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Chapter 6 The Cell 6.1 All organisms are made of cells. Cell theory- The generalization that all living things are composed of cells, and the cells are the basic unit of structure and function in living things. Micrograph- the photograph of the view through a microscope. Organelle- “mini-organ” each part of a cell with a specific job. Similarities between plant and animal cells. Plasma membranes- thin outer covering, which defines the boundary the cell and regulates the traffic of chemicals between the cell and its surroundings. Nucleus- houses the cells genetic material in the form of DNA. Cytoplasm- the entire region of the cell between the nucleus and the plasma membrane. Differences between plant and animal cells. Presence of chloroplasts- the organelle in which photosynthesis occurs. Photosynthesis converts light energy to chemical energy stored in molecules of sugar and other organic compounds. Cell wall- an encasing outside of a the plasma membrane that protects The plant cell and maintains it shape. There are two types of cells. Prokaryotic cells- (bacteria) cells with no nucleus Eukaryotic cells- cells with a nucleus and internal organelles bounded by membranes. 6.2 Membranes organize cells activities Membranes -Membranes isolate teams of enzymes within a cell’s compartments. -Regulate the transport of substances across the boundary - maintain a specific chemical environment within each cell compartment. Membranes are usually made up of proteins and a type of lipid called a phospholipids. Phospholipid molecule- a phospholipid molecule is made up of a two fatty acid tail that is hydrophobic and a head that is hydrophilic. Phospholipid bilayer- is produced when two layers of phospholipids molecules sandwich each other and create a larger membrane. See fig 6-8 pg 116. Functions of membrane proteins - Help cells within a multi-cellular organism communicate and recognize each other. - Move water and sugars across the membrane - Regulate the amount of each substance that travels across the membrane. 6.3 Membranes regulate the traffic of molecules Diffusion Diffusion- is the net movement of particles of a substance from where they are more concentrated to where they ate less concentrated. Equilibrium- when the number of molecules moving across a membrane are equal to the number of molecules moving in the opposite direction. Passive Transport (Fig 6-12) Selectively permeable membrane- a cellular membrane that allows some substances to cross the membrane more easily than others and blocks the passage of some substances all together. Passive transport- diffusion across a membrane when no energy is required by the cell. The cell is not actively involved in the transport. Facilitated transport- When transport proteins provide a pathway for certain molecules to pass. Osmosis (fig 6-13,6-14) Osmosis- the passive transport of water across a selectively permeable membrane. Hypertonic- the solution with a higher concentration of solute. Hypotonic- the solution with the lower concentration of solute. Isotonic- Solutions in which the concentrations of solute are equal. Active transport Active transport- when a cell expends energy to move molecules or ions across a membrane. - During active transport, a specific transport protein PUMPS a solute across a membrane, usually in the opposite way that it travels during diffusion. - Active transport plays a large part in maintaining a cells chemical environment. Transport of large molecules Vesicles- small membrane sacs that specialize in moving products into, out of, and within a cell Exocytosis- a process the removes contents from the inside of a cell by fusing a vesicle containing exporting proteins with the plasma membrane and releasing the product outside of the cell. Endocytosis- takes material into the cell within vesicles that bud inward from the plasma membrane and spill its contents into the cell. 6.4 The cell builds a diversity of products Structure and Function of the Nucleus -The nucleus of a cell contains most of the cells DNA (genetic material). -The nucleus is responsible for directing all of the cells activities. Nuclear Envelope- a pair of membranes that surrounds the nucleus and only allows substances to move into a cells cytoplasm. Nucleolus- a ball like mass of fibers and granules that make up organelles called ribosomes. Ribosomes Ribosomes- The DNA in the nucleus contains instruction for making proteins. These proteins are constructed in a cell by the ribosomes. -Ribosomes work as protein assembly line for membranes and transport proteins. -Ribosomes themselves are a cluster of proteins and nucleic acid. The Endoplasmic Reticulum Endoplasmic reticulum (ER)- an extensive network of membranes within the cytoplasm of a cell that is arranged as tubes and sacs that separate the inside of the ER from the cytoplasm -The ER is the main manufacturing and transportation facility in a cell. It produces many of the cells molecules needed for survival. Rough ER- The rough ER gets its name from the bound ribosomes that dot the outside of the ER membrane. -These ribosomes produce proteins that are packaged in vesicles. Smooth ER- This part of the ER lacks the ribosomes that cover the rough ER. - The function of the smooth ER is to build lipid molecules. Golgi Apparatus Golgi apparatus- many products that are made in the ER travel in vesicles to the golgi apparatus, an organelle that modifies, and routes proteins and other chemical products to their next destination. -The golgi apparatus looks like a series of flattened sacs Vacuoles Vacuoles- Large membrane sacs within the cytoplasm of a cell that store undigested nutrients. Many plant cells have a large central vacuole that stores chemicals essential for plant growth. Lysosomes Lysosomes- membrane bound sacs that contain digestive enzymes used to break down proteins, nucleic acid, and polysaccharides. -There function is to nourish the cell and destroy harmful bacteria within the cell. 6.5 Chloroplasts and the Mitochondria Energize Cells Chloroplasts Chloroplasts- photosynthetic organelles found in some cells of plants and algae. - These organelles allow cells to convert light energy to the chemical energy stored in sugars and other organic compounds. - Chloroplasts are like miniature solar collectors. - These organelles are green colored due to the presence of a pigment called chlorophyll that reacts with light. Mitochondria Mitochondria- organelles that are responsible for cellular respiration (releasing the energy required to drive a cell) in eukaryotic cells. Mitochondria use cellular respiration to produce ATP. ATP- (Adenosine triphosphate) The main energy source that cells use for most of their work. Within the mitochondria an envelope of two membranes has many folds. The more folds there are in the membrane, the more surface area, which means more sites for cellular respiration thus maximizing the cells production of ATP 6.5 An internal skeleton supports the cell and enables movement Cytoskeleton Cytoskeleton (cell skeleton)- a network of flexible fibers that float within a cell’s cytoplasm. Microtubules- Straight hollow tubes that give rigidity, shape, and organization to a cell. Microfilaments- Thin solid rods of protein that enable a cell to move or change shape when protein subunits slid past one another. Flagella and Cilia Many cells rely on external organelles to move and change shape. Flagella- are long, thin, whip-like structures, with a core of microtubules that enable a cell to move. Cilia- are smaller than flagella, but also contain bundles of microtubules, however Cilia only lend to move in 2 directions. Like the ores of a boat.