KA6 - Metabolic Pathways Flashcards
What are metabolic pathways?
Metabolic pathways are integrated and controlled pathways of enzyme catalysed reactions within a cell
What 3 steps could a metabolic pathway have?
Reversible steps
Irreversible steps
Alternative routes
What is the activation energy?
The activation energy of a reaction is the amount of energy required to make a reaction happen
What happens to the activation energy of a reaction due to the binding of an enzyme to its substrate?
The binding of an enzyme to its substrate lowers the activation energy of a reaction
If an enzyme is present, what happens to the amount of energy need to make a product?
Is an enzyme is present, the amount of energy needed to make a product is lowered
What are the two types of metabolic pathways?
Anabolic
Catabolic
What can anabolic pathways be referred to as?
Biosynthesis pathways
What are anabolic pathways?
Anabolic pathways require energy. This energy is used to build up smaller molecules into larger ones
Give two examples of anabolic reactions
DNA replication
Protein synthesis
What can catabolic pathways also be referred to?
Degradation pathways
What are catabolic pathways?
Catabolic pathways release energy. This release of energy occurs when large molecules are broken down into smaller ones
Give two examples of catabolic pathways
Respiration
Digestiom
Why must metabolic pathways be regulated and controlled?
In order to prevent the build up of an end product which is not needed
How are metabolic pathways controlled?
A cell can control a metabolic pathway by the presence or absence of a particular enzyme or by regulation the rate of reaction of key enzymes
What is the most effective way of regulating enzyme activity?
By changing the shape of the enzyme
What is induced fit?
An induced fit occurs when the active site of an enzyme is changed slightly to better fit the substrate after the substrate binds
What is affinity?
Affinity is the term used to describe the degree to which substances bind together
What affinity does an enzymes active site have to the substrate?
An enzymes active site has a high affinity to the substrate as well as being specific to the substrate
What happens as the products are made?
Their shape changes and they are no longer specific to the enzymes active site
What affinity do the products have to the enzymes?
The products have low affinity to the enzymes and are released
What then happens to the active site of an enzyme?
The active site of the enzyme then resumes its normal shape and the enzyme is free to attach to more substrate molecules
What 4 factors affect enzymes?
Temperature
pH
Enzyme concentration
Substrate concentration
What happens as substrate concentration increases?
The rate of the enzyme catalysed reaction increases until all of the active sites are occupied by the substrate
What is the term used to describe the enzyme once all active sites are occupied?
Saturated
What happens after the saturation point?
Adding more substrate will no long increase the reaction rate
What else can stop an enzyme binding to its substrate?
Inhibitors
What are the three types of inhibition?
Competitive inhibition
Non competitive inhibition
Feedback inhibition
What is competitive inhibition?
Competitive inhibition occurs when a competitive inhibitor binds to the active site of an enzyme and therefore prevents the substrate from binding
Why do competitive inhibitors compete with the substrate?
The competitive inhibitors compete with the substrate because they have a similar shape to the substrate and enzymes active site
How can competitive inhibition be reversed?
By increasing the concentration of the substrate. This is because the increases substrate concentration dilutes the inhibitor so that the enzyme molecules bind to the substrate
What is non competitive inhibition?
Non competitive inhibitors bind to a part of the enzyme that is not the active site but they still change the shape of the active site. This prevents the substrate from binding to the enzyme and therefore decreases the reaction rate
Why can’t non competitive inhibition be reversed?
As the non competitive inhibitor does not bind to the enzymes active site, their effects cannot be reversed by increasing substrate concentration
What is feedback inhibition?
Feedback inhibition occurs when the end product of a metabolic pathway reaches a critical concentration. The end product then binds to an enzyme at the start of the metabolic pathway, inhibits it an prevents any further synthesis of the ends product
How does feedback inhibition stop the metabolic pathway?
Feedback inhibition stops the metabolic pathway and prevents further synthesis of the end product until the end product concentration decreases
The higher the concentration of end product, the quicker the metabolic pathway stops
What does feedback inhibition ensure?
That a cell does not produce more end product than necessary
