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The Cell The smallest unit of life that can perform all life processes. “Life is macromolecules that can perform unique functions because they are enclosed in a structural compartment that is separate from the external environment. This separation allows living things to maintain a constant internal environment (homeostasis)”. All living organisms are composed of cells that can: • Respond to their environment • Grow, develop and reproduce • Metabolize • Maintain homeostasis A little bit of history “cells” Robert Hooke “little wretched beasties” Antone van Leeuwenhoek - lenses Anton van Leeuwenhoek (1673) Made microscopes with better magnification First person to observe living cells Spirogyra The Cell Theory (3 parts) Matthias Schleiden Theodor Schwann (botonist) (zoologist) 1. All organisms are made of one or more cells. 2. The cell is the basic unit of all living things. • All organisms are made of one or more cells • The cell is the basic unit of all living things Redi – spontaneous generation 3. All cells come from pre-existing cells Pasteur – spontaneous generation Cell Theory 1. The cell is the basic unit of life. 2. All life forms are made of one or more cells. 3. Cells only arise from pre-existing cells. Why are cells so special? Able to differentiate Stem cell = general, unspecialized cell Becomes specialized with time Examples: skin cells, macrophage cells, neurons Differentiation You can use different terms to describe the type of cell(s) you’re looking at. 3 different sets of words: 1) Unicellular vs. Multicellular Unicellular Uni = one One cell Multicellular Multi = many Many cells 2) Prokaryote vs Eukaryote prokaryote Cells that DO NOT have a cell membrane around their nucleus. example – Bacteria eukaryote Cells that have a membrane around their nucleus. Plant and Animal Cells Eukaryote cells usually 10X larger than Prokaryote cells. 2) Prokaryote vs Eukaryote Prokaryotic Cells No nucleus- DNA unbound No membrane-bound organelles All unicellular organisms All microscopic Eukaryotic Cells Have nucleus with DNA Organelles membranebound Unicellular OR multicellular organisms microscopic OR macroscopic Amoeba sisters – pro & eukaryotes 3. Plant or Animal Have cell walls Have chloroplasts Have large vacuoles Tend to have a square shape Plant Animal No cell walls Have small vacuoles, if any Not so square Eukaryotic Cell structures: structure and function Hank – crash course Organelles Structures within cells that have specific jobs “Little organs” plant cell wall cellulose cell wall cell membranes a dynamic structure – model fluid mosaic functions: Separates cell from its environment Allows cell to maintain homeostasis Acts as selectively permeable membrane (regulates molecules entering and leaving the cell) Cell-cell communication Surface markers - recognition Amoeba sisters - homeostasis Made of phospholipid bilayer with embedded proteins Harvard animation Phospholipid bilayer The protein part of the cell membrane provides: communication, "I.D." tags, anchors to microtubules, gates of exchange for large molecules and pumps for maintaining ionic balance. Special designs for specific function: The “typical” cell membrane vs different types of membranes better suited for function In a “typical” membrane, there is the passive phospholipid bilayer part (75-95%) and the active protein part (5-25%). Those cells that have to do more exchanging of materials, such as glandular cells, have more of the protein membrane. Those cells that have minimal exchange of materials, such as fat cells, have less protein membrane. the cell membrane semi-fluid Selectively permeable microfilaments & microtubules structure movement Cytoskeleton Function: Framework for the cellshape, organize, and support cell Other: made of proteins Cilia and Flagella Function: assist in movement Other: Cilia- short, hair-like Flagella- long, tail-like centrioles Molecular "tags" on microtubules direct traffic inside cells Cytoplasm Function: fill the spaces between organelles and the plasma membrane the nucleus contains the genetic material Nucleus Function: store and protect genetic info (DNA) NOT THE BRAIN- just stores the info Other: Chromosomes: DNA wound up with proteins Nuclear envelope: double membrane with pores endomembrane system endoplasmic reticulum rough ER • transports newly synthesized proteins • alters proteins • folds into tertiary structures smooth ER • site for synthesis of lipids and steroids • site for hydrolysis of glycogen • modifies (detox.) small molecules golgi apparatus • recieves proteins from ER – further modifications • Concentrates, packages, sorts proteins • Polysacc. for plant cell walls synthesized secreting side receiving side Vesicles and vacuoles The function and importance of vacuoles varies greatly according to the type of cell in which they are present. functions of the vacuole include: Isolating materials that might be harmful or a threat to the cell. Breaking down products taken into the cell to be used in metabolism. Exporting unwanted substances from the cell. Allows plants to support structures such as leaves and flowers. Exporting manufactured products from the cell. endocytosis and taking in exocytosis expelling pinocytosis phagocytosis • Uses energy • Encloses material in vesicles exocytosis Vesicle membranes are also phospholipid bilayer special vesicles and vacuoles peroxisomes • the most common vesicle in cells • found in all eukaryotes • contain enzymes to rid the cell of hydrogen peroxide (convert the hydrogen peroxide to water) • some detoxify alcohol and other harmful compounds by transferring hydrogen from the poisons to molecules of oxygen (oxidation). • others initiate production of phospholipids special vesicles and vacuoles lysosomes contain hydrolytic enzymes - break down cellular waste products, fats, carbohydrates, proteins, and other macromolecules into simple compounds, which are then transferred back into the cytoplasm as new cell-building materials • autophagy - recycles the cell's organic material special vesicles and vacuoles Helps maintain homeostasis for water balance (osmotic equilibrium) contractile vacuole central vacuole central vacuole (plants ONLY) Maintaining internal hydrostatic pressure or turgor within the cell contractile vacuole (animals ONLY) found in certain unicellular organisms pumps fluid from in the cell to the outside by alternately filling and then contracting ribosomes site of protein synthesis Mitochondria Function: supply energy by converting food to ATP Other: Highly folded membranes Has own DNA and ribosomes chloroplasts Chloroplast Function: carry out photosynthesis, which turns light energy to chemical energy Other: has own DNA and ribosomes Slide share examples The Cell is like…… CELL ANALOGY PROJECT City 1 City 2 springfield House analogy Amusement park