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| What are bodies within the cytoplasm that serve to physically separate the different metabolic reactions that occur in the cells. | organelles |
| What is the type of microscope used that focuses a beam of electrons through the specimen? | electron microscope |
| What is a transmission electron microscope? | aims an electron beam through a thin section of the specimen, like the light microscope it transmits light through a slide. It uses electromagnets as lenses to focus and magnify sections of preserved cells which are stained with atoms of heavy metals that attach at certain places in the cells. They are used mainly to study INTERNAL structure |
| What is the scanning electron microscope? | Useful for detailed study of the surface of the specimen. The electron beam scans the surface of the sample which is coated with a thin layer of gold. The beam excites electrons on the samples surface and theese secondary electrons are collected and focused on the screen. |
| What are the advantages of a light microscope compared to electron microscope? | Light microscopes can study live cells, whereas electron microscopes can't. Light microscopes are less expensive. |
| Wht are the disadvantages of electron microscopy? | The methods used to prepare the specimen kills the cell. They may introduce structural features seen in micrographs that do not exist in the living cell. Artifacts can occur in light microscopy also. |
| Explain cell fractionation. | Cells are disrupted by centrifuging at various speeds and durations to isolate components of different sizes. It starts with homogenization, the disruption of cells in blender or ultra sound device. This breaks up the cells without damaging the organelles. The cells are then spun 10 minutes for the homogenate. |
| What contains most of the genes that control the eukaryotic cell. It is 5 micrometers in diameter and is enclosed by a nuclear envelope. | nucleus |
| The nuclear envelope is designed to seperate the contents of the ________ from the __________. | nucleus; cytoplasm |
| Describe the structure of the nuclear membrane. | Double membrane, lipid bilayer with associated proteins, contains pores that regulate what goes into and out of the nucleus. Surrounds the nucleus |
| What is the nuclear lamina? | On the nuclear side of the envelope it is lined by a netlike array of protein filaments that maintain the shape of the nucleus. This is is a framework of fibers extending throughout the nuclear interior. |
| Inside the nucleus the DNA is organized along with proteins into material called what?The DNA is in this form when the cell is in interphase. | chromatin |
| In prophase of the cell cycle the DNA once stringy and entangled condenses and becomes thick and is called? | chromosomes |
| The prominent structure in the nucleus that is where components of ribosomes are made and assembled is called?Sometimes there are more than one of these. | nucleolus lor nucleoli |
| What is the site for the seperation of chromosomes during cell division? | Nucleus |
| What organelle assists in the assembly of amino acids into proteins? | ribosomes |
| If a cell has a high rate of protein synthesis what organelle would be in large numbers? | nucleoli and ribosomes. Example: human liver cells have a few million ribosomes. |
| What is a free ribosome? | ribosomes found in the cytosol. Most of the proteins made by free ribosomes will function within the cytosol. Examples are enzymes that catalyze metabolic processes localized in the cytosol. |
| What is a bound ribosome? | They are attached to the endoplasmic retiuculum. They generally make proteins that are destined either for inclusion into membranes, for packaging within certain organelles such as lysosomes, or for export from the cell. |
| Cells that specialize in protein secretion like the cells of the pancreas and other glands that secrete digestive enzymes frequently have a high proportion of ___________? | bound ribosomes |
| Bound and free ribosomes are structurally _______ and __________. | identical and interchangeable. |
| Name the members of the endomembrane system. | nuclear envelope, ER, Golgi apparatus, lysosomes, vacuoles, and the plasma membrane. |
| What are the two distinct though connected regions of the ER. | Smooth ER and the Rough ER |
| What is the function of the rough ER? | site of protein and glycoprotein synthesis, Makes secretory proteins and membrane, transport, and modification. |
| Explain the steps for proteins destined for secretion which are made by ribosomes that are attached to the rough ER. | 1. Ribosomes attached to RER synthesize secretory proteins 2. The growing polypeptide is threaded through ER membrane into the lumen or cisternal space. 3. Protein folds into its native conformation. 4. If is is going to be a glycoprotein enzymes in the ER membrne catalyze the covalent bonding of an oligosaccharide to the secretory protein. 5. Protein departs in a transport vesicle pinched off from transitional ER adjacent to the rough ER site of production. |
| Explain how membranes are produced in the RER. | Membrane proteins are produced by ribomes. As a polypeptide grows, it is inserted directly into the rough ER membrane wher it is anchored by hydrophobic regions of the proteins. Enzymes within the ER membrane make phopholipids from raw materials in the cytosol. NEwly expanded ER membrane can be transported as a vesicle to other parts of the cell. |
| Explain the functions of the smooth ER. | Participates in the making of lipids, phopholipids and steroids. Participates in carbohydrate metabolism. Detoxifies drugs and poisons, Stores calcium ions necessary for muscle contraction. |
| Ribosomes build a cells ________. | protein |
| What is a ribosome made up of? | RNA and protein |
| In eukaryotic cells where are ribosomes made? | nucleolus |
| What is the Golgi apparatus? | organelle made of stacked, flattened membranous sacs (cisternae) that modify, stores and routes products of the ER. |
| What are the two poles of the Golgi apparatus? | cis and trans |
| Explain how the cis face of the Golgi appartus works. | receives products from transport vesicles from the ER. A vesicle fuses its membrane to the cis face of the Golgi and empties its soluble contents into the Golgis cisternal space. |
| Explain the trans face of the Golgi apparatus and how it works. | pinches off vesicles from the Golgi and transports molecules to other sites. |
| Name specific functions of the Golgi. | Removes some sugar monomers and substitutes others making different oligosaccharides. Proteins and phopholipids of membranes may be changed. Golgi enzymes change the oligosaccharide portions of glycoproteins. Makes certain macromolecules by itself, like many polysaccharides secreted by cells (hyalurionic acid- sticky substance that helps glue animal cells together).lt sorts products and targets them fro various parts of the cell by putting molecular tags such as phosphate groups on them. Transport vesicles from the Golgi may have external molecules on their membranes that recognize docking sites on the surface of specific organelles. |
| What is a lysosome? | a lysosome is an organelle which is a membrane bound enclosed bag of hydrolytic enzymes that digest all major classes of macromolecules. |
| What enzymes are found in lysomes to break down the four major macromolecules? | lipases, carbohydrases, proteases, nucleases |
| What is the optimal pH for lysomal enzymes? | 5 |
| What is the importance of a lysomal membrane? | It separates destructive hydrolytic enzymes from the cytosol. Maintains the optimal acidic environment for enzyme activity by pumping Hydrogens inward from the cytosol to the lumen. |
| Where are hydrolytic enzymes and lysosomal membranes synthesized? | RER and then processed in the Golgi apparatus |
| What are the functions of a lysosome? | Intercellular digestion. Recycle cells own organic material. Apoptosis or programmed cell destruction. |
| In a lysosome how do they exhibit intracellular digestion? | The plasma membrane engulfs a substance and pinches off to form a vacuole which then fuses with a lysosme and the hydrolytic enzymes digest the food. |
| How do lysosomes recycle their own organic material? | Autophagy self eating. They engulf other cellular organelles or part of the cytosol and digest them with hydrolytic enzymes. Resulting monomers are released intothe cytosol where they can be recycled into new macromolecules. |
| Explain apoptosis or programmed cell destruction in lysosomes. | This is the destruction of cells by their own lysosmes. It is important during metamorphosis and development. |
| What are two inherited storage diseases that are a result of an impaired lysosomal funciton? | Pompe's disease where the missing enzyme is a carbohydrase that breaks down glycogen. The accumulation of glycogen results in liver damage. Lysosomal lipase is missing in Tay Sachs which causes lipid accumulation in the brain. |
| What is the structure of a vacuole? | organelle which is a membrane enclosed sac that is larger than a vesicle. |
| What is the function of a vacuole? | Food vacuole formed by phagocytosis which is the site of intracellular digestion in some protists and macrophages. Contractile vacuole which pumps excessive water from the cell and is found in some protozoa. Central vacuole which is a large vacuole found in most mature plant cells. |
| What is a tonoplast? | In plants the central vacuole is enclosed by a membrane which is called the tonoplast and is part of the endomembrane system. |
| How does the central vacuole develop in plants? | The combining of smaller vacuoles derived from the ER and Golgi apparatus. |
| The central vacuole is a versatile compartment with many functions. Name them. | Stores organic compounds (protein storage in seeds) Stores inorganic ions ( K+ and Cl-). Separates dangerous metabolic by products from the cytoplasm. Contains soluble pigments in some cells ( red and blue pigments in flowers). Protection from predators by containing poisonous or unpalatable compounds. Plays a role in plant growth by absorbing water and elongating the cell. Contributes to the large ratio of membrane surface are to cytoplasmic volume. |
| What is the function of a peroxisome? | consume oxygen in various metabolic functions. They transfer hydrogen from various substrates to oxygen making hydrogen peroxide. They contain catalase that converts toxic H2O2 to water and oxygen. They breakdown fatty acids to smaller molecules like acetyl CoA. They detoxify alcohol and other harmful compounds. In the liver peroxisomes enzymatically transfere H from poisons to oxygen. |
| What are glyoxysomes? | They are specialized peroxisomes found in heterotrophic fat storing tissue of germinating seeds. They contain enzymes that convert lipid to carbohydrate. These biochemical pathways make energy stored in seed oils available for the germinating seedling. |
| What is the current thought of peroxisome biogenesis? | They pinch off from preexisting peroxisomes. Necessary lipds and enzymes are imported from the cytosol. |
