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Basic Structure of a Cell

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Cell Size and TypesCell Size and Types• Cells, the basic units of organisms,

can only be observed under microscope

• Three Basic types of cells include:

Animal Cell Plant CellBacterial

Cell

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Number of CellsNumber of CellsAlthough ALL living things are

made of cells, organisms may be:

• Unicellular – composed of one cell

• Multicellular- composed of many cells that may organize into tissues, etc.

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Which Cell Type is Which Cell Type is Larger?Larger?

_________ > _____________ > ___________Plant cell Animal cell bacteria

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Multicellular OrganismsMulticellular Organisms• Cells in multicellular organisms

often specialize (take on different shapes & functions)

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Cell SpecializationCell Specialization

•Cells in a multi-cellular organism become specialized by turning different genes on and off

•This is known as DIFFERENTIATION

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Specialized Animal CellsMuscle cells Red blood cells

Cheek cellsSperm Cell

Nerve Cell

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Specialized Plant cells

Xylem cellsPollen

Guard Cells

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Simple or Complex Simple or Complex CellsCells

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Prokaryotes – The first Prokaryotes – The first CellsCells

• Cells that lack a nucleus or membrane-bound organelles

• Includes bacteria• Simplest type of cell• Single, circular chromosome

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ProkaryotesProkaryotes

• Nucleoid region (center) contains the DNA

• Surrounded by cell membrane & cell wall (peptidoglycan)

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

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Eukaryotes

• Cells that HAVE a nucleus and membrane-bound organelles

• Includes protists, fungi, plants, and animals

• More complex type of cells

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Eukaryotic Cell

Contain 3 basic cell structures:

•Nucleus•Cell Membrane•Cytoplasm with

organelles

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Two Main Types of Eukaryotic Cells

Plant Cell

Animal Cell

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OrganellesOrganelles

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OrganellesOrganelles

•Very small (Microscopic)•Perform various functions for

a cell•Found in the cytoplasm•May or may not be

membrane-bound

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•Lies immediately against the cell wall in plant cells

•Pushes out against the cell wall to maintain cell shape

Cell Membrane in PlantsCell Membrane in PlantsCell membrane

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•Nonliving layer•Found in plants, fungi, & bacteria

•Made of cellulose in plants

•Made of peptidoglycan in bacteria

•Made of chitin in Fungi

Cell wallCell WallCell Wall

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Cell WallCell Wall• Supports and

protects cell• Found outside of

the cell membrane

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•Jelly-like substance enclosed by cell membrane

•Provides a medium for chemical reactions to take place

Cytoplasm of a Cytoplasm of a Cell Cell

cytoplasm

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•Contains organelles to carry out specific jobs

•Found in ALL cells

More on CytoplasmMore on Cytoplasmcytoplasm

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•Controls the normal activities of the cell

•Contains the DNA in chromosomes

•Bounded by a nuclear envelope (membrane) with pores

•Usually the largest organelle

The Control Organelle - The Control Organelle - NucleusNucleus

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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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Nuclear EnvelopeNuclear Envelope

• Double membrane surrounding nucleus

• Also called nuclear membrane

• Contains nuclear pores for materials to enter & leave nucleus

• Connected to the rough ER Nuclear

pores

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Inside the Nucleus -The genetic material (DNA) is

found

DNA is spread out And appears as

CHROMATINin non-dividing cells

DNA is condensed & wrapped around proteins forming

as CHROMOSOMES in dividing cells

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What Does DNA do?What Does DNA do?DNA is the hereditary

material of the cell

Genes that make up the DNA molecule code for different proteins

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Nucleolus

• Inside nucleusInside nucleus• Cell may have Cell may have 1 1

to 3to 3 nucleoli nucleoli• DisappearsDisappears

when cell when cell dividesdivides

• Makes Makes ribosomesribosomes that that make proteinsmake proteins

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CytoskeletonCytoskeleton• Helps cell maintain

cell shape• Also help move

organelles around• Made of proteins• Microfilaments are

threadlike & made of ACTIN

• Microtubules are tubelike & made of TUBULIN

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CytoskeletonCytoskeleton

MICROTUBULES

MICROFILAMENTS

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CentriolesCentrioles• Found only in animal

cells• Paired structures

near nucleus• Made of bundle of

microtubules• Appear during cell

division forming mitotic spindle

• Help to pull chromosome pairs apart to opposite ends of the cell

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Centrioles & the Mitotic Centrioles & the Mitotic SpindleSpindle

Made of MICROTUBULES (Tubulin)

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MitochondrionMitochondrion(plural = mitochondria)(plural = mitochondria)

• “Powerhouse” of the cell

• Generate cellular energy (ATP)

• More active cells like muscle cells have MORE mitochondria

• Both plants & animal cells have mitochondria

• Site of CELLULAR RESPIRATION (burning glucose)

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MITOCHONDRIASurrounded by a

DOUBLE membrane

Folded inner membrane called CRISTAE (increases surface areafor more chemical Reactions)

Has its own DNA

Interior called MATRIX

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Interesting Fact ---Interesting Fact ---

• Mitochondria Come from cytoplasm in the EGG cell during fertilization

Therefore …• You inherit your

mitochondria from your mother!

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Rod shape

Cell PowerhouseCell Powerhouse

Mitochondrion( mitochondria )

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What do mitochondria What do mitochondria do?do?

Burns glucose to release energy (ATP)

Stores energy as ATP

“Power plant” of the cell

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Endoplasmic Reticulum - EREndoplasmic Reticulum - ER

Two kinds of ER ---ROUGH & SMOOTH

• Network of hollow membrane tubules• Connects to nuclear envelope & cell

membrane• Functions in Synthesis of cell products

& Transport

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Rough Endoplasmic Reticulum Rough Endoplasmic Reticulum (Rough ER)(Rough ER)

• Has ribosomes on its surface

• Makes membrane proteins and proteins for export out of cell

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Rough Endoplasmic Rough Endoplasmic Reticulum (Rough ER)Reticulum (Rough ER)

• Proteins are made by ribosomes on ER surface

• They are then threaded into the interior of the Rough ER to be modified and transported

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Smooth Endoplasmic Smooth Endoplasmic ReticulumReticulum

• Smooth ER lacks ribosomes on its surface

• Is attached to the ends of rough ER

• Makes cell products that are USED In the cell

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Functions of the Smooth Functions of the Smooth ERER• Makes membrane

lipids (steroids)• Regulates calcium

(muscle cells)• Destroys toxic

substances (Liver)

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Endomembrane System

Includes nuclear membrane connected to ER connected to cell membrane (transport)

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RibosomesRibosomes• Made of PROTEINS and rRNA• “Protein factories” for cell• Join amino acids to make proteins• Process called protein synthesis

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RibosomesRibosomes

Can be attached to Rough ER

OR

Be free (unattached

) in the cytoplasm

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Golgi BodiesGolgi Bodies• Stacks of Stacks of flattened flattened

sacssacs• Have a shipping Have a shipping

side (side (cis facecis face) & a ) & a receiving side receiving side ((trans facetrans face))

• Receive Receive proteinsproteins made by ERmade by ER

• Transport vesiclesTransport vesicles with modified with modified proteins pinch off proteins pinch off the endsthe ends

Transport

vesicle

CIS

TRANS

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Golgi BodiesGolgi BodiesLook like a stack of pancakes

Modify, sort, & packagemolecules from ERfor storage OR transport out of cell

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Golgi Animation Golgi Animation

Copyright Pearson Publishers

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Golgi AnimationGolgi Animation

Materials are transported from Rough ER to Golgi to the cell membrane by

VESICLES

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LysosomesLysosomes• Contain Contain digestive digestive

enzymesenzymes• Break down Break down food, food,

bacteria,bacteria, and and worn out worn out cell partscell parts for cells for cells

• Programmed forProgrammed for cell cell death (APOPTOSIS)death (APOPTOSIS)

• Lyse & Lyse & release release enzymesenzymes to break down to break down & recycle cell parts)& recycle cell parts)

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Lysosome DigestionLysosome Digestion

• Cells take in food by phagocytosis

• Lysosomes digest the food & get rid of wastes

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Cilia & FlagellaCilia & Flagella

• Made of protein tubes called microtubules

• Microtubules arranged (9 + 2 arrangement)

• Function in moving cells, in moving fluids, or in small particles across the cell surface

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Cilia & FlagellaCilia & Flagella

• Cilia are shorter and more numerous on cells

• Flagella are longer and fewer (usually 1-3) on cells

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Cell Movement with Cilia Cell Movement with Cilia & Flagella& Flagella

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Cilia Moving Away Dust Cilia Moving Away Dust Particles from the LungsParticles from the Lungs

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VacuolesVacuoles• Fluid filled sacks for storage• Small or absent in animal cells• Plant cells have a large Central Vacuole• No vacuoles in bacterial cells

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VacuolesVacuoles

• In plants, they store Cell Sap

• Includes storage of sugars, proteins, minerals, lipids, wastes, salts, water, and enzymes

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ChloroplastsChloroplasts• Found only in producers (organisms

containing chlorophyll)• Use energy from sunlight to make

own food (glucose)• Energy from sun stored in the

Chemical Bonds of Sugars

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ChloroplastsChloroplasts

• Contains its own DNA

• Contains enzymes & pigments for Photosynthesis

• Never in animal or bacterial cells

Amazing Interactive Cell

• Bill Nye Cells• Cell Organelles

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Cell SizeQuestion:

Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?

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Factors Affecting Cell Size

• Surface area (plasma membrane surface) is determined by multiplying length times width (L x W)

• Volume of a cell is determined by multiplying length times width times height (L x W x H)

• Therefore, Volume increases FASTER than the surface area

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Cell Size•When the surface area is no

longer great enough to get rid of all the wastes and to get in enough food and water, then the cell must divide

•Therefore, the cells of an organism are close in size

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Cell SizeQuestion:

Are the cells in an elephant bigger, smaller, or about the same size as those in a mouse?

About the same size, but …

The elephant has MANY MORE cells than a mouse!