Chapter 2 Foundations The Cell Lecture Presentation by Steven Bassett Southeast Community College © 2015 Pearson Education, Inc. Introduction • There are trillions of cells in the body • Cells are the structural “building blocks” of all plants and animals • Cells are produced by the division of preexisting cells • Cells form all the structures in the body • Cells perform all vital functions of the body © 2015 Pearson Education, Inc. Introduction • There are two types of cells in the body: • Sex cells • Sperm in males and oocytes in females • Somatic cells • All the other cells in the body that are not sex cells © 2015 Pearson Education, Inc. Cellular Anatomy • The cell consists of: • Cytoplasm • Cytosol • Organelles • Plasmalemma • Cell membrane © 2015 Pearson Education, Inc. Figure 2.2 A Flowchart for the Study of Cell Structure The Cell can be divided into Plasmalemma Cytoplasm Divided into Cytosol Organelles subdivided into Nonmembranous Membranous Organelles Organelles • Cytoskeleton • Mitochondria • Microvilli • Nucleus • Centrioles • Endoplasmic • Cilia reticulum • Flagella • Golgi apparatus • Ribosomes • Lysosomes • Peroxisomes © 2015 Pearson Education, Inc. Cellular Anatomy • Anatomical Structures of the Cell • Organelles • Nonmembranous organelles • Membranous organelles © 2015 Pearson Education, Inc. Cellular Anatomy • Organelles of the Cell • Nonmembranous organelles • Cytoskeleton • Microvilli • Centrioles • Cilia • Flagella • Ribosomes © 2015 Pearson Education, Inc. Table 2.1 Anatomy of a Representative Cell (1 of 2) © 2015 Pearson Education, Inc. Figure 2.1 Anatomy of a Typical Cell Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes © 2015 Pearson Education, Inc. Cellular Anatomy • Organelles of the Cell • Membranous organelles • Mitochondria • Nucleus • Endoplasmic reticulum • Golgi apparatus • Lysosomes • Peroxisomes © 2015 Pearson Education, Inc. Table 2.1 Anatomy of a Representative Cell (2 of 2) © 2015 Pearson Education, Inc. Figure 2.1 Anatomy of a Typical Cell Microvilli Secretory vesicles Golgi apparatus Cytosol Lysosome Mitochondrion Centrosome Peroxisome Centriole Nuclear pores Chromatin Smooth Nucleoplasm endoplasmic reticulum Nucleolus Rough Nuclear envelope endoplasmic surrounding nucleus reticulum Cytoskeleton Fixed ribosomes Plasmalemma Free ribosomes © 2015 Pearson Education, Inc. Cellular Anatomy • Plasmalemma • A cell membrane composed of: • Phospholipids • Glycolipids • Protein • Cholesterol © 2015 Pearson Education, Inc. Table 2.1 Anatomy of a Representative Cell (1 of 2) © 2015 Pearson Education, Inc. Figure 2.3 The Plasmalemma Hydrophilic heads Hydrophobic tails Cholesterol EXTRACELLULAR FLUID Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM a The plasmalemma © 2015 Pearson Education, Inc. Cellular Anatomy • Functions of the Plasmalemma • Cell membrane (also called phospholipid bilayer) • Major functions: • Physical isolation • Regulation of exchange with the environment (permeability) • Sensitivity • Cell-to-cell communication/Adhesion/Structural support © 2015 Pearson Education, Inc. Cellular Anatomy • Structure of the Plasmalemma • Called a phospholipid bilayer • Composed of two layers of phospholipid • Hydrophobic heads are at the surfaces (inside lining and outside lining) • Hydrophilic fatty acids (tails) “face toward each other” • Outer layer consists of glycolipids and glycoproteins • Glycolipids and glycoproteins form a glycocalyx coating • Inner layer does not consist of glycolipids or glycoproteins © 2015 Pearson Education, Inc. Figure 2.3 The Plasmalemma Hydrophilic heads Hydrophobic tails Cholesterol EXTRACELLULAR FLUID Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM a The plasmalemma © 2015 Pearson Education, Inc. Cellular Anatomy • Structure of the Plasmalemma • Composed of protein molecules • Peripheral proteins: attached to the glycerol portions of the fatty acids • Integral proteins: embedded within the cell membrane • Form channels such as gated channels • Channels open and close © 2015 Pearson Education, Inc. Figure 2.3 The Plasmalemma Hydrophilic heads Hydrophobic tails Cholesterol EXTRACELLULAR FLUID Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM a The plasmalemma © 2015 Pearson Education, Inc. Cellular Anatomy • Structure of the Plasmalemma • Composed of sterol molecules • Function to maintain fluidity of the membrane • An example is cholesterol © 2015 Pearson Education, Inc. Figure 2.3 The Plasmalemma Hydrophilic heads Hydrophobic tails Cholesterol EXTRACELLULAR FLUID Glycolipids Phospholipid Integral protein Integral of glycocalyx bilayer with channel glycoproteins Hydrophobic tails b The phospholipid bilayer Cholesterol Peripheral Hydrophilic proteins heads Gated Cytoskeleton channel = 2 nm (Microfilaments) CYTOPLASM a The plasmalemma © 2015 Pearson Education, Inc. Cellular Anatomy • Membrane Permeability of the Plasmalemma • Passive processes • Diffusion • Osmosis • Facilitative diffusion • Active processes • Active transport • Endocytosis • Exocytosis © 2015 Pearson Education, Inc. Cellular Anatomy • Membrane Permeability of the Plasmalemma • Passive process: diffusion • Movement of molecules from an area of high concentration to an area of low concentration • Permeablity, concentration gradient, molecule size and charge, temperature affect the rate of movement • Small inorganic ions and small molecules are involved © 2015 Pearson Education, Inc. Figure 2.4 Membrane Permeability: Active and Passive Processes (1 of 6) Diffusion Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration. The difference between the high and low concentrations is Plasmalemma a concentration gradient. In diffusion, molecules move down a concentration Example: gradient until the gradient is eliminated. When the concentration of CO2 inside a cell is greater than outside Factors Affecting Rate: the cell, CO2 diffuses out of the cell Membrane permeability; magnitude of the and into the extracellular fluid. concentration gradient; size, charge, and lipid solubility of the diffusing molecules; presence of membrane channel proteins; Extracellular CO2 temperature fluid Substances Involved (all cells): Gases, small inorganic ions and molecules, lipid-soluble materials © 2015 Pearson Education, Inc. Cellular Anatomy • Membrane Permeability of the Plasmalemma • Passive process: osmosis • Movement of water molecules from an area of high concentration of water to an area of low concentration of water • Permeability, concentration gradient, and opposing pressure affect the rate of movement • Only water molecules are involved © 2015 Pearson Education, Inc. Figure 2.4 Membrane Permeability: Active and Passive Processes (2 of 6) Osmosis Osmosis is the diffusion of water molecules (rather than solutes) across a selectively permeable membrane. Note that water molecules diffusing toward an area of lower Example: water concentration are moving toward an area If the solute concentration outside of higher solute concentration. Because solute a cell is greater than the inside the cell, water molecules will move concentrations can easily be determined, they across the plasmalemma into the are used to determine the direction and force extracellular fluid. of osmotic water movement. Factors Affecting Rate: Size of the solute concentration gradient; opposing pressure Substances Involved: Water only Water Solute © 2015 Pearson Education, Inc. Cellular Anatomy • Membrane Permeability of the Plasmalemma • Passive process: facilitated diffusion • Solutes are passively transported by a carrier protein • Concentration gradient, size and charge of the solute, temperature, and number of carrier proteins affect the rate of movement • Glucose and amino acids are involved © 2015 Pearson Education, Inc. Figure 2.4 Membrane Permeability: Active and Passive Processes (3 of 6) Plasmalemma Facilitated diffusion Glucose In facilitated diffusion, solutes are Extracellular Example: fluid Nutrients that are insoluble passively transported across a in lipids or too large to fit plasmalemma by a carrier protein. As through membrane in simple diffusion, the direction of channels may be trans- movement follows the concentration ported across the plasma- gradient. lemma by carrier proteins. Many carrier proteins move Factors Affecting Rate: a specific substance in one Magnitude of the concentration direction only, either into or gradient; size, charge, and solubility of Cytoplasm out of the cell, after first the solutes; temperature; availability binding the substance at a of carrier proteins Receptor Carrier Carrier protein releases specific receptor site. Substances Involved (all cells): site protein glucose into cytoplasm