Enzymes Flashcards
What is metabolism?
A collection of life-sustaining chemical reactions that occur within the cells of a living organism.
What is anabolism?
The conversion of simple molecules, such as glucose, nucleotides, and amino acids into complex molecules, such as starch, proteins and lipids. This process requires ATP.
What is catabolism?
The conversion of complex molecules such as starches, proteins and lipids into simple molecules, such as glucose, nucleotides and amino acids. This process releases ATP.
What do enzymes do?
They are special molecules that help cells carry out metabolism.
What is a catalyst?
A substance that increases the rate of a chemical reaction without itself undergoimg any permanent chemical change.
How do catalysts increase the rate of reaction?
By reducing the activation energy required.
Enzymes are known as biological catalysts. Why?
Because they are naturally occurring in the body.
Why do we need enzymes?
Because without enzymes metabolism would occur too slowly and organisms would die as they would not be able to efficiently break down food molecules to produce energy or join small molecules to produce essential larger ones such as proteins.
Recall the composition of enzymes (which are proteins).
- Amino acids join together to form long polypeptide chains; primary structure.
- This chain can keep folding to form helices and sheets: secondary structure.
- This chain can then also form large 3-dimensional structures; tertiary structure.
- 2 or more polypeptide chains can fold together to form a functional protein; quaternary structure.
Summarise the lock and key model.
The substrates join together with the enzymes precisely (as there are many enzymes in the body which are all used for specific substrates). They latch onto the active site of the enzyme to form an enzyme-substrate complex. Then, the enzyme sets the new product free so it can be used for other reactions.
Summarise the induced-fit model.
The induced-fit model postulates that the active site changes shape slightly to allow for better fit of the substrate. It follows nearly the same steps for the lock and key model. Note that the active site will return to its original shape after the reaction.
Enzymes of biological molecules that require certain conditions for optimal functioning. What are these limits?
- Temperature
- pH
- substrate concentration
Recall what collision theory is.
Collision theory states that that the rate of reaction depends on the number of successful collisions that occurred between reactant molecules. That is, the greater the number of successful collisions, the higher the rate of reaction.
Describe what happens to the enzyme activity as you increase temperature.
As you are increasing temperature, you are also increasing the average kinetic energy, and the rate of reaction will gradually increase. However, at a certain point, when the enzyme reaches optimal temperature, the rate of reaction will plummet and start to decrease.
Why does the rate of reaction begin to decrease after reaching optimal temperature?
This is because proteins are biological molecules that lose their specific 3-D shape and become non-functional when heated above their optimal temperatures. This process is referred to as denaturing.
When an enzyme is heated beyond its optimal temperature bonds holding together its 3D shape are disrupted. This means the 3-D shape of the active site is altered, such that the enzyme can no longer accommodate the substrate.
