Enzymes Flashcards
What is an enzyme?
An enzyme is a protein produced by a living organism that acts as a biological catalyst in a chemical reaction by reducing activation energy. Many enzyme names and in -ase. For example amylase and ATPase.
What type of proteins are enzymes?
Enzymes are globular proteins. They fold up into precise shapes.
Why are enzymes essential for life?
Almost all metabolic reactions which take place in living organisms are catalyzed by enzymes and enzymes are therefore essential for life.
What are intracellular enzymes?
Intracellular enzymes are those that work inside the cells.
What are extracellular enzymes?
Extracellular enzymes are secreted by cells and catalyze reactions outside of cells. Digestive enzymes in the gut are extracellular enzymes. Some organisms secrete enzymes outside of their body. Fungi for example often do this in order to digest the food on which they are growing.
What is an active site?
An active site is an area on an enzyme molecule where the substrate can bind. The shape of the active site allows the substrate to fit perfectly.
What is the lock and key hypothesis?
The lock and key hypothesis is a hypothesis for enzyme action; The substrate is the key whose shape fits the lock of the enzyme. The substrate is held in place by temporary bonds which form between the substrate and some of the R groups of the enzymes amino acid. This combined structure is termed as the enzyme substrate complex. The substrate is a complementary shape to the active side of the enzyme and fits exactly into the site. The enzyme shows specificity for the substrate.
In the lock and key hypothesis how many enzymes can act on a substrate molecule?
In the lock and key hypothesis each enzyme will act only on one type of substrate molecule. This is because the shape of the active site will allow only one shape of molecule to fit. The enzyme is said to be specific for the substrate. You can also describe the enzyme as showing specificity.
What is the induced fit hypothesis?
Induced fit is a hypothesis for enzyme action which was recently discovered (1959). The substrate is a complementary shape to the active side of the enzyme but not an exact fit-The enzyme, or sometimes the substrate, can change shape slightly to ensure a perfect fits, but is still described as showing specificity.
What are the two types products which can be formed when an enzyme catalyzes a reaction?
An enzyme may catalyze a reaction in which a substrate molecule is split into two or more molecules. Alternatively it may catalyse the joining together of two molecules, as when making a dipeptide from two amino acids. The enzyme is unchanged by this process so it is now available to receive new substrate molecule after the enzyme product complex which is briefly formed releases the product.
Give an example of an enzyme which proves the induced fit hypothesis.
In lysosozyme the interaction between the substrate and the active site include a slight change in the shape of the enzyme which results from the binding of the substrate. Lysosozymes are found into your saliva and other secretions. It acts as a natural defense against bacteria. It does this by breaking the polysaccharide chain that form the cell walls of bacteria. The tertiary structure of the enzyme shows how the polysaccharide chain in the bacterial cell wall are broken down and the active side of the lysozyme.
What would happen without enzymes?
Enzymes increase the rate of which chemical reactions occur and without enzymes most of the reactions that occur in living cells would occur so slowly that life could not exist.
What is activation energy?
Activation energy is the energy that must be provided to make a reaction take place; enzymes produce the activation energy required for a substrate to change into a product.
Give a method to provide activation energy to substances.
One way of providing the extra energy needed is to heat the substances. For example in the Benedict’s test for reducing sugar you need to heat the Benedict’s reagent and sugar solution together before they will react.
How do enzymes reduce activation energy?
Enzymes reduce the activation energy of the reactions they catalyze. They do this by holding the substrate or substrates in such a way that their molecules can react more easily. As a result reactions catalyzed by enzymes take place rapidly and at much lower temperature than they otherwise would.
Describe the enzyme catalase
The enzyme catalase is found in the tissues of most living things and catalyses the breakdown of hydrogen peroxide into water and oxygen. (Hydrogen peroxide is sometimes produced inside cells. It is toxic so must be gotten rid of quickly). The oxygen that it releases can be collected and measured.
When Is the rate of an enzyme controlled reaction the fastest?
The rate of an enzyme controlled reaction is always fastest at the beginning. This rate is called the initial rate of reaction.
How can you measure the initial rate of reaction?
You can measure the initial rate of reaction by calculating the slope of a tangent to the curve
What does the rate of reaction depend upon?
The rate at which the reaction occurs depends on:
How many enzyme molecules there are
And the speed at which the enzyme can convert the substrate into product, release it, and then bind with another substrate molecule.
What causes the rate of formation of a product to stop?
The reaction begins quickly as at first there are a large number of substrate molecules, at any moment, almost every enzyme molecule has a has a substrate molecule in its active site. However as more and more substrate is converted into product there are fewer substrates to bind with enzyme which causes them to wait for the substrate. eventually reaction stops.
What is a colorimeter?
Colorimeter is an instrument that measures the color of a solution by measuring absorption of different wavelengths of light. the greater the absorption the greater the concentration of the substance using the color.
Which gas is released when hydrogen peroxide reacts with the enzyme catalase?
As soon as the enzyme and substrate are mixed, bubbles of oxygen are released. A large volume of oxygen is collected in the first minute of the reaction however as the reaction continues the rate at which oxygen is releases gradually slows down.
What does amylase break down?
Amylase breaks down starch to the reducing agent maltose, a hydrolysis reaction. Starch reacts with with iodine solution to produce a blue-black color.
