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Transcript
CHAPTER 7 CELL STRUCTURE AND FUNCTION “You are a metropolis of 50 trillion citizens. Each of the cells in your body can be considered a sentient being in its own right. They all act together as a community, performing an ongoing act of prodigious collaboration.” Dr. Bruce Lipton Biologist CHAPTER 7: CELL STRUCTURE AND FUNCTION Section 1. Section 2. Section 3. Section 4. Discovery of Cells Cell Structure Cell Boundaries Diversity of Cellular Life CELL = THE BASIC UNIT OF LIFE Go to Section: Cell Size 10 fold decrease Micrometer: µm = 10-3 mm 10-6 m 0.001 mm Nanometer: nm = 10-3 µm 10-9 m 0.000001 mm 0.000000001 m PERIMICIUM Anton Von LEEUWENHOEK Early 1600’s Discovered living “cells” “Simple” Microscope Blood cells and Bacteria from teeth ROBERT HOOKE 1665 Termed the word “Cell” 1830’s Matthias Schleiden = plants “Botanist” Theodor Schwann = Animals “Zoologist” Rudolf Virchow (1855) = “cells come from other cells” CELL THEORY 1. All organisms are composed of cells. 2. Cells are the basic units of structure and function in living things. 3. New cells are produced from existing cells. Electron Microscopes 1940’s 2 million x TEM “Transmission” SEM “Scanning” Rabbit Trachea (cilia) Bacteria 1-10 microns Control of Cell Size (1 micron = 0.001 mm) Streptococcus Eukaryotic 10 -100 microns Blood Cell As a cell increases in size, its volume increases faster than its surface area. Smaller objects have a greater ratio of surface area to volume. Larger organisms have “more” cells not “larger” cells High surface to volume ratio facilitates the exchange of materials in/out of cells PROKARYOTIC CELLS “Bacteria” “No True Nucleus” Organism is a single cell (unicellular) = a cell that lacks internal structures surrounded by membranes EUKARYOTIC CELLS “True Nucleus” Protists, Fungi, Plants, Animals Organism can be unicellular or multicellular = cells containing internal, membrane bound structures Escherichia coli Advantages of being multicellular? Eukaryotic Cells Animal Cell Cytoplasm = entire region between the nucleus and plasma membrane Cytosol = semifluid substance within the cytoplasm Plant Cell Plasma Membrane (Cell Membrane) = a selective barrier controlling the transport of material in/out of the cell Nucleus Nuclear Envelope = double lipid bilayer enclosing the nucleus (outer and inner) Nuclear Pores = openings within the envelope Chromatin = protein/DNA complex Nucleolus = synthesis of ribosomes Ribosome = synthesize proteins (protein synthesis) Composed of ribosomal RNA (rRNA) and two sub units (proteins) Free ribosomes = suspended in the cytosol Proteins function in the cytosol Bound ribosomes = attached to endoplasmic reticulum Proteins are transported around/in/out of cell Free and Bound are structurally identical and can alternate between the two roles (cell adjusts) Endomembrane System Membranes that are related either through direct physical continuity or by the transfer of membrane segments as tiny vesicles (sacs made of membrane) -Nuclear envelope -Endoplasmic Reticulum -Golgi Apparatus -Lysosomes -Vacuoules (various kinds) -Plasma Membrane Endoplasmic Reticulum (ER) endoplasmic = “within the cytoplasm” reticulum = “little net” Cisternae = network of membranous tubules and sacs ER membrane is continuous with the Nuclear Envelope Smooth ER = lacks ribosomes on surface metabolic processes (synthesis of lipids, metabolism of carbohydrates, and detoxification of drugs and poisons) synthesize sex hormones Rough ER = contains ribosomes on the surface -provide surface area for ribosomes -helps package and sort proteins -forms transport vesicles Golgi Apparatus = modifies, stores, targets, and ships products from the ER especially extensive in cells specialized for secretion Transport vesicles “Cis” face “Trans” face Transport vesicle cis/ trans = opposite polarity “budding” Proteins can be modified along the passage (by enzymes) The Golgi can also manufacture certain macromolecules itself Lysosomes = a membrane-bounded sac of hydrolytic enzymes that the cell uses to digest macromolecules internal pH = ~5 (if burst, enzymes are relatively inactive) Lysosome formation and function The lysosome and enzymes are produced by the ER Golgi Lysosome Phagocytosis = feeding by engulfing smaller organisms or food particles Lysosome digests the food products become cellular nutrients Autophagy = recycling of organic material (worn out organelles) Apoptosis = Programmed destruction of own cells (tadpole tails, human webbed fingers) Vacuoles Food Vacuole = formed from phagocytosis Contractile Vacuole = pump excess water out of the cell (protists) Central Vacuole -Plant Cells -Endomembrane System -Hold reserves of organic compounds -Pigments for color (flower petals) -Poisonous/unpalatable compounds (protection) -Absorb water (growth) Paramecium Osmoregulation Mitochondria Energy transformation = site of cellular respiration (ATP synthesis from organic compounds) Contain ribosomes and own DNA Grow and reproduce on their own Mobile 2 membranes (both phospholipid bilyers) Number of mitochondria is correlated with the cell’s level of metabolic activity Inner membrane has folds (cristae) Chloroplast Energy transformation Photosynthetic production of sugar “Plastid” Amyloplasts (store starch/ amylose) Chromoplasts (have pigments that give fruits and flowers orange/yellow colors) -Own DNA -Grow and reproduce on own -Mobile -Chlorophyll – pigment -2 membranes Cytoskeleton = a network of fibers (protein) extending throughout the cytoplasm Gives mechanical support to the cell and maintains its shape Especially important to animal cells (no cell wall) Provides anchorage for many organelles Can be disassembled and reassembled in a different part of the cell (changing cells shape) Microtubules Cellular functions arise from cellular order A cell is a living unit greater than the sum of its parts Macrophage – defends against bacteria Crawls and reaches with pseudopodia Engulfs bacteria Digests by lysosome (produced by endomembrane system) Ribosomes synthesize the enzymes DNA genetic programming Process requires ATP Mitochondria • YouTube - 3D sperm fertilization project Egeria densa Homo sapiens Paramecium Volvex “colonial” Daphnia “animal” Actinophrys Amoeba Spirogyra “algae” Euglena DO NOT SEEK TO FOLLOW IN THE FOOTSTEPS OF THE MEN OF OLD; SEEK WHAT THEY SOUGHT. - BASHO