HOMEOSTASIS

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Understanding Homeostasis at the Cellular LevelCELL THEORY AND STRUCTURE

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Cell Theory1. All living things are made of cells2. Cells are the basic unit of structure and

function in an organism (basic unit of life)3. Cells come from the reproduction of

existing cells (cell division)

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History of Cells & the Cell Theory

In 1665, Robert Hooke used a microscope to examine a thin slice of cork (dead plant cell walls)

What he saw looked like small boxes Hooke is responsible for naming cells In 1673, Leeuwenhoek was first to view

living organisms Leeuwenhoek used a simple, handheld

microscope to view pond water & scrapings from his teeth

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SCHLEIDEN, SCHWANN &

VIRCHOW In 1838, a German botanist named Matthias Schleiden concluded that all plants were made of cells

In 1839, a German zoologist named Theodore Schwann concluded that all animals were made of cells

In 1855, a German medical doctor named Rudolph Virchow observed, under the microscope, cells dividing

He reasoned that all cells come from other pre-existing cells by cell division

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Remember Endosymbiotic Theory

In 1970, American biologist, Lynn Margulis, provided evidence that some organelles within cells were at one time free living cells themselves – this is called Endosymbiotic Theory

Chloroplasts and mitochondria were the organelles she pointed to as evidence of this theory

Chloroplast and Mitochondria have their own DNA which is different from the DNA of the cell 6

Number of Cells

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• Unicellular – composed of one cell

Ex: bacteria, yeast

• Multicellular - composed of many cells that may organize

Ex: butterfly, flower

Prokaryotes

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• Have a nucleoid region contains the DNA (no nucleus)

• Have a cell membrane & cell wall

• Contain ribosomes to make proteins in their cytoplasm

Eukaryotic Cell

Contain 3 basic cell structures:

Nucleus (containing DNA)

Cell Membrane Cytoplasm with

organelles

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Two Main Types of Eukaryotic Cells

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Plant Cell Animal Cell

Organelles

Called the “organs” of cells Very small in size Have specific functions Found in cytoplasm of cell

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Lysosome Contain digestive

enzymes Break down food

and worn out cell parts

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Nucleolus

Inside nucleus

Produces the ribosomes that make proteins

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Smooth & Rough Endoplasmic Reticulum

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• Smooth ER - lacks ribosomes & detoxifies poisons and synthesizes lipids

• Rough ER - has ribosomes on its surface & makes proteins to EXPORT

Mitochondria

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• Site of Cellular respiration – the capturing of energy from food

• Breaks down glucose to produce energy ATP

Plant Cell Organelles

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• Process called photosynthesis occurs here

Chloroplas

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Plant Cell

• Made of cellulose• Found in plant cells

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Cell wall

Plant Cell Organelles

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Have a large central vacuole

Vacuole

Animal Cell Organelles

19glycogen granule

• Glycogen is stored in the cytoplasm of animal cells for food energy

Animal Cell Organelles

Near the nucleus in an animal cell

Help cell divide20

What are the basic parts of all eukaryotic cells?

Have a cell membrane surrounding the cytoplasm

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Have membrane-bound organelles

Have a nucleus

Differences between plant cells and animal cells

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Animal cells Plant cells

Relatively small in size

Irregular shapeNo cell wall

Relatively large in size

Regular shapeCell wall present

Differences between Plant Cells and Animal Cells

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Animal cells Plant cellsVacuole small or

absentGlycogen as food

storageNucleus at the

center

Large central vacuole

Starch as food storage

Nucleus near cell wall