Metabolism 8.1 HL

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.

Key concepts

Learn and test your biological vocabulary using these 8.1 metabolism flashcards.

Essentials

These slides summarise the essential understanding and skills in this topic. 
They contain short explanations in text and images - great revision.

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Summary

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
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Exam style questions

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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Extra exam question on the role of enzymes in metabolism. Click on the "+" symbol to reveal the question.

Exam style question about the role of specific enzymes.

The question below requires knowledge of the role of specific enzymes in living organisms.

Answer on paper and check your answer against the model answer.

Describe the role of four named enzymes in living systems. (8 marks)








Examiner hint - There is one mark for the name of each enzyme and one for each description of the reaction it catalyses. Make sure the enzyme name matches its function to gain marks. Try to use a variety of enzyme examples, such as those in digestion, the liver, DNA replication etc.

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Extra exam question on ***      Click to open it.

Brief introduction to the skill / understanding tested in the question.

Question text in bold (2 marks).





Hint: Do this in italics, you may gain marks for the method of the calculation if your answer is incorrect.
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Test yourself

Multiple choice questions

This is a self marking quiz containing questions covering the topic outlined above.
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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.

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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.



Extra drag and drop explanation on inhibitors and feedback inhibition in metabolic pathways.  Click to open it.

 Noncompetitive inhibition of enzymes and feedback control of metabolic pathways.

Noncompetitive and feedback inhibition are important concepts in the control of metabolic pathways in vivo (in the living organism).

Drag and drop the correct term into the gap to describe noncompetitive inhibition.

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metabolically glycolytic inhibitors bound active site distorted production substrate feedback inhibited

Noncompetitve are substances that bind to an inhibitor site on the enzyme (not on the ). When the inhibitor is to the enzyme, the active site is and cannot bind with the .

ATP is an allosteric inhibitor of phosphfructokinase, one of the enzymes in the pathway at the beginning of respiration. When cell energy demands are low, phosphfructokinase will be , slowing respiration. When the cell is active, ATP is utilised and the inhibition will cease. This is known as inhibition and automatically adjusts energy by respiration to meet the needs of the cell.

Explanation: Feedback inhibition is the means by which the cells produce products in amounts needed by the cell.


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