Enzymes Flashcards
What are the rates of chemical reactions that occur in living cells controlled by?
The rate of these reactions are controlled by a special group of proteins called enzymes.
What is the definition of enzymes?
Enzymes are biological catalysts, made by all living cells. They speed up cellular reactions and are unchanged in the process.
Why are enzymes known as “biological catalysts?
Enzymes are known as “biological catalysts” because they are chemicals that are made by living cells. Without enzymes, chemical reactions would be too slow to sustain life.
What are the two types of enzyme-controlled chemical reactions?
1) Degradation reactions
2) Synthesis reactions
What is the definition of degradation reactions?
Large complex molecules are broken down into smaller simpler ones.
What is the definition of synthesis reactions?
Small, simple molecules are built into large complex ones.
Give an example of a degradation reaction.
For example, digestion reactions: starch being broken into maltose and then glucose.
Give an example of a synthesis reaction.
For example, glucose (made during plant photosynthesis) being built up into starch.
Explain what happens when an enzyme-controlled reaction takes place.
During an enzyme-controlled reaction the molecule on which an enzyme works, called the substrate, joins temporarily at the active site on the surface of the enzyme. This facilitates the chemical reaction which can now take place quickly and forms the product or products.
What is the definition of a substrate?
The molecule the enzyme is working on.
What is the definition of a product?
Molecule produced at the end of the reaction.
Why are enzymes said to be specific to a particular substrate?
Enzymes are said to be specific to a particular substrate because the shape of the active site of an enzyme molecule is complementary to its specific substrate(usually one type of substrate).
How can we identify starch?
Starch can be identified by using iodine solution.
What colour is iodine when starch is absent?
If starch is absent iodine is brown.
What colour is the iodine if starch is present?
If starch is present iodine is black/blue.
Name the substrate, enzyme and products present in the degradation reaction(catalase and hydrogen peroxide) and how we can measure the rate of reaction.
Substrate: hydrogen peroxide
Enzyme: catalase
Products: oxygen and water
The rate of reaction can be measured by:
Capturing the oxygen in a measuring cylinder and measuring its volume over a period of time
Using detergent to capture the oxygen and measure the height of foam produced over a period of time.
Name the substrate, enzyme, and product produced in the synthesis reaction (making starch) and how we can identify starch.
Substrate: glucose-1-phosphate
Enzyme: phosphorylase
Product: starch
We can identify starch by using iodine solution.
When are enzymes most active?
Each enzyme is most active in its optimum conditions.
What are the two factors affecting enzyme activity?
Enzymes are affected by both pH and temperature.
What is the optimum temperature for human enzymes?
Human enzymes have an optimum temperature of 37 c.
Why does enzyme activity increase when the temperature increases from 0c to 37c?
The enzyme and substrate molecules move more quickly at higher temperatures, substrates collide more often with enzyme active sites therefore more reactions take place.
Explain the term “denatured” in terms of human enzymes.
As the temperature rises above 37c, the chemical bonds break changing the shape of the enzyme. Since the activity of the enzyme will depend on the shape of its active site, and this has changed, the enzyme will stop working. The enzyme is said to be denatured. It is permanently inactive.
What is the effect of temperature on enzyme activity?
As temperature increases enzyme activity also increases until an optimum temperature is reached after which enzyme activity decreases.
What does the pH scale measure?
The pH scale measures acidity and alkalinity.
Explain the pH scale.
0-6.9= acid
7=neutral
8-14=alkali
What is meant by optimum pH?
Although many enzymes are most active at around neutral (pH7), different enzymes have a pH at which they are most active. This is called their optimum pH.
What happens when an enzyme is above or below optimum pH?
Above and below an enzyme’s optimum pH, the enzyme is denatured, therefore its activity is reduced.