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Enzymes: Organic Catalysts
All living organisms depend on metabolic reactions to maintain homeostasis and stay alive.
Examples of metabolic processes include: digestion (hydrolysis), dehydration synthesis, protein synthesis, photosynthesis, cellular respiration, DNA replication.
Problem: most chemical (metabolic reactions are not spontaneous, so they need some help to occur. The role of ENZYMES in living systems is to control the rate of chemical reactions.
http://biochemicalpathways.com/#/map/1
How many different kinds of metabolic reactions occur in us??
Enzymes:
• are organic catalysts they control and often speed up chemical reactions in living organisms (metabolic processes).
• are required for all chemical reactions (metabolism)are proteins: enzymes are polypeptide (amino acid) chains that are folded into complex structures.
• are made by ribosomes (site of protein synthesis)
• have a very specific structure that determines it's function. The amino acid sequence determines the shape of the enzyme, and the shape determines it's function and which kind of reaction it catalyzes. (Lock & Key Theory)
• are reusable enzymes are not altered by the reactions they catalyze.
• names end in ase. The first part of the name indicates what kind of substrate it will bind with.
Ex. lipase acts on maltase acts on
lactase acts onprotease acts onamylase acts on
How Enzymes Work: Lock & Key Theory
All metabolic processes are enzyme controlled reactions. Each reaction requires a specific enzyme.
substrate or reactant the molecules that enter the chemical reactionproduct the molecules that are made by the chemical reaction.
Example:
C6H1206 + 6 O2 ⇒ 36 ATP + 6 CO2 + 6H2O
How Enzymes Work: Lock & Key Theory (continued)
Lock & Key Theory:Enzymes are specific in their function. Each enzyme catalyzes one type of chemical reaction. The substrates "fit" into the active site of the enzyme, the reaction occurs and the products move out of the enzyme.
Why???
Observe the cups of Jello in front of you. Make a table with your observations. Read all the instructions on how to make Jello. Come up with a question.
The instructions state not to use fresh pineapple. You can see why. Why can't you use fresh kiwi, guava, papaya and gingerroot?
Is there anything added to the canned pineapple that is not in the fresh fruit?
How is canned pineapple made?
Why do some people experience a tingling feeling (or get a rash around their mouth) when eating fresh pineapple?
What is in the jello that makes it 'set'
When you mix up the jello with hot water it is a liquid. Why does it 'set' as it cools?
Four Factors That Affect Enzyme Reaction Rate
Relative concentration of Enzyme and Substrate:
1. The more enzyme is present, the faster the chemical reaction can occur. (more product made per unit time)
2. The more substrate that is present, the faster product can be made.
Four Factors That Affect Enzyme Reaction Rate (continued)
3. Temperature: Each enzyme works best at a specific temperature called the optimum temperature. Reaction rate slows down as the temperature falls below the optimum temperature because the molecules move slower. The reaction rate drops and stops above the optimum temperature because the enzymes denature (change shape).
4. pH (presence of acid or base): Each enzyme works within a pH range and works best at a specific pH. Reaction rate slows down as the pH increases or decreases from the optimum pH.
Biological systems control enzyme activity by altering the pH of the environment. Example: enzymes in the human digestive system...
Four Factors That Affect Enzyme Reaction Rate (continued)
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