Chapter 3 - Cell Biology PDF

Chapter 3 – Cell Biology Learning Outcomes: At the end of the lecture, the student should be able to: Identify and describe the function of all major cellular organelles Describe the nature of the plasma membrane in reference to the passage of materials through it. Describe th...

Chapter 3 – Cell Biology Learning Outcomes: At the end of the lecture, the student should be able to: Identify and describe the function of all major cellular organelles Describe the nature of the plasma membrane in reference to the passage of materials through it. Describe the two-step process that results in gene expression Understand and identify the different phases in cell life cycle  Cell Basic units of all living things 2 types of cell: Eukaryote Prokaryote Characteristic Functions of Cells Cell metabolism and energy use Synthesis of molecules Communication Reproduction and inheritance Kinds of Microscope used to study cells: Light microscopes → general features of cells Electron microscopes → fine structures of cells Scanning electron microscope (SEM) → features of the cell surface and the surfaces of internal structures Transmission electron microscope (TEM) → detailed aspects of cell structure Cell Parts / Organelles External Structures Membrane Structure Internal Structures  External Structures Cilia Flagella Microvilli Cilia Cylindrical shaped projections Movement Length→ 10 μm Diameter→ 0.2 μm Surface cells of respiratory tract and female reproductive tract Flagella Longer than cilia Length→ 45 μm Sperm cells Microvilli Cylindrical shaped extensions Not for movement→ Absorption Found on the cells of intestine & kidney Internal Structures Cytoplasm Consists of all the contents outside of the nucleus and enclosed within the cell membrane of a cell Clear; gel like appearance Cytosol Fluid portion of cytoplasm → colloid Contains: Cytoskeleton Cytoplasmic inclusions Cytoskeleton Supports the cell Holds the nucleus and other organelles in place Responsible for changes in cell shape & movement of cell organelles Consists of three groups of proteins: Microtubules Actin filaments Intermediate filaments Microtubules Hollow tubes Composed of protein units → tubulin Internal scaffolding Form essential components of certain cell organelles, such as centrioles, spindle fibers, cilia, and flagella Centrioles Small, cylindrical organelle Length → 0.3–0.5 μm Diameter → 0.15 μm Spindle Fibers Involved in moving and segregating the chromosomes during nuclear division Actin filaments (microfilaments) Small fibrils Bundles, sheets, or networks in the cytoplasm Provide structure to the cytoplasm mechanical support for microvilli Support the plasma membrane Define the shape of the cell Intermediate filaments Protein fibers Provide mechanical strength to cells The Nucleus and Cytoplasmic Organelles  Nucleus Largest ; Central organelle Contains the cell’s DNA Control Center Nucleus contains: Chromosomes Chromatin Nucleoplasm Nuclear envelope Nucleolus Nuclear pore  Ribosomes Protein Synthesizers Found within the cytosol of the cytoplasm and attached to internal membranes  Endoplasmic Reticulum Consists of broad, flattened, interconnecting sacs and tubules System of channels → Passageway in the cell Transporting, Synthesizing and storing materials 2 kinds Rough endoplasmic reticulum (RER) Smooth endoplasmic reticulum (SER) Rough endoplasmic reticulum (RER) Membranes that create a network of channels throughout the cytoplasm Attachment of ribosomes to the membrane gives a rough appearance Synthesis of protein  Smooth endoplasmic reticulum (SER) Closed tubular network without ribosomes. FUNCTIONS: Synthesis of carbohydrates, lipids, and steroid hormones Detoxification of medications and poisons/ foreign substances Storage of calcium ions- sarcoplasmic reticulum - muscle cell Golgi Apparatus Packaging machine Packaging and distribution of materials to different part of the cell Secretory Vesicles Tiny packages Contains materials that can be secreted  Lysosomes Membrane-bound vesicles containing digestive enzymes- from Golgi Destroy cells or foreign matter that the cell has engulfed by phagocytosis. Organelles for Energy Production and Detoxification  Mitochondria Energy Generators of the Cell “Powerhouse of the cell”- cellular metabolism Peroxisomes Smaller than lysosomes Contain enzymes Catalase Cells that are active in detoxification → Liver & Kidney cells Cell Membrane Cell Membrane Plasma membrane Separates the inner contents of a cell from its exterior environment Selectively permeable Provides protective barrier & regulates transport materials in and out the cell Consists: 45–50% Lipids 45–50% Proteins 4–8% Carbohydrates  Membrane Potential An electrical charge difference across the plasma membrane Result of the cell’s regulation of ion movement into and out of the cell Membrane Lipids Phospholipids → form a lipid bilayer Head → polar Tail → nonpolar Cholesterol Membrane Proteins 2 Types of Membrane Proteins Integral proteins Peripheral proteins Integral Protein Embedded protein in the membrane Selectively allows materials cell recognition Ex: Channel proteins Peripheral proteins Typically found on the inner or outer surface of the lipid bilayer Can be attached to the internal or external surface of an integral protein Functions of Membrane proteins 1. Marker molecules 2. Attachement proteins 3. Transport proteins 4. Receptor proteins 5. Enzyme 1. Marker Molecules Cell surface molecules Allow cells to identify other cells or other molecules Mostly glycoproteins or glycolipids  2. Attachment Proteins Integral proteins Allow cells to attach to other cells or to extracellular molecules Proteins: Cadherins→ attach cells to other cells Integrins → attach cells to extracellular molecules 3. Transport Proteins Integral proteins Allow ions or molecules to move from one side of the plasma membrane to the other 3 Characteristics Includes: Specificity Channel proteins Competition Carrier proteins Saturation ATP powered pumps Channel Proteins Tiny channels through the plasma membrane Ions or small molecules can pass through the channel Leak ion channel Gated ion channel Ligand gated ion channel Voltage gated ion channel Carrier Proteins (Transporters) Integral membrane proteins that move ions or molecules from one side of the plasma membrane to the other Specific & Flexible Movement of ions or molecules: Uniport → one specific ion Symport (cotransport) → 2 different ions or molecules in the same direction Antiport (antiport) →2 different ions or molecules in opposite direction ATP-Powered Pumps Move specific ions or molecules across the membrane Require ATP molecules to function  Specificity Each transport protein binds to and transports only a certain type of molecule or ion Chemical structure of the binding site determines the specificity of the transport protein  Competition Result of similar molecules binding to the transport protein  Saturation Rate of movement of molecules is limited by the number of available transport proteins 4. Receptor Proteins Proteins or glycoproteins Contains an exposed receptor site 5. Enzymes Catalyze chemical reactions on either the inner or the outer surface of the plasma membrane  Movement Through the Plasma Membrane TRANSPORT MECHANISMS Transport across the Cell Membrane Non polar materials → can move through the lipid bilayer Water soluble (Polar) materials → need some assistance to cross the membrane 2 General Methods Transporting Passive transport Active transport Passive Membrane Transport Diffusion Simple diffusion Facilitated diffusion Osmosis Passive Transport Movement of substances across the membrane without the expenditure of cellular energy Concentration Gradient Difference in concentration of a substance across a space Diffusion Movement of solutes from an area of higher solute concentration to an area of lower solute concentration Simple diffusion Facilitated Diffusion Osmosis Diffusion of water (solvent) through a semipermeable membrane Water diffuses through the lipid bilayer More water → across a selectively permeable membrane→ less water (Vice versa) Osmotic Pressure Force required to prevent water from moving by osmosis across a selectively permeable membrane Osmotic Tonicity Isotonic → Two solutions that have the same concentration of solutes Hypertonic → A solution that has a higher concentration of solutes than another solution Hypotonic→ A solution that has a lower concentration of solutes than another solution Active Membrane Transport Primary Secondary Vesicular Primary Active Transport Mediated transport process that requires energy Movement of the transported substance to the opposite side of the membrane Release from the ATP powered pump are fueled by the breakdown of ATP Secondary Active Transport Ion-coupled transport Form of active transport Vesicular Transport Movement of larger volumes of substances across the plasma membrane through the formation or release of vesicles Requires ATP Do not demonstrate degree of specificity or saturation →bulk movement of materials Includes: Endocytosis Exocytosis Exocytosis Vesicle contents are expelled from the cell Ex: secretion of mucus by the salivary glands Endocytosis Uptake of material through the plasma membrane by the formation of a vesicle Includes Phagocytosis Pinocytosis Genes and Gene Expression Gene Expression Production of RNA and/or proteins from the information stored in DNA Involves two steps: Transcription (DNA transcribed to RNA) Translation (RNA translated to PROTEINS) Cell Life Cycle 2 Stages of Cell Life Cycle: Interphase Cell division  Interphase cell undergoes normal growth processes Prepares for cell division Longest phase of the cell cycle 3 stages of Interphase: G1 phase S phase G2 phase  Interphase G1 phase (Gap 1 / First Gap) Cell is active at biochemical level Prepares the building blocks of chromosomal DNA for replication  Interphase S phase (Synthesis phase) DNA replicates DNA REPLICATION  Interphase G2 phase (Gap phase) Cell replenishes its energy stores Makes proteins needed for mitosis Cell organelles are duplicated Cytoskeleton is dismantled to provide resources for the mitotic phase Cell Division Prophase Cell begins the division process Nuclear membrane breaks apart Chromosome condense Nucleolus disappears Microtubules form Metaphase 2nd phase of Mitosis Chromosomes are pulled to center of cell Line up along “metaphase plate” Anaphase 3rd phase of mitosis Centromeres divide Precise alignment is critical to division Spindle fibers pull one set of chromosomes to each pole Telophase Nuclear membrane and nucleoli (nucleus) reform Cell plate begins to form Cell prepares for final division Cytokinesis Final stage Cytoplasm, organelles and nuclear material are evenly split 2 new cell are formed Reference: Seeley's Anatomy & Physiology, 10th edition