Transcript Cells
Cytology Studying Cells Cell Theory: Four Basic Concepts 1. Basic building blocks of all animals and plants 2. Smallest functional units of life 3. Products of cell division 4. Basic homeostatic units Studying Cells The Diversity of Cells in the Human Body Figure 3-1 Studying Cells Overview of Cell Anatomy •Extracellular (interstitial )fluid - outside cell •Cell Membrane •Cytoplasm - stuff inside (not including the membrane & nucleus) a. Cytosol = intracellular fluid b. Organelles = “little organs” structures that perform special functions for cell •Nucleus Studying Cells Anatomy of a Representative Cell Figure 3-2 The Cell Membrane Functions of the cell membrane • Physical isolation • Regulation exchange of materials • Sensitivity - receptors allow cell to recognize & respond to specific molecules in environment • Support The Cell Membrane The Cell Membrane Figure 3-3 The Cell Membrane Table 3-2 The Cell Membrane Membrane is Selectively permeable = chooses what can pass through based on • Size • Electrical charge • Shape • Lipid solubility Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Cell Membrane Membrane Transport Processes • Passive transport - no energy needed • Diffusion (including Osmosis) • Facilitated diffusion - diffusion with help of a protein channel • Active Transport - uses ATP energy • Sodium-potassium exchange pump • Phagocytosis - cell eating • Exocytosis - sending materials out The Cell Membrane Membrane Transport Definitions • Diffusion Movement of materials from higher to lower concentration (tries to even out) •Osmosis Diffusion of water across a membrane to where there is more solute (less water) The Cell Membrane Diffusion Figure 3-4 The Cell Membrane Diffusion Across Cell Membranes Figure 3-5 Osmosis & Solutions That Affect It Isotonic = cell maintains balance Hypotonic = water moves in to where there is more solute - cell swells & bursts (hemolysis in RBC’s) Hypertonic = water moves out of cell to where there is more solute - cell shrivels The Cell Membrane Facilitated Diffusion Figure 3-8 The Cell Membrane The SodiumPotassium Exchange Pump Figure 3-9 Phagocytosis Phagocytosis Cell membrane of phagocytic cell Lysosomes A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it. The pseudopodia approach one another and fuse to trap the material within the vesicle. The vesicle moves into the cytoplasm. Vesicle Lysosomes fuse with the vesicle. Foreign object Pseudopodium (cytoplasmic extension) This fusion activates digestive enzymes. CYTOPLASM EXTRACELLULAR FLUID Undissolved residue The enzymes break down the structure of the phagocytized material. Residue is then ejected from the cell by exocytosis. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Figure 3-11 1 of 8 Exocytosis Endoplasmic reticulum EXTRACELLULAR CYTOSOL FLUID Lysosomes Cell membrane Secretory vesicles Transport vesicle Golgi apparatus (a) Membrane renewal vesicles Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings (b) Exocytosis Vesicle Incorporation in cell membrane Figure 3-14 1 of 7 Cell Structures - Organelles Anatomy of a Cell Figure 3-2 The Cytoplasm Organelles • Microvilli - Surface projections increase surface area for absorption •Cilia - Move fluids across cell surface •Flagella - Moves cell through fluid •Ribosome - proteins factories •Lysosomes - “janitors” - hold digestive enzymes to get rid of wastes & bacteria •Mitochondria - “power plant” - make ATP energy The Cytoplasm Key Note Mitochondria provide most of the energy needed to keep your cells (and you) alive. They use oxygen and organic compounds, such as glucose, and make carbon dioxide and ATP. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Nucleus = Control Center Nuclear envelope surrounds nucleus Nuclear pores Allows movement of materials in & out (but NOT DNA) The Nucleus Chromosome Structure DNA makes up 23 pairs of chromosomes contained in nucleus Figure 3-17 The Nucleus Key Note The nucleus contains DNA, the genetic instructions within chromosomes. The instructions tell how to synthesize the proteins that determine cell structure and function. THEREFORE - the nucleus controls everything else by regulating (controlling) protein synthesis! Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings The Nucleus The Genetic Code • Triplet code = Sequence of 3 nitrogen bases (codon) which code for a certain amino acid •A Gene = All the amino acids needed to make 1 protein Protein Synthesis Problem: DNA can’t leave nucleus & protein factories (ribosomes) are in the cytoplasm Solution: Make a copy of DNA & send it out Protein Synthesis: 1. Transcription = DNA is copied to make mRNA 2. Translation = Info from mRNA is used to make a protein with help of tRNA Transcription DNA Translation RNA In Nucleus Protein In Cytoplasm http://www.lewport.wnyric.org/jwanamaker/animations/protein%20synthesis%20-%20long.html The Cell Life Cycle Interphase - Most of a cell’s life performing normal function - time between cell division • Includes DNA replication Mitosis - When copied chromosomes split apart & the 2 nuclei divide Cytokinesis - the last part of mitosis when the cytoplasm divides to create 2 new cells The Cell Life Cycle Occurs in Somatic Cells = all cells in body aside from sex cells (sperm & eggs) Involves: Interphase, Mitosis & Cytokinesis Note: some cells never divide apoptosis = genetically programmed cell death The Cell Life Cycle DNA ReplicationThe Cell Life Cycle Figure 3-21 Interphase Nucleus Early prophase Mitosis begins Spindle fibers Centrioles (two pairs) Metaphase Late prophase Centromeres Anaphase Chromosome with two sister chromatids Telophase Separation Daughter chromosomes Cytokinesis Metaphase plate Cleavage furrow Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Daughter cells Figure 3-22 1 of 8 The Cell Life Cycle Cell Division and Cancer • Tumor (neoplasm) - a mass or swelling made by abnormal cell growth & division • Malignant Tumor = when it no longer responds to normal control mechanisms & spreads into surrounding tissues • Cancer = illness from effects of malignant cells The Cell Life Cycle Key Note Cancer results from mutations that disrupt the control mechanism that regulates cell growth and division. Cancers most often begin where cells are dividing rapidly, because the more chromosomes are copied, the greater the chances of error. Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings Cell Diversity and Differentiation Somatic Cells • All have same genes • Some genes inactivate during development • Cells thus become functionally specialized • Specialized cells form distinct tissues • Tissue cells become differentiated Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings