Cell Organelles Chapter 7 – Section 3

Organelles Eukaryotic cells contain organelles that allow the specialization and the separation of functions within the cell.

Plant Cell Animal Cell

Cell Boundaries Plasma Membrane – semi-permeable membrane Cell Wall Plants, Fungi, and Bacteria have this additional boundary Located outside the plasma membrane Provides additional support and protection (cellulose) Allows molecules to pass through (no selection)

Cytoplasm Clear, jelly-like fluid that supports the cell Site of chemical reactions Houses all of the other organelles

Cytoskeleton Organelles don’t float freely in a cell. They are supported by structures in the cytoplasm – the cytoskeleton. The cytoskeleton is a network of long, thin protein fibers Provides a framework for the cell Provides anchorage for organelles Made of microtubules and microfilaments

Microtubules and Microfilaments of the Cytoskeleton Microtubules – long, hollow protein cylinders that form a rigid skeleton for the cell and assist in moving substances within the cell. Microfilaments – thin protein threads that help give the cell shape and enable the cell and its parts to move.

Nucleus Nucleolus Inside nucleus Makes ribosomes Contains DNA which stores information for making proteins for cell growth, function, and reproduction. Nuclear Envelope – the membrane surrounding the nucleus. It’s similar to the plasma membrane. Nucleolus Inside nucleus Makes ribosomes

Ribosomes Are made in the nucleolus. Found bound to rough ER and floating in the cytoplasm. No membrane Site of protein synthesis (protein assembly) according to directions from the nucleus. Cells have many ribosomes that produce a variety of proteins that are used by the cell or are sent out to be used by other cells. Free-floating ribosomes produce proteins in the cytoplasm to be used by the cell. ER-bound ribosomes produce proteins which will be packaged within membranes or to be used by other cells.

Endoplasmic Reticulum (ER) Highly folded membranes suspended in the cytoplasm Site of protein synthesis and lipid synthesis 2 Types: Rough ER – area on ER where ribosomes attach, make and transport proteins (cellular highway). Smooth ER – area where no ribosomes are attached, makes lipids (like phospholipids, for example), transports proteins, breaks down harmful substances (liver cells).

Golgi Apparatus Flattened system of tubular membranes Modifies proteins by attaching carbohydrates and lipids Sends proteins to the plasma membrane in packages called vesicles to be exported outside the cell. “Post-Office”

Lysosomes Contain digestive enzymes to break-down worn-out organelles, food particles, viruses, and bacteria Can fuse with vacuoles to digest the contents Found only in animal cells “Clean-up crew” of the cell

Centrioles Animal cells only Made of microtubules Function during cell division. More about these in Chapter 9.

Mitochondria “Powerhouse” – energy-generator for the cell In plant and animal cells Converts fuel particles (in the form of sugars) to energy

Chloroplasts Only in plant cells Contain the green pigment chlorophyll Site of photosynthesis – captures light energy and converts it to chemical energy the plant cell can use

Vacuoles Sac-like structure Plant cells contain one large one Animal cells usually don’t contain vacuoles but if they do, they are small. For temporary storage of water, food, enzymes and/or wastes.

Cytoskeleton Provides structure and support Works like poles of a tent Assists organelles in moving around the cell

Cilia Short, hair-like fibers (protein based) that move in a wave-like motion to propel (move) the cell or materials along surface of cell paramecium Tracheal cells (#3 is mucous particle)

Flagella Long, whip-like projections that propel the cell Protein based

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