History of the cell: The development and refinement of magnifying lenses and light microscopes made the observation and description of microscopic organisms and living cells possible.
* Leeuwenhoek – developed and improved simple microscopes; he saw small living things in a drop of pond water and called them “animalcules”.
* He studied cork with a microscope and described the small boxes he decided to call cells after rooms in monasteries. * He named the cell a “cell”.
* A German botanist who concluded that all plants are made of cells.
* A German zoologist who concluded that all animals are made of cells.
* All living things are made of cells. * The cell is the basic unit of structure and function in all living things. * All cells come from pre-existing cells. * MODERN CELL THEORY ADDS: * Energy flow occurs within cells. * Cells contain hereditary information that is passed from cell to cell during cell division. * All cells are basically the same in chemical composition in organisms of similar species.
* Continued advancements in microscopy allowed the observation of cell organelles and internal structure.
* Two types were developed in the mid 1900’s. * The scanning electron microscope (SEM) uses a beam of electrons to scan the surface of a cell.
* Prokaryotes are cells that do not contain a nucleus or other membrane-bound organelles. * They are much smaller that eukaryotes. * Bacteria are prokaryotes.
* Organelles are membrane-bound structures in a eukaryotic cell. * Each organelle has a specific function for cell survival.
All cells, prokaryotic and eukaryotic, have a plasma membrane. It is a phospholipid bilayer. It is selectively permeable as it regulates what goes in and out of the cell.
* The nucleus controls all cellular functions. * It contains chromatin which is made up of DNA and proteins. * DNA is the blueprint for all cellular activity.
The nucleolus is found in the nucleus. It produces ribosomes. It is the dark, dense regions of the nucleus.
* Ribosomes are where proteins are made. * Some are free in the cytoplasm and some are bound to the endoplasmic reticulum. * Ribosomes are NOT membrane-bound and are found in both eukaryotes and prokaryotes.
* The cytoplasm is all cellular contents outside the nucleus in eukaryotic cells.
* The ER is a series of membranous canals for the transport of materials. * They are the sites of chemical reactions. * Rough ER – ribosomes are attached that are producing proteins * Smooth ER – no ribosomes attached; involved in production and storage of lipids
* Also called the Golgi bodies or Golgi complex * It receives proteins from the ER. * It modifies, packages, and ships the proteins.
* Vacuoles are membrane-bound sacs for temporary storage.
* They are the cell’s recyclers. * Lysosomes contain digestive enzymes to digest worn out organelles, food particles, or viruses.
* These are the sites for photosynthesis. * They capture light energy and convert it to chemical energy. * The chemical energy is stored in food molecules.
* These are the sites for cellular respiration. * They are called the “powerhouse of the cell”. * They break down food molecules and release energy.
* This support structure in the cytoplasm is composed of microtubules and microfilaments.
* Centrioles are involved in cell division. They are found only in animal cells.
* These are short, numerous hair-like projections on the cell surface for locomotion or feeding.
* Flagella are longer projections on the cell surface that move with a whip-like motion. * They are primarily used for locomotion.
* The cell wall is an inflexible barrier that protects the cell and gives it support. * They are found in prokaryotes, fungi, plants, and in plant-like protists.
* Plant cells have a cell wall as well as a plasma membrane. * Animal cells only have a plasma membrane.
* Plant cells have chloroplasts and mitochondria. * Animal cells only have mitochondria.
* Plant cells have a large central vacuole for water storage. * Animal cells only have small, temporary vacuoles.
* Animal cells have centrioles. Plant cells do not.