enzyme s chapter 2.5. enzymes are catalysts for chemical reactions in living things
TRANSCRIPT
Enzymes
Chapter 2.5
• Enzymes are catalysts for chemical reactions in living things
Why Are Enzymes So Important?
Why are we devoting one whole lecture topic to a protein molecule?
Nearly all chemical reactions in biological cells need enzymes to make the reaction occur fast enough
to support life.
Image: Jumping rope, Meagan E. Klein
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Enzymes allow chemical reactions to occur under tightly controlled conditions.
• Enzymes are catalysts in living things.
• Enzymes are needed for almost all processes.
• Most enzymes are proteins
What do enzymes do?
• Enzymes act as _________ in cellular reactions.
• Q: What does a catalyst do?
Images: Activation energy graph, WikiFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
…are REUSABLE.
They are not consumed (used up) in the reactions they catalyze.
Enzymes…
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
How do enzymes work?
Enzymes catalyze reactions by weakening chemical bonds, which ________ activation energy.
Image: Activation energy graph, WikiFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
Meet the Enzyme: ___ _______
Important metabolic enzyme that harnesses energy for biological cells to use.
Involved in synthesis of adenosine triphosphate (ATP), from:
- adenosine diphosphate (ADP)
- a phosphate group and - energy from H+ ion
gradient
ATP is the most commonly used "energy currency" of cells.
Reaction:
(ATP synthase)
ADP + Pi -------ATP substrate substrate product
Images: ATP synthase diagram, Tim VickersFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
How do you stop an enzyme?
Irreversible egg protein
denaturation caused by high
temperature (while cooking
it).
__denature it!
• Alteration of a protein shape through some form of external stress
• Example, by applying heat or changing pH.
• Denatured protein can’t carry out its cellular function .
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Factors That Influence Enzyme Activity
• Temperature
• pH
• Cofactors & Coenzymes
• Inhibitors
Image: Animation of Enzyme, WikiFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
What enzymes do I have around the house?detergents textiles (fabric) wine beer vinegar cheeses corn and wheat syrups leatherbiodegradable plastic starch into sugar yeast
Where are they found?
• Enzymes are found in many cleaning and spot removal and odor removal products.
Enzymes are found in all living foods such as fruits and vegetables as they keep ripening.
•Enzymes are found in those agents that cause food spoilage,
•Enzymes are found in many food reactions such as yogurt, cheeses, saurkraut, pickles, fermentations of beer and wine, etc,
•Meat tenderizer is an enzyme
•milk products for lactose intolerant individuals is treated with lactase, an enzyme
Digestive enzymes are enzymes that break down food into usable material. The major different types of digestive enzymes are:
• amylase – breaks down carbohydrates, starches, and sugars which are prevalent in potatoes, fruits, vegetables, and many snack foods • lactase – breaks down lactose (milk sugars) • diastase – digests vegetable starch • sucrase – digests complex sugars and starches • maltase – digests disaccharides to monosaccharides (malt sugars) • invertase – breaks down sucrose (table sugar) • glucoamylase – breaks down starch to glucose • alpha-glactosidase – facilitates digestion of beans, legumes, seeds, roots, soy products, and underground stems • protease – breaks down proteins found in meats, nuts, eggs, and cheese• pepsin – breaks down proteins into peptides
Enzymes…
• Have names that usually end in -_____.
-Sucrase
-Lactase
-Maltase
Image: Animation of Enzyme, WikiFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
Go to: http://redirectyourcarbs.com/carb-redirect-method/?sid=a1
• Factors Affecting Enzyme Activity• Temperature - Enzymes are proteins that function optimally at certain temperatures. They are
inactivated or denatured by temperatures above 50 °C to 60 °C. Enzymes are not inactivated by freezing, but either work slowly or do not work at all.
• pH - Enzymes are sensitive to changes in acidity. For example, the high acidity of stomach juice is needed for the enzyme pepsin to function, whereas an enzyme called trypsin in the small intestine requires alkaline surroundings.
• Concentration of Enzyme - If pH and temperature are kept constant, the rate of reaction is proportional to the amount of enzyme present. The more enzyme there is, the more reactions that occur.
• Co-Enzymes - Some vitamins and minerals (e.g. copper, zinc, iron) in small quantities work with enzymes to speed up reactions.
• Enzyme Inhibitors - A pesticide called DDT stops the action of enzymes in insects, thereby killing them.
How acidic is your body?
• http://scienceforkids.kidipede.com/biology/cells/enzyme.htm
A catalyst lowers activation energy.
• Catalysts are substances that speed up chemical reactions.
• decrease activation energy• increase reaction rate
• Disruptions in homeostasis can prevent enzymes from functioning.
– Enzymes function best in a small range of conditions.– Changes in temperature and pH can break hydrogen
bonds.– An enzyme’s function depends on its structure.
• are specific for what they will catalyze.
• fit with substrate like a lock and key____.
Enzymes…
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
• An enzyme’s structure allows only certain reactants to bind to the enzyme.
– substrates– active site
substrates (reactants)
enzyme
Substrates bind to anenzyme at certain places called active sites.
• The lock-and-key model helps illustrate how enzymes function.
– substrates brought together– bonds in substrates weakened
Substrates bind to anenzyme at certain places called active sites.
The enzyme bringssubstrates together and weakens their bonds.
The catalyzed reaction formsa product that is releasedfrom the enzyme.
When an enzyme is interacting with it’s substrate, during the
chemical reaction, together they are referred to as the …
Image: Enzyme –substrate complex, UC Davis
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
The more cans (substrate), the more $ (product). The more recycling machines (enzymes), the faster the cans turn into $.
Enzymes are like tiny machines within living things.
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
$
$$
$
$
$$
Cofactors & Coenzymes
• Non-protein substances (zinc,
iron, copper, vitamins) are sometimes need for proper enzymatic activity.
• Coenzyme vs Cofactor: What’s the difference?
_________ more general term. Includes inorganic and organic molecules.
_________ type of cofactor, But specifically organic molecules.
Image: Enzyme with Cofactor, Wiki. Ribbon-diagram showing carbonic anhydrase II. The grey sphere is the zinc cofactor in the
active site. From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Meet the Enzyme: Catecholase
• Catecholase is present in most _Fruits_____ and __Vegetables________.
• It is the enzyme that facilitates the ________ of cut or bruised fruits and vegetables by catalyzing the following reaction:
(______________)
_________ + _____ ----------------- _____________ colorless substrate brown product
Image: Bananas T. PortFrom the Virtual Cell Biology Classroom on ScienceProfOnline.com
Meet the Enzyme: Catecholase
Lemon juice and other acids are used to preserve color in fruit, particularly apples, by lowering the ____ and removing the copper (cofactor) necessary for the enzyme to function.
Reaction:
catecholase
catechol + O2 ---------- polyphenol colorless substrate brown product
Images: Apples, T. Port; Lemons, André Karwath; Enzyme with Cofactor, Wiki; pH scale, Edward Stevens, Wiki
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Meet the Enzyme: Bromelain
• Pineapple contains enzyme bromelain, which can digest protein
• Jell-O® is made of gelatin, a processed version of a structural protein called _________ found in many animals, including humans.
• Collagen = big, fibrous molecule makes skin, bones, and tendons both strong and elastic.
• Gelatin you eat in Jell-O ® comes from the collagen in cow or pig bones, hooves, and connective tissues. (Yummie!)
• Examine 2 containers:
a. In one, canned pineapple was used to make Jell-O® .
b. The other, fresh pineapple was used.
Q: Why is one Jell-O solid and the other liquid?
Image: Pineapple, Whaldener Endo
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Meet the Enzyme: Bromelain
(bromelain)
collagen protein + H20 -------------- amino acids substrate products
Bromelain is a ______ enzyme that facilitates hydrolysis of protein.
Remember, hydrolysis cuts molecule by adding water…the reverse of the hydration synthesis pictured to the left.
FYI: Bromelain is used as a meat tenderizer. Breaks down the collagen in meat. So what do you think could happen to your tongue when you eat fresh pineapple?
From the Virtual Cell Biology Classroom on ScienceProfOnline.com
Assignment
• At the end of most lectures, I will give you some type of in-class assignment or homework to evaluate your understanding of today’s topic.
• This assignment will always be open-book.
• Today you may be completing an experiment on the topic of Enzymes.
See the ScienceProfOnline Virtual Cell Biology Classroom: Enzymes Lecture
for a printable Word .doc of this assignment.
Image: Accumulation of polyphenol in apple, T. Port
From the Virtual Cell Biology Classroom on ScienceProfOnline.com