C1.1  Enzymes and Metabolism

Guiding Questions:  
Guiding questions help students view the content of the syllabus through the conceptual lenses of both the themes and the levels of biological organization.

• In what ways do variations in form allow diversity of function in carbohydrates and lipids?
• How do carbohydrates and lipids compare as energy storage compounds?

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​Linking Questions:  
Linking questions strengthen students’ understanding by making connections between topics.  The ideal outcome of the linking questions is networked knowledge.

• How can compounds synthesized by living organisms accumulate and become carbon sinks?
• What are the roles of oxidation and reduction in biological systems?

Resources:

• At SHS, Topic C1.1 is taught in the Carbs and Lipids, Energy Flow and Enzymes units. 
• Quizlet study set for this topic.  Coming soon!
• View the general sequence of the SHS course
• View the SHS units mapped to the IB Biology curriculum roadmap

C1.1.1— Enzymes as catalysts.

• Define catalyst.
• State the role of enzymes in the chemical reactions on which life is based. ​
• State that enzymes speed up chemical reactions without being altered, so can be reused.
  

C1.1.2— Role of enzymes in metabolism.

• Define metabolism.
• Define specificity in relation to enzyme structure and function. 
• Outline how control of metabolism is regulated by enzymes.

C1.1.3—  Anabolic and catabolic reactions.

• Contrast anabolic and catabolic reactions.
• List three examples of anabolic processes. 
• List three examples of catabolic processes.

C1.1.4— Enzymes as globular proteins with an active site for catalysis.

• Outline properties of globular proteins. 
• Explain the relationship between enzyme structure and enzyme specificity, including the structure and function of the active site.​

C1.1.5— Interactions between substrate and active site to allow induced-fit binding.

• Outline the stages of enzyme catalysis of a chemical reaction.
• Describe the induced fit model of enzyme binding.​

C1.1.6- Role of molecular motion and substrate-active site collisions in enzyme catalysis.

• Explain the role of random collisions in the binding of the substrate with the enzyme active site.
• Compare enzyme and substrate movement involved in reactions that occur in the cytoplasm, with large substrates and with immobilized enzymes.

C1.1.7- Relationships between the structure of the active site, enzyme–substrate specificity and denaturation.

• Discuss variation in specificity of different enzymes. 
• Define denaturation.
• Outline the causes and effects of denaturation on enzyme structure and function.

C1.1.8- Effects of temperature, pH and substrate concentration on the rate of enzyme activity.

• Explain the effects of temperature, pH and substrate concentration on enzyme structure and function with reference to collision theory, temporary and permanent denaturation. 
• Draw and interpret graphs showing the effects of temperature, pH and substrate concentration of the activity of enzymes.

C1.1.9- Measurements in enzyme-catalyzed reactions.

• Identify the manipulated (independent), responding (dependent) and controlled variation in experiments of enzyme catalyzed reactions.
• State the unit for enzyme reaction rate.
• State two methods for determining the rate of enzyme reaction rates.
• Describe three investigative techniques for measuring the activity of an example enzyme.

C1.1.10- Effect of enzymes on activation energy. 

• Define activation energy.
• State that activation energy is used to break or weaken bonds in the substrate. 
• Explain the role of enzymes in lowering the activation energy of a reaction.
• Interpret graphs showing the effect of lowering the activation energy by enzymes.

AHL ​​​C1.1.11- Intracellular and extracellular enzyme-catalyzed reactions.

• Compare the location of synthesis of enzymes used within and outside of a cell. 
• State an example of an intracellular metabolic reaction  and an extracellular metabolic reaction.

AHL ​​​C1.1.12- Generation of heat energy by the reactions of metabolism.

• Outline the generation of heat energy by the reactions of metabolism. 
• Describe how birds and mammals maintain a body temperature greater than that of their environment.
• Outline an example of maintaining temperature homeostasis using heat generated by reactions of metabolism.

AHL ​​​C1.1.13- Cyclical and linear pathways in metabolism.

• State the reason for metabolic pathways.
• Contrast linear metabolic pathways with cyclical reaction pathways.
• State and example of a linear metabolic pathway and a cyclic  metabolic pathway.

AHL ​​​C1.1.14- Allosteric sites and non-competitive inhibition.

• Outline the structure and function of an allosteric site. 
• Define enzyme inhibitor.
• Describe mechanism of action of non-competitive enzyme inhibitors.

AHL ​​​C1.1.15- Competitive inhibition as a consequence of an inhibitor binding reversibly to an active site.

• Describe mechanism of action of competitive enzyme inhibitors. 
• Outline the function of statins as an example of a competitive inhibitor.
• Explain why the rate of reaction with increasing substrate concentration is lower with a non-competitive inhibitor compared to a competitive inhibitor.​

AHL ​​​C1.1.16- Regulation of metabolic pathways by feedback inhibition.

• Outline the mechanism and benefit of feedback inhibition.
• Illustrate end-product inhibition of the threonine to isoleucine metabolic pathway.​

AHL ​​​C1.1.17- Mechanism-based inhibition as a consequence of chemical changes to the active site caused by the irreversible binding of an inhibitor.

• Compare reversible and irreversible enzyme inhibition.
• Outline the cause and consequence of mechanism-based inhibition.
• Illustrate mechanism-based inhibition using penicillin as an example.​