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Transcript
Cell Biology Review Pathology 1 - Dr. Gary Mumaugh Introduction The cell is the basic unit of biological organization Basic composition o Protoplasm o Cell membrane o Organelles Human cells vary in size, shape and function o From microscopic to up to two feet long There are 50-100 trillion cells in the human body. Differentiation is when cells specialize. There are over 260 different kinds of human cells. As a result of differentiation, cells vary in size and shape due to their unique function Anatomy of a Typical Cell The Cell Membrane Double phospholipid layer with embedded proteins – also called Plasma Membrane o Protein functions of include forming channels or pores, transporters, receptor sites for hormones Cell membranes are selectively permeable membranes o Only certain substances can get through - Not everything is on the “A” list 1 Cytoplasm of the Cell Mostly water with chemical compounds in solution or colloid o Solution: atoms or ions distributed in medium Polar compounds go into solution Nonpolar compounds go into colloidal suspension The Nucleus All human cells have a nucleus o Except the RBC Control center of the cell Nuclear membrane has pores to allow substances passage Chromatin genetic material (long threads of chromosomes) are inside nucleoplasm Nucleolus - site of ribosome formation Cytoplasm Is the watery solution of minerals, gases, organic molecules and cell organelles that is found between the cell membrane and the nucleus Cytosol is the water portion of the cytoplasm Many of the chemical reaction that occur in the cell happen in the cytoplasm Endoplasmic Reticulum (ER) System of membranes that makes up channels Connects with outer nuclear and cell membranes Types of ER o Rough: for protein synthesis attached ribosomes o Smooth: fat transport and sex hormone synthesis 2 Ribosomes Very small structures made up of protein and ribosomal RNA Distributed throughout cytoplasm Attached to rough Endoplasmic Reticulum Site of protein synthesis The Golgi Apparatus Secretion is the task of the Golgi apparatus o They produce specific proteins to be used elsewhere in tissues o To secrete a substance, small sacs of the membrane break off and fuse with the cell membrane, releasing the substance to the outside of the cell o This is called exocytosis Collection of flat saclike cisternae Concentration and collection of cellular compounds Storage warehouses of the cell Carbohydrate synthesis site The Mitochondria Powerhouses of the cell The aerobic (oxygen requiring) reactions of cell respiration take place here The site of ATP and energy production Cristae - inner folds where cellular respiration occurs Energy requirements of cell determine cristae number 3 Lysosomes Digestive enzyme packages When WBC engulf bacteria, the bacteria are digested and destroyed by lysosomal enzymes Worn out cell parts and dead cells are digested by the lysosomes Function o digest stored food o maintenance and repair of organelles o suicide agents for old or weak cells Centrioles Involved in cellular division and reproduction Form spindle fibers during cell division Guide duplicated chromosomes to daughter cells Centrosome - two centrioles at right angles to each other Cilia and Flagella Hairlike protrusions from cell membrane Nine double fibrils around two single central fibrils Cilia move materials across cell surface Flagellum propels cell through a medium Functions of Cell Organelles ER - Transport of materials in the cell Ribosomes – Site of protein synthesis Golgi apparatus – Cell secretion Mitochondria – ATP production, cell powerhouse Lysosomes – Digestive enzymes Centrioles – Cell division Cilia – Sweeps material across the cell surface Flagellum – Enables a cell to move 4 Think of the “Cell Factory” Boss give orders to the rest of the factory (DNA in the nucleus surrounded by the nuclear membrane). The workers (ribosomes) on the assembly line are in the factory (cytosol) who receive orders for production from the boss’s messanger (mRNA). The raw materials are the amino acids. When things are sent to the mailroom for outside delivery (golgi apparatus), they are eventually shuttled to the gates of the factory (secretory vessels).The gate of the factory controls shipment in and out (cell membrane). The turbines provide power for the factory (mitochondria). Movement of Materials Into and Out of Cells Passive (Physical) Processes o Require no cellular energy and include: Simple diffusion Facilitated diffusion Osmosis Filtration Active (Physiological) Processes o Require cellular energy and include: Active transport Endocytosis Exocytosis Diffusion Movement of molecules from area of high concentration to low concentration Brownian movement - random collision of diffusing molecules Accelerated by increased temperature Gas exchange in the lungs of body tissue is an example O2 - CO2 exchange 5 Facilitated Diffusion Facilitate means to help or assist Molecules move from an area of greater concentration to an area of lesser concentration, but they need help o An example is glucose, which is need for ATP production. o Glucose can’t get through membranes by themselves, so they have a carrier enzyme or transporter to help facilitate diffusion. Osmosis Movement of water through semipermeable membrane from high water concentration to low water concentration Absorption of water by the small intestines and kidney is an example o Isotonic solution - salt concentration is the same outside the cell as inside o Hypotonic solution - salt concentration inside cell is higher than outside cell o Hypertonic solution -salt concentration higher outside the cell than inside Osmotic Pressure – ability of osmosis to generate enough pressure to move a volume of water Osmotic pressure increases as the concentration of nonpermeable solutes increases o Isotonic – same osmotic pressure o Hypertonic – higher osmotic pressure (water loss) o Hypotonic – lower osmotic pressure (water gain) Active Transport The movement of molecules from an area of lesser concentration to an area of greater concentration Opposite of diffusion Requires the energy of ATP to do this An example in the body is sodium and potassium pumps in muscle and nerve cells 6 Filtration Water and dissolved materials are forced through a membrane from an area of higher pressure to an area of lower pressure In the body, blood pressure is an example of this, with filtration occurring through the capillaries Phagocytosis and Pinocytosis Phagocytosis o A moving cell engulfs something o WBC engulfing bateria o Think of “pacman” Pinocytosis o A stationary cell engulfs something o Kidney cells absorbing lost protein DNA and the Genetic Code DNA is a double helix strand of nucleotides, looking like a spiral ladder o The rungs of the ladder are made up of four different bases, arranged in different orders and sequences o These sequences are the genetic code o The DNA of our 46 chromosomes is the genome which contains 20,000 to 30,000 genes If there is a mistake in the DNA, the result is genetic or hereditary disease 7 RNA and Protein Synthesis Protein Functions o structure, enzymes or catalysts, immune response Transcription Messenger RNA copies DNA code, leaves nucleus Translation (tRNA) picks up amino acids Cell Division Cell division is the process by which a cell reproduces itself Two types of cell division o Mitosis One cell with the diploid number of chromosomes divides once to form two cells, each with the diploid number of chromosomes (46) Stages of mitosis Prophase, metaphase, anaphase, telophase Mitosis is essential for growth and for repair and replacement of damaged cells Most nerve and muscle cells seem unable to divide and their loss may involve permanent loss of function o Meiosis: A Reduction Division Reduces genetic material from diploid to haploid Two divisions resulting in four cells Occurs only in the gonads In women, meiosis takes place in the ovaries and is called oogenesis In men, meiosis takes place in the testes and is called spermatogenesis Fertilization is the egg uniting with the sperm Tumors Two types of tumors: o Benign – usually remains localized o Malignant – invasive and can metastasize; cancerous Two major types of genes cause cancer: o Oncogenes – activate other genes that increase cell division o Tumor suppressor genes – normally regulate mitosis; if inactivated they are unable to regulate mitosis Cells are now known as “immortal” 8 Cellular Metabolism Metabolic processes – all chemical reactions that occur in the body o Anabolism Larger molecules are made from smaller ones Requires energy Anabolism provides the materials needed for cellular growth and repair o Catabolism Larger molecules are broken down into smaller ones Releases energy Catabolism breaks down larger molecules into smaller ones Control of Metabolic Reactions Enzymes o Control rates of metabolic reactions o Lower activation energy needed to start reactions o Not consumed in chemical reactions Factors That Alter Enzymes Heat Radiation Electricity Chemicals Changes in pH Energy for Metabolic Reactions Energy is the capacity to change something; it is the ability to do work Common forms of energy: o Heat o Light o Sound o Electrical energy o Mechanical energy o Chemical energy 9