back and forth like oars on a boat
9 + 2 arrangement of microtubules
Cell can control their activity
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32. Cilia and Flagella
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33. Inclusions Collections of miscellaneous materials
Can be called granules
Temporary sites for the storage of nutrients and waste
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34. Nuclear Components Contains chromatin
DNA + proteins
Becomes condensed during cell division into chromosomes
Surrounded by double layer of membrane
Nuclear membrane contains pores to control transport of materials in and out of nucleus
Contains one or more nucleoli
Site of ribosome synthesis
Contains nucleoplasm
Water, nucleic acids, etc.
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35. Getting Through Membranes
Diffusion
Facilitated diffusion
Osmosis
Active transport
Endocytosis
Exocytosis
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36. Diffusion Molecules are in constant, random motion.
Molecules move from where they are most concentrated to where they are less concentrated.
This is called diffusion.
Involves a concentration gradient (diffusion gradient)
No concentration gradient=dynamic equilibrium
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37. The Rate of Diffusion Depends on The size of the molecule
Smaller molecules diffuse faster.
The size of the concentration gradient
The greater the concentration difference, the faster the diffusion.
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38. Diffusion in Cells
Diffusion can only happen if there is no barrier to the movement of molecules.
Can only happen across a membrane if the membrane is permeable to the molecule
Membranes are semi-permeable; they only allow certain molecules through.
Membrane permeability depends on the molecules size, charge, and solubility.
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39. The Direction of Diffusion
Determined solely by the concentration gradient
Diffusion that does not require energy input is passive.
Example:
Oxygen diffusion
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40. Osmosis
The diffusion of water through a selectively-permeable membrane
Occurs when there is a difference in water concentration on opposite sides of the membrane.
Water will move to the side where there is less water
Or more solute
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41. Osmotic Influences on Cells
If a cell has less water (more solute) than its environment
It is hypertonic to its surroundings.
If a cell has more water (less solute) than its environment
It is hypotonic to its surroundings.
If a cell has equal amounts of water (and solute) as its environment
It is isotonic to its surroundings.
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42. Osmotic Influences on Cells
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43. Osmosis in Animal and Plant Cells
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44. Facilitated Diffusion
Some molecules have to be carried across the membrane.
Accomplished by carrier proteins
Still involves diffusion
Follows a concentration gradient
Is passive transport
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45. Active Transport Opposite of diffusion
Moves molecules across a membrane UP their concentration gradient
Uses transport proteins in the membrane
Specific proteins pump specific molecules
Requires the input of energy
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46. Endocytosis Moves large molecules or sets of molecules into the cell
Phagocytosis
Cell eating
Food engulfed by the membrane
Material enters the cell in a vacuole.
Pinocytosis
Cell drinking
Just brings fluid into the cell
Receptor-mediated endocytosis
Molecules entering the cell bind to receptor proteins first.
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47. Exocytosis Moves large molecules or sets of molecules out of the cell
Vesicles containing the molecules to be secreted fuse with the plasma membrane.
Contents are dumped outside the cell.
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48. Endocytosis and Exocytosis
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49. Prokaryotic Cells Two different types of prokaryotes Domain eubacteria
Contains bacteria
Domain archaea
Contains prokaryotes that live in extreme environments
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50. Prokaryotic Cell Structure
Contain DNA and enzymes
Able to reproduce
Engage in metabolism
Surrounded by a plasma membrane
Plasma membrane surrounded by a cell wall
Maintains the shape of the cell
Cell wall surrounded by a capsule
Helps them adhere to hosts
Protects them from destruction
Contain ribosomes
May contain flagella
Facilitates movement
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51. Different Types of Eukaryotic Cells
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52. Summary of Cell Organelles and Their Functions
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