microscopes
TRANSCRIPT
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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 Cellular A. The Discovery of the Cell
1. Early Microscopes 2. The Cell Theory
B. Exploring the Cell C. Prokaryotes and Eukaryotes
1. Prokaryotes 2. Eukaryotes
Section 7-1
Section Outline
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Discovery of the Cell
• There are several scientists that are responsible for understanding the cell. They are: 1. Robert Hooke - Observed a piece of cork and saw thousands of
empty spaces. Coined the term “cell” because they reminded him of the small rooms in the monastery.
2. Anton van Leeuwenhoek - first person to observe living cells. 3. Matthias Schleiden - All plants are made of cells. 4. Theodor Schwann - All animals are made of cells. 5. Rudolf Virchow - New cells come only from other cells.
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The Cell Theory
1. All living things are composed of cells. 2. Cells are the basic units of structure and function in
living things. 3. New cells are produced from existing cells.
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Microscopes
• Compound light microscope - uses two lenses to focus on an image through which light passes through. • Transmission Electron Microscope - sends a beam of electrons through a microscopic slice of a specimen. • Scanning Electron Microscope - sends a beam of electrons over the surface of an object to produce a 3-D image.
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Prokaryotes
• They are cells that have genetic material that is not contained in a nucleus.
• Example - bacteria
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Eukaryotes
• Usually larger and more complicated than prokaryote cells. • Contain a nucleus in which their genetic material is separated from the rest of the cell. • Contain dozens of structures and internal membranes.
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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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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 Structure A. Comparing the Cell to a Factory B. Nucleus C. Ribosomes D. Endoplasmic Reticulum E. Golgi Apparatus F. Lysosomes G. Vacuoles H. Mitochondria and Chloroplasts
1. Mitochondria 2. Chloroplasts
3. Organelle DNA I. Cytoskeleton
Section 7-2
Section Outline
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Comparing the Cell to a Factory • The cell is made up of many tiny structures that act similar to specialized organs. • The structures are known as organelles. • Biologist split the eukaryotic cell into two parts:
– Nucleus – Cytoplasm (jelly-like
substance outside the nucleus.)
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Nucleus
• The nucleus is compared to the main office of the factory. • It is the control center. • The nucleus contains nearly all the cell’s DNA and with it the coded instructions for making proteins and other important molecules.
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Parts of the nucleus • The nucleus is surrounded by a nuclear envelope. • The envelope contains many different pores that allow materials such as proteins, RNA, and other molecules to travel to and from the rest of the cell. • Just like the memos, instructions and blueprints move in and out of the office.
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Parts of the nucleus
• The nucleus contains granular material made up of DNA bound to proteins called chromatin. • During cell division, this chromatin condenses to form thread-like structures called chromosomes. • The nucleus also contains a small, dense region called the nucleolus which is responsible for the assembly of ribosomes.
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Ribosomes
• One of the most important products of the cell is the making of proteins.
• Proteins are assembled on ribosomes.
• Ribosomes are small particles of RNA and protein found in two places throughout the cell:
1. Endoplasmic Reticulum 2. Cytoplasm
• In the factory, they are the machines that produce the product.
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Endoplasmic Reticulum
• The endoplasmic reticulum is the site where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell.
• There are two types of ER’s: 1. Rough ER 2. Smooth ER
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• Rough ER
• Rough ER is responsible for producing proteins that are exported from the cell. • It is called rough because there are ribosomes found on the surface of the ER which gives it a bumpy surface. • The proteins made by these ribosomes enter the ER where they are modified.
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Smooth ER
• Ribosomes are not found on its surface. • Contains enzymes that perform specialized tasks such as the synthesis of membrane lipids and the detoxification of drugs. • Liver cells have large amounts of smooth ER.
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Golgi Apparatus • Proteins that are made in the rough ER move into the golgi apparatus. • They are a stack of apposed membranes. • The function of the golgi apparatus is to modify, sort, and package proteins and other materials from the ER for storage in the cell or secretion outside the cell. • Golgi is the customization shop where the finishing touches are put on the product.
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Lysosomes
• They are small organelles filled with enzymes. • They have two major jobs: 1. Digest or breakdown lipids, carbohydrates, and proteins into small
molecules that can be used by the cell. 2. Ingest and destroy old and worn-out organelles.
• The lysosome can be compared to the cleanup crew of the factory.
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Vacuoles
• Vacuoles are the storage area of the cell. They store things such as water, salts,
proteins, and carbohydrates. • In plants, there is usually a large central vacuole that is filled with liquid. The pressure built up in the vacuole make it possible to support heavy structures. • In single-cell organisms, such as the paramecium, they contain a contractile vacuole that pumps out excess water to help maintain homeostasis. • Homeostasis is the maintenance of a controlled internal environment.
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Mitochondria
• Mitochondria are organelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use. • Mitochondria have two membranes - an outer membrane and an inner membrane that is folded up to create more surface area. • Mitochondria are inherited from the cytoplasm of the ovum, or egg.
• Called the “Powerhouse” of the cell.
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Chloroplasts
• Chloroplasts are organelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis. • They act as solar panels. The chemical that absorbs the sunlight is a green pigment called chlorophyll.
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Organelle DNA
• Mitochondria and Chloroplasts contain their own genetic information in the form of small DNA molecules. • They are believed to be descendants of ancient prokaryotes. • The idea suggests that the ancient prokaryotes developed a symbiotic relationship with the eukaryotes and actually took up residence within the eukaryotic cell. • This idea is called the endosymbiotic theory.
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Cytoskeleton
• The cytoskeleton is a network of protein filaments that helps the cell to maintain its shape. The cytoskeleton is also involved in movement. • The two main types of protein filaments
– Microfilaments - thread-like structures made of actin. – Microtubules - hollow structures made of tubulins.
• Play an important role in cell division. • Make up centrioles, cilia, and flagella.
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Cell membrane
Endoplasmic reticulum
Microtubule
Microfilament
Ribosomes Mitochondrion
Section 7-2
Figure 7-11 Cytoskeleton
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Prokaryotes Eukaryotes
Cell membrane Contain DNA
Nucleus Endoplasmic reticulum
Golgi apparatus Lysosomes
Vacuoles Mitochondria Cytoskeleton
Animal Cells Plant Cells
Centrioles
Cell membrane Ribosomes
Nucleus Endoplasmic reticulum
Golgi apparatus Lysosomes
Vacuoles Mitochondria Cytoskeleton
Cell Wall Chloroplasts
Section 7-2
Venn Diagrams
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Plant Cell
Nuclear envelope
Ribosome (attached)
Ribosome (free)
Smooth endoplasmic reticulum
Nucleus
Rough endoplasmic reticulum
Nucleolus
Golgi apparatus
Mitochondrion
Cell wall
Cell Membrane
Chloroplast
Vacuole
Section 7-2
Figure 7-5 Plant and Animal Cells
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Animal Cell
Centrioles
Nucleolus Nucleus
Nuclear envelope
Rough endoplasmic reticulum
Golgi apparatus
Smooth endoplasmic reticulum
Mitochondrion
Cell Membrane
Ribosome (free)
Ribosome (attached)
Section 7-2
Figure 7-5 Plant and Animal Cells
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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 Boundaries A. 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 Boundaries
• All cells are surrounded by a thin, flexible barrier known as the cell membrane. • Many other cells, especially plant cells, produce a strong supporting layer around the membrane known as the cell wall.
Chapter 7-3
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Cell Membrane
• The cell membrane regulates what enters and leaves the cell and also provides protection and support.
• The cell membrane is composed of a double-layered sheet called a lipid bilayer.
• The lipid bilayer separates the outside surroundings of the cell with the inside of the cell.
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Cell Membrane
• The lipid bilayer is made up of several substances: 1. Lipids 2. Proteins - Form channels and pumps that move
material across the membrane. 3. Carbohydrates - Act like chemical identification cards.
• Because the cell membrane is made up of all these different molecules which have the ability to move around, scientists describe the membrane as a “Fluid Mosaic Model.” • A mosaic is a piece of art that is made up of many pieces put together to make a picture.
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Outside of cell
Inside of cell (cytoplasm)
Cell membrane
Proteins
Protein channel Lipid bilayer
Carbohydrate chains
Section 7-3
Figure 7-12 The Structure of the Cell Membrane
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Cell Walls
• Cell walls are found in plants, algae, fungi, and many prokaryotes. • Most cell walls are porous enough to allow water, oxygen, carbon dioxide, and other substances to pass through easily. • The main function of the cell wall is to provide support and protection for the cell. • Cell walls are made of complex carbohydrates called cellulose.
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Diffusion Through Cell Boundaries
• One of the most important functions of the cell membrane is to regulate the movement of dissolved molecules from the liquid on one side of the membrane to the liquid on the other side.
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Measuring Concentration
• The cytoplasm in a cell is a solution of many different substances. • Remember a solution is made up of two different parts
1. Solute - substance that is dissolved 2. Solvent - substance that is doing the dissolving
• The concentration is the mass of the solute in a volume of solution. • Example
• 12 grams of salt in 3 liters of water. What is the concentration?
12 grams 3 liters = 4 g/L
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Diffusion
• Diffusion is the movement of particles from an area where they are more concentrated to an area where they are less concentrated. • If the particles are equal in both areas, they have reached their equilibrium. • Because diffusion depends upon random particle movements, substances diffuse across membranes without requiring the cell to use energy.
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Selectively Permeable Membrane
• Many substances can diffuse across the membrane, but some substances are too large or too strongly charged to cross the membrane. • For this reason, cell membranes are considered to be selectively permeable. They allow some substances to cross through them, but not others.
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Osmosis
• Osmosis is the diffusion of water through a selectively permeable membrane.
• Terms of osmosis: 1. Isotonic - same strength 2. Hypertonic - above strength 3. Hypotonic - below strength
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Hypertonic
Hypotonic
Isotonic
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Osmotic Pressure
• For organisms to survive, they must have a way to balance the intake and loss of water. • Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane. • Because cells are filled salts, sugars, proteins, and other molecules, they are always hypertonic to fresh water. • This means the cell will take in water causing it to swell. If it takes in too much water, it could burst. • In plant cells, the cell wall prevents the cells from expanding; preventing the cell from bursting.
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Facilitated Diffusion
• Sometimes particles seem to be too large to diffuse through the cell membrane, but yet still do. How? • The cell membrane has proteins embedded within the lipid bilayer. • These proteins have channels that allow larger molecules to pass through them.
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High Concentration
Low Concentration
Cell Membrane
Glucose molecules
Protein channel
Section 7-3
Facilitated Diffusion
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Active Transport
• Sometimes, the cell needs to move particle from low concentrations to high concentrations. • Diffusion will not work in this situation so the cell needs to use energy to move these particles. • This process is called active transport.
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Molecule to be carried
Molecule being carried
Energy
Section 7-3
Figure 7-19 Active Transport
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Endocytosis
• Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane.
• The pocket that results breaks loose from the outer portion of the cell membrane and forms a vacuole within the cell.
• There are two types of endocytosis 1. Phagocytosis - Extensions of the cytoplasm surround
a particle and engulf it, forming a food vacuole. 2. Pinocytosis - Pocket in the cell membrane fills with
liquid and pinches off to form vacuoles.
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Exocytosis
• Exocytosis is the release of large amounts of materials from the cell. • The membrane of the vacuole fuses with the cell membrane
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Phagocytosis
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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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7–4 The Diversity of Cellular Life A. 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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Muscle cell Smooth muscle tissue Stomach Digestive system
Section 7-4
Levels of Organization
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Videos
Click a hyperlink to choose a video. Diffusion Osmosis Passive Transport Active Transport Endocytosis and Exocytosis
Click the image to play the video segment.
Video 1
Diffusion
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Video 2
Osmosis
Click the image to play the video segment.
Video 3
Passive Transport
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Video 4
Active Transport
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Video 5
Endocytosis and Exocytosis
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The latest discoveries in cell study Cell structure activity Career links on histotechnologists Interactive test
Articles on cells
For links on cell theory, go to www.SciLinks.org and enter the Web Code as follows: cbn-3071. For links on cell membranes, go to www.SciLinks.org and enter the Web Code as follows: cbn-3073.
Go Online 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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Section 7-3
Figure 7-15 Osmosis
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