biochemistry unit workbook: pg. 61 textbook: pg. 69
DESCRIPTION
Enzymes are biological catalysts that increase the speed of biochemical reactions within cells. Enzymes are globular proteins that are NOT consumed during reactions. This means they are readily available to catalyze the same reaction over and over again. Enzymes speed up chemical reactions by lowering the activation energy needed for the reaction to proceed. Without the presence of enzymes, biochemical reactions within the cells would not occur fast enough to sustain life.TRANSCRIPT
EnzymesBiochemistry Unit
Workbook: pg. 61
Textbook: pg. 69
Animation: What is an Enzyme?
http://www.sumanasinc.com/webcontent/animations/content/enzymes/enzymes.html
What is an Enzyme? Enzymes are biological catalysts that increase
the speed of biochemical reactions within cells. Enzymes are globular proteins that are NOT
consumed during reactions. This means they are readily available to catalyze the same reaction over and over again.
Enzymes speed up chemical reactions by lowering the activation energy needed for the reaction to proceed. Without the presence of enzymes, biochemical reactions within the cells would not occur fast enough to sustain life.
Activation Energy EXERGONIC
REACTION: products have a
lower energy than the reactants
products have less free energy than that of the reactants and energy is given off from the system.
Activation Energy ENDERGONIC
REACTION : Products have a
higher energy than the reactants
The system requires energy
These reactions cannot occur spontaneously, energy is required to be invested in the products.
What is an Enzyme? The shape of an enzyme is so specific that only
one type of substrate (reactant) is capable of properly binding to the enzyme. If the shape of the enzyme should change or become altered, the enzyme will be inactive and the chemical reaction will not be catalyzed.
Most enzymes end with “ase”. So if you are struggling with the name of an enzyme and you know the name of the substrate, just change the ending to “ase”. So lactase is the enzyme involved with converting lactose into glucose and galactose. Amylose is the substrate for the enzyme amylase.
The Effects of pH
http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/PAELC/launch.html
Digital Experiment: http://lgfl.skoool.co.uk/content/keystage3/biology/pc/learningsteps/DIELC/launch.html Textbook: pg.
72
The Effects of Temperature http://lgfl.skoool.co.uk/content/keyst
age3/biology/pc/learningsteps/TAELC/launch.html
Textbook: pg. 72
How do they work?
http://www.lpscience.fatcow.com/jwanamaker/animations/Enzyme%20activity.html
The Active Site In an enzyme catalyzed
reaction, the substrate binds to a location called the active site.
A substrate-enzyme complex forms when the substrate binds to the enzyme.
The active site involves a small number of key residues that actually bind to the substrates
The rest of the protein structure is needed to maintain these residues in position
Induced Fit Model (vs. lock and key) Initially the active site is
not a direct fit for the substrate. As the substrate begins to
interact with the amino acid side chains of the enzyme, the enzyme modifies its shape to better accommodate the substrate.
This slight change in the shape of the enzyme allows the enzyme to catalyze the reaction. Workbook : pg.
61
Enzyme Helpers Some enzymes require co-factors or co-enzymes to
help them function properly. Co-factors are inorganic, non protein molecules that include zinc, iron, and copper. These metal ions can either bind to the active site or to the substrate to facilitate the formation of the enzyme-substrate complex.
Some of the most important coenzymes include nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+) which are involved in the process of cellular respiration and photosynthesis, respectively. These two molecules carry electrons during both reactions.
Enzyme Inhibitors There is an array of substances that
can inhibit and deactivate enzyme activity by: either: altering the active site or by mimicking the structure of a particular
substrate.
There are two types of inhibition: competitive and noncompetitive.
Workbook : pg. 61
Textbook: pg. 73
Competitive Inhibitors
Compete with the substrate for the enzyme's active site. Enter the enzyme's active site and prevent the normal
substrate from binding.
Noncompetitive Inhibitors
Attaches to a binding site on an enzyme other than the active site.
http://bcs.whfreeman.com/thelifewire/content/chp06/0602001.html
Feedback Cellular Respiration (text pg. 113) – negative feedback Oxytosin and birth (text pg.336) – positive feedback
http://www.northland.cc.mn.us/biology/Biology1111/animations/enzyme.html
Textbook: pg. 74
Allosteric Regulation Cells need to regulate and control chemical reactions
in order to coordinate cellular activities. control enzyme activity by:▪ altering the production of a particular enzyme ▪ preventing an enzyme from functioning.
Some enzymes contain allosteric sites which are receptor sites that are located far from the active site. Allosteric activator: keeps the active site of an enzyme
available to its substrate. Allosteric inhibitor: is a substance that binds to the
allosteric site and induces an inactive form of an enzyme so that the substrate cannot bind.
Workbook : pg. 63
Allosteric Regulation: Activation vs. Repression
http://www.stolaf.edu/people/giannini/flashanimat/enzymes/allosteric.swf
Degradation Reactions
Synthesis Reactions
Intro to Metabolism: 58-68 #1-10Enzymes: 69-77 #1-8
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