The Cell Cell Parts • Cell Membrane, Cell Wall, Cytoplasm • Protein Production- Nucleus, Nucleolus, Endoplasmic Reticulum, Ribosomes, Golgi Bodies, Lysosomes • Energy- Mitochondrion, Chloroplasts (Energy- Mitochondrion, Chloroplasts) • Miscellaneous- Microtubules, Microfilaments, Plastids Cell Membrane It also connects the the endoplasmic reticulum, and the nuclear membrane. In the image below we have colored the membrane to highlight its composition. The yellow represents the phospholipids. The purple represents the membrane proteins Cell Membrane • The Cell membrane performs a number of critical functions for the cell. It regulates all that phospholipids enters and leaves the cell; in multicellular organisms it allows self recognition. In order to understand the function of the cell membrane you must understand its structure. Cell Membrane Close-up • Here we see a cross section of the cell membrane you should notice two different structures: The phospholipids are the round yellow structures with the blue tails, the proteins are the lumpy structures that are scattered around among the phospholipids. This is a simple representation of a phospholipid. the yellow structure represents the HYDROPHILLIC or water loving section of the phospholipid. The blue tails that come off of the sphere represent the HYDROPHOBIC or water fearing end of the Phospholipid. Below is a structural model of a phospholipid that explains what these terms mean. • Cell walls are the rigid structure found surrounding plant cells. They provide support for the plant Cell Wall Cytoplasm • The term cytoplasm refers to everything between the cell membrane and the nuclear envelope. It consists of primarily of water. It also contains various organelles as well as salts, dissolved gasses and nutrients. Cytoplasm • Protein Producing Organelles: Endoplasmic Reticulum, Ribosomes, Golgi Apparatus, Lysosomes • Energy Producing Organelles Mitochondrion, Chloroplasts • Specialty Structures -centrioles, vacuoles, cell walls, cilia, flagella, plastids NUCLEUSnuclear envelope The nuclear envelope is a double membrane. Is has 4 phospholipid layers. It is also has large pores through which materials pass back and forth. Nucleus The headquarters of the cell. It is a large dark spot in EUKARYOTIC cells. It controls all cell activity. Close up you will see that the nuclear membrane has many pores. The nuclear membrane is continuous with the E.R. With the outer membrane removed it is much easier to see the contents of the nucleus. The thick ropy strands are the CHROMATIN. The large solid spot is the NUCLEOLUS. The nucleolus is a knot of chromatin. It manufactures ribosomes. Chromatin Within the nucleus are found chromatin and a structure called the nucleolus. Chromatin is DNA in its active form. It consists of DNA looped around histone proteins. The nucleolus is a knot of chromatin. It is the nucleolus that manufactures ribosomes . Endoplasmic Reticulum • Smooth, no ribosomes • rough, has ribosomes Smooth E.R. • The endoplasmic reticulum is a series of double membranes that loop back and forth between the cell membrane and the nucleus. • These membranes fill the cytoplasm but you cannot see them because they are very transparent. There are two distinct types of E.R.: The rough E.R. has ribosomes and is the site of protein synthesis; the smooth E.R. has no ribosomes • R.E.R. The endoplasmic reticulum is a series of double membranes that loop back and forth between the cell membrane and the nucleus. These membranes fill the cytoplasm but you cannot see them because they are very transparent. • The ribosomes are the organelles which manufacture proteins. They are made of two separate parts. These structures are both made of ribosomal RNA. Ribosome GOLGI BODY The golgi body is Golgi Apparatus responsible for packaging proteins for the cell. Once the proteins are produced by the rough E.R. they pass into the sacklike cisternae that are the main part of the golgi body. These proteins are then squeezed off into the little blebs which drift off into the cytoplasm. Lysosomes are called suicide sacks. They are produced by the golgi body. They consist of a single membrane surrounding powerful digestive enzymes. From this screen you can cut the lysosome and move it around. Lysosome Lysosomes • With the outer membrane removed it is much easier to see the contents of the lysosome. Those lumpy brown structures are digestive enzymes. "suicide sacks” • They dissolve bacteria and other foreign bodies. Under some conditions the lysosomes in a cell will break open and a cell will self destruct in a process called autolysis (giving rise to the name "suicide sacks"). Vacuoles are large empty appearing areas found in the cytoplasm. They are usually found in plant cells where they store waste. As a plant cell ages they get larger. In mature cells they occupy most of the cytoplasm. Vacuole CENTRIOLE ENLARGED Microfilament These are hair like extensions off of the cell membrane. Cilia tend to be small and numerous and flagella tend to be large &few. They beat back and forth rhythmically. In unicellular organisms their job is locomotion. In large multicell organisms their role is to move fluid past the cell. Notice the 9+2 arrangement of the microtubles. Microtubule • Centrioles are found only in animal cells. They function in cell division. Zoom in and notice the 9 groups of 3 arrangement of the protein fibers. The MITOCHONDRION is the powerhouse of the cell. It is the site of respiration. It has a double membrane. From this view you can see very little >>>>>>>>>> The outer membrane is cut to get a better look. With the outer membrane removed it is much easier to see the contents of the mitochondrion. The white folded structure is the inner membrane. Most of AEROBIC RESPIRATION occurs along this membrane. Get a really good look by cutting the inner membrane. >>>next slide>>>>> The inner membranes is ruffled. It has a very large surface area. These ruffles are called cristae. Mitochondria have their own DNA and manufacture some their own proteins. It is thought that the mitochondrion evolved from symbiotic bacteria that took up residence inside the first eukaryotic cells. INSIDE THE INNER MITOCHONDRION • Plastids are large organelles found on plants and some protists but not in animals or fungi. They can easily be seem through a light microscope. The other class of plastid are called leucoplasts (colorless plastids); Plastids they usually store food molecules. Included in this group are amyloplasts or starch plastids shown here in potato root cell. PLASTIDS- Chloroplast • • Chloroplasts represent one group of plastids called chromoplasts (colored plastids). The chloroplast is the site of photosynthesis. It consists of a double membrane. Cut the outer membrane to get a better look inside. With the outer membrane removed it is much easier to see the contents of the chloroplast. The stacks of disk-like structures are called the GRANA. The membranes connecting them are the THYLAKOID MEMBRANES. Grana and Thylakoid Membranes Dissolve the Remaining membrane and zoom in to get a better look. • The membranes that you see here are the site of photosynthesis. It is here that the energy harnessing process of photosynthesis occurs.
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