A1CC1 Chapter 4 - Enzymes and Biological Reactions Flashcards
(45 cards)
What is metabolism?
A series of enzyme controlled reactions in the body.
What are the two types of reaction?
Anabolic and Catabolic
What is anabolic reaction?
Protein synthesis where amino acids are built up into more complex polypeptides.
What is catabolic reaction?
Digestion of proteins, where complex polypeptides are broken down into simple amino acids.
What are the key facts about enzymes?
- Proteins speeding up chemical reactions by lowering the activation energy.
- Can be reused over and over.
- Convert substrates to products.
- Biological catalysts.
What is the structure of an enzyme?
Complex folded polypeptide chains held together in a 3D shape.
In terms of structure of enzymes, what is a primary structure?
Formed from the simple order of amino acids.
How does this then form an enzyme?
Each amino acids is joined to the next to form peptide bonds. Where this structure is then folded into an a-helix or b pleated sheet held together by hydrogen bonds called the secondary structure.
What is the Tertiary Structure of an enzyme?
Where further folding of the secondary structure occurs to form a 3D shape which is held together by hydrogen, ionic and disulphide bonds.
What is important about the tertiary structure of an enzyme?
This is what creates the shape of the ‘active site’ where substrates can bind.
Why do enzymes act in an aqueous environment?
They are soluble and catalyse many reactions including hydrolysis.
What is an enzyme-substrate complex?
An intermediate structure formed during an enzyme-catalysed reaction in which substrate and enzyme bind temporarily, such that the substrates are close enough to react.
What is activation energy?
The minimum amount of energy required to be put into a chemical system for a reaction to occur.
How can enzymes act?
They can act intracellularly or extracellularly.
Give an example of where an enzyme acts intracellularly?
During protein synthesis where the formation of a peptide bond between two amino acids is catalysed.
Give an example of where an enzyme acts extracellularly?
When pancreatic amylase is released from pancreatic cells and travels to the small intestine via the pancreatic duct where it then catalyses the breakdown of starch to maltose.
What are the two models of enzyme action?
- Lock and Key Model
- Induced Fit Model
What does the Lock and Key Model state?
The substrate has a complementary shape to the enzyme’s active site, like a key fitting into a lock. This explains the specificity of many enzymes that many only catalyse one substrate.
What does the Induced Fit Model state?
The enzyme’s active site becomes altered by the binding substrate molecule to accomodate it. This breaks bonds meaning the activation energy decreases. This explains why multiple substrates can bind to one active site.
What factors affect the rate of enzyme action? (5)
- Substrate concentration
- Temperature
- pH
- Enzyme concentration
- Presence of inhibitors
How does substrate concentration affect the rate of enzyme action?
When the substrate concentration increases, there is a greater chance of a successful collision between the substrate and the enzyme resulting in more enzyme-substrate complexes forming, increasing the rate of reaction.
What happens when all active sites are in use?
Reached plateau which represents the maximum rate of reaction for the rest of the conditions.
How does temperature affect the rate of enzyme reaction?
When temperature increases, both enzymes and substrates gain more kinetic energy, so move faster. This increases the chance of a successful collision between them. As temp increases, it reaches the optimum rate.
Why does rate drop of suddenly if temperature is too high?
The rate decreases rapidly due to hydrogen bonds in the tertiary structure breaking due to increased vibration. This results in a change of shape of the active site meaning the enzyme is now denatured and non-functional.
