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Cellular Structure

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Cell Theory The cell theory is the unifying theme

in biology because it emphasizes the similarity of all living things.All organisms are composed of one or

more cells.Cells are the smallest living units of all

living organisms.Cells arise only by division of a

previously existing cell.

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Cell Characteristics The basic processes necessary for living things

to survive are the same for a single cell as they are for a more complex organism. A single-celled organism has to conduct all

life processes by itself. A multi-cellular organism has groups of cells

that specialize to perform specific functions. Small cells function more efficiently than

large cells because they have a higher surface-area-to-volume ratio and therefore shorter diffusion time.

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Examples of Cells

Amoeba Proteus

Plant Stem

Red Blood Cell

Nerve Cell

Bacteria

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Cells and Cell Size

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All cells contain Genetic material

single circular molecule of DNA in prokaryotes

double helix located in nucleus in eukaryotes

Cytoplasm jelly-like substance that fills the cells interior

Plasma membrane encloses the cell Separates the cell interior phospholipid bilayer

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Cell Types

Cell structure is one of the ways in which organisms differ from each other.2 Types of Cells

•Prokaryote – Greek words for pre-nucleus

•Eukaryote – Greek words for true-nucleus

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Prokaryotic Cells Earth’s first cells

were prokaryotes.

The simplest life forms are the prokaryotes.

Prokaryotic cells exist in two major forms: eubacteria and archaebacteria.

ALL are UNICELLULAR

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Prokaryotic Cells

Prokaryotes are the Earth’s most abundant inhabitants. They can survive in a wide range of environments and obtain energy in a variety of ways.

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Prokaryotic Cells

Prokaryotes are cells that

lack a nucleus and membrane bound organelles.

cause disease and infection

grow and divide very rapidly

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Prokaryotic Cells Flagella

Thread like structures used for locomotionFlagellum - singular Bacterial cell wall

Flagellum

Rotarymotor

Sheath

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Eukaryotic Cells

Contain organelles surrounded by membranes Most living organisms

Plant Animal

http://library.thinkquest.org/C004535/eukaryotic_cells.html

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Eukaryote

•Eukaryotes arose from prokaryotes and developed into larger more complex organisms.

•Eukaryotes are cells that contain a nucleus and organelles surrounded by a membrane

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Two Theories of Origin•Autogenic vs. Endosymbiotic

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Eukaryote

•Can be both unicellular or multi-cellular

•Examples of eukaryotes are:

•All fungi, plant, and animal cells

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http://web.jjay.cuny.edu/~acarpi/NSC/images/cell.gif

17http://waynesword.palomar.edu/images/plant3.gif

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Summary of differences!

Prokaryotic Cells Eukaryotic cells

small cells 1um-10um) larger cells (10 um-100um)

always unicellular often multicellular

no nucleus or any membrane-bound organelles in cytosol

always have nucleus and other membrane-bound organelles in

cytosol

DNA is circular, without proteinsCalled a nucleoid

DNA is linear and associated with proteins to form chromatin

ribosomes are small (70S) ribosomes are large (80S)

no cytoskeleton always has a cytoskeleton

cell division is by binary fission cell division is by mitosis or meiosis

reproduction is always asexual reproduction is asexual or sexual

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Nucleus

The Control Center Stores genetic

material (DNA) Double membrane

with pores Largest organelle

Nucleolus – dark center where ribrosomes are made

Chromatin – complex of DNA and protein that makes up chromosomes

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Cytoskeleton Long slender protein tubes and fibers that

extend from the nucleus to the plasma membrane.

Provide the interior framework of an animal cell.

The cytoskeleton contains three types of elements responsible for cell shape, movement within the cell, and movement of the cell:

Actin filaments MicrotubulesIntermediate filaments

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Cytoskeleton Actin filaments

Muscle fibers used in locomotion

Actin/myosinShape – expand

and contract

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MicrotubulesTubulinhollowTransportatio

n system – railroad tracks that move•Protein

complexes•RNA

Cytoskeleton

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Cytoskeleton

MicrotubulesFlagellumSpindle fibres

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Cytoskeleton Intermediate filaments

Frame for confinementAnchors proteins together so they can

work as a complexSolid

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Cytoskeleton

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o Found in ALL cells

o Membrane that encloses the cytoplasm.

Cell Membrane

o Called plasma membrane

o Controls what enters and leaves the cell

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Cell MembraneFluid Mosaic Model

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Ribosomes

Ribosomes are RNA-protein complexes composed of two subunits that join and attach to messenger RNA.site of protein synthesisAlone in cytoplasm

• makes proteins for use within the cellAttached to ER

• makes proteins for export out of the cell

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Endoplasmic ReticulumER –Made up of a lipid bilayer

with embedded proteins•Rough ER - studded with ribosomes

•Site of protein synthesis and processing

•Smooth ER - lacks ribosomes

•Site of synthesis of phospholipids and the packaging of proteins into vesicles

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Endoplasmic reticulum

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Golgi apparatusGolgi bodies

•Stacked flattened sacks

•Site where cell products are packaged for export

• Proteins are modified by being combined with fats or carbohydrates

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Golgi apparatus

Vesiclebuddingfrom roughendoplasmicreticulum

Fusionof vesiclewith Golgiapparatus

Migratingtransportvesicle

Protein

Proteins

Transportvesicle

Golgiapparatus

Ribosome

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Lysosomes

Vesicles produced by the Golgi apparatus.

Lysosomes contain digestive enzymes and are involved in intracellular digestion of food particles, disease causing bacteria and worn out cell parts

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Organelles With DNA

Mitochondria site of cell

respiration

Chloroplastssite of

photosynthesis

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Mitochondria

Very active cells have more mitochondria

Has its own DNA Found in both plants and animals

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Chloroplasts

• Chloroplasts are larger and more complex than mitochondria

•Contain green pigment called chlorophyll that absorbs sunlight in the first step of photosynthesis

•Found ONLY in PLANTS

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Chloroplasts

•Thylakoids are the site of photosynthesis

•Grana – stacked thylakoids

•Stroma – fluid around the grana

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Cell Wall

•provides support

•Found in PLANT cells only

•Made from cellulose

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Vacuoles

Found in PLANT and ANiMAL cells The vacuole acts a container, storing

water and dissolved particles Plants have a large central vacuole

for water storageTurgor Pressure

Unicellular animals can use contractile vacuoles for movement

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Plant vs. Animal Cells

PLANT CELL

ANIMAL CELL

Cell membraneMitochondria

Golgi apparatusNucleus

CytoskeletonRibosomes

Endoplasmic reticulum

Lysosomes

HAVE:Cell Wall

LARGE vacuolesChloroplasts

DO NOT HAVE:Cell Wall

LARGE vacuolesChloroplasts

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Eukaryotic Plant Cell

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Eukaryotic Animal Cell

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Endosymbiosis Endosymbiosis theory suggests that

eukaryotes arose from a symbiotic relationship between various prokaryotes.

Heterotrophic bacteria became mitochondria.

Cyanobacteria became chloroplasts.

Host cell was a large eukaryotic cell.

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Cell Differentiation Cell specialization occurs during the

development of a multi-cellular organism. The genetic information necessary for all

cellular functions remains in each cell but may not be used.

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Cell Humor