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emily changon 6 December 2012
Transcript of Biology
RNA is Ribonucleic acid, a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins, although in some viruses RNA rather than DNA carries the genetic information.
Endoplasmic reticulum is a network of membranous tubules within the cytoplasm of a eukaryotic cell, continuous with the nuclear membrane. It usually has ribosomes attached and is involved in protein and lipid synthesis.
Golgi Apparatus is a complex of vesicles and folded membranes within the cytoplasm of most eukaryotic cells, involved in secretion and intracellular transport.
Secretory vesicles is a membrane-bound organelle in which molecules destined for export are stored prior to their release, or exocytosis.
All of these things come together and make up a cell 3.) Describe the methods that you would have the team use to determine whether the structure is a mitochondrion, ribosome, lysosome, nucleolus, or indeed a new organelle. First I would have the team look at the structure and determine whether it was smooth or not. Then I would have them compare it to mitochondrion, ribosome, lysosome, and nucleolus to determine whether it was a new organelle or not. 4.)Discuss how cellular structures, including the plasma membrane, specialized endoplasmic teticulum, cytoskeletal elements, and mitochondria, function together in the contraction of skeletal muscle cells. Membrane provides structure, ER creates the molecules that the ribosomes within the mitochondria use. The ATP produced fires the motor molecules at once which leads to contraction. a.) Describe the structure of the membrane. You may want to include a labeled diagram with your description. The fundamental structure of the membrane is the phospholipid bilayer, which forms a stable barrier between two aqueous compartments. In the case of the plasma membrane, these compartments are the inside and the outside of the cell. Proteins embedded within the phospholipid bilayer carry out the specific functions of the plasma membrane, including selective transport of molecules and cell-cell recognition. b.) Explain the following methods of membrane transport and describe, in terms of structure, how materials enter and exit the cell. (osmosis, Facilitated diffusion, and active transport) Osmosis is the diffusion of water across a selectively permeable membrane.
Facilitated diffusion is the spontaneous passage of molecules and ions, bound to specific carrier proteins, across a biological membrane down their concentration gradients.
Active transport is the movement of a substance across a biological membrane against its concentration or electrochemical gradient with the help of energy input and specific transport proteins.
They all control how materials enter and exit the cell through those processes 2.)Compare active and passive transport. Active transport is diffusion of a substance against its concentration while passive transport is just the diffusion of a substance across a biological membrane.
Two examples of active transport is the uptake of glucose in the intestines in humans and the uptake of mineral ions into root hair cells of plants.
Two examples of passive transport is diffusion of oxygen into an aerobically respiring cell and diffusion of carbon dioxide out an aerobically respiring cell. 3.) The cytoplasm in typical plant and animal cells is slightly less than 1% saline. Ocean water is approximately 3% saline and pure water is 0%. a.) explain what will happen to the plant cell if it is placed in ocean water. b.) Explain what will happen to the plant cell if it is placed in pure water. c.) Explain what will happen to the animal if it is placed in ocean water. d.) Explain what will happen to the animal if it is placed in pure water. e.) Explain why all of the above happens. If a plant cell is placed in ocean water osmosis occurs because the concentration of substances dissolved in the cytoplasm is lower than the concentration of salt in salt water. The cytoplasm and the salt water are separated by the cell membrane, which is semi-permeable it lets water through but not dissolved substances. So, water will pass by osmosis from the cytoplasm to the salt water, and the cell will shrink as it loses water. Plant cells always have a strong cell wall surrounding them. When the take up water by osmosis they start to swell, but the cell wall prevents them from bursting. Plant cells become "turgid" when they are put in pure water. Turgid means swollen and hard. The pressure inside the cell rises, eventually the internal pressure of the cell is so high that no more water can enter the cell. This liquid or hydrostatic pressure works against osmosis. In pure water, animal cells swell up and burst: they do not become turgid because there is no cell wall to support the cell membrane. Plasmolysis occurs, when water goes out of the cell. Water always flows to the location with lower water concentration, and salt water would have a lower water concentration than a cell. All of the above happens because of osmosis. 4.) Membranes are important structural features of cells. a.) Describe how membrane structure is related to the transport of materials across a membrane. Membrane is really thin so materials can exit/enter easily. Also cell membrane consists of protein & phospholipid bilayer. The protein molecules act as carriers which "pump" molecules across the membrane, contain channels allowing transport of small molecules through the membrane.The phospholipid bilayer allows small molecules such as water to pass through it rapidly. Cellular Respiration and photosynthesis are two processes that lead to production of ATP. They work through the activity of a protein called ATP synthase. ATP synthase works based upon the process called diffusion, where molecules (in this case hydrogen ions) move from an area of high concentration to low concentration. Membranes provide the barrier to separate area that is high in H+ (hydrogen ions/protons) to one that is low. The energy that is required for H+ to traverse the membrane is coupled to ATP synthase which drives it to generate ATP. Check the links for more information. Essentially, membranes allow this concentration gradient to exist which provides the energy to mediate ATP synthesis. b.) Describe the role of membranes in the synthesis of ATP in either cellular respiration or photosynthesis. Eukaryotic Plant Cells Eukaryotic Animal cells a type of cell lacking a membrane-enclosed nucleus and membrane enclosed organelles; found only in the domains bacteria and archaea. a cell that is a structural and functional unit of a plant. Is an organism whose cells contain complex structures enclosed within membranes. Cytosol the aqueous component of the cytoplasm of a cell, within which various organelles and particles are suspended
Plasma membrane/cell membrane- membrane enclosing the cell
Nucleoulus- nonmembranous organelle involved in production or ribosomes; a nucleus has one or more nucleoli
Chromatin-material consisting of DNA and proteins; visible as individual chromosomes in a diving cell
Ribosomes- nonmembranous organelles that make proteins; free in cytoplasm or bound to rouch ER or nuclear envelope
Endoplasmic reticulum- network of membranous sacs and tubes; active in membrane synthesis and other synthetic and metabolic processes; has rough(ribosome-studded) and smooth regions
Golgi apparatus- organelle active in synthesis, sorting, and secretion of cell products
Lysosome- digestive organelle where macromolecules are hydrolyzed
Vacuole-food and water
Mitochondrion-organelle where cellular respiration occurs and most ATP is generated
Peroxisome-organelle with various specialized metabolic functions; produces hydrogen peroxide
Cytoskeleton-reinforces cell's shape, function in cell movement; components are made of protein
Centrosome- region where the cell's microtubules are initiated; in an animal cell, contains a parif of centrioles
Flagellum-locomotion organelle present in some animal cells; composed of microtubules
Endomembrane system Cytosol
Plasma membrane/cell membrane
Cell wall-outer layer that maintains cell's shape and protects cell from mechanical damage; made of cellulose. other polysaccharides, and protein
Vacuole- water prominent organelle in older plant cells; functions inculde storage, breakdown of waste products; enlargement of vacuole is a major mechanism of plant growth
Chloroplast- photosynthetic organelle,converts energy of sunlight to chemical energy stored in sugar molecules
Centrosomes Nucleoid-region where the cell's DNA is located
Plasma membrane-membrane enclosing the cytoplasm
Cell Wall-rigid structure outside the plasma membrane