BIOL1002 Chapter 5 THE WORKING CELL
BIOL1002 Chapter 5 THE WORKING CELL Biol1002
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This 3 page Class Notes was uploaded by Jakyia Notetaker on Tuesday September 27, 2016. The Class Notes belongs to Biol1002 at North Carolina A&T State University taught by Dr.Mack in Fall 2016. Since its upload, it has received 3 views. For similar materials see Biological Sciences in Biological Sciences at North Carolina A&T State University.
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Date Created: 09/27/16
Chapter 5 the working cell Harnessing cellular structures - Sperm cells generates energy by breaking down sugars. Enzymes within the cell carry out a process called glycolysis - During this, the energy released from the breakdown of glucose so it can produce ATP *Cells control their chemical environment using energy, enzymes, and the plasma membrane. Energy is defined as the capacity to cause change. There are two kinds of energy - Kinetic energy is the energy of motion - Potential energy is stored energy. Conservation of Energy and Heat Physical principle known as conservation of energy explains that it is not possible to destroy or create energy. *Energy can only be converted from on form to another. Heat is a type of kinetic energy contained in the random motion of atoms and molecules. All energy conversions generate some heat. Entropy is a measure of disorder, or randomness, in a system. Every time energy is converted from one form to another, entropy increases. Chemical Energy Chemical energy arises from the arrangement of atoms and can be released by a chemical reaction. Living cells and automobile engines use the same basic process to make the chemical energy stored in their fuels available for work. In other cases, this process breaks organic fuels into smaller waste molecules that have much less chemical energy than the fuel molecules did, thereby releasing energy that can be used to perform work. Cellular respiration is the energy releasing chemical breakdown of fuel molecules and the storage of that energy in a form the cell can use to perform work. - Humans convert about 34% of our food energy to useful work - The rest of it is generated into body heat. Food Calories A calorie(cal) is the amount of energy that can raise the temperature of 1 gram (g) of water by 1degree C. *Food calories are kilocalories, equal to 1,000 calories. The energy of calories is used to fuel the activities in life Chemical energy released by the breakdown of organic molecules during cellular respiration is used to generate molecules of ATP (Adenosine triphosphate) - ATP is the universal package of energy - As ATP is converted to ADP, if you don’t regenerate ATP then it will run out. - It stores energy obtained from food. - ATP consist of an organic molecules called adenosine plus a tail of three phosphate groups - Its broken down to ADP, adenosine diphosphate, and a phosphate group, releasing energy. - The release of the phosphate at the tip of the triphosphate tail makes energy available to cells. A lot of ATP is found in our skeletal muscles. ATP energies other molecules in cells by transferring phosphate groups to those molecules. Enzymes - Metabolism is the total of all chemical reactions in an organism. - Most metabolic reactions require the assistance of enzymes, proteins that speed up chemical reactions without being consumed by the reaction - All living cell contain thousands of different enzymes, each promoting a different chemical reaction. *Enzymes are proteins, they are not lipids or carbs Activation Energy Activation energy is the energy that must be invested to start a reaction by - Activating the reactants and triggering a chemical reaction. - Enzymes enable metabolism to occur by reducing the amount of activation energy required to break the bonds of reactant molecules. Enzyme Activity Each enzyme recognizes a substrate, a certain reactant molecule The active site has a shape and chemistry that fits the substrate molecule. This interaction is called induced fit because the entry of the substrate induces the enzyme to change shape slightly, making the fit between the substrate and active site snugger. - After the products are released from the active site, the enzyme can accept another molecule of its substrate. - The ability to function repeatedly is a key characteristic of enzymes. - Many enzymes are named for their substrate, but with an -ase ending. Enzymes inhibitors Certain molecules inhibit a metabolic reaction by - binding to an enzyme and disrupting its function Some of these enzyme inhibitors are actually substrate imposters that plug up the active site. - Other inhibitors bind to the enzyme at a site remote from the active site, but the binding changes the enzymes shape so that the active site no longer accepts the substrate. - In each case, an inhibitor disrupts the function of an enzyme by altering its shape. Many beneficial drugs work by inhibiting enzymes. - Penicillin blocks the active site of an enzyme that bacteria use in making cell walls. - Ibuprofen inhibits an enzyme involved in sending pain signals. - Many cancer drugs inhibit enzymes that promote cell division. - Many toxins and poisons also work as inhibitors. Passive Transport: Diffusion across membranes - Molecules constantly vibrate and wander randomly. - Diffusion is the movement of molecules spreading out evenly into the available space. - Imagine a membrane separating pure water from a mixture of dye dissolved in water. Passive transport is the diffusion of a substance across a membrane without the input of energy. - In passive transport, a substance diffuses down its concentration gradient from where the substance is more concentrated to where it is less concentrated. *Moves from a high to low concentration. Facilitated diffusion is a type of passive transport because it does not require the cell to expend energy. The diffusion of water across a selectively permeable membrane is osmosis. *Water will always follow salt/sugar Osmosis and water Valance Compared to another solution, a hypertonic solution has a higher concentration of solute - Water moves out cells will shrink. A hypotonic solution has a lower concentration of solute - water rushes in cell will burst. An isotonic solution has an equal concentration of solute - water is balanced no change. Active Transport requires that a cell expend energy to move molecules across a membrane. Cellular energy (usually proved by ATP) is used to drive a transport protein that pumps a solute against the concentration gradient. Active transport allows cells to maintain internal concentrations of small solutes that differ from environmental concentrations. Exocytosis is the movement of materials out of cytoplasm of a cell via membranous vesicles or vacuoles that fuse with the plasma membrane. In endocytosis, a cell takes material in via vesicles that bud inward. For example, in a process called phagocytosis (cellular eating) a cell engulfs a particle and packages it within a food vacuole.
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