CHAPTER 4, STRUCTURE AND FUNCTION OF THE CELL

1. CHAPTER 4, STRUCTURE AND FUNCTION OF THE CELL

2. SECTION 3-2, INTRODUCTION TO THE CELL Both Living and Nonliving Things are composed of molecules made from chemical elements such as carbon, hydrogen, oxygen, and nitrogen.  The organization of these molecules into Cells is one feature that distinguishes Living Things from all other matter.  The CELL is the smallest unit of matter that CAN Carry on ALL the PROCESSES OF LIFE.

4. CELL SIZE 1. A few types of cells are large enough to be seen by the unaided eye.  The Female Egg is the largest cell in the body, and can be seen without the aid of a microscope. 2. Most cells are visible only with a microscope. 3. MOST CELLS ARE SMALL FOR TWO REASONS:

5.     A.   Cells are limited in size by the RATIO between their Outer Surface Area and Their Volume.  A SMALL CELL HAS MORE SURFACE AREA THAN A LARGE CELL FOR A GIVEN VOLUME OF CYTOPLASM.  This is important because the nutrients, oxygen, and other materials a cell requires must enter through it surface.  As a cell grows larger at some point its surface area becomes too Small to allow these materials to enter the cell quickly enough to meet the cell's need.

6. B.  THE CELL'S NUCLEUS (THE BRAIN) CAN ONLY CONTROL A CERTAIN AMOUNT OF LIVING, ACTIVE CYTOPLASM.

7. CELL SHAPE

8. Cells contain a variety of Internal Structures called ORGANELLES. • 2. An organelle is a Cell Component that PERFORMS SPECIFIC FUNCTIONS FOR THE CELL. • 3. Just as the organs of a multicellular organism carry out the organism's life functions, the Organelles of a cell Maintain the Life of the Cell.

9. 4.  There are many different cells; however, there are certain features common to all, or most Cells. 5. The entire cell is Surrounded by A THIN MEMBRANE, called the CELL MEMBRANE. 6. Inside the Cell are a Variety of Organelles, most of which are surrounded by their own Membrane.

10.  THE ACTIVITIES OF THE CELL. The center of the Cell . A Large Organelle near the center is the NUCLEUS.  IT CONTAINS THE CELL'S GENETIC INFORMATION AND CONTROLS the activities of the cell.

11. 8. The PRESENCE OR ABSENCE of a NUCLEUS is important for Classifying Cells. 9. ORGANISMS WHOSE CELL CONTAIN A NUCLEUS AND OTHER MEMBRANE-BOUND ORGANELLES ARE CALLED EUKARYOTES.

12. 10.   ORGANISMS WHOSE CELLS NEVER CONTAIN (OR LACK) A NUCLEUS AND OTHER MEMBRANE-BOUND ORGANELLES ARE CALLED PROKARYOTES.

13. 11.  UNICELLULAR ORGANISMS such as bacteria and their relatives are Prokaryotes. 12.   All other organisms are Eukaryotes; plants, fish, mammals, insects and humans. 13.   The difference between Prokaryotes and Eukaryotes is such an important distinction that Prokaryotes are placed in Two Kingdoms, Separate from Eukaryotes.

15. PARTS OF THE EUKARYOTIC CELL THE CELL MEMBRANE 1. A Cell cannot survive if it is totally isolated from its environment. The Cell Membrane is a complex barrier separating the cell from it's external environment. 2. This "Selectively Permeable" Membrane regulates what passes into and out of the cell.

17. 3. All cells, from all organisms, are surrounded by a CELL MEMBRANE. 4. The Cell Membrane is a thin layer of Lipid and Protein that separates the cell's content from the world around it. 5. The Cell Membrane Functions like a GATE, Controlling what ENTERS and LEAVES the Cell. 6.  The Cell Membrane CONTROLS the ease with which substances pass into and out of the cell-some substances easily cross the membrane, while others cannot cross at all.  For this reason, the Cell Membrane is said to be SELECTIVELY PERMEABLE.

18. 7. Cell Membranes are made mostly of PHOSPHOLIPID MOLECULES

19. MEMBRANE PROTEINS There are many kinds of Proteins in membranes; they HELP to MOVE Material INTO and OUT of the Cell.

20. CYTOPLASM (SIET-oh-PLAZ-uhm)                            1.  EVERYTHING BETWEEN THE CELL MEMBRANE AND THE NUCLEUS IS THE CELL'S CYTOPLASM. 2.  CYTOPLASM consists of TWO MAIN COMPONENTS:  CYTOSOL and ORGANELLES. 3.  CYTOSOL is a jellylike mixture that consists MOSTLY OF WATER, along with PROTEINS, CARBOHYDRATES, SALTS, MINERALS and ORGANIC MOLECULES.

21. MITOCHONDRIA (MET-oh-KAHN-dree-uh)                 1. Mitochondria are found scattered throughout the Cytosol, and are relatively Large Organelles. 2. Mitochondria are the sites of Chemical Reactions that transfer Energy from Organic Compounds to ATP.  Energy contain in food is released. Converted to ATP.  ATP is the molecule that most Cells use as their main Energy Currency ORGANELLES THE "POWERHOUSE" OF THE CELL.

22. RIBOSOMES (RIE-buh-SOHMZ) 1. Unlike most other organelles, Ribosomes Are Not Surrounded by a membrane. 2. Ribosomes are the site of PROTEIN SYNTHESIS (Production or Construction) in a cell. 3. They are Most Numerous Organelles in almost all cells. 4. Some are free in the Cytoplasm; others line the membranes of ROUGH ENDOPLASMIC RETICULUM.

23. ENDOPLASMIC RETICULUM (ER) (EN-doh-PLAZ-mik  ri-TIK-yuh-luhm)            1. The ER is a system of membranous tubules and sacs. 2. The ER functions Primarily as an Intracellular Highway, a path along which molecules move from one part of the cell to another.

24. Can be ROUGH OR SMOOTH.     A. ROUGH ER is studded with RIBOSOMES and processes PROTEINS to be exported from the cell.     B. SMOOTH ERIS NOT Covered with RIBOSOMES and processes LIPIDS and CARBOHYDRATES. The Smooth ER is involved in the synthesis of steroids in gland cells, the regulation of calcium levels in muscle cells, and the breakdown of toxic substances by liver cells.

25. GOLGI APPARATUS  (GOHL-jee) 1. The Golgi Apparatus is the Processing, Packaging and Secreting Organelle of the Cell. 2. The Golgi Apparatus is a system of membranes. Made of Flattened SAC like Structures called CISTERNAE. 3. It works Closely with the ER, the Golgi Apparatus modifies proteins for export by the cell.

26. LYSOSOMES (LIE-suh-sohmez) 1. Lysosomes are small spherical organelles that enclose hydrolytic enzymes within a single membrane. 2. Lysosomes are the Site of Food Digestion in the Cell. 3.  Lysosomes are formed from pieces of the GOLGI APPARATUS that break off. 4. Lysosomes are common in the Cells of Animals, Fungi, and Protists, But Rare in Plant Cells.

27. THE NUCLEUS 1. The Nucleus is often the most Prominent Structure within a Eukaryotic Cell. 2. It maintains its shape with the help of a Protein skeleton known as the NUCLEAR MATRIX. 3. The Nucleus is the CONTROL CENTER (BRAIN) of the Cell. 4. Most Cells have a Single Nucleus some cells have more than one. 5. The nucleus is surrounded by a Double Layer Membrane called the NUCLEAR ENVELOPE.

28. PLANT CELLS 1. Most of the Organelles and other parts of the cell are common in ALL Eukaryotic Cells.  Cell from different organisms have even greater difference in structure. 2. Plant Cells have Three Additional Structures Not found in animals cells - CELL WALLS, VACUOLES, AND PLASTIDS that are extremely important to Plant Function. 3. In addition to their unique structures, Plant Cells have: MITOCHONDRIA, RIBOSOMES, AND the other organelles.

29. CELL WALL 1.  One of the most important differences between Plant and Animal CELLS is the Presence of a CELL WALL IN PLANT CELLS. 2. Fungi such as Mushrooms and Yeast also have Cell Walls.  Cell Walls of Fungi are made of CHITIN. 3.  A Cell Wall DOES NOT REPLACE the Cell Membrane; Cells with WALLS also have a CELL MEMBRANE.  Plant Cells are covered by a Rigid Cell Wall that lies Outside the Cell Membrane. 4. The Rigidity of Cell Walls Helps SUPPORT and PROTECT the Plant.

30. VACUOLES 1. The SECOND prominent structure in Plant Cells is the large VACUOLE. 2.  The VACUOLE is a large membrane-bound sac that takes up a large amount of space in most Plant Cells. 3. The VACUOLE serves as a STORAGE AREA, and may contain stored PROTEINS, IONS, WASTE, OR OTHER CELL PRODUCTS. 4. VACUOLES of some plants contain Poison that discourages animals from eating the plant's leaves. 5. Cells of Animals and other organisms also MAY contain VACUOLES, but they are much smaller and are usually involved in FOOD DIGESTION.

31. PLASTIDS 1.   A THIRD distinguishing feature of PLANT CELLS is the presence of STRUCTURES CALLED PLASTIDSTHAT MAKE OR STORE FOOD. 2.  A common kind of PLASTID is the CHLOROPLAST, (figure 4-17) an organelle that converts SUNLIGHT, CARBON DIOXIDE, AND WATER INTO SUGARS.  This process is called PHOTOSYNTHESIS.