Unit A – Cells and

Systems

Chapter 2 – Cells and

Cell Systems

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Cells – Key Ideas• Unicellular organisms perform the same basic functions as

multicellular organisms• Cells are specialized to carry out specific functions• Cells are generally more efficient when they work together to

perform a specific function• Cells in the human body are organized into tissues• Groups of tissues are organized into organs. • Groups of organs are reffered to as organ systems• Some diseases are caused when cells are invaded by microscopic

living things• Your health depends on how well your cell systems work together

2.1 – Cells and Cell

Systems

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Cell OrganizationTISSUE – a group of cells that are similar in shape and functionTissues are often organized into larger structures called organsORGAN – a structure composed of one or more different types of tissues; specialized to carry out a specific functionMany organs are made up of several different types of tissues.

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Organ (see fig.1 p.41)

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Cellular Organization• Organ Systems – groups of

organs that have related functions

• See Table 1 p.42

2.2 – Unicellular Organisms

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Unicellular Organisms•Many organisms are composed of just ONE cell•These are called micro-organisms or microbes•These single cells are also responsible for feeding, digesting, excreting, and reproducing

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The Importance of Micro-organismsNot all cause diseaseSome are useful to create foods that we like such as cheese and yogurtWe have many micro-organisms in our bodies that are either harmless or beneficial

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BACTERIA (fig.2 p44)•Some can make their own food•Some are parasitic•Bacteria can be found in every environment on Earth•Are PROKARYOTIC

•No nucleus•No mitochondria

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Protists (fig.4 p45)

• Protists – a unicellular organisms that are neither plant nor animal; is a eukaryotic cell

• Anywhere there is water you will find protists

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Plant-Like Protists - Diatoms

• found in both fresh water and salt water

• Contain chlorophyll

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Plant-Like Protists - Euglena

• Similar to both plant and animal cells

• Can feed upon smaller cells

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Animal-Like Protists - Amoeba

• Changes its shape as it moves

• It moves by stretching out a branch of cytoplasm called a pseudopod

• Pseudopod is anchored to an object and the rest of the amoeba is dragged towards it

• Pseudopod is also used to eat

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Animal-Like Protists - Paramecia

• Cilia help move it

• Cilia beat to create a current that draws food into its mouth

• Eats bacteria and other small cells

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Fungi• multicellular or unicellular

• Examples include• Bread mould• Mushrooms• Puff balls

• Harmful effects• Cause ringworm• Dutch elm disease• Athlete’s foot

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Yeast• unicellular fungi• Must rely on other organism as a source of

food

2.3 – The Need For Cell

DivisionWhy The Split?

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Is Smaller Better?• The bigger a cell is, the longer messages take

to reach the nucleus, or for the rest of the cell to receive instructions

• Cells must be small for information to travel quickly

• See fig.1 p.49

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Is Smaller Better?• Small cells are needed so waste can be

removed quickly and nutrients received quickly

• Cells that do a lot of work are usually smaller so that the nutrients and wastes can enter or leave more quicker

2.4- Cell Specialization

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Cell SpecializationMulticellular organisms benefit from cell specializationCell Specialization – the development of cells to perform a specific function

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Specialized Plant CellsThin-walled plant cells are found in the flexible tissues of leaves, flowers etc..

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Specialized Plant CellsThick-walled plant cells are specialized for support

Thick cell walls are stretchable and flexible

E.g. celery stalk

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Specialized Plant CellsVery thick-walled cells provide rigid support

Cell usually dies because cell walls are too thick for nutrients to pass in and out of

E.g tree trunk

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Specialized Animal Cells – Nerve Tissue

Conduct electrical signals in the body

Tend to be long and thin

Coated by fatty material

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Respiratory CellsLung Cells are very thin- Why?

Some cells produce mucus

Mucus – a slippery substance that coats the cells lining the cavities open to the air

Mucus traps particles that enters the lungs

Cilia move the particles and mucus out

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Blood TissueRed Blood Cells White Blood Cells

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Stomach tissueCells are covered by mucus to protect them from the strong acid

Cells have many Golgi Apparatuses to produce and store the proteins that break down food

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Fat TissueMost of the cyctoplasm is occupied by vacuoles

Nutirents are converted to fat and stored in the cells

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Small IntestineAbsorb nutrients from food

Finger-like projections called villi – increase surface area for absorption

2.5 – Cell Wars

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Cell Wars – The InvadersDisease – any condition that is harmful or interfers with the well-being of an organism

Infection- the action of disease-producing organisms, which invade the body and interfer with the normal activities of the cellCan rob nutrients or produce waste products that are poisonous

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BacteriaTetanus, strep throat and pneumonia are examples

Spoil food and contaminate water

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FungiSeveral disease are caused by fungi eg. Athlete’s foot

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ProtistsPlasmodium- causes malaria

Giardia lamblia – causes beaver fever

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VirusesVirus – a small strand of genetic information covered by a protein coat; invade living cells and uses it to make more virusesViruses are not true cellsThey do not contain a nucleus, cytoplasm, organelles or a cell membrane

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VirusesCause colds

Cold sores

Influenze

AIDS

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The DefendersSome white blood cells ingest the invader directly where lysosomes will destroy them and the WBCPus – a creamy white substance made of strands of protein and cell fragments that remain after invaders have been attacked by white blood cellsWhite blood cells also kill cells that have been damaged the intruders

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AntibodiesAntibody – a large molecule produced by a special type of white blood cell; aids the immune systemInvading cells have Markers, on their cell membranes or protein coats.These markers have a specific shapeAntibodies are designed to fit the shape and lock onto them

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Antibodies