HOMEOSTASIS

Understanding Homeostasis at the Cellular Level CELL THEORY AND STRUCTURE

Cell Theory All living things are made of cells Cells are the basic unit of structure and function in an organism (basic unit of life) Cells come from the reproduction of existing cells (cell division)

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

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

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

Number of Cells Unicellular – composed of one cell Ex: bacteria, yeast Multicellular - composed of many cells that may organize Ex: butterfly, flower

Prokaryotes 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

Two Main Types of Eukaryotic Cells Plant Cell Animal Cell

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

Lysosome Contain digestive enzymes Break down food and worn out cell parts

Nucleolus Inside nucleus Produces the ribosomes that make proteins

Smooth & Rough Endoplasmic Reticulum Smooth ER - lacks ribosomes & detoxifies poisons and synthesizes lipids Rough ER - has ribosomes on its surface & makes proteins to EXPORT

Mitochondria Site of Cellular respiration – the capturing of energy from food Breaks down glucose to produce energy ATP

Plant Cell Organelles Chloroplast Process called photosynthesis occurs here

Plant Cell Cell wall Made of cellulose Found in plant cells

Plant Cell Organelles Vacuole Have a large central vacuole

Animal Cell Organelles Glycogen is stored in the cytoplasm of animal cells for food energy glycogen granule

Animal Cell Organelles Near the nucleus in an animal cell Help cell divide

What are the basic parts of all eukaryotic cells? Have a cell membrane surrounding the cytoplasm Have membrane-bound organelles Have a nucleus

Differences between plant cells and animal cells Relatively small in size Relatively large in size Irregular shape Regular shape No cell wall Cell wall present

Differences between Plant Cells and Animal Cells Vacuole small or absent Large central vacuole Glycogen as food storage Starch as food storage Nucleus at the center Nucleus near cell wall