Energy Concepts. Study Objectives:

Transcription

1 Energy Concepts Study Objectives: 1. Define energy 2.Describe the 1 st law of thermodynamics Compare kinetic and potential energy, be able to give or recognize examples of each 3. Describe the major forms of energy and explain how energy flows from one type to another: radiant, electrical, mechanical, chemical, and heat (2 nd law of thermodynamics) 4. Describe the structure of ATP and explain the role of ATP in the body. How is it recycled? What organelle produces ATP? 5. Define the following terms: metabolism, catabolism, anabolism, synthetic reactions, decomposition reactions, reversible reactions 6. Describe the characteristics and function of enzymes. How do they work? 7. Describe the various factors that effect enzyme activity: concentrations, temperature, ph, inhibition, and allosteric regulation Muma 1

2 Energy Concepts Outline I. Energy -the ability to do work or to put matter into motion A. 1 st Law of Thermodynamics - conservation of energy i. Energy is not created or destroyed, it is only converted from one form to another B. Types of energy i. Kinetic- energy doing work, energy of motion ii. Potential- inactive or stored energy C. Forms of Energy i. Radiant - travels in waves Example: Light waves are essential for photosynthetic organisms; vision in animals ii. Electrical - flow of charged particles Example: Nerve impulses are created by the movement of Na+ and K+ ions iii. Mechanical - directly involved in moving matter Example: Muscle contraction iv. Chemical potential energy stored in chemical bonds and is released when bonds are broken 1. Found in food, fuel, ATP II. Types of Reactions A. Synthesis reaction (A+B AB) i. Atoms or molecules combine to form larger molecules ii. Endergonic reaction absorbs energy into the chemical bonds B. Decomposition reaction (AB A+B) i. Larger molecule is broken down into smaller molecules ii. Exergonic - chemical energy is released 2

3 C. Reversible reaction: (A + B C + D) i. Chemical reaction that can proceed in either direction ii. Direction of the reaction will shift depends on the concentration of the reactants and products III. Energy Conversions A. 2 nd Law of Thermodynamics - Heat is a product of all energy conversions i. Heat= the kinetic energy contained in the random motion of molecules ii. Entropy = measure of disorder or randomness 1. Therefore, all energy transformations increase the entropy of the universe. 2. Living things are organized, therefore they have low entropy 3. To maintain low entropy, constant input of energy is needed 4. Where do we get this energy??? IV. ATP and Cellular Work A. The chemical energy in food is released in cellular respiration to make ATP in the mitochondria B. ATP is used to drive different types of cell work: i. active transport ii. muscle contraction iii. impulse conduction iv. we use 10 million ATP molecules per second 3

4 C. The Structure of ATP i. ATP (adenosine triphosphate) - chemical energy used by all cells ii. Consists of adenosine plus a tail of three phosphate groups iii. Energy is released by breaking high energy phosphate bond (-7.3 kcal/mol) D. ATP is always recycled i. ATP ADP + P + Energy ii. Cellular work uses (spends) ATP so more must be made iii. ATP is recycled from ADP and phosphate through cellular respiration V. Metabolism - the sum of all the chemical reactions that occur in the body A. Two types of metabolic reactions i. Catabolic breaking down molecules, releases energy which is captured in the bonds of ATP ii. Anabolic uses energy from ATP to synthesize large molecules B. Enzymes i. Few metabolic reactions occur without the assistance of specialize proteins called enzymes ii. Enzymes are protein molecules that speed up the rate of chemical reactions (biological catalyst) iii. Enzymes lower the activation energy for chemical reactions 1. Activation energy is the energy required to trigger a chemical reaction iv. Characteristics of Enzymes 1. Each enzyme is very selective it catalyzes specific reactions 2. Each enzyme recognizes a specific substrate 3. Enzymes can function over and over again (can be reused) 4

5 v. How an enzyme works 1. Each enzyme binds a specific reactant molecule (substrate) at its active site. 2. After the reactants are converted, the products are released and the enzyme remains unchanged. 3. Enzyme + Substrate Enzyme-substrate complex Product + Enzyme vi. Factors Affecting Enzyme Activity 1. Concentration a. Increase in substrate or enzyme concentration will increase the rate b. At some substrate concentrations, the active sites on all enzymes are engaged and has reached saturation 2. Temperature a. Increase in temperature, increases the rate of enzymatic reactions by increasing kinetic energy of molecules b. However, at a point the rate will drop off sharply due to denaturing of the enzyme at high temperatures 3. ph enzymes work best at an optimal ph a. If it is more acidic or basic than the optimal ph the rate of enzymatic activity will decrease 4. Enzyme inhibitors or activators- can inhibit or activate a metabolic reaction a. Competitive inhibition - binds to the active site, as substrate impostors i. Can be reversible or irreversible 5

6 b. Noncompetitive - bind at a different site (allosteric), changing the shape of the enzyme s active site 5. Allosteric Regulation a. Feedback inhibition the accumulation of the end product turns off the metabolic pathway b. Most allosterically regulated enzymes are constructed of two or more polypeptide chains. c. The whole protein oscillates between two conformational shapes, one active, and one inactive. d. Binding of regulatory molecules can either inhibit or stimulate enzyme activity. 6

7 Post Lecture Practice 1. Review Energy Concepts PowerPoint slides #1-10. Describe in your own words in a short paragraph what is happening in the diagram below. Include the specific types of energy and how the First and Second Law of Thermodynamics apply. (Act like I don t know anything about this drawing and you are teaching me about the flow of energy ) 7

8 2. Explain how ATP is used as a source of energy for cellular processes. You can draw and describe a diagram OR use words to get your point across. Include in your answer: a. the general structure of ATP b. how is it used and recycled during cellular processes c. give examples of two specific mechanisms that you have learned about so far that use ATP 3. Describe the role enzymes play in living organisms. Include in your answer: a. Define enzyme, substrate, and product b. Describe the characteristics of an enzyme c. Give an example of two variables that can affect the activity of an enzyme and explain why these variables change the course of an enzymatic reaction. 8