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What is a chemical reaction? What are products? What are reactants?

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Presentation on theme: "What is a chemical reaction? What are products? What are reactants?"— Presentation transcript:

1 What is a chemical reaction? What are products? What are reactants?
Warm Up What is a chemical reaction? What are products? What are reactants? Describe the building of a monomer into a polymer as a chemical reaction.

2 Chemical Reactions and Energy
Chemical reactions happen when bonds are broken and/or formed. Reactants (what you start with) Products (what you end with) Chemical Reaction: Reactants  Products Na+ + Cl-  NaCl (arrow points away from reactants and towards products)

3 quantity of E is constant, quality is not
Energy Energy (E)~ the ability to do work; Kinetic energy~ energy of motion; Potential energy~ stored energy Thermodynamics~ study of E transformations 1st Law: conservation of energy; E can be transferred (from one thing to another) or transformed (go from PE to KE or KE to PE), E can not be created or destroyed quantity of E is constant, quality is not 3

4 Energy and Life Metabolism: All of the chemical processes in a living organism; managing the material and energy resources of the cell Catabolic pathways: process that break things down (hydrolysis) for example: cellular respiration; releases energy Anabolic pathways: building process such as (dehydration synthesis) for example: protein synthesis; photosynthesis; consumes energy 4

5 Free Energy Free energy: E that is available to do work
Exergonic (Exothermic)reaction: net release of free E to surrounding (catabolic processes) We get energy from breaking down food. Endergonic (Endothermic) reaction: absorbs free E from surroundings (anabolic processes) We need energy to build us (proteins) 5

6 How is ATP used for energy?
When we break down glucose (cellular respiration), the energy that was stored in the glucose is now stored in ATP. How is the ATP used to do work? The process is called Energy Coupling: use of exergonic process to drive an endergonic one Adenosine triphosphate Water is added to ATP to break off the last phosphate group (hydrolysis): This releases free E ATP + H2O ADP + P + energy 6

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8 The ATP Cycle 8

9 Enzymes What are Enzymes?
Enzymes are organic catalysts. Catalysts speed up chemical reactions. How do they speed up chemical reactions? Lower the activation energy of a reaction (the energy needed for the reaction to happen) Do not change the reaction – only speed up a reaction that would have occurred anyway. 9

10 What does a Chemical Reaction look like
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11 How do enzymes speed up reactions?
Boardworks High School Science Enzymes Enzymes speed up reactions by lowering the activation energy (Ea) of a reaction. The activation energy is the energy needed to start a reaction. Different reactions have different activation energies. Draw the following graph: reaction (time) energy (kJ) Ea without enzyme Ea with enzyme

12 http://www. stolaf. edu/people/giannini/flashanimat/enzymes/prox-orien
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13 What are enzymes made of?
Enzymes are protein molecules, and so are made up of amino acids. Most enzymes contain between 100 and 1,000 amino acids. These amino acids are joined together in a long chain, which is folded to produce a unique 3D structure.

14 Why is shape important? The shape of an enzyme is very important because it has a direct effect on how it catalyzes a reaction. Why do enzymes have different shapes? An enzyme’s shape is determined by the sequence of amino acids in its structure, and the bonds which form between the atoms of those molecules. Photo credit: University of Chicago Medical Center Structure of human insulin-degrading enzyme (IDE) in complex with beta-amyloid, a peptide that forms harmful plaques in the brains of people with Alzheimer’s disease. The molecular surface of IDE is represented by light yellow. The N- and C-terminal domains of IDE are colored green and red, respectively. The beta-amyloid (blue) is entrapped inside the degradation chamber of the IDE molecule. Different types of enzymes have different shapes and functions because the order and type of amino acids in their structure is different.

15 Why are enzymes so specific?
Enzymes are very specific about which reactions they catalyze. Only molecules with exactly the right shape will bind to the enzyme and react. These are the reactant, or substrate, molecules. The part of the enzyme to which the reactant binds is called the active site. This is a very specific shape and the most important part of the enzyme. Photo credit: JC Revy / Science Photo Library The image shows a molecular computer graphics image of ribonuclease A, an enzyme involved in the destruction of messenger RNA (mRNA) in the cytoplasm of bacteria. On the left is its substrate, shifted away from the active site. Enzymes are biological catalysts; proteins that speed up the rates of reactions within cells. Each enzyme is specific for a particular reaction; interaction occurs (typically as a weak bond) between an active site on the enzyme and a reactant (or substrate) due to the arrangement of mutually attractive groups of atoms. This image displays the molecular surface (blue) & polypeptide chain: colors are used to represent the polarity of constituent amino acids.

16 What happens at the active site?
Lock and Key Model: In the same way that a key fits into a lock, so a substrate is thought to fit into an enzyme’s active site. The enzyme is the lock, and the reactant is the key. + + enzyme substrate + enzyme-substrate-complex products

17 The lock and key model Teacher notes
This four-stage animation demonstrates the principles of the ‘lock and key’ model. While showing the animation, the specific shape of the active site could be highlighted. Suitable prompts could include: What is special about the shape of the active site? Is the enzyme the ‘lock’ or the ‘key’?

18 Enzymes: true or false? Teacher notes
This true-or-false activity could be used as a review exercise on enzymes, or at the start of the lesson to gauge students’ existing knowledge of the subject matter. Colored cards (red = false, yellow = don’t know, green = true) could be used to make this a whole-class exercise.

19 Over the next several days you will be completing lab activities to learn about the different properties of enzymes. Homework: Read the lab, get it written into your notebook, include prelab questions, and describe your procedures.

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21 Factors affecting enzymes
Boardworks High School Science Enzymes If the temperature and pH changes sufficiently beyond an enzyme’s optimum, the shape of the enzyme irreversibly changes. This affects the shape of the active site and means that the enzyme will no longer work. When this happens the enzyme is denatured. denatured normal heat pH

22 Enzymes and temperature
Boardworks High School Science Enzymes Teacher notes This five-stage animation could be used as a precursor to running the experiment in the lab, or as a summary exercise.

23 Catalytic proteins: change the rate of reactions w/o being consumed
Enzymes Catalytic proteins: change the rate of reactions w/o being consumed Free E of activation (activation E): the E required to break bonds Substrate: enzyme reactant Active site: pocket or groove on enzyme that binds to substrate Induced fit model binding of substrate changes shape of the active site so that the substrate can bind 23

24 Factors affecting enzymes
Boardworks High School Science Enzymes The rate of enzyme-catalyzed reactions depends on several factors. What are some of these? Factors that affect the rate of a reaction include: temperature substrate concentration pH surface area enzyme concentration pressure. All enzymes work best at only one particular temperature and pH: this is called the optimum. Different enzymes have different optimum temperatures and pH values.


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