Cell Structure & Function Cell Theory Cells are fundamental to biology Cells are the basic living units within organisms (all chemical rxns. of life take place within cells) All organisms are made of cells Single-celled organisms (bacteria/protists) Multicellular organisms (plants/animals/fungi)
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Cell Structure & Function
Cell Theory Cells are fundamental to biology Cells are the basic living units within organisms
(all chemical rxns. of life take place within cells) All organisms are made of cells
Single-celled organisms (bacteria/protists)Multicellular organisms (plants/animals/fungi)
Cell Structure & Function
Basic Aspects of Cell Structure & Function Plasma membrane
Lipid bilayerProteins
DNA-containing region Cytoplasm Eukaryotic v. Prokaryotic cells
Prokaryotic v. Eukaryotic Cells
Two major classes of cellsProkaryotic cells (pro-, “before”)
Cell lacks a “true” nucleus
DNA is coiled in a nucleoid region
Cells lack nuclear membrane
Prokaryotic v. Eukaryotic Cells
[attachment structure]
[organelles that synthesize proteins]
[enclosing the cytoplasm][rigid structure outside the p.m. ]
[jelly-like outer coating]
[locomotion organelle]
[DNA location]
Prokaryotic v. Eukaryotic Cells
Eukaryotic cells (eu-, “true”)
Nucleuscontains most of the cells nuclear material, DNAusually the largest organelle
Bordered by a membranous envelope
Prokaryotic v. Eukaryotic Cells
Plant v. Animal CellsBoth contain
Plasma membrane(functions as a selective barrier)
Nucleus (gene-containing organelle)Cytoplasm (region between nucleus and p.m.)
Consists of organelles in a fluid (cytosol)
Prokaryotic v. Eukaryotic Cells
Plant v. Animal CellsOrganelles
Bordered by internal membranesCompartmentalizes the functions of a cellMaintains organelle’s unique environment
Most organelles are found in both plant andanimal cells
Plant v. Animal Cells
chloroplasts
Cell wall
Eukaryotic Cells
Major Cellular ComponentsNucleusRibosomesEndoplasmic reticulumMitochondriaChloroplasts (plants)Cytoskeleton
Eukaryotic Cells
Genetic control of the cellNucleus
Contains most of the genes (inherited DNAmolecules) of the cellGenes - portion of DNA that codes for proteinsProtein synthesis occurs at the ribosome
NucleusNuclear envelope encloses the
nucleus Double membrane separates
contents from cytoplasm Pores allow movement of
materials
DNA is organized along withproteins into a fibrous material(chromatin)
Upon nuclear division thechromatin fibers condense intochromosomes
Nucleolus Synthesis of rDNA -->
ribosomal subunits -->ribosome
Ribosomes
Sites of protein synthesis Composed of 2 subunits Size
Prokaryotes (70S)Eukaryotes (80s)
Except ribosomes ofmitochondria andchloroplasts (70S)
Ribosomes
Particles made from rDNAand cytoplasmic proteins
Either suspended in thecytosolEnzyme productionProteins in cytosol
Attached to theendoplasmic reticulum(ER)Synthesize membrane
proteins and secretedproteins
Eukaryotic Cells
Endomembrane systemResponsible for the manufacture and
distribution of cellular productsThis system includes the:
Endoplasmic reticulum (ER)Golgi apparatusLysosomesVacuoles
Endoplasmic reticulum
Reticulum, “little net” Consists of a physically connected network
of membranous tubules and sacs ER membrane separates the internal
compartment from the cytosol 2 distinct regions
Rough ERSmooth ER
Rough ER
Ribosomes on outersurface of the membrane
Produce 2 types ofproteinsMembrane proteinsSecretory proteins
Some products are sentvia transport vesiclesMembranous spheres that
bud from ER
Transport vesicles
Smooth ER
Cytoplasmic surfacelacks ribosomes
Smooth ER of various celltypes functions in diversemetabolic processesSynthesis of lipids
(steroids)Metabolism of
carbohydrates (sugarregulation by the liver)
detoxification of drugsand poisons
Golgi Apparatus
Consists of stacks offlattened unconnectedmembranous sacs(unlike ER)
Products of ER aremodified, stored andthen sent to otherdestinations:Plasma membraneOther organelles
Lysosomes
Membrane-bound sac of digestive enzymesStrong enzymes contained safelyBreak down:
Proteins, polysaccharides, fats and nucleic acids
Functions:Digest food contained in food vacuolesDestroy harmful bacteriaRecycle damaged organelles (autophagy)Programmed cell destruction
Vacuoles
Membrane-bound sacswithin the cell
Larger than vesicles 3 types
Food vacuoles(formed by phagocytosis)
Contractile vacuoles(freshwater protists)
Central vacuoles(plant cells)
Eukaryotic Cell
Genetic controlNucleusRibosomes
Endomembrane SystemEndoplasmic reticulum (ER)Golgi apparatusLysosomesVacuoles
Energy-converting OrganellesChloroplastsMitochondria
Chloroplasts
Organelles of plants andsome protists thatperform photosynthesis
Process of converting:
Light energy
usable chemical energy
Chloroplasts
Structure double-membrane
separates it from rest ofcell
Thylakoid disks chlorophyll trap light energy
StromaFluid outside the
thylakoidsContains chloroplast DNA
and ribosomes
Mitochondria
Found in nearly alleukaryotic andprokaryotic cells
Site of cellularrespiration:
Energy from sugar
Converted to ATP
Mitochondria
Structure Enclosed by a double-
membraneOuter membrane is
smooth Inner membrane is
convoluted Infoldings called cristae Increase of surface area
Mitochondrial matrixContains enzymes,
mitochondrial DNA andribosomes
Membrane Structure
Composed of mostly proteins and lipids (butcarbohydrates are also important)
Most abundant lipids in most membranes arephospholipidsAmphipathic structure
Phosphate group• Hydrophilic (likes water) because it
has an electrical chargeTwo fatty acids
• Hydrophobic (fears water) - no charge
Membrane Structure
Cell membranes arephospholipid bilayers
Stable boundary between 2aqueous compartments
Hydrophobic tails aresheltered from the water
Hydrophilic headsexposed
Membrane Structure
Membrane proteins Some bound to the
surface only Some span the
phospholipid bilayer(transmembraneproteins)
Fluid Mosaic Model
Membrane is a mosaic of protein moleculesbobbing in a fluid bilayer of phospholipids
Prokaryote v. Eukaryote
AbsentPresent (in some)EndosporesAbsentPresent (in most)Cell walls
80S(mitochondria/chloroplast 70S)
70S in sizeRibosomes
Complex(ex. ER, golgi apparatus)
Relatively simpleInternal membranesPresentAbsentNucleolusPresentAbsentNuclear membraneLarger ( 2 - 100um)Small ( < 2 um )Size
Algae, fungi, protists,plants, animals
Bacteria, ArchaeaPhylogenetic groupEukaryoteProkaryoteProperties
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