C1.1 Enzymes Flashcards
Explain how do enzymes lower activation energy?
Enzymes provides a template for the substrate molecule(s) to come together in the correct orientation, thus facilitating the reaction.
The catalytic R groups in the active site may cause distortion, stretching or bending of existing critical bonds present in the substrate molecules.
This encourages the bonds to break and hence facilitate the subsequent rearrangement of atoms to form the product molecules.
It may provide a conducive micro-environment so that the reaction can proceed optimally.
Eg. it may provide an acidic environment in contrast to the naturally neutral surroundings of the cell.
Describe and explain metabolism
Metabolism is the complex network of interdependent and interacting chemical reactions
Because of enzyme specificity, many different enzymes are required by living organisms
Metabolism enables cell to survive and carry out its functions
Consists of anabolic and catabolic reactions
Contrast anabolism and catabolism
Anabolism is an endergonic reaction, requiring ATP. It also releases water through condensation. Some examples of anabolic reactions are transcription and transltion, protein synthesis and photosynthesis, glycogen synthesis and DNA replication.
In contrast, catabolism is an exergonic reaction, only requiring ATP in the initial stages. Water is used through hydrolysis. Catabolism usually releases energy.
Explain why living organisms need enzymes when metabolic reactions occur spontaneously.
The rate of metabolic reactions occurring spontaneously is too slow to support life / meet the demands of the living system; Therefore, enzymes are required to accelerate the rate of metabolic reactions to the point where they are rapid enough to support the demands of the living systems.
Define the term enzyme
An enzyne is a globular protein ;
that acts as a biological catalyst.
Explain the Induced Fit Model of Enzyme Action.
Binding of substrate induces shape of active site to change slightly 🡪 better fit with substrate. The active site is flexible such that both substrate and active site can fit together.
Rearrangement of chemical groups within active site.
For example, hexokinase
Explain the Lock and Key Model of Enzyme Action
What is the effect of altering substrate concentration on rate of reaction of the enzyme?
Rate of enzyme activity is directly proportional to substrate concentration. As the rate of substrate concentration increases, rate of reaction increases. This increases the number of collisions and hence effective collisions betwee enzyme and substrates, increasing amount of enzyme-substrate complexes formed thus increasing rate of formation of products. However, at high substrate concentrations, the rate of enzyne activity remains constant an plateaus because all active sites are occupied.Frequency of effective collisions between enzyme and substrate remains the same as substrate concentration increases.
What is the effect of varying temperature on the rate of reaction of the enzyme?
Before an optimum temperature is reached, as temperature increases, rate of reaction increases due to more kinetic energy contributing to increased collisions and thus effective collisions between the enzyme and the substrate. More complexes are form and enzyme activity increases. At optmum temperature, rate of formation of ES complexes is at its peak. However, past that point, the bonds in the enzyme vibrate more and break. The active site of the enzyme loses its 3D structure and it can no longer bind with substrate molecules. Hence, less ES complex formed enzyme activity decreases to 0.
What is the effect of varying pH on the rate of reaction of the enzyme?
Enzymes can have an optimum pH ay which activity is highest. Differing enzymes can have varying optimum pH levels. Enzyme activity remains relatively low as pH is above or below optimum pH. Slight changes in pH alters the charges of amino acid residue at the active site and substrate, preventing formations of enzyme-substrate complexes. Larger changes in pH can completely alter the 3D shape of active site by breaking ionic bonds , causing the enzyme to denature completely.
