Problem 117

Question

One of the many remarkable enzymes in the human body is carbonic anhydrase, which catalyzes the interconversion of carbon dioxide and water with bicarbonate ion and protons. If it were not for this enzyme, the body could not rid itself rapidly enough of the $\mathrm{CO}_{2}$ accumulated by cell metabolism. The enzyme catalyzes the dehydration (release to air) of up to $10^{7} \mathrm{CO}_{2}$ molecules per second. Which components of this description correspond to the terms enzyme, substrate, and turnover number?

Step-by-Step Solution

Verified

Answer

The enzyme in the description is carbonic anhydrase which catalyzes the reaction. The substrates are carbon dioxide ($\mathrm{CO}_{2}$) and water ($\mathrm{H}_{2}\mathrm{O}$) that undergo interconversion. The turnover number is $10^{7}$ molecules per second, indicating the enzyme's catalytic speed.

1Step 1: Identifying the enzyme

An enzyme is a biological catalyst that speeds up chemical reactions in living organisms. In the given description, we are told about carbonic anhydrase as "one of the many remarkable enzymes in the human body." So, the enzyme in this case is carbonic anhydrase.

2Step 2: Identifying the substrate

The substrate is the reactant on which enzymes work. In the given description, we are told that carbonic anhydrase catalyzes the interconversion of carbon dioxide and water with bicarbonate ion and protons. Therefore, the substrates are carbon dioxide ($\mathrm{CO}_{2}$) and water ($\mathrm{H}_{2}\mathrm{O}$).

3Step 3: Identifying the turnover number

The turnover number of an enzyme is the number of reactions an enzyme can catalyze per unit time. In the given description, we are told that the enzyme can catalyze the dehydration (release to air) of up to $10^{7}$ $\mathrm{CO}_{2}$ molecules per second. Therefore, the turnover number here is $10^{7}$ molecules per second.

Key Concepts

Carbonic AnhydraseEnzyme Turnover NumberChemical Reaction Substrates

Carbonic Anhydrase

Carbonic anhydrase is a crucial enzyme found in various tissues throughout the body. It plays a significant role in maintaining the acid-base balance in blood and tissues. This enzyme is responsible for catalyzing the reversible reaction between carbon dioxide ($\mathrm{CO}_{2}$) and water ($\mathrm{H}_{2}\mathrm{O}$) to form bicarbonate ion ($\mathrm{HCO}_{3}^{-}$) and protons ($\mathrm{H}^+$).
Some key points about carbonic anhydrase include:

It helps to rapidly expel carbon dioxide, a metabolic waste, from the body.
The enzyme is highly efficient, ensuring that metabolic processes are not slowed down by the accumulation of $\mathrm{CO}_{2}$.
It is involved in various physiological processes, such as respiration and renal function.

In short, carbonic anhydrase is vital for efficient respiration and maintaining the body's pH levels. Without it, the body would struggle to manage carbon dioxide levels efficiently.

Enzyme Turnover Number

The turnover number of an enzyme, also known as k_cat, is a measure of its catalytic activity. It indicates how many substrate molecules one enzyme molecule can convert into product per second under optimal conditions.
In the exercise, carbonic anhydrase has an incredibly high turnover number of $10^7$ molecules per second. This high turnover rate is a reflection of the enzyme's efficiency and speed.
Here are some important considerations about turnover numbers:

A high turnover number typically indicates a very efficient enzyme, capable of processing substrate quickly.
The turnover number can vary significantly between different enzymes.
This metric is essential for understanding how enzymes influence metabolic rates.

So, the turnover number provides valuable insight into an enzyme's performance and its capability to sustain biological processes.

Chemical Reaction Substrates

In enzymatic reactions, substrates are the molecules upon which enzymes act. They are the starting materials that undergo transformation during the chemical reaction.
In the case of carbonic anhydrase, the substrates involved are carbon dioxide ($\mathrm{CO}_{2}$) and water ($\mathrm{H}_{2}\mathrm{O}$). These substrates are integral to the reaction that produces bicarbonate ions and protons.
Key aspects of enzyme substrates include:

Substrates bind to the active site of an enzyme, initiating the reaction.
The specificity of the enzyme-substrate interaction influences the efficiency of the reaction.
A well-defined enzyme-substrate interaction is crucial for proper metabolic function.

Therefore, understanding substrates is essential for grasping how enzymes catalyze reactions and impact physiological processes.

Problem 113

Problem 118

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