Chapters 4 & 5: The Cell

Transcription

1 Chapters 4 & 5: The Cell Honors Biology The History of the Microscope and Cell Theory Robert Hooke uses a simple microscope to look at cork Anton van Leeuwenhoek observed single celled organisms Schleiden and Schwann state that all living things are composed of cells Rudolf Virchow added all cells come from preexisting cells. Cell Theory states All living things are composed of cells and all cells come from other cells. 2 Types of Microscopes Light Microscope Electron Microscope (EM) - uses a beam of electrons Scanning Electron Microscope (SEM) studies cell surface Transmission Electron Microscope (TEM) - studies internal cell structure 3

2 Cell Size Cell size is limited by the ability to carry out cell processes Cells need enough surface area to allow nutrients in and wastes out 30 µm Surface area of one large cube = 5,400 µm 2 30 µm 10 µm 10 µm Fig m 1 m 100 mm (10 cm) 10 mm (1 cm) 1 mm 100 µm 10 µm 1 µm 100 nm 10 nm 1 nm Human height Length of some nerve and muscle cells Chicken egg Frog egg Most plant and animal cells Nucleus Most bacteria Mycoplasmas (smallest bacteria) Viruses Ribosome Proteins Lipids Small molecules Atoms Unaided eye Light microscope Electron microscope 4 All Cells Basic shared features: plasma chromosomes ribosomes cytoplasm (area between the nucleus and the plasma ) 5 Bacteria and archea Prokaryotes Smaller than eukaryotic cells No nucleus has a nuceoid where the DNA coils Often have cell walls, capsules, and pili Flagella Bacterial chromosome Fig. 4-3b Pili Nucleoid Ribosomes Plasma Cell wall Capsule Flagella Fig

3 Eukaryotic Cells NUCLEUS: Nuclear envelope eukaryote (Greek: eu=true, Chromosomes Smooth endoplasmic reticulum karyon=kernal/nucleus) Nucleolus Rough endoplasmic reticulum animals, plants, protists, fungi Lysosome contains organelles ( little Centriole organs ) in the cytoplasm Ribosomes Peroxisome Golgi apparatus CYTOSKELETON: Microtubule Four categories: Plasma Intermediate filament Microfilament manufacturing, breakdown, energy processing, and structure/movement/ communication NUCLEUS: Rough endoplasmic reticulum Nuclear envelope Chromosome Ribosomes Nucleolus Smooth endoplasmic reticulum Golgi apparatus Central vacuole Microtubule Chloroplast cellular metabolism happens within organelles with complex enzyme interactions Cell wall Intermediate filament Plasmodesmata Microfilament Peroxisome Plasma Cell wall of adjacent cell 7 Membrane Structure Hydrophilic head Membrane forms a barrier between the cell and its surroundings Phosphate group Membranes also separate part of the cell from each other Phospholipids are the main component Contain: hydrophobic heads Symbol and hydrophilic tails form a bilayer Membranes also contain proteins 8 Endo System Includes: nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosome, vacuoles, and plasma Function in the synthesis, storage, and export of molecules Connected to each other or vesicles are used to transfer products Nuclear envelope Ribosomes Smooth ER Transport vesicle buds off Rough ER 4 Ribosome Secretory protein inside transport vesicle 3 Sugar chain 1 2 Glycoprotein Polypeptide Rough ER Receiving side of Golgi apparatus Golgi apparatus Golgi apparatus Transport vesicle from ER New vesicle forming Shipping side of Golgi apparatus Transport vesicle from the Golgi 9

4 Energy Conversion Mitochondria - carry out cellular respiration using sugar to make ATP enclosed by two s with embedded proteins Outer Inner Cristae Fig Chloroplasts - convert light energy to form chemical energy Chloroplast Stroma Fig enclosed by two s with embedded proteins Inner and outer s Granum Inter space 10 Endosymbiosis States that mitochondria and chloroplasts were once prokaryotic cells that began living in larger cells Evidence: Both mitochondria and chloroplasts contain DNA and ribosomes (the kind found in prokaryotic cells) Engulfing of aerobic prokaryote Host cell Some cells Engulfing of photosynthetic prokaryote Host cell Fig Cytoskeleton Function in cellular support and motility Types: Microfilaments - structure Intermediate filaments - structure Microtubules - structure and movement Nucleus Nucleus Actin subunit Fibrous subunits Fig Microfilament 7 nm Intermediate filament 10 nm Microtubule 12

5 Cell Movement Cilia and flagella Composed of microtubules wrapped in an extension of the plasma Cilia Cross sections: Outer microtubule doublet Central microtubules Radial spoke Flagellum Microtubules found in a arrangement Flagellum Dynein arms Plasma Triplet Basal body Basal body 13 Extracellular Matrix Helps to hold the cells together in tissues Protects and supports the plasma Composed of glycoproteins (like collagen) Integrins - span the and transmit information between the ECM and the cell Glycoprotein complex with long polysaccharide Collagen fiber Connecting glycoprotein Integrin Plasma Microfilaments EXTRACELLULAR FLUID Fig CYTOPLASM 14 Cellular Junctions Allow for interactions between cells Tight junctions - form seals around cells and prevent leakage of extracelluar material Anchoring junctions - fastening cells together Gap junctions - allow for molecules to pass through Tight junctions Anchoring junction Gap junctions Plasma s of adjacent cells Extracellular matrix 15

6 Cell Walls Found in plant cells (also some bacteria and protists as well as fungi) Provide support Made of cellulose Contain plasmodesmata channels between cells plasma extends between cells so molecules can easily pass through Vacuole Primary cell wall Secondary cell wall Cytoplasm Plasma Walls of two adjacent plant cells Plasmodesmata Fig Fluid Mosaic Model Membranes are made up of phospholipids and proteins that can drift around amongst each other Two types of proteins: Integral - part of the protein is within the (If it goes all the way through, it is called a trans protein.) Peripheral - found only on the outside of the Many proteins are enzymes Membranes are selectively permeable Phospholipid bilayer! Messenger molecule Activated molecule Receptor Hydrophobic regions of protein! Enzymes Hydrophilic regions of protein! 17 Membrane Formation Membranes form spontaneously When a mixture of phospholipids and water is shaken, it will form water filled bubbles Water Water Water-filled bubble made of phospholipids 18

7 Passive Transport Requires no energy Molecules of dye Membrane Equilibrium Diffusion - tendency for particles to spread out evenly Two different substances Membrane Equilibrium Diffusion happens down a concentration gradient Fig Passive Transport: Osmosis Movement of water across a Moves in response to solute concentrations Solute molecule Lower concentration of solute Selectively permeable Water molecule H 2 O Higher concentration of solute Equal concentration of solute Solute molecule with cluster of water molecules Net flow of water 20 The ability of a solution to cause a cell to gain or lose water Isotonic - concentration same on both sides Hypertonic - concentration of solute is higher Hypotonic - concentration of solute is lower Osmoregulation - maintaining water balance Tonicity Animal cell Plant cell Isotonic solution (A) Normal Hypotonic solution (B) Lysed Hypertonic solution (C) Shriveled Plasma (D) Flaccid (E) Turgid (F) Shriveled (plasmolyzed) Fig

8 Passive Transport: Facilitated Diffusion Using a protein to aid in transport across a Ex. aquaporins transport water Solute molecule Some proteins function as a hydrophobic tunnel Transport protein Proteins are specific to the substrate 22 Active Transport Moving substances against their concentration gradient Require energy (ATP) Transport protein Solute Protein changes shape 1 Solute binding 2 Phosphorylation 3 Transport Phosphate detaches 4 Protein reversion 23 Bulk Transport Movement of large molecules Exocytosis - used to EXPORT Endocytosis - used to IMPORT Phagocytosis - engulfment by wrapping part of the cell around it Pinocytosis - taking in fluids Receptor-mediated endocytosis - interactions with specific proteins to pull items into the cell Phagocytosis EXTRACELLULAR FLUID Pinocytosis Specific molecule Pseudopodium Food or other particle Plasma Receptor-mediated endocytosis Receptor Coated pit CYTOPLASM Coat protein Food vacuole Vesicle Coated vesicle Food being ingested Plasma Coated pit Material bound to receptor proteins 24

9 Energy Transformation Cells carry out thousands of chemical reactions Energy - capacity to do work Kinetic energy - energy of movement Fuel Gasoline Energy conversion Heat energy Combustion Kinetic energy of movement Waste products Carbon dioxide Potential energy - stored energy Oxygen Energy conversion in a car Water Chemical energy is potential until teh reaction happens Heat First Law of Thermodynamics - energy cannot be created or destroyed, it can only be transferred or transformed Glucose Oxygen Cellular respiration Energy for cellular work Energy conversion in a cell Carbon dioxide Water Second Law of Thermodynamics - energy conversion decease oder of the universe (entropy) 25 Chemical Reactions Exergonic reaction - chemical reaction that releases energy Potential energy of molecules Reactants Energy released Products Amount of energy released Endergonic reaction - chemical reaction that requires energy Potential energy of molecules Reactants Energy required Products Amount of energy required 26 Adenosine triphosphate Source of energy that powers cellular work Three parts: adenine (a nitrogenous base), ribose (5-carbon sugar), and three phosphate groups Hydrolysis of ATP releases energy by removing a phosphate group ATP Adenine Ribose Adenosine Hydrolysis Phosphate group +! 27

10 Enzymes: Activation Energy Enzymes speed up chemical reactions Enzymes do this by lowering the activation energy of a reaction Energy Reaction without enzyme Reactants Reaction with enzyme E A without enzyme E A with enzyme Net change in energy (the same) Activation Energy (EA) - the amount of energy needed to start a reaction Progress of the reaction Products Fig Enzyme Catalysis Enzymes have unique shapes that determine how they work Active site - where the substrate interacts with the enzyme Enzymes need certain conditions to work (temp, ph, etc.) 1 Enzyme available with empty active site Active site Glucose Fructose 4 Products are released Enzyme (sucrase) Substrate (sucrose) 2 3 Substrate is converted to products Fig Enzyme Inhibition Blocking an enzyme from working Competitive inhibitors - compete for the active site Noncompetitive inhibitors - bind to another site on the enzyme and change the shape of the active site Competitive inhibitor Substrate Enzyme Active site Normal binding of substrate Noncompetitive inhibitor Enzyme inhibition Fig