Cell Theory and Structure Discovery of the Cell

Cell Theory and Structure

Discovery of the Cell • Scientists did not start using simple compound microscopes until the mid 1600’s. • Robert Hooke used an early compound microscope to look at slices of cork. http: //www. smithlifescience. com/cork 2. GIF • Hooke named the ‘seemingly empty’ chambers ‘cells. ’ • Around the same time, Anton von Leeuwenhoek was using a single-lens microscope to observe unicellular organisms in pond water for the first time.

Cell Theory • Additional observations of cells in other living things led scientists to 3 basic conclusions, known as the cell theory. • Cell Theory states: ▫ All living things are composed of cells. ▫ Cells are the basic units of structure and function in living things. ▫ New cells are produced from existing cells.

There are two categories of cells…… • Prokaryotes ▫ No nucleus ▫ Few organelles ▫ Small in size ▫ Ex: Bacteria n Eukaryotes – Nucleus – Many organelles – Large in size – Ex: Humans, plants, fungi, etc. http: //www. cod. edu/people/faculty/fancher/Eukaryotic. Cell. jpg http: //www. cod. edu/people/faculty/fancher/Prokaryotic. Cell. jpg

Cell Structure • All cells, both prokaryotes and eukaryotes, have DNA and a cell membrane. • Cells also contain organelles – specialized structures within the cell that perform certain tasks. • These organelles float around in the cell’s cytoplasm, which is mostly made of water.

Prokaryotes……. they’re simple. • Prokaryotes only have a few basic structures: ▫ ▫ DNA Cell/plasma membrane Cell wall Ribosomes ▫ Some use structures like pili, cilia, and flagellum to move in aquatic environments. http: //scienceblogs. com/clock/2006/11/cell_structure. php

…. but they come in many varieties. http: //images. google. com/imgres? imgurl=http: //www. harlem-school. com/10 TH/sci_pdf/graphics/prokaryotic_entities. gif&imgrefurl=http: //www. harlemschool. com/10 TH/sci_pdf/sci. html&h=396&w=284&sz=32&hl=en&start=12&tbnid=d. Qs. SJBBu 88 u. Fi. M: &tbnh=124&tbnw=89&prev=/images%3 Fq%3 Ddifferent%2 Bshaped, %2 Bprokaryotic%26 gbv%3 D 2%26 svnum%3 D 10%26 hl%3 Den%26 sa fe%3 Dactive

Eukaryotes are more complex. • Eukaryotes can be multicellular or unicellular. • Eukaryotes contain many organelles…….

Do you know your Organelles?

Cell (plasma) membrane • Regulates what materials enter and leave the cell.

Nucleus • Controls most cell processes and contains nearly all of the cell’s DNA

Ribosomes • assemble proteins. ▫ Some are free floating while others are attached to the endoplasmic reticulum.

Endoplasmic Reticulum (ER) • There are two types: ▫ Rough – chemically modifies proteins that are produced by the ribosomes on its surface. ▫ Smooth – contains specialized enzymes and makes lipid components for the cell membrane.

Golgi apparatus • Sorts, modifies, and/or packages proteins and other materials from the ER for storage or secretion from the cell.

Lysosomes and peroxisomes • Lysosomes contain enzymes that are specialized to digest lipids, carbs, proteins so their monomers can be reused • Peroxisomess contain enzymes that are specialized to digest toxic substances

Cytoskeleton http: //scienceblogs. com/clock/2006/11/cell_structure. php • A network of protein filaments (microtubules and microfilaments) that help the cell move and maintain its shape

Mitochondria • Provides the cell with usable chemical energy ▫ It is the site of cellular respiration.

How are they different? http: //staff. tuhsd. k 12. az. us/gfoster/standard/BCELL 1_files/image 005. jpg http: //scienceblogs. com/clock/2006/11/cell_structure. php

Plant cells have special features…. . • Plants contain: ▫ Chloroplasts – create and store usable energy through the process of photosynthesis. ▫ Cell wall – provides the cell with rigid structure. ▫ 1 Large vacuole – used for the storage of water and some other materials �Animal cells usually have many small vacuoles

Some organelles have their own DNA…. • Only two organelles have their own DNA – mitochondria and chloroplasts. • Endosymbiotic Theory – suggests that mitochondria and chloroplasts are the decendents of ancient prokaryotes that developed symbiotic relationships with ancient cells. http: //micro. magnet. fsu. edu/cells/chloroplasts/images/chloroplastsfigure 1. jpg http: //en. citizendium. org/images/c/c 7/Mitochondria. SMALL 2. jpg