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Discovery of the Cell • Robert Hooke (1635-1703) – invented the

term cell; studied dead plant cells such as cork.

• Anton van Leeuwenhoek (1632-1723) - 1st to observe living cells.

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Discovery of the Cell • Matthias Schleidan (1804-1881) – concluded

that all plants are composed of cells. • Theodor Schwann (1810-1882) - concluded all

animals were composed of cells. • Rudolf Virchow (1821 – 1902) - reasoned that

cell come only from other cells.

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Protocells:One theory of the origins of cells states

that the first life on earth consisted of several types of tiny protocells, cell-like organisms. These organisms were able to survive and reproduce in a very limited environment because of their simplicity. Over time, some of these protocells came together and shared their specialization in a symbiotic relationship. These colonies of protocells eventually became the cells we know today.

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Basic Structure of a Cell

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Introduction to Cell Introduction to Cell TheoryTheory

1. Cells are the basic units of organisms2. Cells come only from other cells3. All living things are made of cellsBasic types of cells:

Animal Cell Plant CellBacterial

Cell

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Number of CellsOrganisms may be:• Unicellular – composed of one cell

• Multicellular- composed of many cells that may organize

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Prokaryotes lack a nucleus or membrane-bound structures called organelles Ex: bacteria

Eukaryotes have a nucleus and membrane-bound organelles Ex: animals, plants, fungi & protists

Cells May be Prokaryotic or Eukaryotic

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ProkaryotesCenter region contains the DNA

•Cell membrane & cell wall

• Contain ribosomes (no membrane) to make proteins in their cytoplasm

•Evolved 3.5 billion years ago

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Eukaryotic Cell

Contain 3 basic cell structures:

• Nucleus• Cell Membrane• Cytoplasm with

organelles• Evolved 1.5 billion

years ago

Prokaryotes vs. Eukaryotes

Cells do not contain a nucleus

Cells contain a nucleus

No membrane bound organelles

Membrane bound organelles

DNA is found (no specific area)

DNA is found in nucleus

Ex: bacteria Ex: animal cell, plant cell

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Two Main Types of Eukaryotic Cells

Plant Cell

Animal Cell

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OrganelleOrganelless

Very small size

Can only be observed under a microscope

Have specific functions

Found throughout cytoplasm

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Controls the normal activities of the cell

Bounded by a nuclear membrane (envelope)

Contains chromosomes

Control Organelle

Nucleus

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Each cell has fixed number of chromosomes that carry genes

Genes control cell characteristics

Nucleus

More on the More on the NucleusNucleus

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Nucleolus• Cell may have Cell may have 1 to 1 to

33 nucleoli nucleoli• Inside nucleusInside nucleus• DisappearsDisappears when when

cell dividescell divides• Makes ribosomesMakes ribosomes

that make that make proteinsproteins

Ribosomes

• Produce PROTEINS by following coded instructions from the nucleus

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Smooth & Rough Endoplasmic Reticulum

Rough ER has ribosomes on its surface & makes proteins to EXPORT

Smooth ER lacks ribosomes & makes proteins USED In the cell

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Golgi Bodies• Stacks of Stacks of flattened flattened

sacssacs• Have a shipping side Have a shipping side

& a receiving side& a receiving side• Receive & Receive & modify modify

proteinsproteins made by ER made by ER• Transport vesiclesTransport vesicles

with modified with modified proteins pinch off proteins pinch off the endsthe ends

Transport

vesicle

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Lysosome• Contain digestive Contain digestive

enzymesenzymes• Break down food and Break down food and

worn out cell parts worn out cell parts for cells for cells

• Programmed for cell Programmed for cell death (lyse & release death (lyse & release enzymes to break enzymes to break down & recycle cell down & recycle cell parts)parts)

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Plants have a large central vacuole

Stores sugars, proteins, minerals, wastes, & pigments

VacuoleVacuole

Vacuole

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Cell Cell PowerhousePowerhouseSite of Cellular respiration

Mitochondrion

( mitochondria )

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Active cells like muscles have more mitochondriaBurn sugars to produce energy ATP

In Animal Cells:In Animal Cells:

Mitochondria

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Contain the green pigment chlorophyll

Traps sunlight to make to make sugars (food)

Process called photosynthesis

In Plant Cells:In Plant Cells:

Chloroplast

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Animal Cell OrganellesAnimal Cell Organelles

•Near the nucleus•Paired structures•Help cell divide

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CytoskeletonMicrofilaments: thread-like structures that help support

the cell and help the cell moveMicrotubules: tube-like

structures that are important in cell division; these also form cilia and flagella in some cells

Cell Parts that Aren’t Cell Parts that Aren’t OrganellesOrganelles

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Lies immediately against the cell wall in plant cells

Made of protein and phospholipids

“Selectively permeable”

Cell (Plasma) membrane

Surrounding the Surrounding the CellCell

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Living layerControls the movement of materials into and out of the cell

Selectively permeable

Cell membrane

Cell or Plasma Cell or Plasma MembraneMembrane

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Cytosol: cytoplasm w/o organelles

Jelly-like substance enclosed by cell membrane

Provides a medium for chemical reactions to take place

Cytoplasm of a Cytoplasm of a Cell Cell

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Contains organelles to carry out specific jobs

Examples: chloroplast & mitochondrion

Cytoplasm

More on More on CytoplasmCytoplasm

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Dead layerLarge empty spaces present between cellulose fibers

Freely permeable

Cell wall

Plant CellPlant Cell

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Plant CellPlant Cell

Made of cellulose which forms very thin fibers

Strong and rigidFound in plant cells

Cell wall

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Protect and support the enclosed substances (protoplasm)

Resist entry of excess water into the cell

Give shape to the cell

Cell wall

Plant CellPlant Cell

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Different kinds of Different kinds of plant cellsplant cells

Onion Epidermal Cells

Root Hair Cell

root hair

Guard Cells

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mitochondrion

nucleus

glycogen granule

cell membrane

cytoplasm Animal cellAnimal cell

No cell wall or chloroplastStores glycogen in the cytoplasm for food energy

vacuole

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Different kinds of Different kinds of animal cellsanimal cells

white blood cell

red blood cell

cheek cells

sperm

nerve cell

muscle cell

Amoeba

Paramecium

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Similarities between Similarities between plant cells and animal plant cells and animal

cellscellsBoth have a cell membrane surrounding the cytoplasm

Both have a nucleus

Both contain mitochondria

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Differences between Differences between plant cells and animal plant cells and animal

cellscellsAnimal cells Plant cells

Relatively smaller in

sizeIrregular shape

No cell wall

Relatively larger in size

Regular shapeCell wall present

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Animal cells Plant cells

Vacuole small or absent

Glycogen as food storage

Nucleus at the center

Large central vacuole

Starch as food storage

Nucleus near cell wall

Differences between Plant Differences between Plant Cells and Animal CellsCells and Animal Cells

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Compound MicroscopeCompound Microscope

• Instrument for observing small objects

•Magnify images up to 2000X their size

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Different parts of Different parts of a microscopea microscope

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Eyepiece

Fine adjustmentArm

Stage

Condenser control knob

Base

Body tubeCoarse adjustment

Iris diaphragm

Revolving nosepiece

Objective

ClipCondenser

Mirror

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Observing an Object:

Because the light rays from an object cross before reaching your eye, the image you see through most microscopes will be inverted and upside down.

Magnification: the increase of an object's apparent size.

Resolution: the power to show details clearly. Resolution allows the viewer to see two objects that

are very close together as two objects rather than as one. Resolution is controlled by the quality of the lenses being used - the better the lenses, the better the resolution.

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Care and handling:

A microscope is a delicate piece of equipment and should be treated gently. Always use two hands when moving the microscope. Place one hand around the arm of the microscope and the other under the base for support. Always carry the microscope upright and close to the body when moving any distance. Place the microscope flat on the table, but not too near the edge where it might be knocked off.

If it becomes necessary to clean the lenses on the microscope, ask your facilitator for a piece of "lens paper". Other materials, such as paper towel, can scratch the surface of the lens.

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Preparing Specimens for Viewing:

• In most instances, light must pass through any object to be viewed with a light microscope. For this reason, the object must be fairly thin. Thick objects must be sliced into thin sections for viewing.

• Many objects do not have distinct, contrasting colors. This makes it difficult to see details. To improve the viewing of these objects, they are stained. Staining is the use of a biological to make the details visible.

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Making a Slide: • Place a clean slide on the table.

• For liquid samples, place one or two drops in the center of the slide. For solid samples, place the sample in the center of the slide and add one drop of water or staining solution.

• Hold the plastic cover slip by the edges. Do not get fingerprints on the cover slip. Set one edge against the slide and lower it until it contacts the liquid. The liquid should spread across the whole area of the cover slip.

• Never use a slide under the microscope without a cover slip. Its major purpose is to protect the objective lens for the liquid on the slide.

• Unless otherwise instructed, wipe the sample and cover slip off the slide with a paper towel when finished. Throw the paper towel and its contents away. Return the microscope slide to its container.

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The cell is the Basic The cell is the Basic Unit of LifeUnit of Life

• Cell is the smallest unit of living organisms

• Unicellular organisms are made of one cell only

• The cells of multicellular organisms are specialized to perform different functions

– e.g. mesophyll cells for photosynthesis and root hair cells for water absorption

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Levels of organizationLevels of organization

• Cells are grouped together and work as a whole to perform special functions

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TissueTissue

•A group of similar cells to perform a particular function–Animals : epithelial tissue, muscular tissue

–Plants : vascular tissue, mesophyll

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OrganOrgan

• Different tissues group together to carry out specialized functions– Heart : consists of muscles,

nervous tissue and blood vessels

– Leaf : consists of epidermis, mesophyll and vascular tissue

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Stoma

Air Space

Spongy Mesophyll Cell

Chloroplast

The Structures of a Leaf (Plant Organ)

Palisade Mesophyll Cell

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The Structures of a Heart (Animal Organ)

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SystemSystem• Several organs and tissues work together

to carry out a particular set of functions in a co-ordinated way– Human : digestive, respiratory, excretory,

circulatory and reproductive systems– Plant : root and shoot systems

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Human Body SystemsHuman Body Systems Examples of systems : Digestive System Respiratory System Circulatory System Nervous System Reproductive System

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Examples of a Human Body System

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Examples of a Human Body System

The Respiratory System

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Examples of a Human Body System

Circulatory System

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Examples of a Human Body System

Nervous System

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Levels of OrganizationLevels of Organization

CELLS (muscle cells,nerve cells)TISSUES (muscle, epithelium)ORGANS (heart, lungs, stomach)

SYSTEMS (circulatory system)ORGANISM (human)

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It’s You!