1.7 - Enzyme action Flashcards
What are enzymes?
Enzymes are globular proteins that act as catalysts. Catalysts alter
the rate of a chemical reaction without undergoing permanent changes themselves. They can be reused repeatedly and are therefore effective in small amounts.
What is activation energy?
Many reactions require an initial amount of energy to start. The minimum amount of energy needed to activate the reaction in this way is called the activation energy.
What is Free Energy?
Free energy is t he energy of a system that is available to perform work.
How do enzymes work?
There is an activation energy level, like an energy hill or barrier, which must initially be overcome before the reaction can proceed. Enzymes work by lowering this activation energy level. In this way enzymes allow reactions to take place at a lower temperature than normal.
Why are enzymes useful?
enables some metabolic processes to occur rapidly at the human body temperature of 37°C. which is relatively low in terms of chemical reactions. Without enzymes these reactions would proceed too slowly to sustain life as we know it.
What type of proteins are enzymes?
Globular
What is the functional region of an enzyme called?
A specific region or the enzyme is functional, this is known as the active site
What is the active site?
The active site is made up of a relatively small number of amino acids. The active site forms a small depression within the much larger enzyme molecule.
The molecule on which the enzyme acts is called the substrate. This fits neatly into this depression and forms an enzyme-substrate complex
What is the induced fit model?
The induced fit model of enzyme action proposes that the active sire forms as the enzyme and substrate interact. The proximity of the substrate (a change in the environment or the enzyme) leads to a change in the enzyme that forms the functional active site. In other words, the enzyme is flexible and can mould itself around the substrate in the way that a glove moulds itself to the shape of the hand.
Define a catalyst.
a substance that alters the rate of a chemical
reaction without undergoing permanent change
Explain why enzymes are effective in tiny quantities
They are not used up in the reaction and so can be
used repeatedly.
Outline why changing one of the amino acids that make up the active site could prevent the enzyme from functioning.
The changed amino acid may no longer bind to the substrate, which will then not be positioned correctly, if at all, in the active site.
Explain why changing certain amino acids that are not part of the active site also prevents the enzyme from functioning.
The changed amino acid may be one that forms hydrogen bonds with other amino acids. If the new amino acid does not form hydrogen bonds the tertiary structure of the enzyme will change, including the active site, so that the substrate may no longer fit.
What is the lock and key model?
One earlier model of enzyme action proposed that enzymes work in the same way as a key operates a lock- each key has a specific shape that fits and operates only
a single lock. In a similar way, a substrate will only fit the active
site of one particular enzyme.
Give a limitation of the lock and key model?
One limitation of this model is that the enzyme, like a lock, is considered to be a rigid structure. However, scientists had observed that other molecules could bind
to enzymes at sites other than
the active site. In doing so, they altered the activity of the enzyme. This suggested that the enzyme’s shape was being altered by the binding molecule. In other words, its structure was not rigid but flexible.