Chapter 2 - Cell Structure & Function Lesson 2.1 : Cell Structures ● Pg 73 for overview What is a Cell? Organelles : internal structures in eukaryotic cells that carry out specialized functions. - Eukaryotic cells contain membrane bound organelles, whereas prokaryotic cells do not Organelles & Functions : Plasma Membrane - forms a barrier around the cytosol of the cell - Maintains internal environment that allows organelle to carry out its function Nucleus and Nuclear Envelope - almost all eukaryotic cells have nucleus which contains DNA - Nucleus is surrounded by a double membrane called the nuclear envelope. Nuclear envelope is made up of 2 lipid bilayers folded together. - Different protein membranes embedded into the bilayer to transport molecules across the nuclear envelope. - Allows water & gas to freely pass Nucleolus - The nucleus is filled with nucleoplasm, a fluid similar to cytosol - a dense, irregular shaped region where subunits of ribosomes are assembled from proteins and RNA Endomembrane System (pg 74 & 75 )- A group of interacting organelles between the nucleus and the plasma membrane - Makes lipids, enzymes and other proteins for secretion or insertion into cell membranes - Destroys toxins and recycles wastes Endoplasmic Reticulum - extension of nuclear envelope that folds into sacs & tubes Rough ER : areas with ribosomes attached to the surface - Ribosomes synthesize polypeptide chains and proteins can fold in the ER - Proteins can be carried to different parts of the cell Smooth ER : areas without attached ribosomes (no proteins made) - Ribosomes from rough ER end up in smooth ER as enzymes Vesicles - a small membrane-bound organelle that transport, store or digest substances within a cell Vacuoles - a liquid -filled organelle that stores and disposes of wastes and aids in cellular metabolism and water balance - Large central vacuole present in plant cells Lysosome - Contains digestive enzymes that aid in waste disposal Golgi Bodies - folded membrane that looks like stacked pancakes - folded membranes where the final packaging of proteins occurs - The new proteins and enzymes are sorted and packaged in vesicles to be exported from the cell Mitochondria - The site of most ATP (an energy molecules) synthesis during aerobic Respiration The number of mitochondria varies depending on the type of cell and organism. Cells that have a high demand for energy have many mitochondria Plastids - involved in photosynthesis and storage in plants and algae Chloroplasts - the site of photosynthesis in eukaryotic cells - Oval or disk shape Chromoplast- an organelle that makes and stores pigments other than chlorophyll Amyloplast- an organelle that stores starch Cilia : tiny hair like structures that propel cells through fluids Flagella : microtubules propel The Cell Surface Cell Wall- around the plasma membrane - Only found in plant cells and gives structure to the plant cells Cell Junction- a structure that allows cells to interact with one another and the surrounding environment Fluid Mosaic Model : - Membranes are not rigid with molecules locked into place. There are lipid molecules with proteins embedded that float freely Molecules freely move between the two layers Membranes contain a mosaic (wide assortment) of proteins. Some proteins involved in transport & attachment Proteins larger than lipid molecules, so move slower in membrane Membrane asymmetry, protein in one half of lipid bilayer differ from those in other half, impacts differences in functions Lipid or protein components have carbohydrates linked to them forming glycolipids and glycoproteins Phospholipid Bilayer : - Phospholipids are the dominant lipids found in membranes - When added to an aqueous solution, many phospholipids form a bilayer A bilayer forms spontaneously in water because the hydrophobic ends are attracted to one another and face the interior What are Integral Membrane Proteins? Integral Membrane Proteins : protein imbedded in lipid bilayer - At least one region interacts with the hydrophobic core - Most are transmembrane proteins, have polar regions exposed to the aqueous environment on both ends
