Cell Structure PDF

Topic 3: Cellular Basis of Life Topic 3: Cellular Basis of Life (Corresponding Textbook Material: Chapter 4) Objectives: Introduction to the basic characteristics and types of c...

Topic 3: Cellular Basis of Life Topic 3: Cellular Basis of Life (Corresponding Textbook Material: Chapter 4) Objectives: Introduction to the basic characteristics and types of cells (I) Define and describe the basic tenants of cell theory List the basic characteristics of all cells Compare and contrast the basic structural differences between prokaryotic and eukaryotic cells Provide examples of organisms that are composed of prokaryotic and eukaryotic cells Structures of the cell surface (II.A.) Identify and describe the basic structure and function of each of the following: − Plasma membrane − The four major types of cell − Cell wall junctions − Cilia and Flagella Structures of the nucleus (II.B) Identify and describe the basic structure and function of the following: − Nuclear membrane − Molecular structure for transcribing − Chromosomes/chromatin genetic information − Nucleolus Structures of the Cytoplasm, Part 1 (II.C.1. through II.C.6.) Identify and describe the basic structure and function of the following: − Cytosol − Endoplasmic reticulum (rough ER, − Cytoplasm smooth ER, Golgi apparatus) − Ribosomes − Vesicles The Creation of Proteins Describe the overall process of creating and transporting functional proteins, beginning with transcription in the nucleus. Structures of the Cytoplasm, Part 2 (II.C.7. through II.C.12) Identify and describe the basic structure and function of the following: − Vacuoles − Chloroplasts − Lysosomes − Cytoskeleton (microtubules, − Peroxisomes microfilaments, and intermediate − Mitochondria filaments  Topic 3: Cellular Basis of Life I) Introduction to cells A) According to Cell Theory, cell is the fundamental structural and functional unit of life. 1) The activity of an organism depends on the individual and collective activity of its cells. 2) The activity of the cell is dictated by subcellular structures. 3) The continuity of life has a cellular basis (i.e. all cells originate from other cells). B) The number of cells in an organism can vary from 1 to millions depending on the size of the organism. C) Cells can be thought of in somewhat the same way we think of a manufacturing plant. D) Basic characteristics of all cells 1) Plasma membrane 2) Semifluid substance called cytosol 3) Chromosomes (carry genetic information) 4) Ribosomes (make proteins)  Topic 3: Cellular Basis of Life E) Types of Cells 1) Prokaryotic Cells a) Characteristics i) No nucleus—DNA in an unbound region called the nucleoid ii) No membrane-bound organelles iii) Cytoplasm bound by the plasma membrane b) Examples i) Bacteria ii) Archaea 2) Eukaryotic Cells a) Characteristics i) DNA in a nucleus that is bounded by a membranous nuclear envelope ii) Membrane-bound organelles iii) Cytoplasm in the region between the plasma membrane and nucleus iv) Eukaryotic cells are generally much larger than prokaryotic cells b) Examples i) Animal cells ii) Plant cells iii) Fungal cells  Topic 3: Cellular Basis of Life Animal Cell Plant Cell  Topic 3: Cellular Basis of Life II) Structures of the Eukaryotic cell A) Structures of the cell surface 1) Plasma membrane a) Structure: i) Phospholipid bilayer ii) Transport and receptor proteins iii) Cholesterol (a steroid) iv) Glycolipids (lipids with attached carbohydrates) b) Function: i) Separates intracellular fluids from extracellular fluids ii) Control what enters and leaves the cell iii) Communication 2) Cell wall (in plants and fungi) a) Structure: i) Carbohydrate fibers in a carbohydrate or protein matrix. ii) Not a membrane. b) Function: Protection, Structural support 3) Cilia and Flagella (mostly in animals) a) Structure: i) Extension of the plasma membrane containing a complex of proteins (i.e. microtubules) that support and move the structure. ii) Structural differences result in very different movement patterns between flagella and cilia. iii) Generally only one or two flagella per cell, whereas there may be many cilia per cell. b) Function: Move the cell through fluid (cilia and flagella) or move fluid past the cell (cilia) 4) Cell Junctions a) Tight junctions (in animal cells)—Form an impermeable connection between adjacent cells so that extracellular fluids cannot pass between the adjacent cells b) Desmosomes (in animal cells)—Act like rivets that form mechanically strong connections between adjacent cells  Topic 3: Cellular Basis of Life c) Gap junctions (in animal cells)—Channels that connect the cytoplasms of adjacent cells and allow for communication and exchange of ions, sugars, amino acids, and other small molecules. d) Plasmodesmata (in plant cells)—Channels that connect the cytoplasm of adjacent cells (functions much like a gap junction in animal cells) B) Structures of the Nucleus 1) Nuclear envelop—Double-layered membrane surrounding the nucleus 2) Chromosomes/Chromatin—Contains genetic information in the form of DNA (Deoxyribonucleic acid) that provides the blueprints for proteins 3) Nucleolus—Contains structures for assembling rRNA and imported proteins into ribosomal subunits 4) Structures for transcribing the genetic information into RNA (ribonucleic acid) Transcribe—1) To make a full written or typewritten copy of (dictated material, for example). 2) To transfer (information) from one recording and storing system to another. C) Structures of the cytoplasm 1) Cytosol—a watery solution of dissolved proteins, salts, sugars, and other solutes within the cytoplasm. 2) Cytoplasm—all the fluid (cytosol) and structures (organelles) within the cell that are not a part of the nucleus. 3) Ribosomes a) Structure: Structures made of protein and rRNA b) Function: Carries out polypeptide synthesis through the process of translation i) Free ribosomes synthesize soluble polypeptides. ii) Membrane-bound ribosomes synthesize polypeptides to be incorporated into membranes.  Topic 3: Cellular Basis of Life 4) Endoplasmic reticulum a) Rough ER i) Structure: Network of branching membranous sacs Ribosomes present ii) Function: Produce proteins that will be used to carry messages, act as membrane pumps, act as enzymes, or provide structure. b) Smooth ER i) Structure: Network of branching membranous sacs No ribosomes present ii) Function: Manufacture phospholipids for the plasma membrane Synthesize lipids and steroids needed by the cell (e.g. in the testes) Absorb and transport fats (e.g. in the intestines) Break down lipids that are poisonous to the cell (e.g. in the liver) Storage of calcium (e.g. in muscles) 5) Golgi apparatus a) Structure: Flattened membranous sacs b) Function: i) Modify and package proteins and other cell products received in vesicles from the ER. ii) Ship out the ‘finished’ product in vesicles to appropriate part of the cell or to the plasma membrane for secretion from the cell.  Topic 3: Cellular Basis of Life 6) Vesicles a) Structure: Membranous sac b) Functions: Transportation of materials within the cell i) Exocytosis – moving substances from the cell interior to the extracellular space ii) Endocytosis – moving substances (e.g. macromolecules) from extracellular space to the cell interior Phagocytosis – pseudopods engulf solids and bring them into the cell’s interior Pinocytosis—fluids (and associated small particles) brought into the cell through invagination of the cell membrane iii) Transcytosis – moving substances into, across, and then out of a cell iv) Vesicular trafficking – moving substances from one area in the cell to another (would include all of the above plus additional movements)  Topic 3: Cellular Basis of Life 7) Vacuoles a) Structure: Large membranous sacs similar to vesicles b) Function: Storage i) Food vacuoles—store and digest ‘food’ ingested by phagocytosis (found in many protists) ii) Contractile vacuoles—collect and pump excess water out of cells (found in many freshwater protists) iii) Central vacuoles—store organic compounds and water (found in plant cells) 8) Lysosomes a) Structure: A membranous sac containing hydrolytic enzymes b) Function: Lysosomal enzymes hydrolyze proteins, fats, polysaccharides, and nucleic acids. i) Lysosomal enzymes work best in the acidic environment inside the lysosome. 9) Peroxisomes a) Structure: A membranous sac containing enzymes b) Function: i) Peroxisome enzymes remove hydrogen atoms from certain molecules and transfers them to oxygen, producing hydrogen peroxide that is then converted to water. ii) Peroxisomes perform reactions with many different functions (e.g. in the liver, peroxisomes detoxify alcohol and other poisons). 10) Mitochondria a) Structure: Double-membrane organelle that contains its own DNA and RNA b) Function: Synthesizes most of the cells ATP via aerobic cellular respiration (ATP is the cell’s primary energy carrying molecule) 11) Chloroplasts (in plants) a) Structure: i) Double-membrane organelle that contains its own DNA and RNA ii) Stroma—the internal fluids iii) Thylakoids—membranous sacs that are stacked to form granum Thylakoid membranes contain the green pigment chlorophyll that captures sunlight for photosynthesis b) Function: Production of ATP and sugars via photosynthesis  Topic 3: Cellular Basis of Life 12) Cytoskeleton a) Structure: system of protein fibers including microtubules, microfilaments, and intermediate filaments. b) Functions: i) Gives the cell shape and structural stability ii) Cell movement iii) Movement of materials within a cell References The American Heritage® Dictionary of the English Language, Fourth Edition. Retrieved June 7, 2011, from Dictionary.com website: http://www.thefreedictionary.com/transcribe