The cell is the smallest unit of life!

The Cell Theory 1. All living things are composed of one or more cells. 2. Cells are organisms’ basic units of structure & function. 3. Cells come only from existing cells.

Scientist who developed The Cell Theory Matthias Schleiden- concluded that plants were composed of cells. Theodor Schwann- concluded that animals were composed of cells. Rudolph Virchow- determined that cells only came from other cells.

Protocells One theory of the origins of cells states that the first life on earth consisted of several types of tiny protocells, cell- like organisms. These organisms were able to survive and reproduce in a very limited environment because of their simplicity. Over time, some of these protocells came together and shared their specialization in a symbiotic relationship. These colonies of protocells eventually became the cells we know today.

Discovery of Cells Robert Hooke – discovered the first cells, cells he observed were dead, in 1665 while looking at cork. Anton van Leeuwenhoek – first person to observe living cells in 1675.

Types of Cells Prokaryotes - cells with no nucleus or organelles with membranes. Bacteria and blue-green bacteria are prokaryotic cells. Eukaryotes - cells that contain a nucleus and organelles surrounded by a membrane. The cells of protozoa, algae, fungi, plants, and animals are eukaryotic cells.

Types of Organisms Unicellular = living organism that consist of only 1 cell. Multicellular = living organism consisting of more than 1 cell.

Cell Organelles (Plant & Animal Cell Organelles) Cell membrane A complex barrier of lipid molecules separating the cell from its external environment. These molecules can move apart to allow larger particles to move in or out of the cell. The "selectively permeable" cell membrane regulates what passes into & out of the cell. Some substances, like H2O, move freely through the cell membrane by a process known as osmosis. In osmosis, particles move easily from an area of high concentration to an area of low concentration by molecular motion only. Cells can push particles in the opposite direction, from low concentration to high, but it takes energy from the cell.

Cytoplasm A thick, aqueous solution of salts surrounding the organelles inside the cell membrane. Nutrients and minerals spread through the cytoplasm to all parts of the cell. The constant motion of this gel-like substance is called cytoplasmic streaming.

Nucleus The structure inside the cell that directs cell activities. Contains the DNA of a cell.

Ribosome The sites of protein synthesis in a cell. These small, spherical structures are the most numerous organelles in almost all cells. Some ribosomes produce protein to be used within the cell and some produce protein that is "exported" to other parts of an organism.

Endoplasmic Reticulum A membrane system of folded sacs and tunnels in the cytoplasm. Rough "ER" is covered with ribosomes. It is common in cells that export proteins and directs the proteins flow. Smooth "ER" as few or no ribosomes. It functions as a pathway for molecules to follow.

Golgi Apparatus A stack of membranes or sacs that acts to prepare substances for export from the cell. Once the Golgi apparatus has enclosed the final product in a vesicle, or pouch, the product is sent through the cell membrane.

Mitochondria Respiration centers of a cell. Large organelles scattered through most cells, they are most numerous in cells that use a lot of energy like liver and muscle cells.

Microtubules/Microfilaments Long, slender protein tubes are called microtubules; the fine protein threads are called microfilaments. These form the inner framework of a cell called the cytoskeleton.

(Animal Cell Organelles) Lysosome Digestive centers of a cell. They produce many different types of enzymes and digest things from food particles to a cell's own worn out parts. “garbage disposals of the cell”

Centrioles Pair of rod-shaped bodies composed of microtubules. Distribute chromosomes during cell division.

Cilia/Flagella Structures that extend from the surface of cell and aid in movement. Cilia are short, hair like extensions that occur in large #’s on the surface of some cells. Flagella are whip like, longer than cilia, that occur singulary or in pairs.

(Plant Cell Organelles) Cell wall On the outside of some cells, bacteria and plants, this structure functions for support and protection. There are pores in the cell wall allowing substances to come in contact with the cell membrane.

Types of cell walls: Primary cell wall - formed during cell growth, it is composed of parallel layers of cellulose and pectin. This structure allows the cell to expand as it grows. While it does provide support, it is not nearly as strong as the secondary cell wall. Secondary cell wall - formed after cell growth stops, it is composed of interwoven cellulose and lignin fibers. This structure is very strong, but does not give. It gives plants their "woody" characteristic.

Vacuole Most common in plant cells, they are storage sites within a cell. Some animal cells may have these but they are very small compared to the large vacuole in plant cells

Plastids Pigment producing organelle in cells. Chloroplast – Contain green pigment called chlorophyll that absorbs sunlight. Chromoplast – Synthesize and store pigments such as orange carotenes, yellow xanthophylls, & various red pigments, some of which trap sunlight for energy. Leucoplast – Store food such as starches, proteins, & lipids.

The End