- Summary list for 8.1 Metabolism
- Mindmaps
- Exam style question about enzymes
- Model answer
- Exam style question about the role of specific enzymes.
- Model answer
- Model answer
- Multiple choice questions
- 8.1 Enzymes and metabolism 1/1
This topic covers the way enzyme pathways form a cell's metabolism as well as specific examples of these pathways. The action of enzymes and their substrates is required as well as the way in which competitive and non-competitive inhibitors change the rate of reaction. The skill of calculating a rate of reaction from a graph of data is also part of this topic.
Summary list for 8.1 Metabolism
Metabolic pathways
- A chain or a cycle of enzyme-catalysed reactions makes a metabolic pathway.
- Enzymes catalyse chemical reactions by lowering the activation energy.
Competitive inhibitors
- Competitive inhibitors for example in medicine - ethanol and Fomepizole used as competitive inhibitors for antifreeze poisoning.
Non-competitive inhibitors
- Non-competitive inhibitors. E.g. Drugs for treatment of malaria.
- End-product inhibition can control metabolic pathways - e.g. In the pathway that converts threonine to isoleucine.
Skills
- The use of databases to identify potential new anti-malarial drugs. In the ER role play: students will have seen this
- In the Enzyme inhibition experiment students will calculate and plot rates of reaction from raw experimental results.
- They will also distinguish different types of inhibition from graphs at specified substrate concentration.
Mindmaps
These diagram summaries cover the main sections of topic 8.1 Metabolism
Study them and draw your own list or concept map from memory.
Exam style question about enzymes
Answer the question below, which addresses the role of enzymes.
Explain how enzymes increase rates of reaction in metabolic pathways. (4 marks)
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Click the + icon to see a model answer.
Multiple choice questions
This is a self marking quiz containing questions covering the topic outlined above.
Try the questions to check your understanding.
START QUIZ!
The diagram below shows part of the metabolic pathway known as Glycolysis
What is meant by the term "metabolic pathway"?
A chain or a cycle of enzyme-catalysed reactions makes a metabolic pathway.
How do enzymes change a reaction to speed up reaction rates?
Enzymes catalyse chemical reactions by lowering the activation energy.
When chemicals collide with more energy than the "activation energy" a reaction happens.
Inhibitors can prevent enzymes from working correctly.
The diagram shows the structure of an enzyme, its substrate and an inhibitor.
What is the best description of the inhibitor in this situation?
Competitive inhibitors are often used in medicine, they block the active site.
Ethanol and Fomepizole (which has a similar shape) are used as competitive inhibitors to treat antifreeze poisoning.
Cells control metabolic pathways using several different methods?
Which of the following is not a method which is used by cells to control metabolism
Cells can control metabolism using, expression of genes, inhibition, end product inhibition or hormones.
Methylation of DNA may control the expression of genes, but not methylation of enzymes.
End product inhibition is a common mechanism which controls metabolic pathways.
Which statement most correctly describes what happens to the amount of inhibition when the concentration of the end product increases?
End-product inhibition can control metabolic pathways by inhibiting an enzyme 'upstream' in the metabolic pathway of the product's synthesis. - e.g. In the pathway that converts threonine to isoleucine.
The greater the concentration of end product the greater the inhibition.
The graph below shows the rate of reaction of an enzyme with and without an inhibitor present.
What type of inhibitor is most likely to be involved?
To distinguish different types of inhibition from graphs at specified substrate concentration, remember that a competitive inhibitor will not be able to inhibit enzymes which already have their active site occupied by a substrate. In high substrate concentrations the substrate gets into the active site before the inhibitor more often.
What is the initial rate of reaction show by the data in the graph below?
The tangent is drawn at the start of the curve, showing the rate at the start.
The rate of reaction is the amount of product per second.
18g per litre divided by 10 seconds.
Drag and drop activities
Test your ability to construct biological explanations using the drag and drop questions below.
Competitive inhibition of enzymes and antibiotics
You need to know specific examples of enzyme inhibition.
Drag and drop the correct term into the gap to describe the use of antibiotics as enzyme inhibitors.
temporarily cell wall active site competitive binary fission substrate slowing "look-alike" metabolic pathways
Nonpermanent competitive enzyme inhibitors bind to the of an enzyme in competition with the . As they are noncompetitive, they bind to the active site, the rate of reaction but do not damage the enzyme. They are generally molecules with a very similar molecular shape to the substrate, molecules
Beta lactams are antibiotics which act as inhibitors of the enzymes in bacteria which synthesise peptidoglycans, a polymer found in bacterial cell walls. They bind to the active site of the enzyme, preventing it from completing the structure when the bacterium divides by .
They do not harm humans (bar possible side effects) as the enzyme is not found in human as human cells do not have a cell wall.
Explanation. Many antibiotics are inhibitors of prokaryotic enzymes, not found in animal eukaryotes. They are ineffective against viruses because they use host metabolic pathways.
How much of Metabolism 8.1 HL have you understood?
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