Chapter 8

Chapter 7Cell Structure & Function, Part I

1CellsAre so small that 50,000 can fit in this letter OBuild and break down macromoleculesRelease energy from foodsUse energy to make cell parts

27-1 Life Is CellularConsider this statement: The cell theory revolutionized how biologists thought about living things.

3Before microscopespeople believed that diseases were caused by curses and supernatural spirits. No idea of organisms such as bacteria!

4Anton van Leeuwenhoek (1600s)First described natural (living) cells as seen through a simple microscope (a magnifying glass). Drew what he observed in a drop of water: animalcules.

5Robert Hooke (1665)First used the word cells to describe structure of slice of cork. Soon scientists accepted that cells were basic units of all forms of life.

6Schleiden & Schwann (1830s)Examined plants (Schleiden) and animals (Schwann) and concluded that all living things are made up of cells.

7Rudolph Virchow

Cells come from existing cells.

Janet Plowe

The cell membrane is a defined physical structure.

Review: Biologists and Their Discoveries That Led to The Cell TheoryRobert Hooke

Anton van Leeuwenhoek

Matthias Schleiden

Theodor Schwann

Rudolph Virchow

Janet PloweFirst light microscope, cork made of cellsSimple microscope, living organisms in water

Plants made of cells

Animals made of cells

Cells come from existing cellsCell membrane is physical structure The Compound Light MicroscopeHas a series of lenses that magnify an object in steps.Visible light is passed through the object and then through the lenses.Allowed biologists to achieve greater magnification and see more details inside cells.

11MagnificationThe two lenses are called:EyepieceObjectiveThe eyepiece has a magnification of 10xThe magnification of the objective lenses vary and are marked on the lensTotal magnification = (Eyepiece) X (Objective)Example: 10 X 40 =

400X12How Does a Microscope Work?

the eyethe imagethe specimenThe image is always seen upside down and backwards from its actual position

The Parts of the Microscope and Their Function

MagnificationSupport body tubeSupports slideFocuses imageSharpens the imageSupports microscopeReflects lighttowards eyepieceRegulatesamount of lightHolds slide In placeHold objectives-rotates to changemagnificationMagnificationMaintainsproper distancebetween lensesProper ProceduresCarry the microscope with one hand under the base while grasping the arm with the other handPlace microscope ~5 inches from the edge of the tableBe careful of the cord when moving around the lab tables!!

Proper Procedures3. Rotate the nosepiece to obtain the proper objective lens Make sure the lens clicks into place!!4. Look through the eyepiece and switch on the lampThis is your field of view!

Proper Procedures

5. Place slide on stage, center specimen over stage 6. Locate specimen on low power using coarse adjustment 7. Carefully switch to medium or high power8. Focus image with fine adjustmentAvoid damaging slide! Do not use course adjustment with high power!Storing the Microscopethe 10X objective is in place the stage is all the way down the power is off the cord is wrapped around the base

Four steps prepare the microscope for storage:All living things are composed of cells.Larger organisms (like humans) many cells.The cell is the basic unit of structure & function in living things.Basic unit of matter --- atom. Basic unit of life --- cell.New cells are produced from existing cells.Cells come from the reproduction of previously existing cells making exact copies of themselves.The Cell Theory19Basic Cell Structures in all CellsTypical cells range in size from 5-50 micrometers.Bacteria- 0.2 micrometersGiant amoeba- 1000 micrometers (naked eye can see)Cell membrane is thin, flexible barrier surrounding cell. Plants have strong cell wall to contain turgor pressure.Protects cell while allowing interaction with environment.Basic Cell Structures in all CellsNucleus or nucleoid- Structure or material that contains genetic material and controls activities.Cytoplasm- juice material inside cell membrane- contains many important structures

Prokaryotes - no true nucleus or organellesEukaryotes - containing membrane-bound nucleus as well as membrane bound organellesTwo Basic Cell Types:

22ProkaryotesOrganism with a cell that lacks internal structures surrounded by membranes.Have cell membrane and cytoplasmNo nuclei, but contain DNA within cytoplasmMost are single-celled organisms- smaller & simplerAll bacteria are prokaryotesCarry out every activity associated with lifeGrow, reproduce, respond to changes in environment

23Eukaryotes

Vary in shape, some large Have cell membrane and cytoplasmHave nuclei and many other organellesSome single-celled beingsMany multi-celled beingsAll plants, animals, fungi, and many microorganisms are eukaryotes

247-2 Eukaryotic Cell Structures

The Cell MembraneLocation?Outer boundary of animal and protist cells. Outer edge of cytoplasm.Also called a plasma membrane, it serves as the boundary between the cell and the external environment.Flexible- allows cell to change its shape if needed. Function?Controls the movement of materials that enter and exit the cell. Oxygen Nutrients Waste products Excess water

26Cell Membrane contdSome materials exit and enter through protein passageways.Some materials pass directly through the membrane.

27Cell WallLocation?Outer most boundary in plant, bacteria and fungi cellsIn plants, cell walls contain cellulose molecules which form fibers to protect the cell & give it support.In fungi, walls made of chitin, a nitrogen-containing polysaccharide.Function? Provides support and protection for the cellHelps maintain cell shape

28NucleusFunction?Is the organelle that manages cell function in a eukaryotic cell.Surrounded by a nuclear envelope, four layers thick. Large pores allow materials to pass between the nucleus and the rest of the cell. Contains DNA, the master instructions for building proteins. Stores hereditary information of DNA

Location?In all cells but bacteria cellsOften most prominent structure in center of cell

29Nucleus contdDNA forms strands of chromatin, which is packed into chromosomes at reproduction.Also inside the nucleus is the nucleolus, which produces tiny cell particles. These particles are ribosomes, which are the sites where proteins and enzymes are assembled. Ribosomes do not have a membrane.

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Nucleolus

Location?Dark spherical mass inside the nucleusFunction?Assembly of ribosomes begin here

Nuclear Envelope

Location?Surrounds nucleusFunction?Double membrane layer that contains pores which allow material to move into and out of the nucleusSteady stream of RNA and other info-carrying molecules to the rest of the cellMost cells need to make proteins and store other materials. Most of this work is done in the fluid of the cell- the cytoplasm.Assembly, Transport & Storage

33Cytoplasm

Location?The clear fluid composing about 50% of the cell.Contains many structures called organellesSome cells may contain cytoskeletonFunction?Establishes living condition to supply and transport materials for cell activitiesAssembly and Transport (contd)Endoplasmic reticulum (ER): a folded system of membranes where the cells chemical reactions take place. Enzymes to make lipids are also found here

Location?Extend from nuclear envelop to cell membraneDescription?Rough E.R. contain ribosomesSmooth E.R. do not contain ribosomesFunction?Transport materialsRough E.R. modify proteins for secretionSmooth E.R. contains enzymes that make lipids35Ribosome

Location?In nucleus, cytoplasm, and Rough E.R.

Function?Produce proteins following coded instruction that come from the nucleusProtein StorageGolgi apparatus: a series of membrane sacs that take lipids and proteins made on the ER and distributes them where needed- to other organelles and the cell membrane. Proteins travel in little packages called vesicles.

Vesicles may be sent out of the cell, absorbed into other organelles, or stay at the Golgi until needed.37

Vacuoles

Location?Saclike structures in the cytoplasmDescription?Animal & Protists Small, multiple vacuolesFunction? Store materials such as water, salts, proteins and carbohydratesRemove excess water from cell (contractile vacuole)Plant Vacuoles

Location?Saclike structure in the cytoplasmDescription?Plant cells Single, large central vacuoleFunction? Store materials such as water, salts, proteins and carbohydratesPressure in plant vacuole aid in support of plant cell (lack of water wilting)39Lysosomes:

Location?Throughout the cytoplasm of the cellRare in plant cells

Function?Small organelles filled with enzymes that break down lipids, carbohydrates and proteins from food into particles that can be used by the rest of the cell.Also a cell cleaner to break down old organelles and dead pathogens.40Energy Transformers: Mitochondria

Location?Throughout the cytoplasmMore numerous in cells that have high energy requirements.Function?Organelles that release energy in the form of ATP from stored food molecules (glucose)The name of this process? Cellular RespirationNote: Mitochondria contain some of their own genetic info or DNA that is essential to the function of the mitochondrion.

41Chloroplasts Chlorophyll pigment transforms light energy directly into chemical energy and stores it as sugars and starches. Chloroplasts contain stacks of sacs called grana surrounded by a fluid called stroma.

Location?Found in cytoplasm of plants, some protists and bacteria Function?Use energy from sunlight to make energy-rich food molecules (glucose). The name of this process? Photosynthesis Note: Chloroplasts contain some of their own genetic info or DNA that is essential to the function of the chloroplast.

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Plant Mitochondria

Human Liver Cell MitochondriaStructures for Support & LocomotionCytoskeleton: a framework of tiny rods and threads within the cytoplasm.Provides support for organelles.Helps maintain cell wall shape.Composed of microtubules (hollow) and microfilaments (solid).

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Structures for Support & MovementLocation?Extending from nucleus to cell membrane in some cells

Description?Made up of protein filaments called microtubules and microfilaments

Function?Helps cell maintain shape and involved in many forms of cell movement

Cilia & FlagellaBoth are structures adapted for movement.Cilia are short hairs that beat in a wave. Moves fluids over surface rather than moving cell itself.Flagella are larger, whiplike projections.

47Structures for Reproduction: Centrioles

Location?Paired structures just outside the nuclear envelope in the cytoplasmOnly in animal cellsFunction?During cell division, centrioles separate and take up positions on opposite sides of the nucleus Help organize the spindle that separate the chromosomes

Review: Cell Structures and Functions

ESmooth E.R.JRibosomeDRough E.R.KLysosome (Special vesicle)MVesicle/VacuoleCChromosomeHNucleusINucleolusESmooth E.R.ACell MembraneBCentrioleFGolgi ApparatusGMitochondrionMVesicle/Vacuole

Cell Quiz Answer KeyElectron Microscopes (1940s-present)Rather than using light, they use a focused beam of electrons that pass over or through the surface of an object in a vacuum, and finally onto a fluorescent screen where it forms an image. Only dead cells or organisms can be observed.

51Organization of CellsCellsUnicellular or multicellularTissuesFunction to perform activityOrgansTwo or more tissuesOrgan systemsGroup for life functions

52Analogies: The Cell As a FactoryWalls & roofTransportation SystemMain OfficeAssembly linePackaging & ShippingEnergy source

A Comparison of CellsStructureProkaryotic CellsEukaryotic CellsAnimalPlantCell membraneYesYesYesCell WallYesNo YesNucleusNoYesYesRibosomesYesYesYesStructureProkaryotic CellsEukaryotic CellsAnimalPlantEndoplasmic reticulumNoYesYesGolgi App.NoYesYesLysosomesNoYesYesVacuolesNoSmall or noneYesMitochondriaNoYesYesChloroplastsNoNoYesCytoskeletonNoYesYes