introduction to physiology: the cell and general...
TRANSCRIPT
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Chapter 2:The Cell and Its Functions
Slides by Dr. Abbas S. Dakhil, Ph.D.
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Organization of the Cell
• Cells: the basic structural and functional unit
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The different substances that make up the cell are collectively calledprotoplasm. Protoplasm is composed mainly of five basic substances:.
• Water
• Electrolytes
• Proteins
• lipids
• Carbohydrates
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Physical Structure of the Cell
The cell contains highlyorganized physicalstructures, calledintracellular organelles.
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Membranous Structures of the Cell
The cell membrane iscomposed mainly of a lipidbilayer of phospholipidmolecules, but with largenumbers of proteinmolecules protrudingthrough the layer.Also, carbohydrate moietiesare attached to the proteinmolecules on the outside ofthe membrane and toadditional protein moleculeson the inside.
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Endoplasmic Reticulum
granular endoplasmic reticulum contains ribosomes and they functionto synthesize new protein molecules
agranular, or smooth, endoplasmic reticulum. Synthesis of lipid substances
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Golgi Apparatus
“transport vesicles” (also called endoplasmic reticulum vesicles, orER vesicles) and processed it to form lysosome and secretory vesicles
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Lysosomes
• intracellular digestive system
• Lysosomes ingest (1) damaged cellular structures, (2) food particlesthat have been ingested by the cell, and (3) unwanted matter such asbacteria
• Contain 40 different hydrolase (digestive) enzymes
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Peroxisomes
• Contain oxidases rather than hydrolases
• Oxidases are capable of combining oxygen with hydrogen ionsderived from different intracellular chemicals to form hydrogenperoxide (H2O2).
• H2O2 is a highly oxidizing substance and is used in associationwith catalase, another oxidase enzyme to oxidize many substancesthat might otherwise be poisonous to the cell
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Secretory Vesicles
• secretory vesicles or secretory granules are formed by the endoplasmicreticulum–Golgi apparatus system and are then released from theGolgi apparatus into the cytoplasm.
• Secretory vesicles store protein proenzymes (enzymes that are notyet activated). The proenzymes are secreted later through the outercell membrane.
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Mitochondria
• Mitochondrion is composed mainly of two lipid bilayer–proteinmembranes: an outer membrane and an inner membrane
• Many infoldings of the inner membrane form shelves onto whichoxidative enzymes are attached.
• In addition, the inner cavity of the mitochondrion is filled with amatrix that contains enzymes that are necessary for extractingenergy from nutrients.
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Nucleus
• The nucleus is the control center of the cell
• The nuclear membrane (nuclear envelope), is separate bilayermembranes, one inside the other. The outer membrane is continuouswith the endoplasmic reticulum of the cell cytoplasm,
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Functional Systems of the Cell
1. Ingestion by the Cell—Endocytosis
• The principal forms of endocytosis are pinocytosis and phagocytosis.
Mechanism of pinocytosis.
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Functional Systems of the Cell
2. Digestion of Foreign Substances Inside the Cell—Function ofthe Lysosomes
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Functional Systems of the Cell
Extraction of Energy from Nutrients—Function of theMitochondria
almost all these oxidative reactionsoccur inside the mitochondria, andthe energy that is released is used toform the high-energy compoundATP.• carbohydrates are convertedinto glucose• proteins are converted into
amino acids• fats are converted into fatty
acids
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Functional Systems of the Cell
Functional Characteristics of ATP
ATP is a nucleotide composed of (1) the nitrogenous base adenine, (2)the pentose sugar ribose, and (3) three phosphate radicals.
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Functional Systems of the Cell
Uses of ATP for Cellular FunctionAdenosine triphosphate (ATP) (formed in the mitochondrion) provideenergy for three major cellular functions: (1) membrane transport, (2)protein synthesis, and (3) muscle contraction.