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Cell Organelles and Features. Plasma/Cell Membrane. Found in both prokaryotes and eukaryotes Structure: Composed of: phospholipids, cholesterol, and proteins Organization: Phospholipids form a bilayer Proteins and cholesterol are embedded in the bilayer. Cell-Membrane = Fluid Mosaic Model.
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Plasma/Cell Membrane • Found in both prokaryotes and eukaryotes • Structure: • Composed of: phospholipids, cholesterol, and proteins • Organization: • Phospholipids form a bilayer • Proteins and cholesterol are embedded in the bilayer
Cell-Membrane = Fluid Mosaic Model • Membrane’s lipids and proteins move laterally within the bilayer • The “pattern” of the mosaic is always changing
Function of the Membrane Components • Phospholipids • Control what enter and exit the cell • Give structure to the cell • Proteins • Control what enter and exit the cell • Interact with external environment • Facilitate chemical reactions • Receive signals • Cholesterol • Maintain fluidity of cell
Nucleus • Structure: • Nucleoplasm • Nuclear envelope with nuclear pores • Double membrane • Nucleolus • Contains DNA
Functions of Nucleus • Nucleoplasm • Surrounds and protects DNA • Nuclear envelope and nuclear pores • Controls what enters and exits the nucleus • Nucleolus • Production of ribosomes (structures that synthesize proteins)
Ribosomes • NOT technically organelles • Made of proteins and RNA, but have NO membrane • Some ribosomes are free-floating in cytoplasm others are bound to the endoplasmic reticulum
Endoplasmic Reticulum (ER) • Structure: system of membranous tubes and sacs (cristernae) • Two types of ER: Rough and Smooth • Rough ER is covered with ribosomes • Smooth ER lacks ribosomes
Function of the ER • Both types of ER serve as intracellular highway along which molecules move from one part of the cell to the other • RER • Produces phospholipids and proteins • SER • Build lipids, such as cholesterol and steroid hormones • Detoxifies blood and poisons
Golgi Apparatus • Structure: system of flattened, membranous sacs • Function: • Modifies proteins that it receives from the RER • Exports protein to the appropriate location
Vesicles • Structure: • small, spherically shaped sacs • Surrounded by single membrane • Vesicles are classified by their contents • Often migrate and merge with plasma membrane to release contents • Types of Vesicles: lysosomes, peroxisomes, glyoxysomes, endosomes
Lysosomes • Contain digestive enzymes • Created by the Golgi apparatus • Responsible for breaking down cells when it is time for the cell to die = autolysis Food Vacuoles are referred to as endosomes
Peroxisomes • Contain enzymes that breakdown alcohol and drugs into peroxide (H2O2) • Neutralize free radicals • Not created by the Golgi apparatus • Special type of peroxisome = glycoxysomes • Found in seeds of some plants
Ribosomes, ER, Golgi, and Vesicles all play a role in protein synthesis • Proteins are assembled by ribosomes on the RER • Vesicles transport proteins to the Golgi apparatus • Golgi modify proteins and package them into new vesicles • Vesicles fuse with the plasma membrane to release proteins outside the cell • Vesicles containing enzymes that remain inside the cell form lysosomes, peroxisomes, endosomes, etc.
Mitochondria • Structure: • Outer and inner membrane • Inner membrane has many folds = cristae • Contain DNA • Function: transfer energy from organic molecules to ATP (cellular respiration)
Cytoskeleton • Structure: Network of thin tubes and filaments that crisscross in the cytosol • Three major components: • Microtubules • Microfilaments • Intermediate filaments • Function: • Give shape and support to the cell • Acts as a system of internal tracks for intracellular movement
Cilia and Flagella • Structure: Hairlike structures that extend from the surface of the cell • Part of the cytoskeleton • Function: Assist in movement
Centrioles • Structure: two short cylinders of microtubules at right angles • In the cytoplasm near the nuclear envelope • Part of the cytoskeleton of animal cells • Function: organize microtubules during cell division
Do all cells contain all of these organelles in the same concentration?
What organelle(s) would you find a lot of white blood cells?