Cell Structure and FunctionChapter 4

Principles of Modern Cell Theory

Every living organism is made up of oneor more cells.

The smallest living organisms are singlecells. Cells are the functional units of multicellular

organisms.

All cells arise from preexisting cells.

Relative Sizesin Biology

Most cells are 1-100 m.Larger cells would betoo slow at exchangingnutrients.

Light Microscope Uses lenses of glass to focus visible light rays on the specimen.

The Microscope: Viewing Cells

Cells first described by Robert Hookeand refined by Anton van Leeuwenhoekin the late 1600s.

Electron Microscope Uses beams of electrons focused by magnetic fields. Transmission Electron Microscopy (TEM)

Visualize internal features of a cell.

Scanning Electron Microscopy (SEM) Visualize surface structures of a cell.

The Microscope: Viewing Cells Cells Share Common Features Plasma Membrane

Encloses the cell. Mediates interactions between the cell and its

environment.

Cytoplasm The materials and structures within the plasma

membrane.

DNA and RNA DNA used as a hereditary blueprint RNA used to copy the blueprint and implement its

construction.

Obtain energy and nutrients from the environment.

The Plasma Membrane

Composed of phospholipidsand proteins.

Isolates the cells contentsfrom the externalenvironment.

Regulates the flow ofmaterials into and out fo thecell.

Allows for interaction withother cells and theextracellular environment.

The Cytoplasm Includes all of the material between the plasma

membrane, outside the region of DNA. The fluid that makes up the cytoplasm is called

the cytosol. It consists of water,

salts, and organicmolecules.

Location of mostmetabolic activity inthe cell.

The cytoplasm is a very crowded place.

Two Types of Cells Prokaryotic: before the nucleus

Bacteria and Archaea Simpler life forms

Eukaryotic: true nucleus Bodies of animals, plants, fungi, and protists. Possess many more organelles which contribute to

complexity membrane bound structures that perform specific

functions.

Prokaryotic Cells

The Prokaryotic Cell Unique Properties of Prokaryotes

Nucleoid Regional location of non-membrane bound

circular chromosomal DNA. Plasmids

Small rings of DNA that are located outsidethe nucleoid.

Novel Propulsion and Attachment Prokaryotic flagella (movement) Pili (attachment and sharing)

Prokaryotic Flagella Assembly

http://www.nanonet.go.jp/english/mailmag/2004/011a.html

Animated video from Dr. Keiichi Namba.

Prokaryotic Flagella Assembly

http://www.nanonet.go.jp/english/mailmag/2004/011a.html

The Prokaryotic flagella is a long helical filamentmade of many protein subunits.

- The motor is assembled inside the cell in concentric ringsthat use H+ for power to rotate at 20,000rpm.

- The filament pushes through the membrane and assembles20-30,000 protein subunits folding on the outside of the cell.

ProkaryoticDiversity

ThiocapsaThiocapsa sp.sp.

Anabaena

AgrobacteriumAgrobacterium

BeggiatoaBeggiatoa

Desulfovibrio desulfuricans

Helicobacter pylori

Leptospira

Nitrosococcus

Planctomyces

Prochlorococcus

The Eukaryotic Animal Cell

The Eukaryotic Plant CellCytoskeleton

Made up of thinmicrofilaments,medium-sizedintermediate filaments,and thick microtubules.

Cytoskeleton Functions of the Cytoskeleton

Intermediate filaments determine cell shape. Microtubules and microfilaments assemble

and disassemble, causing cell movement. Microtubules and microfilaments move

organelles within the cell. Microfilaments form centrioles, the spindle

that apportions the genetic material duringcell division.

Movement in Eukaryotes

Both are composedof microtubules.

Cilia are shorter and morenumerous.

Rowing motion.

Flagella are longer andfewer in number.

Provide force perpendicularto the cell membrane.

The Nucleus Organelle that housesgenomic DNA.

The nuclear envelopeis a double membranedotted with nuclearpores.

Nuclear pores keep nuclearmaterial in, while allowing water,ions, and small molecules to pass.

Chromatin The interior of the nucleus is filled with

chromatin, DNA associated with proteins,which form chromosomes for cell division.

Chromosomes are longstrands of DNA and itsassociated proteins thatbecome condensed(thicker and shorter) forcell division.

Nucleolus

Little Nuclei Site of ribosome

synthesis. Consists of ribosomal

RNA (rRNA), proteins,ribosomes in stages ofsynthesis, and DNA. DNA contains the

genes for rRNA.

Ribosomes

Two subunit complex of RNAand proteins.

Synthesize proteins frommessenger RNA (mRNA).

Located freely throughout thecytoplasm or associated withthe nuclear envelope andendoplasmic reticulum.

Protein structures from the RCSB Protein Databank

The Cytoplasm Contains aSystem of Membranes

A set of membrane bound organelles thatconnect the nucleus with the outside.

Three major components: The endoplasmic reticulum

Contacts the nucleus directly.

Vesicles Membrane bound sacs that act as shuttles between to

an from the organelles.

The golgi apparatus Final modifications to the exported product.

The Endoplasmic Reticulum (ER) Network within the cytoplasm Interconnected membrane-enclosed

tubes and channels through thecytoplasm.

Composed of two parts:Smooth ER

Without ribosomes.Rough ER

With ribosomes.

Smooth Endoplasmic Reticulum:Without ribosomes.Manufacture of lipids.Detoxification in the liver.Creates vesicles through budding.

Rough Endoplasmic Reticulum:With ribosomes.Site of protein synthesis.Manufacture of membrane proteins,

digestive enzymes and protein hormonesSynthesis of new ER membrane.Aide in tertiary structure folding.

The Golgi Apparatus

Set of membranesderived from the ER.

Modify, sort, andpackage proteins: Modifies some molecules

Example: adding carbohydratesmake glycoproteins.

Synthesizes polysaccharides Example: Cellulose and pectin.

Sorts proteins and lipids from the ER to theirdestination.

Packages molecules into vesicles for transport.

Protein Synthesisand Export

1. The protein is synthesized onribosomes and transported intochannels of the rough ER.

2. Protein is packaged into vesicles.3. Vesicles fuse with Golgi and

carbohydrates (or othermodification) are added.

4. Completed protein is packagedin vesicles.

5. Vesicles merge with the plasmamembrane to release the protein.

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Lysosomes The cells digestive system. Enclosed vesicles housing digestive

enzymes (to break apart food subunits) Merge with food vacuoles to digest food

into amino acids, fatty acids, andmonosaccharides.

Recycle by breaking down defectiveorganelles and membrane sections.

Food Vesicles Recycling

Formation ofLysosomes andFood Vacuoles

1. Enzymes synthesized in ER.2. Golgi modifies enzymes.3. Lysosome buds from Golgi.4. Lysosome fuses with food

vacuole and enzymesdigest food.

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Vacuoles Sacs of cellular membrane filled with fluid

containing various molecules.

Temporary vacuoles include food and recyclingvacuoles visited by lysosomes.

Permanent vacuoles help maintain cell integrityby regulating water.Contractile vacuoles

of freshwater protists.Central vacuoles of

plant cells.

Contractile vacuoles offreshwater protists

Contains a pore to release excess liquid and salts acquiredthrough osmosis.

Central vacuoles of plant cells Regulator of

water balance. Dump site for

toxins. Storage for

sugars andamino acids.

Provides rigidityfor cell shape.

Energy Generation in Cells Through two organelles:

MitochondriaConvert sugar to ATP.

ChloropastsCapture energy from sunlight.

Both thought to be evolved from bacterialendosymbionts. Organisms living within another organism for the

mutual benefit of both species. Ribosomal RNA of both organelles matches that

of bacteria, not eukaryotes.

Mitochondria Powerhouse of the cell Allow eukaryotic cells to use oxygen in the

otherwise anaerobic digestion of food, obtaining16x more ATP.

Mitochondria Found in higher numbers in very active cells.

Example: Muscles Less abundant in less active cells.

Example: Bone and cartilage.

Chloroplast Organelle where photosynthesis occurs. Found in all plant cells and some protists. Contain chlorophyll which directly captures

energy from the sun.

Bioflix Animationsof Animal and Plant Cells

Bioflix can be found in the Study Area of Mastering Biology.

Homework

Read the article by Keiichi Namba on theProkaryotic flagella, and the section in your

book titled "Cilia and Flagella" with Figure 4-6and 4-7 on the Eukaryotic flagella.

Compare and contrast how the Prokaryotic andEukaryotic flagella are made and organized, and

how they move a cell. Be sure to discuss onething unique about each structure.