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Levels of Structural Organization Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Figure 3.4 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings I. Anatomy of the Generalized Cell Cells are the building blocks of all living things Carry out all chemical activities needed to sustain life The activity of a cell depends on its shape and the number and types of cellular organelles. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The trillions of cells in the human body have about 200 different varieties. All cells have three main regions: 1. Nucleus 2. Cytoplasm 3. Plasma membrane Figure 3.1a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 1. Nucleus Control center of the cell Contains genetic material (DNA) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 2. Cytoplasm Cytoplasm is the material outside the nucleus and inside the plasma membrane. Contains three major elements: 1. Cytosol- fluid that suspends other elements 2. Organelles- “little organs” that perform functions for the cell 3. Inclusions- chemical substances such as stored nutrients or cell products Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 3. Plasma Membrane Semi-permeable barrier for cell contents Structure: Double phospholipid layer that also contains proteins, cholesterol, and glycoproteins Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Figure 3.4 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 1. The Nucleus Chromatin Composed of DNA and protein and is scattered throughout the nucleus Only present when the cell is not dividing It condenses to form chromosomes when the cell divides Nuclear envelope (membrane) Barrier of the nucleus Contains nuclear pores- that allow for exchange of material with the rest of the cell Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings 2. Plasma Membrane Outer barrier of the cell Controls what goes in and out of the cell (selectively permeable) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Membrane Anatomy Structure of plasma membrane consists of 2 layers of phospholipids with proteins and other molecules floating in the layers Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Phospholipids Forms the majority of the double layer Hydrophilic (water loving) “heads” arrange themselves together and form the inner and outer surfaces of the membrane Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Hydrophobic (water hating) “tails” arrange themselves together and form the interior of the membrane Many molecules are not able to pass through the membrane and need other specialized molecules to help them move in and out. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Proteins can form channels and carriers to allow substances to move in and out Glycoproteins Membrane proteins that have carbohydrates attached Determine blood type; involved in cell to cell interactions; site where toxins, bacteria, and viruses can bind to Cholesterol Found throughout the membrane to keep it more fluid Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Plasma Membrane Specializations Microvilli Finger-like projections that increase surface area for absorption Found in cells that line certain organs, such as the small intestine Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Mitochondria “Powerhouses” of the cell Carry out reactions where oxygen is used to break down food Provides ATP for cellular energy Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Ribosomes Sites of protein synthesis Found at two locations Free in the cytoplasm As part of the rough ER Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Endoplasmic reticulum (ER) Fluid-filled tubules for carrying substances Two types of ER Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Rough endoplasmic reticulum Studded with ribosomes Synthesizes proteins Smooth endoplasmic reticulum Functions in lipid metabolism and detoxification of drugs and pesticides Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Rough Endoplasmic Reticulum Ribosome mRNA Rough ER As the protein is synthesized on the ribosome, it migrates into the rough ER cistern. In the cistern, the protein folds into its functional shape. Short sugar chains may be attached to the protein (forming a glycoprotein). Protein The protein is packaged in a tiny membranous sac called a transport vesicle. Transport vesicle buds off Protein inside transport vesicle The transport vesicle buds from the rough ER and travels to the Golgi apparatus for further processing or goes directly to the plasma membrane where its contents are secreted. Figure 3.5 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Golgi apparatus Modifies and packages proteins that are sent to it by the rough ER Proteins in cisterna Rough ER Cisterna Lysosome fuses with ingested substances Membrane Transport vesicle Golgi vesicle containing digestive enzymes becomes a lysosome Pathway 3 Golgi apparatus Pathway 1 Pathway 2 Secretory vesicles Proteins Golgi vesicle containing proteins to be secreted becomes a secretory vesicle Secretion by exocytosis Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Golgi vesicle containing membrane components fuses with the plasma membrane Plasma membrane Figure 3.6 Extracellular fluid Cytoplasmic Organelles Lysosomes Contain enzymes that digest worn-out or non-usable materials within the cell Peroxisomes Membranous sacs of oxidase enzymes Detoxify harmful substances such as alcohol and formaldehyde Break down free radicals (highly reactive chemicals) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Centrioles Builds the structures necessary for cell division Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cytoplasmic Organelles Figure 3.4 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Cells that connect body parts Fibroblast-elongated cell in connective tissue; has large rough ER and golgi; important in building collagen (important protein in the skin) Erythrocyte- Red Blood Cell- concave shape provides extra surface area to carry oxygen; contains so much pigment that it has no other organelles. Figure 3.8a Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Epithelial cell-hexagon shape, usually found in the lining of organs and other body surfaces; packs together in sheets and resists tearing when pulled Figure 3.8b Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Skeletal muscle and smooth muscle cells- elongated and can shorten and extend to move bones or change size of organs Figure 3.8c Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Fat cell- huge circular shape; has a large lipid droplet in the cytoplasm; used to store lipids for energy Figure 3.8d Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Macrophage- has many lysosomes that help digest bacteria and viruses; important cell in the immune system Figure 3.8e Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Nerve cell- extensive plasma membrane and has a large rough ER; helps send signals throughout the body and allows the brain to communicate with the body Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity Oocyte- largest cell in the body; has many copies of the organelles; female reproductive cell Sperm- elongated shape; only cell that has a flagella; large amounts of mitochondria; male reproductive cell Figure 3.8g Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings