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Cell Structure and Function7.1 Life is CellularObjective

Explain what the cell theory is.

Robert Hooke 1665

ANTON VAN LEEUWENHOEK made his own lenses made first compound microscope drew pictures that we can still identify today.

Schleiden concluded all plants are made of cellsSchwann concluded all living things are made up of cells

Lynn Margulls Proposes the idea that certain organelles, tiny structures within some cells, were once free- living cells themselves.

CELL THEORY 1. ALL LIVING THINGS ARE COMPOSED OF CELLS2. CELLS ARE THE BASIC UNIT OF STRUCTURE AND FUNCTION IN LIVING THINGS3.ALL CELLS ARE PRODUCED FROM OTHER CELLS

Exploring the Cell How do microscopes work?

Lesson OverviewLife Is CellularExploring the Cell How do microscopes work?

Most microscopes use lenses to magnify the image of an object by focusing light or electrons.

Lesson OverviewLife Is CellularLight Microscopes and Cell Stains A typical light microscope allows light to pass through a specimen and uses two lenses to form an image. The first set of lenses, located just above the specimen, produces an enlarged image of the specimen. The second set of lenses magnifies this image still further.

Lesson OverviewLife Is CellularBecause light waves are diffracted, or scattered, as they pass through matter, light microscopes can produce clear images of objects only to a magnification of about 1000 times. Lesson OverviewLife Is CellularLight Microscopes and Cell Stains Another problem with light microscopy is that most living cells are nearly transparent, making it difficult to see the structures within them.

Lesson OverviewLife Is CellularUsing chemical stains or dyes can usually solve this problem. Some of these stains are so specific that they reveal only compounds or structures within the cell.

Lesson OverviewLife Is CellularLight Microscopes and Cell Stains Some dyes give off light of a particular color when viewed under specific wavelengths of light, a property called fluorescence.

Lesson OverviewLife Is CellularFluorescent dyes can be attached to specific molecules and can then be made visible using a special fluorescence microscope.

Fluorescence microscopy makes it possible to see and identify the locations of these molecules, and even to watch them move about in a living cell.

Lesson OverviewLife Is CellularElectron Microscopes Light microscopes can be used to see cells and cell structures as small as 1 millionth of a meter. To study something smaller than that, scientists need to use electron microscopes.

Electron microscopes use beams of electrons, not light, that are focused by magnetic fields.

Electron microscopes offer much higher resolution than light microscopes. There are two major types of electron microscopes: transmission and scanning. Lesson OverviewLife Is CellularElectron Microscopes Transmission electron microscopes make it possible to explore cell structures and large protein molecules.

Because beams of electrons can only pass through thin samples, cells and tissues must be cut first into ultra thin slices before they can be examined under a transmission electron microscope.

Transmission electron microscopes produce flat, two-dimensional images.

Lesson OverviewLife Is CellularIn scanning electron microscopes, a pencil-like beam of electrons is scanned over the surface of a specimen.

Because the image is of the surface, specimens viewed under a scanning electron microscope do not have to be cut into thin slices to be seen.

Scanning electron microscopes produce three-dimensional images of the specimens surface.

Lesson OverviewLife Is CellularElectron Microscopes Because electrons are easily scattered by molecules in the air, samples examined in both types of electron microscopes must be placed in a vacuum in order to be studied.

Researchers chemically preserve their samples first and then carefully remove all of the water before placing them in the microscope.

This means that electron microscopy can be used to examine only nonliving cells and tissues. Lesson OverviewLife Is Cellular

Lesson OverviewLife Is CellularProkaryote Cells that do not contain nuclei.Cells that have genetic material that is not contained in a nucleus.

Examples of prokaryotes

EukaryotesCells that contain nuclei.Contains a nucleus in which their genetic material is separated from the rest of the cell.

Examples of Eukaryotes

Gather your thoughtsWhat is the main difference between prokaryotic cells and eukaryotic cells?

Do bacterial cells conatin a nucleus?

What else do eukaryotic cells contain that prokaryotic cells dont?

Construct a ChartTraitProkaryotesEukaryotesNucleusOrganellesCell MembranesOrganismswww.phschool.com code: cbd-30727-2 Eukaryotic Cell Structure

Objectives:Describe the function of the cell nucleus.Describe the function of the major cell organelles.Identify the main roles of the cytoskeleton.Organelles Structures that act as specialized organs. Also called little organs.

Cytoplasm The portion of the cell outside the nucleus.

NucleusContains nearly all the cell`s DNA and with it the coded instructions for making proteins and other important molecules. NucleusNuclear Envelope It surrounds the nucleus and is composed of two membranes.

It is dotted with nuclear pores, which allows material to move into and out of the nucleus:MessagesInstructionsBlueprints moving in and out.

Gather your thoughtsWhat is the nucleulus?

Where is the DNA that a nucleus contains?

Why is DNA important?Organelles That Store, Clean Up, and SupportWhat are the functions of vacuoles, lysosomes, and the cytoskeleton?

Lesson OverviewLife Is CellularOrganelles That Store, Clean Up, and Support What are the functions of vacuoles, lysosomes, and the cytoskeleton?

Vacuoles store materials like water, salts, proteins, and carbohydrates. Lysosomes break down lipids, carbohydrates, and proteins into smallmolecules that can be used by the rest of the cell. They are also involved in breaking down organelles that have outlived their usefulness. The cytoskeleton helps the cell maintain its shape and is also involved in movement. Lesson OverviewLife Is CellularVacuoles and Vesicles Many cells contain large, saclike, membrane-enclosed structures called vacuoles that store materials such as water, salts, proteins, and carbohydrates.

Lesson OverviewLife Is CellularVacuoles and Vesicles In many plant cells, there is a single, large central vacuole filled with liquid. The pressure of the central vacuole in these cells increases their rigidity, making it possible for plants to support heavy structures such as leaves and flowers.

Lesson OverviewLife Is CellularVacuoles are also found in some unicellular organisms and in some animals.

The paramecium contains an organelle called a contractile vacuole. By contracting rhythmically, this specialized vacuole pumps excess water out of the cell.

Vacuoles and Vesicles Lesson OverviewLife Is CellularVacuoles and Vesicles Nearly all eukaryotic cells contain smaller membrane-enclosed structures called vesicles. Vesicles are used to store and move materials between cell organelles, as well as to and from the cell surface.

Lesson OverviewLife Is CellularLysosomes Lysosomes are small organelles filled with enzymes that function as the cells cleanup crew. Lysosomes perform the vital function of removing junk that might otherwise accumulate and clutter up the cell.

Lesson OverviewLife Is CellularLysosomes One function of lysosomes is the breakdown of lipids, carbohydrates, and proteins into small molecules that can be used by the rest of the cell.

Lesson OverviewLife Is CellularLysosomes Lysosomes are also involved in breaking down organelles that have outlived their usefulness.

Biologists once thought that lysosomes were only found in animal cells, but it is now clear that lysosomes are also found in a few specialized types of plant cells as well.

Lesson OverviewLife Is CellularThe Cytoskeleton Eukaryotic cells are given their shape and internal organization by a network of protein filaments known as the cytoskeleton.

Certain parts of the cytoskeleton also help to transport materials between different parts of the cell, much like conveyer belts that carry materials from one part of a factory to another.

Microfilaments and microtubules are two of the principal protein filaments that make up the cytoskeleton.

Lesson OverviewLife Is CellularMicrofilaments Microfilaments are threadlike structures made up of a protein called actin.

They form extensive networks in some cells and produce a tough, flexible framework that supports the cell.

Microfilaments also help cells move.

Microfilament assembly and disassembly is responsible for the cytoplasmic movements that allow cells, such as amoebas, to crawl along surfaces. Lesson OverviewLife Is CellularMicrotubules Microtubules are hollow structures made up of proteins known as tubulins.

They play critical roles in maintaining cell shape.

Microtubules are also important in cell division, where they form a structure known as the mitotic spindle, which helps to separate chromosomes. Lesson OverviewLife Is CellularCytoskeletonA network of protein filaments that help the cell to mantain its shape. The cytoskeleton is also involves in movement.

Microtubules In animal cells, structures known as centrioles are also formed from tubulins.

Centrioles are located near the nucleus and help to organize cell division. Centrioles are not found in plant cells.

Lesson OverviewLife Is CellularMicrotubules Microtubules help to build projections from the cell surface, which are known as cilia and flagella, that enable cells to swim rapidly through liquids.

Microtubules are arranged in a 9 + 2 pattern.

Small cross-bridges between the microtubules in these organelles use chemical energy to pull on, or slide along, the microtubules, allowing cells to produce controlled movements. Lesson OverviewLife Is CellularCentriolesImportant in cell division, which helps to separate chromosomes. They are in the nucleus and help organize cell division.They are not found in plant cells.

RibosomesAre small particles of RNA and proteins found throughout the cytoplasm.Proteins are assembled on ribosomes.They produce proteins by following coded instructions that come from the nucleus.

Endoplasmic ReticulumThs site where lipid components of the cell membrane are assembled, along with proteins and other materials that are exported from the cell.

Gather your thoughtsWhat are ribosomes composed of?What do ribosomes produce?What happens to these proteins after theyre produced by ribosomes?If this were an illustration of smooth ER, how would it be different?What is the function of smooth ER?Golgi ApparatusTo modify, sort, and package proteins and other materials from the endoplasmic reticulum for storage in the cell or secretion outside the cell.

ER- Golgi conection

Organelles That Capture and Release EnergyWhat are the functions of chloroplasts and mitochondria?

Lesson OverviewLife Is CellularOrganelles That Capture and Release EnergyWhat are the functions of chloroplasts and mitochondria?Chloroplasts capture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis.

Mitochondria convert the chemical energy stored in food into compounds that are more convenient for the cells to use.

Lesson OverviewLife Is CellularOrganelles That Capture and Release EnergyAll living things require a source of energy. Most cells are powered by food molecules that are built using energy from the sun.Chloroplasts and mitochondria are both involved in energy conversion processes within the cell.

Lesson OverviewLife Is Cellular

Chloroplasts Plants and some other organisms contain chloroplasts.

Chloroplasts are the biological equivalents of solar power plants. They capture the energy from sunlight and convert it into food that contains chemical energy in a process called photosynthesis. Lesson OverviewLife Is CellularChloroplasts Two membranes surround chloroplasts.

Inside the organelle are large stacks of other membranes, which contain the green pigment chlorophyll.

Lesson OverviewLife Is CellularMitochondria Nearly all eukaryotic cells, including plants, contain mitochondria.

Mitochondria are the power plants of the cell. They convert the chemical energy stored in food into compounds that are more convenient for the cell to use.

Lesson OverviewLife Is CellularMitochondria Two membranesan outer membrane and an inner membraneenclose mitochondria. The inner membrane is folded up inside the organelle.

Lesson OverviewLife Is CellularMitochondriaOrganelles that convert the chemical energy stored in food into compounds that are more convenient for the cell to use.

ChloroplastsOrganelles that capture the energy from sunlight and convert it into chemical energy in a process called photosynthesis.

Organelle DNAChloroplasts and mitochondria contain their own genetic information in the form of small DNA molecules.Lynn Maegulis, suggested that mitochondrias and chloroplasts are descendant of ancient prokaryotes. Cell Walls The main function of the cell wall is to provide support and protection for the cell.

Prokaryotes, plants, algae, fungi, and many prokaryotes have cell walls. Animal cells do not have cell walls.

Cell walls lie outside the cell membrane and most are porous enough to allow water, oxygen, carbon dioxide, and certain other substances to pass through easily. Lesson OverviewLife Is CellularCell Membranes All cells contain a cell membrane that regulates what enters and leaves the cell and also protects and supports the cell.

Lesson OverviewLife Is CellularCell Membranes The composition of nearly all cell membranes is a double-layered sheet called a lipid bilayer, which gives cell membranes a flexible structure and forms a strong barrier between the cell and its surroundings.

Lesson OverviewLife Is CellularThe Properties of Lipids Many lipids have oily fatty acid chains attached to chemical groups that interact strongly with water.

The fatty acid portions of such a lipid are hydrophobic, or water-hating, while the opposite end of the molecule is hydrophilic, or water-loving.

Lesson OverviewLife Is CellularThe Properties of Lipids When such lipids are mixed with water, their hydrophobic fatty acid tails cluster together while their hydrophilic heads are attracted to water. A lipid bilayer is the result.

Lesson OverviewLife Is CellularThe Properties of Lipids The head groups of lipids in a bilayer are exposed to water, while the fatty acid tails form an oily layer inside the membrane from which water is excluded.

Lesson OverviewLife Is CellularThe Fluid Mosaic Model Most cell membranes contain protein molecules that are embedded in the lipid bilayer. Carbohydrate molecules are attached to many of these proteins.

Lesson OverviewLife Is CellularThe Fluid Mosaic Model Because the proteins embedded in the lipid bilayer can move around and float among the lipids, and because so many different kinds of molecules make up the cell membrane, scientists describe the cell membrane as a fluid mosaic.

Lesson OverviewLife Is CellularThe Fluid Mosaic Model Some of the proteins form channels and pumps that help to move material across the cell membrane.

Many of the carbohydrate molecules act like chemical identification cards, allowing individual cells to identify one another.

Lesson OverviewLife Is CellularThe Fluid Mosaic Model Although many substances can cross biological membranes, some are too large or too strongly charged to cross the lipid bilayer.

If a substance is able to cross a membrane, the membrane is said to be permeable to it.

A membrane is impermeable to substances that cannot pass across it.

Most biological membranes are selectively permeable, meaning that some substances can pass across them and others cannot. Selectively permeable membranes are also called semipermeable membranes. Lesson OverviewLife Is Cellular7-3 Cell Boundaries

Cell MembraneThe cell membrane regulates what enters and leaves the cell and also provides protection and support. The composition of nearly all cell membranes is a double- layered sheet calles a lipid bilayer.

The cell membrane regulates what enters and leaves the cell and also provides protection and suport. Lipid Bilayer- A membrane with a doble- layer

Cell WallsThe main function of the cell wall is to provide support and protection of the cell.

Cytoplasm Contains a solution of many different substances in water.Solution- A mixture of two or more substances.Solute Substances dissolved in the solution.

Concentration A solution is the mass of solute in a given volume of solution.Mass/ Volume12 Grams of salt3 Lt. Water12 Grams of Salt6 Lt. of WaterWhat solution has the most concentration?ConcentrationThe first solution is twice as concentrated as the second solution.12 g./ 3 L. or 4 g/L

12 g./6L or 2g/LMore concentrationIf you dissolved 12 grams of salt in 3 liters of water, what is the concentration for salt in the solution?Suppose you added 12 more grams of salt to the solution. What would be the resulting concentration?What if you then added another 3 liters of water to that solution concentration?Which solution of the ones discussed would be called the most concentrated?DiffusionParticles move constantly. The particles tend to move from an area where they are more concentrated to an area where they are less concentrated.

Equilibrium- when the concentration of the solute is the same throughout a system.Diffusion depends upon random particle movemnts, substances diffuse across membranes without requiring the cell to use energy.OsmosisIs the diffusion of water through a selectively permeable membrane.

PermeableSome substances can pass across then and others cannot. Isotonic- The concentration of solutes is the same inside and outside. Same Strength

Hypertonic Solution has a higher solute concentration than the cell. Above Strength

Hypotonic Solution has a lower solute concentration than the cell. Below Strength

Watch this for a better explanation on hypertonic and hypotonic http://www.youtube.com/watch?v=DpVbcJY4amA

http://www.youtube.com/watch?v=1vQzqk2hzj8&feature=related

Gather your thoughtsIn the beaker on the left, which solution is hypertonic and which is hypotonic? Pg. 185

In this model, to which material is the membrane permeable, water or sugar?

Visual Activitywww.phschool.comCode: cbp-3075Osmotic pressureFor organisms to survive, they must have a way to balance the intake ans loss of water.

Cells in large organisms are not in danger of bursting.

Plant cells and bacteria are surrounded by tough cel walls. The cell walls prevent the cells from expanding even under tremendous osmotic pressure. Facilitated DiffusionCell membranes have protein channels that make it easy for certain molecules to cross the membrane.

Cell membrane protein facilitate the diffusion of glucose, or other substances across the membrane.

The net movement of molecules across a cell membrane will occur only if there is a higher concentration of the particular molecules on one side than on the other side. No energy is required.

Active TransportSometimes it must move materials in the opposite direction, against concentracion difference.

It requires energy.

It can be by transport proteins or pumps that are found in the membrane.

Larger molecules can be processes by endocytosis and exocytosis.

EndocytosisThe process of taking material into the cell by means of infolding of the cell membrane.

The poket that results breaks loose from the outer portion of the cell membrane and forms a vauole

PhagocytosisThe cell engulfs particle and package it within a food vacuole.

PinocytosisCells take up liquid form the surrounding enviroment by introducing valuoles of water.

The release of large amounts of material from the cell. The membrane of the vacuole surrounding the material fuses with the cell membrane forcing the contents out of the cell.

Quick LabHow can you model permeability in cells?

Materials: graduated cylinder, plastic sandwich bag, starch, twist tie, 500 ml beaker, iodine solution

Procedure:1- Pour about 50 ml of water into a plastic sandwich bag. Add 10 ml of starch. Secure the bag with a twist tie, and shake it gently to mix in the starch.

2- Put on your goggles, plastic gloves and apron.3- Pour 250 ml of water into a 500 mL beaker.4- Place the sandwich bag of water and starch into the beaker of water and iodine.5- After 20 minutes, look at the sandwich bag in the beaker. Observe and record any changes that occurred.

http://staff.tuhsd.k12.az.us/gfoster/standard/bcell1.htmhttp://io.uwinnipeg.ca/~simmons/cm1503/membranefunction.htm