The Cell The basic unit of life

The Cell Theory All living things are composed of cells. Cells are the basic unit of life. All cells come from preexisting cells.

The Discovery of Cells Van Leeuwenhoek & his microscope The invention of the microscope led to the first observations of cells. Anton Van Leeuwenhoek (1632-1723) is considered the “father of microscopy. Robert Hooke (1635-1703) observed cork under a microscope. The tiny chambers which made up the cork reminded him of the rooms in a monastery. These rooms were called cells.

Robert Hooke and his Cork

Methods of Studying Cells Light Microscopes: use multiple lenses and light for illumination. The highest magnification at best resolution is about 1000X which will get you to about 1µ. This gets a rough look at the larger cell organelles.

Methods of Studying Cells 2. Electron Microscopes Uses a beam of electrons which has a much smaller wavelength, therefore much greater resolution. .

Methods of Studying Cells A. Transmission EM (TEM): electron beam goes through specimen using electromagnets to focus. Image appears on a fluorescent screen and is photographed. Can resolved to a nanometer (10-9 m) or about 1,000,000X

TEM of Chromosome

Methods of Studying Cells B. Scanning EM (SEM) Scans the surface of an object which has been covered with a thin layer of gold. Produces three dimensional images. Less magnification but excellent surface resolution.

SEM image of X and Y chromosomes

Cytology: study of cells Light microscopy •resolving power~ measure of clarity Electron microscopy •TEM~ electron beam to study cell ultrastructure •SEM~ electron beam to study cell surfaces

Human Cells

Four major Cell Types 1. Epithelial 2. Muscle 3. Connective 4. Nerve

1. Epithelial Cells FUNCTION: Movement materials in, out, or around the body. Protection of the internal environment against the external environment. Secretion of a product. Epithelial covers body surfaces and lines body cavities. Functions include lining, protecting, and forming glands. Three types of epithelium occur: 1. Squamous epithelium is flattened cells. 2. Cuboidal epithelium is cube-shaped cells. 3. Columnar epithelium consists of elongated cells. Any epithelium can be simple or stratified. Simple epithelium has only a single cell layer. Stratified epithelium has more than one layer of cells. Pseudostratified epithelium is a single layer of cells so shaped that they appear at first glance to form two layers. Functions of epithelial cells include: movement materials in, out, or around the body. protection of the internal environment against the external environment. Secretion of a product. Glands can be single epithelial cells, such as the goblet cells that line the intestine. Multicellular glands include the endocrine glands. Many animals have their skin composed of epithelium. Vertebrates have keratin in their skin cells to reduce water loss. Many other animals secrete mucus or other materials from their skin, such as earthworms do. Cuboidal epithelial lining of intestine

2. MUSCLE CELL – 3 types Facilitates movement by contraction of individual muscle cells SKELETAL MUSCLE CELLS facilitates movement of the animal by contraction of individual muscle cells (referred to as muscle fibers). Three types of muscle fibers occur in animals (the only taxonomic kingdom to have muscle cells): skeletal (striated) smooth cardiac SMOOTH CARDIAC

3. Connective Cells Connective tissue serves many purposes in the body: binding supporting protecting forming blood storing fats filling space Connective cells are separated from one another by a non-cellular matrix. The matrix may be solid (as in bone), soft (as in loose connective tissue), or liquid (as in blood). Two types of connective tissue are Loose Connective Tissue (LCT) and Fibrous Connective LCT occurs beneath epithelium in skin and many internal organs, such as lungs, arteries and the urinary bladder. This tissue type also forms a protective layer over muscle, nerves, and blood vessels. Fibrous Connective Tissue has many fibers of collagen closely packed together. FCT occurs in tendons, which connect muscle to bone. Ligaments are also composed of FCT and connect bone to bone at a joint.

Connective tissue: Blood Cells (Red, Platelet and White)

Macrophage killing bacteria

Connective - Bone Bone has calcium salts in the matrix, giving it greater rigidity and strength Bone also serves as a reservoir for calcium Bone, shown in Figure 8, has calcium salts in the matrix, giving it greater rigidity and strength. Bone also serves as a reservoir (or sink) for calcium. Protein fibers provide elasticity while minerals provide elasticity. Two types of bone occur. Dense bone has osteocytes (bone cells) located in lacunae connected by canaliculi. Lacunae are commonly referred to as Haversian canals. Spongy bone occurs at the ends of bones and has bony bars and plates separated by irregular spaces. The solid portions of spongy bone pick up stress.

Connective Sperm and Egg

4. Nerve Cell Functions in the integration of a stimulus and response Nervous tissue, functions in the integration of stimulus and control of response to that stimulus

Sizes of living things

As cell size increases, the surface area to volume ratio decreases Rates of chemical exchange may then be inadequate for cell size Cell size, therefore, remains small

Animal cell anatomy

The Cell Membrane “The gatekeeper of the cell” A thin, outer covering of the cell. Controls what goes in and out of cell.

Microtubules in blue, actin in green, intermediate filaments in red