Key Card for Animal Cell©2002 The Science Source®

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B102

1. Vacuole2. Lysosome or Peroxisome3. Ribosome4. Cell Membrane5. Golgi Body with Vesicles6. Pinocytotic Vesicle Formation7. Smooth Endoplasmic

Reticulum

8. Centrioles9. Centrosomal Area

10. Mitochondrion11. Outer Membrane of

Nuclear Envelope12. Nuclear Pores13. Nucleolus

14. Chromosome15. Inner Membrane of

Nuclear Envelope16. Nucleus17. Rough Endoplasmic

Reticulum18. Cytoplasm with

Organelles

ORGANELLE DESCRIPTIONS

CELL WALL

Mechanically strong extracellular material depositedoutside the plasma membrane of plant cells. Primarycell walls are elastic and found on cells that can growand elongate. Secondary cell walls are more rigid and,when present, are deposited inside the primary cellwall. Cells with secondary walls are common inwood.

CENTRIOLESA short cylindrical array of nine triplet microtubules.Found in animal cells and cells of most eukaryoticorganisms that produce flagellate cells.

CENTROSOMERegion close to the nucleus in eukaryotic cells. It is anarea involved in the development of microtubules(often referred to as a microtubule organizing center)that are necessary for cell movements, e.g. the mitoticspindle. Each pole of the spindle of a dividing nucleuswould have a centrosome. In animal cells and mostplants and fungi with motile cells, the centrosomecontains a pair of centrioles.

CHLOROPLASTS

Organelles present in photosynthesizing, usuallygreen, eukaryotic plant cells. They share severalproperties with mitochondria, i.e., they are bounded bytwo membranes, have circular DNA and bacterial sizeribosomes. The interior of a chloroplast has anelaborate system of membranes that contain thephotosynthetic apparatus. These membranes are calledthylakoids and when they become stacked, they arereferred to as grana.

CHLOROPLAST STROMA

The interior space in a chloroplast. It containsenzymes that are involved in the incorporation of CO2

into sugars.

CHROMATIN

Complex of the DNA and proteins in the nucleus of aeukaryotic cell.

CHROMOPLAST

A membrane-bounded vacuole in some plant cells.Chromoplasts contain pigments and the latter are oftenorange-yellow carotenoids

CYTOPLASM

All the material and organelles inside the plasmamembrane and outside of the nucleus.

CYTOSOL

Everything in the cytoplasm other than the membrane-bounded organelles.

ENDOPLASMIC RETICULUM

The endoplasmic reticulum (ER) consists of flattenedsheets, sacs and tubes that extend through thecytoplasm. The sheets may be continuous with theouter membrtme of the nuclear envelope. If the ER isstudded with ribosomes that are synthesizing proteins,it is called rough ER. In contrast, smooth ER lacksribosomes and is involved in lipid synthesis.

GOLGI BODY

A system of stacked, membrane-bounded sacs. TheGolgi is involved in processing macromolecules forsecretion and delivery to other components of the cell.

GRANUM

Group of stacked membrane-bounded discs inchloroplasts. They contain chlorophylls and are thesite of the light-trapping reactions in photosynthesis

LYSOSOMESMembrane-bounded vesicles that contain enzymesinvolved in the digestion of foreign elements.Conditions that result in the release of these enzymesinto the cytoplasm may result in cell death.

MIDDLE LAMELLA

A mucilaginous layer between plant cells with primarywalls. The layer is rich in pectin.

MITOCHONDRIA

Organelles present in eukaryotic cells and bounded bytwo membranes. They are often referred to as thepower plants of cells as they are the site of aerobicrespiration that combines oxygen with food moleculesto generate ATP, an important energy containingmolecule. Like chloroplasts, mitochondria usuallycontain circular DNA (similar to the organization ofDNA in bacterial cells) that codes for some of themitochondria! proteins. Ribosomes in mitochondria

are smaller than those in the cytosol and of the samesize as bacterial ribosomes.

NUCLEAR ENVELOPE

The double membrane structure that surrounds thenucleus and separates it from the rest of the cytoplasm.It has nuclear pores that allow for communicationbetween the nucleus and the cytoplasm.

NUCLEAR PORES

Openings in the nuclear envelope that allow forcommunication between the nucleus and thecytoplasm.

NUCLEOLUS

Site in the nucleus where ribosomes are synthesized.

NUCLEOPLASM

Matrix of the nucleus, not including nucleolus andchromosomes.

NUCLEUS

This is the most conspicuous organelle in most cells.It is separated from the cytoplasm by the nuclearenvelope that consists of an inner and outer membranelayer. Nuclear pores in the envelope allow the nucleusto communicate with the cytoplasm. The nucleuscontains most of the cell's genetic material in the DNAthat makes up the chromatin fibers of thechromosomes. The nucleolus is in the nucleus and it isthe site at which ribosomes are assembled.

PEROXISOMES

Membrane-bounded vesicles that containoxidative enzymes concerned with the generationand destruction of hydrogen peroxide, a moleculethat would cause serious damage if it werereleased into the cytoplasm

PLASMA MEMBRANEThe outer boundary of the cell; also called the cellmembrane. A sheet of lipid molecules (bilayer) withproteins embedded in it. The plasma membranecontrols movement of materials into and out of thecytoplasm.

PLASMODESMATA

Cytoplasmic connections between plant cells. Formedduring mitosis at the cell plate as cell wall precursorscondense.

PRIMARY CELL WALL

The cell wall produced outside of the plasmamembrane of young and growing plant cells. Thesewalls are elastic and allow for elongation and changesin shape. They contain mostly cellulose andhemicellulose.

RIBOSOMES

Particles composed of RNA and protein that areinvolved with messenger RNA in the synthesis ofproteins.

SECONDARY CELL WALL

Walls formed inside the primary cell wall when cellsdifferentiate for some special function and lose theability to grow or elongate. Conductive cells havesecondary wall as do most of the cells in a woodyplant. Secondary cell walls have lignins that resistdecomposition and breakdown.

VACUOLES

Membrane-bounded structures in the cytoplasm thatmay contain enzymes, crystals and dissolvedmaterials. Animal cells have small vacuoles whereasplant cells characteristically have large vacuoles.Plant vacuoles may store waste materials but also helpto maintain the shape of plants. If large amounts ofwater are removed from the vacuoles, wilting occurs.

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