BIO 1010 Unit 3: Cells, Tissues and Organs Chapter Three: Cells PDF

BIO 1010 – Unit 3: Cells, Tissues and Organs Chapter Three: Cells Cell Theory A unifying theme in biology and the foundation for Cell Biology Life on earth represents a continuous line of descent from those early cells Tenants: All organisms are composed of cells All cells come only from preexisting...

BIO 1010 – Unit 3: Cells, Tissues and Organs Chapter Three: Cells Cell Theory A unifying theme in biology and the foundation for Cell Biology Life on earth represents a continuous line of descent from those early cells Tenants: All organisms are composed of cells All cells come only from preexisting cells Cells are the smallest structural and functional unit of organisms Cell Size Perspective…..1 inch contains 25,400 micrometers (µm) Microscope Comparison Dissection/ Stereoscope Light Microscope Specimen? Live or Dead 2D or 3D? 3D Live or Dead 2D manily, some 3D if living Magnification ? 40X up to 2000x Resolution? 120nm View? Surface 200nm Internal and some surface sturctures Scanning Transmission Electron Electron Microscope Microscope Dead Dead 3D 2D up to 100,000x up to 200,000x 10nm 0.2nm Surface Internal Dissection Scope Micrographs Compound Light Micrographs Cornflower leaf cross section Peanut Stem Plant Mitosis Escherichia coli Tardigrade Transmission Electron Micrographs chloroplast Golgi body mitochondria Scanning Electron Micrographs Tardigrade Yersinia pestis (plague) Pollen grains Snowflake Micrographs Pine Pollen Micrographs LM TEM SEM IFM Cell size is limited due to diffusion of substances in and out of the cell Diffusion is affected by Surface Area available Temperature Concentration Gradient Distance across the cell Larger cells Increased Diffusion Time need to take in more macromolecules Have larger energy requirements Cells: Surface Area to Volume Ratio Cell surface: the only part of the cell that interacts with environment All substances enter and exist via this membrane The surface-area-to-volume ratio requires that cells be small Large cells - surface area relative to volume decreases Internal volume is living cytoplasm, which demands nutrients and produces wastes specialized cells for have modified membranes increase surface area Surface Area to Volume Ratio All cells exhibit basic similarities Centrally located genetic material Every cell contains DNA Prokaryotes: singular circular molecule Eukaryotes: DNA in nucleus The Cytoplasm (a location) Contains a semifluid matrix known as the cytosol Contains sugars, amino acids, proteins and organelles The plasma membrane Encloses a cell and separates its contents from its surroundings A phospholipid bilayer about 5 to 10 nm thick Responsible for a cells ability to interact with the environment The Two Major Categories of Cells Prokaryotic cells Domains Bacteria and Archaea ~ 3.5 billion years ago. Eukaryotic cells: Domain Eukarya: Protists and Kingdoms Plantae, Fungi, Animalia ~ 2.1 billion years ago. Prokaryotes Are smaller than eukaryotic cells Lack internal structures surrounded by membranes Lack a nucleus Have a rigid cell wall Asexual Reproduction Higher Plant Cells Versus Animal Cells Plants: Cell walls Cell plate and plasmodesmata Plastids and vacuoles Animals: Internal or external skeletons; no cell walls Divide by pinching in two; no cell plate nor plasmodesmata Centrioles present during cell division. No plastids nor vacuoles Cell Structure and Communication Cell Structure and Communication Cell Structure and Communication Cell Wall surrounds protoplasm. Protoplasm consists of all living cell components. Bound by plasma membrane Cytoplasm consists of all cellular components between the plasma membrane and the nucleus. Cytosol - Fluid within cytoplasm containing organelles Organelles - Persistent structures of various shapes and sizes with specialized functions Most, but not all, are bound by membranes. Cell Structure and Communication: Cell Wall Cellulose : Main structural component of cell walls (long chains of glucose monomers). Also contain matrix of: Hemicellulose - Holds cellulose fibrils together Pectin - Gives stiffness (like in fruit jellies) Glycoproteins - Proteins with associated sugars Middle lamella: first produced when new cell walls are formed. Shared by two adjacent cells Cell Structure and Communication: Cell Wall Cell Structure and Communication: Cell Wall Cell Structure and Communication: Cell Wall v Flexible primary walls laid down on either side of middle lamella. Secondary walls produced inside primary walls. Derived from primary walls by thickening and inclusion of lignin Cellulose microfibrils embedded in lignin for strength. Secondary cell wall structure Cell Structure and Communication: Cell Wall Cell Structure and Communication: Plasmodesmata v v Series of pores that allow cytoplasmic strands to extend between Allow fluids and dissolved substances to pass between cells Cell Structure and Communication: Plasmodesmata Two adjacent cells connected by plasmodesmata Cellular Membranes 4 components: 1. Phospholipid Bilayer 2. Membrane Proteins 3. Interior Protein Network 4. Cell-Surface markers All of these components together are referred to as the Fluid-Mosaic Model Cell Components: Plasma Membrane Plasma Membrane: semipermeable outer boundary of the living part of the cell. Regulates movement of substances into and out of cell Phospholipid bilayer with interspersed proteins Fluid mosaic model - dynamic structure Composed of 4 basic components: Phospholipid bilayer Membrane proteins Interior protein network Cell surface markers The Fluid Mosaic Model 35 Cell Components: Nucleus Nucleus: control center of cell and contains DNA. Sends coded messages from DNA to be used in other parts of the cell Bound by two membranes, which together constitute the nuclear envelope Structurally complex pores occupy up to one-third of the total surface area. Permit only certain kinds of molecules to pass between nucleus and cytoplasm Cell Components: Nucleus v Contains fluid nucleoplasm in which are: Nucleoli - Composed primarily of RNA Chromatin Strands –Composed of DNA and proteins –Coil and become chromosomes Cell Components: Nucleus Cell Components: Endoplasmic reticulum enclosed space consisting of a network of flattened sacs and tubes forming channels throughout the cytoplasm. Facilitates cellular communication and channeling of materials Synthesizes membranes for other organelles and modifies proteins Cell Components: Endoplasmic reticulum Rough ER - Ribosomes distributed on outer surface of ER. Associated with protein synthesis and storage Smooth ER - Devoid of ribosomes and associated with lipid secretion Cell Components: Ribosomes consist of two subunits that are composed of RNA and proteins Link amino acids to construct complex proteins Subunits assembled in nucleolus. May occur on outside of rough ER, or in cytoplasm, chloroplasts or other organelles Cell Components: Golgi Body (Dictyosomes) Stacks of flattened discs or vesicles that act as the “post office” of the cell AKA Golgi apparatus in animals Cell Components: Golgi Body (Dictyosomes) Golgi Body (Dictyosomes) function: To modify carbohydrates attached to proteins that are synthesized and packaged in the ER. To assemble polysaccharides and collect them in small vesicles. Vesicles pinched off from margins of dictyosomes. migrate to plasma membrane, fuse with it, and secrete contents to the outside of cell. Contents may include cell wall polysaccharides, floral nectars, and essential oils in herbs. Cell Components: Plastids site of manufacture and storage of important chemical compounds used by the cell. Many types: Chloroplast Chromoplast Leucoplast Gerontoplast Cell Components: Plastids: Chloroplast most conspicuous plastid. Bound by double membrane and contain: Grana made up of thylakoids Thylakoid membranes contain chlorophyll. First steps of photosynthesis occur in thylakoid membranes. Stroma - Matrix of enzymes involved in photosynthesis Small circular DNA molecule Encodes for production of certain proteins for photosynthesis Cell Components: Plastids: Chloroplast Cell Components: Plastids: Others Chromoplasts Synthesize and accumulate carotenoids (yellow, orange, red) Chromoplasts in red pepper cells Leucoplasts Colorless May synthesize starches (amyloplasts) Or oils (elaioplasts) Amyoplasts with starch grains in Potato Cell Components: Mitochondria release energy from cellular respiration. Double membranes, own DNA and RNA Folded inward membrane = cristae. Increases surface area for enzymatic rxns. Cell Components: Microbodies Small, spherical bodies distributed throughout the cytoplasm that contain specialized enzymes. Bound by a single membrane Peroxisomes - Serve in photorespiration, breakdown hydrogen peroxide Glyoxisomes - Aid in conversion of fat to carbohydrates Cell Components: Vacuoles In mature cells, 90% of volume may be taken up by central vacuoles. Bounded by vacuolar membranes = tonoplasts Filled w/ called cell- sap (slightly acidic) Acts to maintain pH, cell pressure and is storage for a variety of secondary metabolites… salts, sugars, organic acids, small proteins and anthocyanins (red, blue, purple pigments) Cell Components: Cytoskeleton Involved in movement within cell and in cell’s architecture Network of microtubules and microfilaments Microtubules: Control addition of cellulose to cell wall Involved in movement of flagella and cilia Found in fibers of spindles and phragmoplasts in dividing cells Are thin, hollow, tubelike and composed of tubulins (proteins) Microfilaments - Role in cytoplasmic streaming Higher Plant Cells Versus Animal Cells Plants: Cell walls Cell plate and plasmodesmata Plastids and vacuoles Animals: Internal or external skeletons; no cell walls Plasma membrane called cell membrane. Divide by pinching in two; no cell plate nor plasmodesmata Centrioles present during cell division. No plastids nor vacuoles So How did Eukaryotic Cells Arise????? Endosymbiotic Theory Endosymbiotic Theory Protists have membrane bound organelles E.T. suggests that key organelles originated through a symbiosis with aerobic bacteria to become…. Mitochondria from non-sulfur purple bacteria Chloroplast from cyanobacteria Mitochondria Chloroplast Endosymbiotic Theory: the Origin of the Eukaryotic Cell nucleus aerobic bacterium mitochondrion protomitochondrion a. cyanobacterium protochloroplast b. chloroplast Endosymbiotic Theory Evidence Size M/C are double membraned Genetic M/C both have their own circular DNA and ribosomes Genomes and specific genes are very similar to bacteria Mitochondria reproduction very similar to binary fission Same porins (transport proteins) between M/C & bacteria 56 Animal Cells versus Plant Cells Animal Cells Heterotrophic = eats for its energy Organelles not found in most plants: Contain Lysosomes Contain Centrioles Flagella Plant Cells Photoautotrophic = creates its food from solar energy Unique to plant cells Contain chloroplasts Central vacuole Cell wall Shared Organelles: Nucleus, nucleolus, Rough and Smooth Endoplasmic Reticulum Golgi Apparatus Mitochondria Peroxisomes Cell-to-Cell Communication: Plant Cells freely permeable cell wall composed of cellulose Plasmodesmata = series of tiny pores between plant cells that allow for the movement of materials among cells. Cellular Membranes 4 components: 1. Phospholipid Bilayer 2. Membrane Proteins 3. Interior Protein Network 4. Cell-Surface markers All of these components together are referred to as the Fluid-Mosaic Model The Fluid Mosaic Model 61 Cell Membranes are Selectively Permeable Regulates the passage of molecules in and out of the cell Allows cell to control chemical composition despite changing in external environment Some molecules require no energy (ATP) to transported across the membrane Small, non-charged molecules such as CO2, O2, glycerol & alcohol Follow the concentration gradient (Gradual change in chemical concentration btwn 2 different areas) Others do require energy (ATP) to be transported across the membrane Types of Membrane Transport: Overview 63 Types of Membrane Transport }Passive Transport: ◦ No ATP requirement ◦ Molecules flow with concentration gradient (high to low) ◦ Diffusion, Facilitated Diffusion, Osmosis }Active Transport ◦ Requires carrier protein ◦ Molecules flow against concentration gradient (low to high) ◦ Requires energy in form of ATP 64 Types of Passive Transport –Simple Diffusion: the movement of small, non-polar molecules and water through micropores along concentration gradients –Facilitated diffusion: diffusion of ions and polar molecules with the help of a protein but no energy. – Ex/ Aquaporin – protein that allows for quick water transport –Osmosis: The diffusion of water across a selectively permeable membrane Diffusion across a membrane (passive transport) substances move through membranes without work by the cell from areas of high concentration to areas of lower concentration *****Net: there is still movement but the concentration gradient is stable Facilitated Diffusion across Membrane Ions and polar molecules Requires a protein carrier Does not require energy 67 Osmosis: the diffusion of water across a membrane Occurs when molecules cannot cross the membrane Water travels from an area of lower solute concentration to an area of higher solute concentration Solute? Solvent? How is this important to cellular life? Water balance between cells and their surroundings is crucial to organisms. Cells must engage in osmoregulation, the control of water balance. Tonicity plays a huge part in osmoregulation. Tonicity: the ability of a solution to cause a cell to gain or lose water Depends on the concentration of solutes on both sides of the membrane. Note: only influenced by the solutes that cannot cross the cell membrane unassisted. Hyper = greater, more Hypo = less than, lower Iso – equal, same Tonicity: The ability of a solution to cause a cell to gain or lose water Most often tonicity refers to the solution the cell is surrounded by. Hypotonic Hypertonic If the cell is in a ……. Hypertonic solution = more solutes outside than within the cell Hypotonic solution = less solutes outside than within the cell Isotonic solution = equal number of solutes Hypotonic Solution Surrounding solution is hypotonic Less solutes outside of the cell than within the cell Water moves into the cell the balance the solute concentration Cell swells, turgor pressure Isotonic Solution Surrounding solution and the cell solution is isotonic Equal solute concentration No net movement of water Animal Cell remains the same, plant cells membranes start to shrink from cell wall Hypertonic Solution Surrounding solution is hypertonic Crenation More solutes outside of the cell than within the cell Water moves out of the cell the balance the solute concentration Cell shrinks Osmotic Effects on Cells 75 Active Transport Move against concentration gradient (low to high) Requires carrier proteins and energy (ATP) Cell with large active transport requirements need lots of ATP for energy Kidney cells Carrier proteins are often called Pumps Ex./ Sodium-Potassium Pump Sodium Potassium Pump Questions???