BIO 100 Chapter 5 Notes
BIO 100 Chapter 5 Notes BIO 100
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This 3 page Class Notes was uploaded by Lauren Tebbe on Wednesday September 28, 2016. The Class Notes belongs to BIO 100 at Eastern Kentucky University taught by Kenneth Blank in Fall 2016. Since its upload, it has received 4 views.
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Date Created: 09/28/16
Chapter 5 BIO notes 1 What is Energy? o Energy is defined as the capacity to do work, to make things happen o The 2 basic forms of energy are potential and kinetic. Potential is stored energy and Kinetic is the energy of motion. o Potential and Kinetic energy is constantly being converted and in the process some is lost as heat and other unusable forms. 2 Measuring Energy o The unit of measurement for energy is called a joule or calorie. o A calorie is the amount of heat required to raise the temperature of 1 gram of water by 1 degree of Celsius. o The caloric value of food is listed in nutrients labels and diet charts in terms of kilocalories. 3 Energy Laws o 2 energy laws govern energy flow and help us understand the principles of energy conversions, the laws of thermodynamics. o First law is called the law of conservation of energy and tells us that energy cannot be created or destroyed but it can be changed from one form to another. o The second law tells us that energy cannot be changed from one form to another without a loss of usable energy. o Heat is diffuse energy and the least usable form. o Every energy transformation leads to an increase in the amount of disorganization or disorder. o Entropy refers to the relative amount of disorganization, all energy transformations lead to this. 4 ATP: Energy for Cells o ATP (adenosine triphosphate) is the energy currency of cells. Cells use ATP to carry out nearly all of its activities including synthesizing proteins, transporting ions across the plasma membranes and causing organelles and cilia to move. 5 Structure of ATP o ATP is a nucleotide, the type of molecule that serves as a monomer for the construction of DNA and RNA. o It contains the sugar ribose, nitrogen-containing base adenine, and 3 phosphate groups. o 3 phosphates are negatively charged and repel one another, taking energy to link them by chemical bonds. o ATP stores more potential energy than ADP because there is energy is the bond attaching the third phosphate group that ADP does not have. 6 Use and Production of ATP o Continual breakdown and regeneration of ATP is known as the ATP cycle. ATP is rebuilt from ADP + P o ATP's instability makes it a very effective energy carrier o Production of ATP is worthwhile for the cell because… 1. ATP releases energy quickly, which facilitates the speed of enzymatic reactions 2. When ATP becomes ADP + P, the amount of energy released is usually just enough for biological purpose 3. The structure of ATP allows its breakdown to be easily coupled to an energy-requiring reaction. o A coupled reaction brings them together in such a way that the energy- releasing reaction can drive the energy-requiring reaction. o A cell has 2 main ways to couple ATP breakdown to an energy-requiring reaction: ATP may be used either to energize a reactant or to change its shape. Both are achieved by transferring a phosphate group to the reactant. o During cellular respiration, mitochondria complete the breakdown of carbs and use the released energy to build ATP molecules. 7 Metabolic Pathways and Enzymes o Chemical reactions in a cell usually occur in a particular order, they are part of a series of linked chemical reactions called metabolic or biochemical pathways beginning with a particular reactant and terminating with an end product. o Enzymes are protein molecules that function as organic catalysts to speed chemical reactions. They bring together particular molecules and causes them to react with one another. o The molecule acted on by an enzyme is called a substrate 8 An Enzyme's Active Site o The active site accommodates the substrate and the substrate fits into the enzyme seemingly as a key fit a lock. o The slight change in shape that the active site undergoes is called induced fit model because the enzyme is induced to undergo a slight alteration to achieve optimal fit. o Enzyme inhibition occurs when an active enzyme is prevented from combining with its substrate. Some can be poisonous. Some are useful in drugs. The reactants of enzymatic reactions. o The activity of almost every enzyme in a cell is regulated by feedback inhibition. IT competes with the substrate for the enzyme's active site and when product is used up, inhibition is reduced and then more product can be produced. o Without the activity of the first enzyme, the entire metabolic pathway shuts down. 9 Energy of Activation o The energy needed to cause molecules to react with one another is called the energy of activation. This acts as a metabolic speed bump, limits how fast a reaction can proceed from reactants to products. o Enzymes lower the amount of activation energy needed, and act as catalysts that speed up the overall rate of the reaction. o DO not change the amount of energy, just alter the rate. 10 Cell Transport o The plasma membrane is selectively permeable, meaning that certain substances can freely pass through, transport, and others are prohibited. o Can enter cell in 3 ways: passive, active, or bulk o In passive substances move from high to love concentrations and no energy is required. Active however goes from low to high. Bulk does require energy 11 Passive Transport: No Energy Required o One form of passive includes diffusion where molecules move down their concentration gradient until equilibrium is achieved and they are distributed equally. o Diffusion occurs when molecules are in motion and does not need to occur across the membrane o A solution contains both a solute and a solvent. Solutes are solids or gases and solvents are liquids. o Facilitated diffusion occurs when an ion or a molecule diffuses across a membrane faster than expected, either by way of a specific channel protein or with the assistance of a carrier protein. o Water moves through channels called aquaporins. o Osmosis is the diffusion of water across a semipermeable membrane from an area of high to low concentrations. Occurs through the channel proteins called aquaporins. o A cell in a hypotonic solution has a lower solute concentration that the solution does o Cell walls do not burst in hypotonic solution because of turgid. o A cell surrounded by a hypertonic solution, a solution has a higher solute concentration than the cell's cytoplasm o Plasmolysis shrink the cytoplasm due to osmosis. o Isotonic solutions in which the cell neither gains nor loses water that is the concentration of water is the same on both sides of the membrane. 12 Active Transport o Molecules or ions move through the plasma membrane accumulating on one side of the cell. o Molecules move against their concentration gradients that requires ATP o The passage of salt across a plasma membrane is the primary importance in cells because the salt causes water to move to that side of the plasma membrane. o Sodium potassium pump is vital in nerve conductions undergoes a change in shape that allows it to combine alternately with sodium ions and potassium ions. o ATP is used to change the shape of a reactant with ATP hydrolysis 13 Bulk Transport o Used with macromolecules that can't be moved by transport proteins. Vesicle formation takes them into or out of our cell. o Exocytosis is out of the cell and endocytosis is into the cell o Food intake is phagocytosis and water intake is pinocytosis. o Receptor-mediated endocytosis are receptors for particular substance found at one location in the plasma membrane. More effective than ordinary pinocytosis.