Question

a. aldohexose b. antibody c. cellulose d. \(\mathrm{CH}_{2} \mathrm{O}\) e. cysteine f. denaturation g. disaccharides h. disulfide i. DNA j. enzymes k. fibrous l. globular m. glycogen n. glycoside linkage o. hormone p. hydrophobic q. inhibition r. ketohexoses s. oxytocin t. pleated sheet u. polypeptide v. polysaccharides w. primary structure x. saliva y. substrate z. sucrose occurs when an enzyme's active site is blocked by a foreign molecule

Short answer

The short answer is: q. inhibition

Step-by-step solution

Enzymes are proteins that act as biological catalysts, which means they speed up chemical reactions happening within an organism. Each enzyme has an important part called the active site, which is a unique region where the substrate molecules bind and undergo a chemical reaction. In simple terms, enzymes help substrates transform into products, largely by the interactions between the enzyme's active site and the substrates. #Step 2: Analyze the terms for describing the blocking of an enzyme's active site#

The list contains terms related to carbohydrates (ex. aldohexose, cellulose), proteins (ex. antibody, polypeptide), and nucleic acids (ex. DNA), but these are not directly involved in enzyme inhibition. We are looking for a term that specifically refers to blocking or interfering with an enzyme's action at its active site. Knowing that, we should focus on the term 'inhibition' and examine its meaning in a Biochemical context. #Step 3: Define inhibition in Biochemistry#

Inhibition, in Biochemistry, refers to the process in which a substance, known as an inhibitor, reduces or completely blocks the activity of an enzyme. Inhibitors can interact with enzymes and affect their activity in different ways, one of which is by binding to the enzyme's active site and preventing the substrate from binding. #Step 4: Identify the term corresponding to the situation described in the exercise#

From our analysis, it is clear that the term 'inhibition' best describes the situation when an enzyme's active site is blocked by a foreign molecule. Thus, the correct answer is: q. inhibition

Key concepts

Active Site

Enzymes are remarkable biological catalysts involved in almost every cellular process. To understand their function, we must explore the concept of the 'active site.' This is a specific region on an enzyme where the substrates—the molecules upon which enzymes act—attach themselves. The architecture of an active site is highly selective, allowing only specific substrate molecules to fit, much like a key fits into a lock.

An active site is made up of specific amino acids that create a three-dimensional space suitable for the enzyme's particular function. This area not only binds to the substrates but also orients them in a way that facilitates the biochemical reaction they are to undergo. The enzyme's shape is dynamic and can change slightly to accommodate the substrate—this is called 'induced fit'.

In biochemical reactions, the fit of the substrate at the active site is critical to ensuring that the enzyme catalyzes only its specific reaction, avoiding unwanted side reactions and increasing the efficiency of the biological processes.

Substrate

The 'substrate' is a foundational concept in biochemistry. It refers to the specific molecule or molecules that an enzyme acts on and converts into a new product or products through a chemical reaction. The substrate initially binds to the enzyme's active site, and the unique match between a substrate's shape and the shape of the active site determines the specificity of the reaction.

For example, the substrate for an enzyme that digests proteins would be a protein that fits into the enzyme's active site. Once bound, the enzyme catalyzes a reaction to break the protein down. It's interesting to note that enzymes can sometimes work with multiple substrates, but they generally have a 'preferred' substrate with which they work most efficiently.

This specificity is due to the shape, size, and chemical properties of both the enzyme and the substrate, which must align perfectly for the reaction to occur. Substrates are converted into products while the enzyme, exhibiting a remarkable trait, remains unchanged after the reaction, ready to catalyze another round.

Biochemical Reactions

Biochemical reactions are the chemical processes that take place within living organisms. They are the foundation of life, underlying everything from cellular metabolism to DNA replication. These reactions are often complex and highly regulated, with enzymes playing a pivotal role as catalysts.

Enzymes lower the activation energy required for reactions to proceed, thereby increasing the rate at which substrates are converted into products. This function allows biological systems to thrive under conditions that would otherwise be insufficient to sustain the myriad of necessary reactions.

Examples of Biochemical Reactions

One prime example of a biochemical reaction is the breakdown of glucose during cellular respiration. This provides energy in the form of ATP that cells use to perform various functions. Another example is DNA synthesis, where enzymes help to form the long chains of nucleotides that constitute genetic material. Understanding biochemical reactions, therefore, is essential for grasping not only basic biological processes but also for the development of medical and biotechnological applications, such as drug design and metabolic engineering.