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Biology 1105- Lesson 4

by: Hannah Dolan

Biology 1105- Lesson 4 BIOL 1105

Hannah Dolan
Virginia Tech

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Notes on the Structure of Cells
Principles of Biology
Dr. Jonathan I. Watkinson
Class Notes
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This 5 page Class Notes was uploaded by Hannah Dolan on Tuesday September 6, 2016. The Class Notes belongs to BIOL 1105 at Virginia Polytechnic Institute and State University taught by Dr. Jonathan I. Watkinson in Fall 2016. Since its upload, it has received 10 views. For similar materials see Principles of Biology in Science at Virginia Polytechnic Institute and State University.

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Date Created: 09/06/16
Lesson 4: Cell Structure 4.1 Cell Theory 1. All organisms are composed of one or more cells and life processes of metabolism and hereditary occur in these cells 2. Cells are the smallest living things- basic units of all organisms 3. Cells arise only by division of a previously existing cell Rate of diffusion is affected by:  Surface area available  Temperature  Concentration gradient  Distance Surface Area-to-Volume ratio: as a cells size increases its volume increases  Increased size means diffusion is harder to do 4 Major features of all cells: 1. Nucleoid/ Nucleus- o Where genetic information is stored 2. Cytoplasm- o A semifluid matrix that fills the interior o Cytosol: contains organic molecules and ions 3. Ribosomes- o Protein Synthesis 4. Plasma membrane o Encloses the cell and seperates its contents from its surroundings o Phospholipid bilayer:  Tails- non polar; hydrophobic  Head- polar; hydrophilic o Receptor proteins o Transport Proteins Prokaryotes- (simplest) 1 singular circular molecule of DNA in the center of the nucleoid Eukaryotes- (more complex) DNA found in the nucleus which is surrounded by the nuclear envelope 4.2 Prokaryotic Cells  Simplest organisms- small  Consists of cytoplasm surrounded by a plasma membrane encased within a cell wall  Ribosomes: Carry out protein synthesis  Bacterial cell walls (protection and structure) consist of peptidoglycan (carbohydrate matrix)  Archaea lack peptidoglycan  Flagella- long threadlike structure protruding from the surface of the cell that are used in locomotion 4.3 Eukaryotic Cells  Endomembrane system: Plant Cells:  Large membrane bound sac called a central vacuole o Stores proteins, pigments, and waste  Have mitochondria Both:  Vesicles- Store and transport a variety of materials  Chromosomes: compact units of DNA tightly wound around proteins  Cytoskeleton: internal protein scaffolding  Nucleus: largest organelle; contains DNA  Nucleolus: region where intensive synthesis of ribosomal RNA takes place.  Nuclear Envelope: two phospholipid bilayer membranes o Endoplasmic Reticulum (ER) o Nuclear Pores: allows ions and small molecules to pass freely while controlling the passage of proteins and RNA protein complexes. o Inner surface of the Nuclear Envelope is covered with a network of fibers that make up the nuclear lamina- nuclear lamins Chromatin: DNA Packaging  DNA divided into multiple linear chromosomes and organized with proteins into a complex structure called chromatin The Nucleolus: Ribosomal subunit manufacturing  Ribosomes must be constructed before carrying out protein synthesis Ribosomes: *not membrane bound*  Synthesize proteins and RNA  2 Subunits: 1. Ribosomal RNA *Join to form a ribosome only when actively synthesizing a protein* 2. Proteins  Requires 2 other forms of RNA 1. Messenger RNA:  Carries coding information from DNA  Information used to direct synthesis 2. Transfer RNA:  Carries amino acids  Found in cytoplasm or with internal membranes  Universal organelle- found in all cell types 4.4 The Endomembrane system: The largest of the internal membranes Phospholipid bilayer embedded with proteins Intercellular Transport o Exocytosis- exiting the cell o Endocytosis- entering the cell 2 Largest compartments: 1. Rough ER:  Ribosomes on the surface – proteins synthesized will be exported and sent to lysosomes/vacuoles  Proteins can be modified by short chain carbohydrates: glycoproteins  *proteins to be transported out of the cell are sent to the Golgi for modification and packaging* 2. Smooth ER;  Contains enzymes- synthesis of carbohydrates and lipids as well as steroids and hormones  Store intracellular Ca 2+ - keeps cytoplasmic level low- used as a signaling molecule  The Golgi Apparatus:  Flattened stacks of membranes- individual stacks are called Cisternae  Collection, packaging, and distribution of molecules  Front side: CIS face- near the ER:  Materials arrive here  TRANS face: away from the ER:  Discharges secretory vesicles  Lysosomes:  Contain digestive enzymes  Enzymes catalyze the rapid breakdown of proteins, Nucleic Acids, Lipids, and Carbohydrates  Acidic pH  Activated by using with a food vesical or an old warn out organelle  Micro bodies:  Enzyme bearing and membrane enclosed  *Peroxisome:  Catalase core-breaks down hydrogen peroxide  Contains enzymes involved in oxidation of fatty acids  Vacuoles:  Used by plants for storage and water balance  Central vacuole  Tonoplast: membrane surrounding the vacuole 4.5 Mitochondria and Chloroplasts: Cellular Generators  Metabolic processes Mitochondria:  Bound by 2 membranes: 1. Smooth outer membrane 2. Inner folded membrane- many contiguous layers called cristae  Cristae: 2 parts: 1. Matrix 2. Inter membrane space  Contains their own DNA-produces proteins for oxidative metabolism  Metabolizes sugar to generate ATP Chloroplasts:  Plant cells only  Manufacture their own food  2 membranes: 1. Closed compartments of stacked membranes called grana inside the inner membrane 2. Thylakoids- light capturing* 4.6 The Cytoskeleton Three types of fibers: 1. Actin filaments (microfilaments)  2 protein chains loosely twined together  +/- ends 2. Microtubules  Largest of the cytoskeletal elements  Ring of 13 protein protofilaments 3. Intermediate filaments  Most durable  A system of fibrous proteins twisted in an overlapping arrangement Centrioles:  Barrel shaped organelles  Centrosomes: region surrounding the pair of centrioles  Pericentriolar material: contains ring-shaped structures composed of tubulin  Cytoskeleton can aid in moving things  Actin filaments and microtubules- muscle cells 4 components to move along microtubules: 1. Vesicle/organelle 2. Motor proteins 3. Connector molecules (connects vesicle to motor molecule) 4. Microtubules 4.7 Extracellular Structures and Cell Movement  Myosin: protein that aids in forward motion o Muscle contraction  Flagella: o Undulate: waves up and down o Basal body  Cilia: o Short cellular projections  Plant Cell Wall: o Primary walls- laid down when the cell is still growing o Middle lamella- glues cells together o Secondary walls- deposited inside the primary walls of fully expanded cells  Animal cells; o Secrete an extracellular matrix  An elaborate mixture of glycoproteins o Collagen o Fibronectin - integrins- extends into the cytoplasm and attached to microfilaments and intermediate filaments  Extracellular Matrix- o similar to peptidoglycan wall of bacteria o protect, cushion, and strengthen cell o plants- cell wall  Endosymbiotic theory- o Engulfment of bacteria by proto-eukaryote led to symbiosis o Bacteria evolved into organelles-  Ex. Mitochondria- double membrane, has its own DNA, size


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