The Cell • Techniques used to study cell structure and function. • A tour of the cell. • Introduction to the Biology of Cells. • Cell organelles.Inner life the Cell http://www.youtube.com/watch?v=GVqJdAqTD4Q&feature=relatedThe Fundamental Units of Life • All organisms are made of cells • The cell is the simplest collection of matter that can live • Cell structure is correlated to cellular function • All cells are related by their descent from earlier cellsCell Size • The logistics of carrying out cellular metabolism sets limits on the size of cells  The surface area to volume ratio of a cell is critical • As the surface area increases by a factor of n2, the volume increases by a factor of n3  Small cells have a greater surface area relative to volumeTo study cells, biologists use microscopes and the tools of biochemistry • Scientists use microscopes to visualize cells too small to see with the naked eye • In a light microscope (LM), visible light passes through a specimen and then through glass lenses, which magnify the image • The quality of an image depends on  Magnification, the ratio of an object’s image size to its real size  Resolution, the measure of the clarity of the image, or the minimum distance of two distinguishable points  Contrast, visible differences in parts of the sampleMicroscopy • LMs can magnify effectively to about 1,000 times the size of the actual specimen • Various techniques enhance contrast and enable cell components to be stained or labeled • Most subcellular structures, including organelles (membrane-enclosed compartments), are too small to be resolved by an LMElectron Microscopes • Two basic types of electron microscopes (EMs) are used to study subcellular structures  Scanning electron microscopes (SEMs) focus a beam of electrons onto the surface of a specimen, providing images that look 3-D  Transmission electron microscopes (TEMs) focus a beam of electrons through a specimen • TEMs are used mainly to study the internal structure of cellsCells • The basic structural and functional unit of every organism is one of two types of cells: prokaryotic or eukaryotic • Only organisms of the domains Bacteria and Archaea consist of prokaryotic cells • Protists, fungi, animals, and plants all consist of eukaryotic cells • Basic features of all cells:  Plasma membrane  Semifluid substance called cytosol  Chromosomes (carry genes)  Ribosomes (make proteins)Prokaryotic cells • Characterized by having:  No nucleus • DNA is in an unbound region called the nucleoid  No membrane-bound organelles  Cytoplasm bound by the plasma membraneEukaryotic cells • Characterized by having:  DNA in a nucleus that is bounded by a membranous nuclear envelope  Membrane-bound organelles  Cytoplasm in the region between the plasma membrane and nucleus • Eukaryotic cells are generally much larger than prokaryotic cellsPlasma membrane • A selective barrier that allows sufficient passage of oxygen, nutrients, and waste to service the volume of every cell • The general structure of a biological membrane is a double layer of phospholipidsThe endomembrane system regulates protein traffic and performs metabolic functions in the cell • The cell is compartmentalized.  Important for the physical separation of cell functions.  Allows different chemical environments to exist within the cell.  Two examples: • pH: allows enzymes to function efficiently. – Lysozymes • Ionic gradients: generation of ATP – mitochondria • Organelles are involved with five types of process: 1. Information storage, processing, and execution — nucleus 2. Protein, carbohydrate, and lipid biosynthesis — endomembrane system 3. Energy storage — lipid & polysaccharide granules (glycogen, starch) 4. Energy metabolism — chloroplast & mitochondrion 5. Structural and transport functions — cytoskeleton, plasma membraneTour of an Animal CellThe Eukaryotic CellThe Nucleus: Information Central • The nucleus contains most of the DNA in a eukaryotic cell  is usually the most conspicuous organelle • Ribosomes use the information from the DNA to make proteins • The nuclear envelope encloses the nucleus, separating it from the cytoplasm  The nuclear membrane is a double membrane; each membrane consists of a lipid bilayerThe Nucleus • Pores regulate the entry and exit of molecules from the nucleus • The shape of the nucleus is maintained by the nuclear lamina, which is composed of protein • In the nucleus, DNA and proteins form genetic material called chromatin  Chromatin condenses to form discrete chromosomes • The nucleolus is located within the nucleus and is the site of ribosomal RNA (rRNA) synthesisRibosomes: Protein Factories • Ribosomes are particles made of ribosomal RNA and protein • Ribosomes carry out protein synthesis in two locations:  In the cytosol (free ribosomes)  On the outside of the endoplasmic reticulum or the nuclear envelope (bound ribosomes)The Eukaryotic CellThe endomembrane system regulates protein traffic and performs metabolic functions in the cell • Components:  Nuclear envelope  Endoplasmic reticulum  Golgi apparatus  Lysosomes  Vacuoles  Plasma membrane • These components are either continuous or connected via transfer by vesicles • The endoplasmic reticulum (ER) accounts for more than half of the total membrane in many eukaryotic cells  The ER membrane is continuous with the nuclear envelope • There are two distinct regions of ER:  Smooth ER, which lacks ribosomes  Rough ER, with ribosomes studding its surfaceFunctions of Smooth and Rough ER • The smooth ER  Synthesizes lipids  Metabolizes carbohydrates  Detoxifies poisons  Stores calcium • The rough ER  Has bound ribosomes, which secrete glycoproteins (proteins covalently bonded to carbohydrates)  Distributes transport vesicles, proteins surrounded by membranes  Is a membrane factory for the cellThe Eukaryotic CellThe Golgi Apparatus: Shipping and Receiving Center • The Golgi apparatus consists of flattened membranous sacs called cisternae • Functions of the Golgi apparatus:  Modifies products of the ER  Manufactures certain macromolecules  Sorts and packages materials into transport vesicles3D-Golgi!Movement from ER to GolgiThe Eukaryotic CellLysosomes: Digestive Compartments •