Unit%#5:%Cell%Structure%&%Func2on%

Classifica(on,,Cell,Type,,Cell,Organelles,,and,Cell,Specializa(on,

CELL%TYPE%How,are,prokaryo(c,cells,and,eukaryo(c,cells,similar?,different?,

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Cell Theory •  All living things are

composed of cells. •  Cells are the basic unit

of structure and function in living things.

•  New cells are produced from existing cells.

Many scientists were involved in creating this theory: Robert Hooke (1665), Matthias Schleiden (1838), Theodor Schwann (1838), & Rudolf Virchow (1855).

TEDATalk:,50Acent,,foldscopes,(The,NEW,foldable,microscope!),(9,minutes),

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Two Broad Categories of Cells:

•  PROKARYOTES - “before” a nucleus - smaller, less complex

•  EUKARYOTES - contains a “true” nucleus - larger, more complex - contains membrane-bound organelles

Eukaryotic Cell

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Endosymbiosis theory raised by Lynn Margolis in 1970 suggests that mitochondria and chloroplasts of eukaryotes are actual descendents of ancient prokaryotes. These cells formed a symbiotic relationship. Evidence: mitochondria and

chloroplasts contain their own DNA, own ribosomes, and can replicate on their own.

hNps://www.youtube.com/watch?v=AFQmAnmLZtE,

CLASSIFICATION%How,are,living,things,classified,based,on,cell,type?,

Taxonomy,is,the,science,of,classifica(on.%

Prokaryotes% Eukaryotes%

Archaea% Bacteria% Eukarya%

Pro2sta% Fungi%

Animalia% Plantae%

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Two Common Eukaryotic Cells:

•  ANIMAL cells and PLANT cells •  Both cells are divided into functional compartments called

ORGANELLES. •  Many of these organelles are MEMBRANE-BOUND. •  Both cells are filled with a fluid-like substance that supports the

organelles called the CYTOSOL. •  CYTOPLASM refers to the cytosol and all the organelles other

than the nucleus

CELL%ORGANELLES%How,are,animal,cells,different,from,plant,cells?,

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The Nucleus - “The Control Center”

•  Controls cell’s activities

•  Contains DNA that is attached to histone proteins that make up long fibers called chromatin. Each fiber is a chromosome.

•  Covered by a double membrane perforated with pores called a nuclear envelope.

•  Contains a condensed center called the nucleolus, which produces ribosomes.

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Vacuoles - “Storage Tank” •  Membranous sacs that come in different

shapes and sizes and have a variety of functions such as: –  Storage of food in animal cells

•  Plants have a large central vacuole that can act as a lysosome or: –  Helps plant cell grow in size by storing

water –  Can store vital chemicals or wastes –  In flower petals, vacuoles contain pigments

that attract pollinators. –  May contain poisons that protect against

plant-eating animals.

•  Paramecium contain contractile vacuoles. –  Collect excess water from the cell and then

expels it to the outside.

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Lysosomes - “The Trash Collectors” •  Contain digestive enzymes •  Play an important role in apoptosis

(cell suicide)

•  Protists engulf food particles that get digested by lysosomes to release nutrients into the cell. •  White blood cells ingest bacteria and lysosomes destroy them. •  Damaged & old organelles get recycled.

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Cytoskeleton •  Eukaryotic cells contain a

meshwork of protein fibers, collectively called the cytoskeleton, extending throughout the cytoplasm of a cell.

•  Provide structural support

and are involved in various types of cell movement.

•  Three main kinds of fibers:

–  Microfilaments –  Intermediate filaments –  Microtubules

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Flagella & Cilia •  Flagella are long, whip-like

structures used to propel a cell

•  Cilia are numerous, short hair-like structures that propel protists such as Paramecium. –  Cilia are also found on cells

lining the human windpipe to sweep away mucus containing trapped debris out of our lungs.

•  Flagella and cilia are both composed of microtubules.

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Centrioles •  Aides in cell division •  NOT found in plant

cells •  Composed of

microtubules

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Ribosomes

•  Produces,protein,for,the,cell,•  Made,of,ribosomal%RNA%

(rRNA),

•  Produced,in,the,nucleolus%•  Two,subunits,that,come,

together,to,form,the,ribosome,

•  Found,either,“free”%floa(ng,the,cytosol,or,“aMached”%to,the,endoplasmic,re(culum.,

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Endoplasmic Reticulum - “The Highway System”

•  A network of flattened sacs and tubes •  Rough ER has ribosomes on its surface. Functions in

modifying proteins. •  Smooth ER has no ribosomes. Functions in

synthesizing lipids.

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Golgi Apparatus - “The Post Office” •  Flattened sacs looking like a stack of pita bread. •  Receives, modifies, and sends out substances

manufactured by the ER in membrane-bound sacs called vesicles.

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Chloroplasts - “The solar panels” •  Not found in animal cells! •  Found in plants, some protists, and some bacteria

cells. •  Contains its own DNA and ribosomes, has two

membranes, and can replicate on its own •  Contains chlorophyll (green pigment that absorbs

light) •  Carries out photosynthesis:

Converts solar energy into chemical energy of glucose

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Mitochondria - “The power house” •  Contains its own maternal DNA and can replicate on its own. •  Carries out cellular respiration:

Converts chemical energy of glucose into usable energy of ATP

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Cell Wall •  NOT found in animal cells! •  Plant cell walls are composed mostly of cellulose. •  Cell walls have strength & elasticity. •  Provides structural support •  Prokaryotes also have cell walls but they are composed of

different material.

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Cell Membrane - “The Gatekeeper”

•  ALL cells are surrounded by a plasma membrane. •  Aids in structural support and acts as a gatekeeper to

determine what substances pass into and out of the cell. •  Composed of:

–  phospholipid bilayer –  proteins –  carbohydrate chains.

GENERAL%CELL%IMAGES%How%are%plant%and%animal%cells%structurally%similar?%Different?%

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89 Lesson 7.2 7.2 A Typical Animal Cell

ANIMAL CELL

Cellmembrane

Centrioles

Vesicle

Rough endoplasmicreticulum

Ribosomes (attached)Ribosomes (free)

Golgiapparatus

Mitochondrion

Lysosome

Cytoskeleton

Smooth endoplasmic reticulum

Nucleus (contains DNA)

Vacuoleosomes

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88 Lesson 7.2 7.2 A Typical Plant Cell

PLANT CELL

Cellwall

Cellmembrane

Vesicle

Golgiapparatus

Rough endoplasmicreticulum

Smooth endoplasmicreticulum

Ribosomes (attached)Ribosomes (free)

Mitochondrion

Cytoskeleton

Chloroplast

Central vacuole

Nucleus (contains DNA)

Vacuole

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87 Lesson 7.2 7.2 A Typical Prokaryotic Cell

Cellwall

Cellmembrane

PROKARYOTIC CELL

DNARibosomes

Cellwall

me

Vacuole