chapter seven- the cell
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Chapter seven lecture for Lab Biology on the cell.TRANSCRIPT
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7-1 Life Is Cellular
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The Discovery of the Cell
Cells are the basic units of life.
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The Discovery of the Cell
The cell theory states:•All living things are composed of cells.
•Cells are the basic units of structure and function in living things.
•New cells are produced from existing cells.
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Exploring the Cell
Electron Microscopes•1000 times more powerful than light microscopes.•used to visualize nonliving, preserved cells and tissues.
Scanning electron microscopes (SEMs)
Produce three-dimensional images of cellsSpecimens do not have to be cut into thin slices
Transmission electron microscopes (TEMs)
Used to study cell structures and large protein moleculesSpecimens must be cut into ultra-thin slices
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Exploring the Cell
Scanning Electron Micrograph of Neurons
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Exploring the Cell
Confocal Light MicroscopesConfocal light microscopes scan cells with a laser beam.
This makes it possible to build three-dimensional images of cells and their parts.
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Exploring the Cell
Scanning Probe MicroscopesScanning probe microscopes allow us to observe single atoms.Images are produced by tracing surfaces of samples with a fine probe.
DNA
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Prokaryotes and EukaryotesCells come in a variety of shapes and sizes.All cells:
• are surrounded by a barrier called a cell membrane.
• at some point contain DNA.
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Cells are classified into two categories, depending on whether they contain a nucleus.
The nucleus is a membrane-enclosed structure that contains the cell's genetic material in the form of DNA. The nucleus controls many of the cell's activities.
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Eukaryotes- cells contain nuclei.
Prokaryotes- cells do not contain nuclei.
~ ~nucleus ~ ~
DNA just floats around ~~
~ ~
~
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Prokaryotic cells are simpler than eukaryotic cells.
Bacteria are prokaryotes.
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Eukaryotic cells are generally larger and more complex than prokaryotic cells. Eukaryotic cells generally contain dozens of structures and internal membranes.Many eukaryotic cells are highly specialized.
Plants, animals, fungi, and protists are eukaryotes.
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7-2 Eukaryotic Cell Structure
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The parts that make up a eukaryotic cell are known as organelles.Cell biologists divide the eukaryotic cell into two major sections: the nucleus and the cytoplasm.
The Cytoplasm is the fluid outside the nucleus.
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Plant Cell
Nuclear envelopeRibosome (free)
Ribosome (attached)
Mitochondrion
Golgi apparatus
Vacuole
NucleolusNucleus
Smooth endoplasmic reticulum
Rough endoplasmic reticulum
Cell wallCell membrane
Chloroplast
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Eukaryotic Cell Structures
Smooth endoplasmic reticulum
Ribosome (free)
Ribosome (attached)
Golgi apparatus
Mitochondrion
Rough endoplasmic reticulum
Cell membrane
Nucleus
Nuclear envelope
Nucleolus
Centrioles
Animal Cell
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Nucleus
Cell membrane
Cytoplasm
Draw and label- cell membrane, nucleus, cytoplasm.
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Nucleus
NucleusThe nucleus is the control center of the cell.
The nucleus contains nearly all the cell's DNA. DNA contains coded instructions for making proteins and other molecules.
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Nucleus
The Nucleus
Nucleolus Nuclear envelope
Nuclear pores
Chromatin
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Nucleus
The nucleus is surrounded by a nuclear envelope composed of two membranes.
The envelope is dotted with nuclear pores, which allow material to move in and out of the nucleus.
Nuclear envelope
Nuclear pores
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Nucleus
The granular material in the nucleus is called chromatin (contains DNA and proteins).
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Nucleus
When a cell divides, chromatin condenses to form chromosomes.
Chromosomes contain the genetic information that is passed from one generation of cells to the next.
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Nucleus
Most nuclei also contain a nucleolus.
The nucleolus is where the assembly of ribosomes begins.
Nucleolus
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Draw and label- chromatin(DNA)
Chromatin (DNA)
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Ribosomes
RibosomesOne of the most important jobs carried out in the cell is making proteins.
Proteins are assembled on ribosomes found throughout the cytoplasm.
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Ribosomes
Ribosomes produce proteins by following coded instructions that come from the nucleus.
Cells that are active in protein synthesis are often packed with ribosomes.
Ribosome (attached)
Ribosome (free)
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Endoplasmic Reticulum
Eukaryotic cells contain an internal membrane system called the endoplasmic reticulum, or ER.
The endoplasmic reticulum is where lipids that make the cell membrane are assembled, along with proteins and other materials that are exported from the cell.
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Endoplasmic Reticulum
Ribosomes
Endoplasmic Reticulum
Ribosomes are found on the surface of rough ER.
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Endoplasmic Reticulum
There are two types of ER—rough and smooth.
The portion of the ER involved in protein synthesis is called rough endoplasmic reticulum, or rough ER.
Rough ER is abundant in cells that produce large amounts of protein for export.
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Endoplasmic Reticulum
Smooth ER does not have ribosomes on its surface.
Smooth ER contains collections of enzymes that perform specialized tasks, such as synthesis of membrane lipids and detoxification of drugs.
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Draw and label- ribosomes, endoplasmic reticulum
ribosomes
Endoplasmic reticulum
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Golgi Apparatus
The Golgi apparatus appears as a stack of membranes.
Proteins produced in the rough ER move into the Golgi apparatus.
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Golgi Apparatus
The Golgi apparatus modifies, sorts, and packages proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside the cell. From the Golgi apparatus, proteins are then “shipped” to their final destinations throughout the cell or outside of the cell.
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Draw and label- golgi apparatus
Golgi apparatus
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Lysosomes
Lysosomes are filled with enzymes that can break down large molecules and old organelles.Lysosomes are like recycling centers!
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Vacuoles
Vacuoles
Some cells contain saclike structures called vacuoles that store materials such as water, salts, proteins, and carbohydrates.
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Vacuoles
In many plant cells there is a single, large central vacuole filled with liquid.
The pressure of the central vacuole allows plants to support heavy structures such as leaves and flowers. Vacuole
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Vacuoles
Vacuoles are also found in some unicellular organisms and in some animals.
The paramecium contains a contractile vacuole that pumps excess water out of the cell.
Contractile vacuole
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Draw and label- vacuole
Vacuole
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Mitochondria and Chloroplasts
Mitochondrion = power
Nearly all eukaryotic cells contain mitochondria.
Mitochondria convert food molecules into a more usable energy source.
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Mitochondria and Chloroplasts
Mitochondria are enclosed by two membranes—an outer membrane and an inner membrane.
The inner membrane is folded up inside the organelle.
Mitochondria and Chloroplasts
Chloroplast
Chloroplasts Plants and some other organisms contain GREEN chloroplasts.
Chloroplasts capture energy from sunlight and convert it into chemical energy during photosynthesis.
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Mitochondria and Chloroplasts
Chloroplasts are surrounded by two membranes.
Chloroplasts contain the green pigment chlorophyll.
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Draw and label- mitochondria, chloroplasts
MitochondriaChloroplasts
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Cytoskeleton
CytoskeletonEukaryotic cells are given their shape and internal organization by the cytoskeleton.
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Cytoskeleton
The cytoskeleton helps the cell maintain its shape and can be involved in movement. Eukaryotic cells are given their shape and internal organization by the cytoskeleton.
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7-3 Cell Boundaries
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7-3 Cell Boundaries
All cells are surrounded by a thin, flexible barrier known as the cell membrane.
Many cells also produce a strong supporting layer around the membrane known as a cell wall.
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Cell Membrane
Cell Membrane
The cell membrane regulates what enters and leaves the cell and also provides protection and support.
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Cell Membrane
Cell Membrane
Outside of cell
Cell membrane
Inside of cell (cytoplasm)
Protein channel
Proteins
Lipid bilayer
Carbohydrate chains
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Cell Membrane
The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer.
Lipid bilayer
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Cell Membrane
The lipid bilayer gives cell membranes a flexible structure that forms a barrier between the cell and its surroundings.
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Cell Membrane
Most cell membranes contain protein molecules embedded in the lipid bilayer, some of which have carbohydrate molecules attached to them.
Protein channel
Proteins
Carbohydrate chains
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Cell Walls
Cell walls are found in plants, algae, fungi, and many prokaryotes.
The cell wall provides support and protection for the cell.
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Cell Walls
Cell WallThe cell wall lies outside the cell membrane. Most cell walls are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily.
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PLANT CELL ANIMAL CELL
Draw two eukaryotic cells
Draw and label- cell wall
Cell wall
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Diffusion Through Cell Boundaries
Diffusion Through Cell BoundariesEvery living cell exists in a liquid environment.
The cell membrane regulates movement of dissolved molecules from the liquid on one side of the membrane to the liquid on the other side.
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Diffusion Through Cell Boundaries
Measuring Concentration A solution is a mixture of two or more substances.The substances dissolved in the solution are called solutes.
The concentration of a solution is the mass of solute in a given volume of solution, or mass/volume.
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Diffusion Through Cell Boundaries
Diffusion– Solutes tend to move from areas of high concentration towards areas of low concentration.
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When the solute is evenly spread through the solution, the system has reached equilibrium.
It will never become concentrated in one area like it was before!
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Diffusion Through Cell Boundaries
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Diffusion Through Cell Boundaries
There is a higher concentration of solute on one side of the membrane as compared to the other side of the membrane.
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Diffusion Through Cell Boundaries
Solute particles move from the side of the membrane with a higher concentration of solute to the side of the membrane with a lower concentration of solute. The solute particles will continue to diffuse across the membrane until equilibrium is reached.
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Diffusion Through Cell Boundaries
When equilibrium is reached, solute particles continue to diffuse across the membrane in both directions, but the concentrations do not change.
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Diffusion Through Cell Boundaries
Diffusion depends upon random particle movements. Therefore, substances diffuse across membranes without requiring the cell to use energy.
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Osmosis
Osmosis is the diffusion of water through a selectively permeable membrane.Osmosis is diffusion so it requires no energy!
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Osmosis
How Osmosis Works
Movement of water
Dilute sugar solution (Water more concentrated)
Concentrated sugar solution (Water less concentrated)
Sugar molecules
Selectively permeable membrane- only lets
water through
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Osmosis
Water tends to diffuse from a highly concentrated region to a less concentrated region.
If you compare two solutions, the more concentrated solution is hypertonic (“above strength”).The more dilute solution is hypotonic (“below strength”).
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Osmosis
When concentrations of solutions are the same on both sides of a membrane, the solutions are isotonic (”same strength”).
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Osmosis
Osmotic Pressure Osmosis exerts a pressure known as osmotic pressure on the hypertonic side of a selectively permeable membrane.
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Osmosis
The cell is filled with salts, sugars, proteins, and other molecules so it is hypertonic(lots of solutes) compared to fresh water.This causes water to move into the cell. The cell becomes swollen or bursts.
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Osmosis
Cells in large organisms are not in danger of bursting because they are bathed in fluids, such as blood, that are isotonic.
Other cells are surrounded by tough cell walls that prevent the cells from expanding even under tremendous osmotic pressure.
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Facilitated Diffusion
Facilitated DiffusionCell membranes have protein channels that act as carriers, making it easy for certain molecules to cross.
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Facilitated Diffusion
The movement of specific molecules across cell membranes through protein channels is known as facilitated diffusion. Hundreds of different protein channels have been found that allow particular substances to cross different membranes.
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Facilitated Diffusion
Facilitated Diffusion
Protein channel
Glucose molecules
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Facilitated Diffusion
Although facilitated diffusion is fast and specific, it is still diffusion.
Therefore, facilitated diffusion will only occur if there is a higher concentration of the particular molecules on one side of a cell membrane as compared to the other side.
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Active Transport
Active TransportSometimes cells move materials in the opposite direction from which the materials would normally move—that is against a concentration difference. Active transport is the moving of substances against diffusion, so it requires energy.
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Active Transport
Molecular TransportIn active transport, small molecules and ions are carried across membranes by proteins in the membrane.Energy use in these systems enables cells to concentrate substances in a particular location, even when diffusion might move them in the opposite direction.
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Molecule to be carriedActive Transport
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Active Transport
Endocytosis and Exocytosis Large molecules and even solid clumps of material may undergo active transport by means of the cell membrane.Endocytosis is the process of taking material into the cell by means of infoldings, or pockets, of the cell membrane. The pocket breaks loose from the outer portion of the cell membrane and forms a vacuole within the cytoplasm.
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Active Transport
Two examples of endocytosis are:• phagocytosis• pinocytosis
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Active Transport
In phagocytosis, extensions of cytoplasm surround a particle and package it within a food vacuole. The cell then engulfs it.
Phagocytosis requires a considerable amount of energy.
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Active Transport
In pinocytosis, tiny pockets form along the cell membrane, fill with liquid, and pinch off to form vacuoles within the cell.
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Active Transport
ExocytosisMany cells also release large amounts of material from the cell, in a process called exocytosis.During exocytosis, the membrane of the vacuole surrounding the material fuses with the cell membrane, forcing the contents out of the cell.
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7-4 The Diversity of Cellular Life
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Unicellular Organisms
Unicellular Organisms
Unicellular organisms are made up of only one cell.Unicellular organisms dominate life on Earth.
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Multicellular Organisms
Multicellular Organisms
Organisms that are made up of many cells are called multicellular.There is a great variety among multicellular organisms.
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Multicellular Organisms
cell specialization- cells develop differently to perform different tasks.
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Multicellular Organisms
Specialized Animal CellsAnimal cells are specialized in many ways.
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Multicellular Organisms
Red blood cells transport oxygen.
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Multicellular Organisms
Cells in the pancreas produce proteins.
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Multicellular Organisms
Muscle cells allow movement.
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Multicellular Organisms
Specialized Plant CellsPlants exchange carbon dioxide, oxygen, water vapor, and other gases through tiny openings called stomata on the undersides of leaves. Highly specialized cells, known as guard cells, regulate this exchange.
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Multicellular Organisms
Stomata enclosed by guard cells.
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Levels of Organization
Levels of Organization
The levels of organization in a multicellular organism are:individual cellstissuesorgansorgan systems
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Levels of Organization
Levels of Organization
Smooth muscle tissueMuscle cell Stomach Digestive system
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Levels of Organization
In multicellular organisms, cells are the first level of organization.
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Levels of Organization
TissuesSimilar cells are grouped into units called tissues.
A tissue is a group of similar cells that perform a particular function.
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Levels of Organization
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Levels of Organization
Most animals have four main types of tissue:
muscleepithelialnervousconnective
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Levels of Organization
Organs
Organs are groups of tissues that work together to perform a specific function.
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Levels of Organization
Organ Systems
A group of organs that work together to perform a specific function is called an organ system.