Chapter 2: CellsChapter 2: Cells

Aim: How are all cells Aim: How are all cells alike?alike?

Cell TraitsCell TraitsHave an outer covering called a

cell membraneCytoplasm-contains hereditary

material that controls life of cellCell come in many sizes and

shapesTwo groups:

1. Prokaryotic: no membrane-bound structures

2. Eukaryotic: membrane-bound structures

Aim: What are the Aim: What are the functions of each part of a functions of each part of a cell?cell?

1. Cell Wall1. Cell WallFound in plants, algae, fungi, and most bacteria

Tough, rigid outer coveringProtects the cellGives it shapeMade up of celluloseLignin-makes cell wall rigid

2. Cell Membrane2. Cell MembraneProtective layer around all cells

Regulates interactions between the cell and environment

Water moves freely through itFood particles enter through itWastes leave through it

3. Cytoplasm3. CytoplasmGelatin-like substanceConstantly flowing inside cell membrane

Important chemical reactions occur in it

Cytoskeleton-enables cells to move

Life processes occur hereEukaryotic cells have organelles in cytoplasm

4. Nucleus4. NucleusDirects all cell activitiesSeparated from cytoplasm by a membrane

Contains DNANucleolus

5. Chloroplast5. ChloroplastOnly in plantsFood is made hereContains chlorophyllChlorophyll uses the Sun’s energy to make glucose (sugar)

6. Mitochondrion6. MitochondrionStores energy from foodReleases energy by breaking down foods into CO2 & H2O

Active cells have more mitochondrion◦Example: muscle cells

7. Ribosomes7. RibosomesMakes protein for the cellNot-membrane boundSome float in cytoplasmSome attached to endoplasmic reticulum

Made in the nucleolusReceive directions from hereditary material on when and how to make proteins

8. Endoplasmic 8. Endoplasmic Reticulum(ER)Reticulum(ER)Extends from the nucleus to the

cell membraneSeries of folded membranesMaterials are processed and

moved around in the cellTakes up a lot of spaceSmooth ER-no ribosomes

attachedRough ER-ribosomes attached

9. Golgi Bodies9. Golgi BodiesStacked flatten membranesSort proteins and other

substances and package them into vesicles

Vesicles deliver these substances to areas inside the cell

Also carry substances to the cell membrane that need to be released

10. Vacuole10. VacuoleTemporary storage for materialsStores water, waste products,

food and other materialsPlant cells-vacuole very large

11. Lysosomes11. LysosomesContain digestive chemicals that

break down food molecules, cell wastes, and worn out cell parts

Membrane keeps chemicals from leaking into cytoplasm and destroying the cell

Aim: What is the difference Aim: What is the difference between tissue, organs and between tissue, organs and organ systems?organ systems?

Aim: What is the Cell Aim: What is the Cell Theory?Theory?

Cell TheoryCell TheorySummarizes conclusions made

by Rudolf Virchow and other scientists

1.All organisms are made up of one or more cells

2.The cell is the basic unit of organization in organisms

3.All cells come from cells-cell division

Aim: How do viruses Aim: How do viruses multiply?multiply?

VirusesVirusesNonliving particlesNo nucleus or other organellesLack cell membraneDiscovered with electron

microscopeVariety of shapesCan only make copies of itselfExamples:

◦Cold sores◦AIDS◦Colds◦Flu

Multiplying of VirusesMultiplying of VirusesNeed a host cellActs in 2 Ways:1.Active Viruses:

◦ Causes host cell to make new viruses

◦ Figure 15

2.Latent Viruses◦ Virus enters the cell and its

hereditary material becomes part of the cell’s hereditary material

◦ As the host cell reproduces so does the virus

Virus can be latent for many yearsEnvironmental factors can activate

the virus◦Example: cold sores

Viruses affect on Viruses affect on OrganismsOrganismsAttack animals, plants, fungi, protists

and all prokaryotesSome viruses only infect specific cells

◦Ex: potato leafroll virusSome affect a range of hosts

◦ex: rabiesAttaches to the host cell by the wind

or inhaled by an animalVirus and attachment site of host cell

must match exactlyBacteriophages-viruses that infect

bacteria◦Differ from other viruses-enter and

release DNA differently

Aim: Why are vaccines Aim: Why are vaccines important?important?

VaccinesVaccinesUsed to prevent diseasesMade from weakened virus particles

that can cause diseaseMade for measles, mumps, smallpox,

chicken pox, polio and rabiesEdward Jenner developed first

vaccine in 1796-smallpoxAntibiotics treat only bacterial

infectionsViral infections can be fought by

making interferons

Public health measures for preventing viral diseases:◦Vaccinating people◦Improving sanitary conditions◦Quarantining patients◦Controlling animals that spread

diseaseThrough research scientists are

discovering helpful uses of some viruses