Cells: The Living Units

Transcription

1 Golgi Apparatus Cells: The Living Units Chapter 3, PPT 2 Membrane Yes, stacked and flattened Description Stacked and flattened membranous sacs Modify, concentrate, and package proteins & lipids made at Rough ER Traffic director / post office Golgi Apparatus Special Details Release secretory vesicles Lysosomes Membrane Yes Description Spherical bags containing digestive enzymes Lysosomes Digest particles taken in by endocytosis (bacteria, viruses, and toxins) Degrade worn out and nonfunctional organelles and tissues Perform metabolic functions Break down bone to release calcium ions Lysosomes Special Details Large and abundant in phagocytes 1

2 Peroxisomes Membrane Yes Description Spherical bags containing powerful digestive enzymes (Oxidases and peroxidases) Neutralize dangerous free radicals Oxidase converts them to H 2 O 2 (hydrogen peroxide) Peroxidases catalyze H 2 O 2 à H 2 O + O 2 What are the three elements of the cytoplasm? 1. Cytosol 2. Cytoplasmic Organelles 3. Inclusions What is cytosol? Viscous fluid in which the other elements are suspended What is an inclusion Chemical substances that may or may not be present, depending on the cell Which organelles are nonmembranous? Cytoskeleton, centrioles, ribosomes How many membranes does mitochondria have? Two What is Cristae Folds of inner membrane in mitochondria What is matrix? Gel-like substance in the inner portion of mitochondria What does it mean if a cell has a lot of mitochondria? It needs a lot of energy What is the formula for cellular respiration? C 6 H 12 O 6 + 6O 2 à 6CO 2 + 6H 2 O + ATP What organelle synthesizes (makes) protein? Ribosomes Where are ribosomes for that cell made? In free floating ribosomes Where are ribosomes for other cells made? On the rough ER What do we call the extensive system of interconnected tubes and parallel membranes enclosing fluid-filled cavities? The Endoplasmic Reticulum 2

3 What special feature do you find in the membrane of smooth ER? Integral Enzymes What do they do? Catalyze reactions Name two functions of the smooth ER: Lipid metabolism, absorption, transport Cholesterol & sex hormone synthesis Detox of drugs, pesticides and carcinogens Breakdown of stored glycogen to free glucose What two things are synthesized in the rough ER? Proteins and lipids What is the function of the Golgi Apparatus? Modify, concentrate, and package proteins & lipids made at Rough ER What is a secretory vesicle? A membranous sac that is released to be secreted Do lysosomes and perxisomes have membranes? Yes What are the membranes made of? Phospholipid bilayer In one word, what does a lysosome do? Digest In one word, what does a peroxisome do? Neutralize In two words, what does a mitochondria do? Make ATP / energy In three words, what does the Golgi do? Package, modify, transport Endomembrane System System of organelles that work together Structure ER Golgi Apparatus Secretory vesicles Lysosomes Nuclear envelope Produce, store, and export biological molecules Degrade potentially harmful substances 3

4 Endomembrane System System of organelles that work together Structure ER Golgi Apparatus Secretory vesicles Lysosomes Nuclear envelope Produce, store, and export biological molecules Degrade potentially harmful substances Figure 3.23 Cell skeleton Cytoskeleton Three types of rods (no membranes) 1) Microtubules 2) Intermediate Filaments 3) Microfilaments Microtubules Size: Largest diameter Composition: Hollow tubes, tubulin subunits Radiate from a centrosome region : Determine overall shape of cell, distribution of organelles (polymerization and depolymerization) Intermediate Filaments Size: Intermediate Composition: Tough, insoluble protein fibers : Internal guy-wires to resist pulling motions on cell Microfilaments Size: Thinnest elements Composition: Actin : Strengthen cell surface Membrane changes of endocytosis and exocytosis Cytoskeleton Wonder of the Cell Video Motor proteins walking on 28:43-29:45 Cytoskeleton & 38:25-42:01 4

5 Centrosome Microtubule organizing center Microtubules anchored near nucleus Contains paired centrioles Small barrel-shaped organelles oriented at right angles to form mitotic spindle Cellular Extensions Cilia Whip-like, motile cellular extensions Occur in large numbers on exposed surfaces of certain cells Move substances in one direction across cell surfaces Flagella Long singular cilia Propels cell itself Nucleus THE NUCLEUS Control center of cell Genetic Library Contains all instructions to build body s proteins Dictates kinds and amounts of proteins to be synthesized One nucleus Most cells Multinucleate Skeletal muscle cells Bone destruction cells Some liver cells Anucleate Mature red blood cells Nucleus #s Three structures/regions 1. Nuclear envelope 2. Nucleoli 3. Chromatin Nucleus 5

6 Nuclear Envelope Double membrane barrier separated by fluid filled space Outer membrane continuous with rough ER Nuclear pores - areas where 2 membranes fuse Selectively permeable Contains nucleoplasm Like cytoplasm/cytosol Nucleoli Where ribosome subunits are assembled Usually 1 or 2 per nucleus Contain DNA that issues genetic instructions for synthesizing ribosomal RNA (rrna) Chromatin Structure 30% DNA 60% Histone Protein Compact the DNA Gene regulation 10% RNA Form chromosomes when cell is ready to divide CELL GROWTH AND REPRODUCTION Figure 3.29 Cell Life Cycle Series of changes a cell goes through from the time it is formed until it reproduces 2 major phases Interphase Cell growth Regular functions Mitotic phase Cell division Interphase Period from cell formation to cell division Metabolic phase Growth phase 6

7 Subphases of Interphase G 1 (gap 1) Cell is metabolically active Synthesizing proteins Rapid growth Can take minutes to years G 0 Phase of cells that permanently cease dividing Subphases of Interphase S (synthetic) phase DNA replication New histone proteins formed What did histones do? G 2 (gap 2) Final, brief phase of interphase Enzymes, proteins, and organelles are replicated Mitotic Phase - Cell Division Essential for body growth and tissue repair Two parts Mitosis nuclear division Cytokinesis division of the cytoplasm DNA Replication DNA helix begins to unwind Helicase enzyme untwists double helix and separates DNA into two chains (exposes nucleotides) Free nucleotides serve as a template for a new strand New DNA segments spliced together by DNA ligase DNA Replication Cell Division - Preview Figure

8 4 Phases Prophase Metaphase Anaphase Telophase Mitosis Prophase Distinct pairs of chromosomes become apparent (tightly coiled DNA and protein) Each pair of chromosomes is made of identical sister chromatids, held together by a centromere Pairs of centrioles migrate to opposite ends of the cell, form spindle fibers between them Nuclear envelope and nucleolus disappear Early & Late Prophase Metaphase Chromosomes line up midway between centrioles Centromere holding each pair of chromosomes together attaches to spindle fiber between centrioles Figure Anaphase Centromere holding chromosome pair together separates Individual chromosomes migrate in opposite directions on the spindle fibers toward polar centrioles Cytokinesis begins Telophase Chromosomes complete migration toward centrioles Nuclear envelopes develop around each set of chromosomes Nucleoli develop Spindle fibers disappear Cleavage furrow nearly complete 8

9 Cytokinesis Division of the cytoplasm Contractile ring causes plasma membrane to draw inward and form a cleavage furrow Furrow deepens until it pinches into two daughter cells Each daughter cell is smaller and has less cytoplasm than mother cell but is genetically identical Protein Synthesis Preview Protein Synthesis Gene Segment of DNA that carries instructions for creating one protein Nucleotide bases are letters of DNA (A, G, T, C) Triplet/Codons - sequence of 3 bases that form words or amino acids trna - transfer RNA rrna - ribosomal RNA mrna - messenger RNA Transcription Transfer of information from a DNA gene s base sequence to the complementary base sequence of an mrna molecule Codon - 3-base sequence of mrna Translation Language of nucleic acids is translated into the language of proteins Anticodon - 3-base sequence of trna 9