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Chapter Chapter 44

The Cell: The Cell: The Fundamental Unit of LifeThe Fundamental Unit of Life

Lecture Lecture 1: Cell Theory and 1: Cell Theory and Structural OrganizationStructural Organization

•• Fundamental unit of lifeFundamental unit of life

•• Smallest unit that displays all the basic Smallest unit that displays all the basic

elements of lifeelements of life

The CellThe Cell

1.1. All living things are made of one or more cellsAll living things are made of one or more cells

Cell TheoryCell Theory

22. Cells are capable of performing all vital . Cells are capable of performing all vital

physiological functions, including physiological functions, including

respiration/energy flow, growth, movement, and respiration/energy flow, growth, movement, and

reproductionreproduction

Cell TheoryCell Theory

33.. Each new cell arises from the division of Each new cell arises from the division of

another, preanother, pre--existing cellexisting cell

Cell TheoryCell Theory

4. Each cell passes its hereditary information 4. Each cell passes its hereditary information

(DNA) on to its daughter cells when it divides(DNA) on to its daughter cells when it divides

Cell TheoryCell Theory

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55. Each cell maintains its own internal balance . Each cell maintains its own internal balance

(homeostasis)(homeostasis)

Cell TheoryCell Theory

6. (6. (MulticellularMulticellular organisms) Homeostasis at higher organisms) Homeostasis at higher

levels of organization reflects the combined and levels of organization reflects the combined and

coordinated actions of many cellscoordinated actions of many cells

Cell TheoryCell Theory

•• Is a virus alive?Is a virus alive?

1.1. Made of cells?Made of cells?

2.2. Performs all vital functions?Performs all vital functions?

3.3. Arise from preArise from pre--existing cells?existing cells?

4.4. Passes on hereditary information?Passes on hereditary information?

5.5. Maintains homeostasis?Maintains homeostasis?

Thought QuestionThought Question

•• Two broad categoriesTwo broad categories

•• ProkaryotesProkaryotes

•• EukaryotesEukaryotes

Cell TypesCell Types

•• UnicellularUnicellular

•• All cells identical All cells identical –– no specialized functionno specialized function

•• Lack nucleus, other membraneLack nucleus, other membrane--bound organellesbound organelles

•• Example: bacteriaExample: bacteria

ProkaryotesProkaryotes

•• May be unicellularMay be unicellular

•• Examples: yeast, amoebasExamples: yeast, amoebas

EukaryotesEukaryotes

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•• May be May be multicellularmulticellular

•• Examples: plants, animalsExamples: plants, animals

EukaryotesEukaryotes

•• Cells of Cells of multicellularmulticellular organisms can specializeorganisms can specialize

•• ExamplesExamples: muscle cells, nerve cells, storage : muscle cells, nerve cells, storage

cells, epithelial cells, gametes, blood cells, etccells, epithelial cells, gametes, blood cells, etc

EukaryotesEukaryotes

•• Some definitionsSome definitions

•• MulticellularityMulticellularity: Single organism composed of : Single organism composed of

more than one cellmore than one cell

•• DifferentiationDifferentiation: Process whereby cells differ : Process whereby cells differ

in structure and function, despite containing in structure and function, despite containing

identical DNAidentical DNA

•• SpecializationSpecialization: Cells differentiate for a : Cells differentiate for a

specific purposespecific purpose

EukaryotesEukaryotes

•• 2 classes of cells2 classes of cells

•• Gametes Gametes –– reproductive cellsreproductive cells

•• Purpose: reproductionPurpose: reproduction

Eukaryotic CellsEukaryotic Cells

•• 2 classes of cells2 classes of cells

•• Somatic cells: all other cellsSomatic cells: all other cells

•• All somatic cells contain identical DNA, All somatic cells contain identical DNA,

but do not perform the same functionbut do not perform the same function

Eukaryotic CellsEukaryotic Cells An ExperimentAn Experiment

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Stem CellsStem Cells

•• All somatic cells contain all genetic informationAll somatic cells contain all genetic information

•• External signals tell them how to differentiateExternal signals tell them how to differentiate

SignificanceSignificance

•• Differ greatly in appearance and functionDiffer greatly in appearance and function

•• 4 basic components in common4 basic components in common

1.1. Plasma membranePlasma membrane

•• IsolationIsolation

•• ProtectionProtection

•• SensitivitySensitivity

•• SupportSupport

•• GatekeeperGatekeeper

Eukaryotic CellsEukaryotic Cells

•• Differ greatly in appearance and functionDiffer greatly in appearance and function

•• 4 basic components in common4 basic components in common

2. 2. CytoplasmCytoplasm

•• Material inside theMaterial inside the

cell but outside thecell but outside the

nucleusnucleus

•• Contains the Contains the cytosolcytosol

and organellesand organelles

Eukaryotic CellsEukaryotic Cells

•• Differ greatly in appearance and functionDiffer greatly in appearance and function

•• 4 basic components in common4 basic components in common

33. . The nucleusThe nucleus

•• Control center Control center –– thethe

“brain of the cell”“brain of the cell”

•• Contains the DNAContains the DNA

Eukaryotic CellsEukaryotic Cells

•• Differ greatly in appearance and functionDiffer greatly in appearance and function

•• 4 basic components in common4 basic components in common

33. . OrganellesOrganelles

•• “Organs” of the cell“Organs” of the cell

•• Perform specificPerform specific

functionsfunctions

•• Some membraneSome membrane--

boundbound

•• Others nonOthers non

membranemembrane--boundbound

Eukaryotic CellsEukaryotic Cells