Cell Organelles By Diana L. Duckworth Rustburg High School Campbell County

Nucleus Enclosed by nuclear envelope –Double membrane, each a lipid bilayer –Two membranes merge in pores Protein lined channels for exit of mRNA and ribosomes from nucleus Within nucleus one or more nucleoli –Site for the manufacture of ribosomes Chromatin – DNA in combination with proteins –Diffuse mass uncoiled chromatin so DNA can be transcribed; condensed (tightly coiled) during cell division

Nucleus Pores Ribosomes Chromatin

Nuclear Envelope Nucleoli (nucleolus – singular)

Endoplasmic Reticulum (ER) Membrane system within cytoplasm Connected to nuclear envelope Two kinds of ER –Smooth endoplasmic reticulum Synthesis of lipids, phospholipids, steroids Detoxifies drugs (good & bad) Stores calcium ions in muscle cells –Rough Endoplasmic Reticulum Ribosomes attached to ER Synthesis of proteins and hormones for sectretion

Rough Endoplasmic Reticulum

Ribosomes – Free or Attached to ER Free manufacture proteins for use in cytoplasm; attached to ER they manufacture proteins for export outside cell.

Golgi Apparatus Stack of flattened membranous sacs (cisternae) Finishing and distribution of export products & does make some polysaccharides for export Vesicles from ER bud off and merge with one side of Golgi apparatus (near E.R.) Cisternae mature through the stack Finished products bud off from other side in transport vesicles

Golgi Apparatus

Formation of Golgi & export of products

Lysosomes Digestive vesicle produced by Golgi –Acidic environment in lysosome –Contains enzymes that break down macromolecules & recycle components Function by engulfing material from cytoplasm (autocytosis) or by merging with food vacuoles –Food vacuoles form when cell engulfs something from outside cell (phagocytosis)

Vacuoles Membrane bound sacs serve a variety of purposes Food vacuoles form when cell engulfs material from outside cell (phagocytosis) Plant cell vacuoles surrounded by membrane called tonoplast –Used as storage for cell wastes, water –Get larger by merging with smaller vacuoles –Occupy most of volume of plant cell, cytosol is thin region between vacuole & membrane

Mitochondria Site of cellular respiration –Generate ATP from extracting energy from sugars, fats & other fuels Enclosed by membranes that are not part of cellular membrane system –Has at least 2 membranes separating interior from cytosol –Contain both ribosomes and DNA –Some membrane proteins are imported from cytosol Grow and reproduce within cell, separate from cellular reproduction

Mitochondria one.html

Chloroplasts Conversion of light energy to chemical energy in sugars One of group of organelles – plastids Surrounded by 2 membranes (not ER) Internal membrane system called thylakoids Stacked thylakoids called granas Surrounding fluid called stroma & contains DNA, ribosomes, enzymes nthScienceWork/CellTheoryParts. htm

Peroxisomes Single membrane bound vesicles Contain enzymes initiate breakdown of complex molecules into smaller molecules –By-product is hydrogen peroxide (toxic) –Enzymes convert this to water Do NOT form by budding from ER –Grow larger by adding proteins formed in cytosol & lipids made in ER –Split in two when become too large

Cytoskeleton – 3 components Microtubules – largest; hollow rods –function in cell division –Mobility of organelles –Shape & support cell –Responsible for beating of cilia & flagella Microfilaments (Actin filaments & Myosin filaments) –Resist tensional forces on cell –Contractile apparatus in muscle cells, cell motility Intermediate filaments –Control shape of cell; more permanent

Extracellular Components of Cells Plant cell walls –Protection; prevents excessive water uptake; maintains shape –Cellulose (polysaccharide) fibrils embedded in matrix of other polysaccharides and proteins Extracellular matrix of animal cells (ECM) –Glycoproteins (collagen) secreted by cells –Communicates with cytoskeleton & can affect development & differentiation of cells

Generalized Animal Cell

Generalized Plant Cell