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Cells and Cell OrganellesThe cell theory states:

All organisms are composed of one or more cells.

Cells are the basic unit of structure and function inorganisms.

All cells come only from other cells.

Cell Theory

How many cells in your body?

• 50 million million (trillion)

• That’s 50,000,000,000,000 cells!!!!!!

• And not only that, there are manydifferent types.

• Cells are diverse– But only two BASIC types

Two Basic Cell Types

Plants, animals, protistsBacteriaExamples

packed intochromosomes

loose, sometimescircular

DNAstructure

YesNoOrganellesPresent

yesNoTrueNucleuspresent

largevery smallRelative size

Eu = truekaryote = nucleus

Pro = beforekaryote = nucleus

Name

EukaryoteProkaryote

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Prokaryotic Cell

• Note the lack of nucleus, DNA free floating• DO HAVE cell membrane, ribosomes, and

cell wall (sometimes)

Eukaryotic Cell

• DO HAVE a membrane-bound nucleus

• DO HAVE membrane-bound organelles: mitochondria,chloroplasts (plants), cell wall (plants), smooth andrough endoplasmic reticulum, golgi apparatus,lysosomes, vacuoles, etc.

Lots of internalmembrane-boundstructures!

Eukaryotic CellRelative sizes-- Note that:

Eukaryotes (plant and animal cells) are 10-100 µm

Prokaryotes (bacteria) are 1-10 µm.

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Cell MembraneCell Membrane

• Both prokaryotic and eukaryotic cells havethis “cell membrane”

• Holds the CYTOPLASM inside the cell andkeeps unwanted things out of the cell

• Gives cells their shape and flexibility• Helps to maintain HOMEOSTASIS by

allowing certain substance to flow in and outof the cell – SELECTIVE PERMIABILITY

Structure of Cell Membrane

• The cell membrane is a PHOSPHOLIPID BILAYER

• PHOSPHOLIPID BILAYER

Water

Hydrophilic head

Hydrophobic tail

Fluid Mosaic ModelPhospholipids, cholesterol, and proteins that

make up the cell membrane all flow like thesurface of a wavy lake, moving and shifting.

Structure of the Cell Membrane

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Fluid Mosaic ModelFluid Mosaic Model Cell Walls

• Located outside the cell membrane

• Can be made of thick fibers of cellulose(plants), chitin (fungi), or peptodoglycan(some bacteria)--all of these are carbs

• Animal cells DO NOT have cell walls

Cell Wall of Plants

Is this a prokaryotic or eukaryotic cell?

Nucleus

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Nucleus• Control Center of the cell• Contains CHROMATIN (loose DNA)

– Bundles into CHROMOSOMES when cell is ready todivide (it packs before moving)

• Contains a NUCLEOLUS, which is made up of amass of nucleotides used for making DNA andRNA

Chromatin Chromosomes

Chromatin in the Nucleus

• Directs PROTEIN SYNTHESIS(building proteins)

• It contains the “blueprints” for theorganism; this is the DNA

The Nucleus and the Nuclear Membrane

The Nuclear Membrane or Envelope is a double membrane with pores to letcertain things in and out of the nucleus.

Outside the Nucleus:the Cytoplasm

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Outside the Nucleus:The Cytoplasm

• Lots of action!

• Many organelles and ribosomes arefloating around

• Cytoplasm includes organelles and thegel-like fluid they are suspended in

Endoplasmic Reticulum (ER) andRibosomes

The endoplasmic reticulum (ER) is a system of membranechannels and little sacs that acts as a “workspace” forcellular reactions.

Rough ER is studded with ribosomes and is whereproteins are made and processed.

Smooth ER has no ribosomes and is where the cellmakes phospholipids and packages proteins into vesicles(small storage sacs), among other functions.

Ribosomes can be attached to ER or free. They are tinyorganelles that make proteins.

After leaving the ER, proteins are often sent to the Golgifor folding and finishing.

Smooth and Rough Endoplasmic ReticulumSmooth andRough ER

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Smooth andRough ER

Golgi Apparatus

Golgi Apparatus andLysosomes

Golgi Apparatus:• A flattened set of membranes• The “post office” of the cell• Processes and packages proteins for export• Makes lysosomes

Lysosomes:• Small sacs full of hydrolytic (digestive)

enzymes• Break apart (digest) foreign substances

Golgi Apparatus And Lysosomes

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Vacuoles

Used for storage– Waste products

– Food and water

– Enzymes, etc.

– In plants, this is usually very large, called acentral vacuole

Vacuoles

Mitochondrion Mitochondrion

• plural = mitochondria• The “powerhouse” of the cell• Double membrane• Site of CELLULAR RESPIRATION

– Releases energy from food molecules– Creates ATP, an energy containing molecule that

acts as a “battery” to power other cell reactions– ATP is the “energy currency” of the cell

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MitochondrionChloroplast

Chloroplast

• Only found in green plant cells

• Trap energy from sunlight to build foodmolecules– Stored for later use

• Double membrane

Chloroplast

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The eukaryotic cytoskeleton is a network ofmicrofilaments and microtubules thatextends from the nucleus to the plasma (cell)membrane.

Microfilaments and microtubules:•Give cell its shape•Help organelles move within the cell•Help the cell move

The CytoskeletonCentrioles are shortcylinders made ofmicrotubules.

Centrioles are only foundin animal cells and areinvolved in building andtaking apart microtubulesduring cell division and inthe organization of ciliaand flagella.

Centrioles

Cilia (small and numerous) and flagella (large andsingle) are made of microtubules and are involvedin cell movement.

Cilia andFlagellaEnd of Show

• Extra pictures follow

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Animal Cell Anatomy Plant Cell Anatomy