Chapter 12: The Protein Catalyst Flashcards
What is an Enzyme?
is a specialized protein that speeds up or starts a chemical reaction without being changed by the reaction
- allows chemical reactions in the cells to happen fast enough to meet the new body’s need
Thousands of enzymes in a cell each have a unique what?
They each have a unique function
What is a Catalyst?
A catalyst is a substance that speeds up a reaction between substances without being affected by the reaction
Enzymes are related to catalysts how?
Enzymes are a group of proteins that act as catalysts
Why do cells only need a low concentration of many different enzymes to function?
Since enzymes do not change during chemical reactions, cells only need a low concentration of many different enzymes
What is Activation Energy?
is the energy need to start a reaction
- enzymes lower the amount of energy needed to start a reaction
What do Digestive Enzymes do?
Digestive enzymes decrease the amount of heat energy needed during digestion
Enzymes are specific to what?
Enzymes are specific to the compounds with which they will react
What is the Lock-and-Key Model?
- Enzyme is compared to a lock
- The key represents the substance being changed, known as the substance
- The key must be inserted in the right spot in the right way
- The keyhole, or active site, is where the substrates attaches to the enzymes
The Lock-and-Key model is limited for what reason?
is limited by research indicating that the substrate does not turn when inserted into the active site and an enzyme is not a perfect match to the substrate
What is the Induced-Fit Model?
The induced-fit model addresses the limitations of the lock-and-key model
What happens in the Induced-Fit Model?
The active site temporarily changes the shape of the enzyme to allow the reaction to occur, then returns to its original configuration after the reaction
All enzymatic reactions follow the same basic process, what are they?
- Enzymes and substrate combine to form an enzyme-substrate complex
- Enzyme-substrate complex is unstable and breaks apart, leaving the enzyme to act again on another substrate
How do Coenzymes work?
- By attaching to the enzyme and changing its shape so the substrate can fit in the active site
- attaching to the substrate and changing its shape so it will fit the active site of the enzyme
- acting as a transfer agent by accepting an atom or molecular group and transferring it to another compound
Vitamins and minerals are important coenzymes including?
The B Vitamins, Calcium, Magnesium and Zinc
What is the Nomenclature for enzymes (accepted in 1961)?
- Enzymes are named for the types of reactions or substances for which they are the catalyst
- The root name for the enzyme and the substrate are the same
- Enzymes end in -ase
What is the exception to this naming system for enzymes?
Some enzymes had already been identified before the new naming systems
What are the 3 categories of digestive enzymes?
- Proteases break apart proteins
- Lipases break apart lipids
- Carbohydrases break apart starches and sugars
Some enzymes have more than one what?
Some enzymes have more than one name
What is the other name for the Enzyme Sucrase?
Sucrase is also known as invertase because the mixture of glucose and fructose is often called Invert Sugar
What is Water Availability and how does it apply to Enzymatic Reactions?
Water must be available to act as a reactant as well as a solvent in enzymatic reactions
Lack of water does what to enzymatic activity?
The lack of water slows or stops enzymatic activity
Enzymatic reactions will not occur in what kind of products?
Enzymatic reactions will not occur in dry products
- Water must be a reactant in the breakdown of carbohydrates, lipids, and proteins
How does the concentration of a solution affect Enzyme Activity?
- The more substrate in the solution, the greater the rate of the reaction is
- The rate of enzymatic reaction increases as the concentration increases, up to the saturation point
How does Temperature affect Enzyme Activity?
Heat increases enzyme activity, as in blanching vegetables before freezing
How do Acids and Bases affect Enzyme Activity?
A pH that is too high or too low will denature an enzyme
What are Electrolytes?
can prevent enzymes from reacting with a substrate
What are Enzyme Inhibitor?
prevents enzyme-substrate complexes from forming
What do Enzyme Inhibitors do?
- Change the shape of the enzyme or the substrate
2. Help protect foods from bacteria and mold by stopping the digestive enzymes they release from working
Where do Enzyme Inhibitors occur?
The occur naturally in a wide variety of foods from animal and plant sources
How are Enzymes used by the food industry to develop food products?
- Converting one food product into another, such as with milk to cheese
- Extracting food components from food systems such as the separation of juice from insoluble residues
- Playing a key role in developing ingredients
What are the Positive Effects of Enzymes and the Food Supply?
- Make food easier to eat
- Preserve food
- Improve flavour, quality, or appearance
- Plays a role in fermentation
What are the Negative Effects of Enzymes and the Food Supply?
- Break down the structure of fruits and vegetables
- Unpleasant flavour and odour changes
- Undesirable changes in texture and colour
Carbohydrases react with sugars and starches for commercial uses such as to…?
- Make corn syrup and high-fructose corn syrup
- Ferment wine and beers
- Stabilize chocolate syrup
- Clarify fruit juices
Lipases are used to?
- Extract unwanted egg yolk from egg white to improve the whipping properties of egg white
- Improve flavour and texture of various products including cheese, ice cream, margarine, butter, and many baked goods
Proteases are used to do what?
- Tenderize meat by breaking long protein fibres, as in solutions for marinated meat
- Reduce the size of proteins extracted from malt and grains during beer and ale production
- Reduce mixing time
- Increase pliability of dough
- Change food into a different product, such as milk to cheese
How do researchers uses enzymes to preserve food?
Ripe fruits and vegetables are stored in an oxygen-free environment to prevent deterioration by oxidases
What is Enzymatic Browning?
Colour changes from enzymatic browning may be desirable for raisins or figs, but not sliced apples or pears
How can we prevent browning of cut fruit, in the food industry?
Uses acids as enzyme inhibitors
