Cells: A Detailed Overview - PDF

# Cells ## Today, we'll answer these questions: - What is a cell? - How was it discovered? - What are the postulates of Cell Theory? - What are the structure and function of major and subcellular organelles? ## What is a Cell? Cells are the basic building blocks of all living things. The human bo...

# Cells ## Today, we'll answer these questions: - What is a cell? - How was it discovered? - What are the postulates of Cell Theory? - What are the structure and function of major and subcellular organelles? ## What is a Cell? Cells are the basic building blocks of all living things. The human body is composed of trillions of cells. They provide structure for the body, take in nutrients from food, convert those nutrients into energy, and carry out specialized functions. Cells also contain the body's hereditary material and can make copies of themselves. ## The Cell's Size - The smallest cell is the **Mycoplasma gallicepticum**, a disease-causing bacteria in birds. It can be as small as **0.3 nanometers**. - The largest cell is the **ostrich egg**, which can reach up to 6 inches in diameter. ## What is a Cell? (continued) Cells have many parts, each with a different function. Some of these parts, called **organelles**, are specialized structures that perform certain tasks within the cell. In this lesson, we are going to explain the postulates of the cell theory. The three postulates of the cell theory offer the basis on how an organism is considered as a living thing. ## Thinking Break: Here are some examples of cells. What do they remind you of? Where do you think we can find them? - Bacteria - Red blood cells - Nerve cell - Columnar epithelial cells - Skeletal Muscle cell - Fat cell - Smooth Muscle cell - Skin cells - Algae ## Discovery of Cells Cells were first recorded by Robert Hooke around 1665. He was improving the design of a microscope when he decided to observe a piece of cork. Up close, he saw box-like structures. These are what we now know as cell walls. ## Anton van Leeuwenhoek and the Microscope The microscopes we use today are far more complex than those used in the 1600s by Antony van Leeuwenhoek, a Dutch shopkeeper who had great skill in crafting lenses. He observed the movements of protista (a type of single-celled organism) and sperm, which he collectively termed "animalcules". Until 1675, He published his observations on tiny living organisms which he named animalcules. ## Robert Brown and the Nucleus One of the leading botanists in his time, Robert Brown in 1831 was able to compare diverse kinds of plant specimens under the microscope. He markedly indicated that there is a common thing about them - they are all composed of cells, and inside the cell is a dark dense spot which he termed as the nucleus. ## Matthias Schleiden and Theodor Schwann - A few years later, German botanist Matthias Schleiden (1838) concluded that all plant parts are made of cells. - Theodor Schwann (1839), also a botanist and a close friend of Schleiden, stated that all animal tissues are composed of cells, too. ## Rudolf Virchow and the Cell Theory In 1858, Rudolf Virchow concluded that all cells come from pre-existing cells. ## The Cell Theory Their discoveries led to the development of **The Cell Theory**. The discoveries made by Hooke, Leeuwenhoek, Schleiden, Schwann, Virchow, and others led to the formulation of the cell theory. The cell theory describes the properties of all cells. ## The 3 Postulates of Cell Theory 1. **All living things are composed of one or more cells.** A living organism can be made of just one cell (like an amoeba) or trillions (like the human body!). 2. **The cell is the basic unit of life.** To be considered a life form, something needs to have at least one cell. 3. **All cells arise from pre-existing cells.** A cell cannot exist spontaneously nor come out of a nonliving thing. ## Activity: Create A Timeline Directions: Create a timeline of the discoveries made by the various scientists who contributed to the development of the cell theory. ## Organelles Each cell contains materials that carry out basic life processes. Cell structures can only be observed under high magnification electron microscope and are separated internally into numerous membranous compartments called **organelles** (little organs). These organelles perform a variety of functions like production of proteins, storage of important materials, harvesting energy, repairing cell parts, digestion of substances, and maintaining the shape and structure of the cell. In this lesson, you will describe the structure and function of major subcellular organelles. ## Organelles: Cell Membrane - **Separates cell from external environment;** - **controls passage of organic molecules, ions, water, oxygen and wastes into and out of the cell.** ## Organelles: Cytoplasm - **Provides structure to cell;** - **site of many metabolic reactions;** - **medium in which organelles are found** ## Organelles: Nucleolus - **Location of DNA** ## Organelles: Nucleus - **Cell organelle that houses DNA and directs synthesis of ribosomes and proteins** ## Organelles: Ribosomes - **Protein synthesis** ## Organelles: Mitochondria - **ATP production or cellular respiration** ## Organelles: Peroxisomes - **Oxidizes and breaks down fatty acids and amino acids and detoxifies poisons** ## Organelles: Vesicles and Vacuoles - **Storage and transport; digestive function in plant cells** ## Organelles: Centrosome - **Organizing center of microtubules in animal cells** ## Organelles: Lysosomes - **Digestion of macromolecules; recycling or worn out organelles** ## Organelles: Cell Wall - **Protection, structural support and maintenance of cell shape** ## Organelles: Chloroplast - **Photosynthesis** ## Organelles: Endoplasmic Reticulum - **Modifies proteins and synthesizes lipids** ## Organelles: Golgi Apparatus - **Modifies, sorts, tags, packages and distributes lipids and proteins** ## Organelles: Flagella - **Cellular Locomotion** - **Examples: bacteria & sperm cell** ## Organelles: Cilia - **Cellular Locomotion** - **Movement of particles along extracellular surface of plasma membrane, and filtration** - **Examples: paramecium**