Question

Name the enzyme whose substrate is (a) Urea (b) Cellulose

Short answer

(a) Urease, (b) Cellulase

Step-by-step solution

Identifying Information about Urea

We know that urea is a simple organic compound that organisms need to break down to another form to excrete it. In mammals, this breakdown occurs in the liver and kidney.

Determining the Enzyme for Urea

Urea is broken down by the enzyme known as **urease**. Urease catalyzes the hydrolysis of urea into carbon dioxide and ammonia, which organisms then eliminate more easily.

Identifying Information about Cellulose

Cellulose is a polysaccharide consisting of glucose monomers that form structural components in the plant cell walls.

Determining the Enzyme for Cellulose

The enzyme responsible for breaking down cellulose is **cellulase**. Cellulase catalyzes the cellulose into simpler sugars like glucose.

Key concepts

Urea Metabolism

Urea metabolism is an essential process in many organisms, playing a particularly vital role in nitrogen excretion. The primary enzyme responsible for this process is called **urease**. Urease is a catalyst that helps convert urea, a simple organic compound found in urine, into carbon dioxide ( CO_2 ) and ammonia ( NH_3 ).
This reaction is crucial as these products are much easier for the body to eliminate.

• Urea is produced in the liver during the urea cycle, a part of protein metabolism.
• The enzyme urease is often found in certain bacteria, fungi, and plants, facilitating this conversion.

The significance of urease's function is not just limited to excretion but includes environmental applications, such as maintaining the nitrogen balance in soil due to its presence in certain bacteria. By understanding urease, scientists can tackle issues like soil health and waste management more effectively.

Cellulose Digestion

Cellulose is a complex carbohydrate found in the cell walls of plants, making it a vital structural component that bears strength and rigidity. However, breaking down cellulose into usable energy forms is challenging for many organisms. The enzyme **cellulase** is key here, acting as the catalyst for cellulose digestion. Cellulase breaks down cellulose into simpler sugars, predominantly glucose, which organisms can then metabolize for energy.
Some interesting points about cellulose and cellulase:

• Most animals cannot produce cellulase on their own.
• Ruminant animals, like cows and sheep, harbor microbes in their stomachs that produce cellulase to digest plant material.
• This process is crucial for the carbon cycle, as it enables the recycling of organic matter back into the ecosystem.

Overall, cellulase plays a pivotal role in making energy stored in plant biomass accessible to a wider array of organisms, thereby maintaining ecological balance.

Enzyme Catalysis

Enzymes are essential proteins that facilitate chemical reactions by lowering the energy barrier, making them happen faster than they would naturally. The term **enzyme catalysis** refers to this acceleration aspect.
Some key features of enzyme catalysis include:

• Specificity: Enzymes are highly specific to their substrates, meaning they only catalyze specific reactions.
• Efficiency: They can increase the rate of reaction significantly, often by many orders of magnitude.
• Regulation: Enzyme activity can be regulated by factors such as temperature, pH, and the presence of inhibitors or activators.

Enzymes such as urease and cellulase exemplify these principles effectively. Urease specifically acts on urea, while cellulase targets cellulose. This precise mechanism ensures the right reactions occur within biological systems, maintaining life functions and supporting various industrial applications, such as drug manufacturing and food production.