Some vitamins are essential to an organism because they function as

Answer Explanation

The action of enzymes vary with pH. Enzymes are proteins that catalyze biochemical reactions, and their activity is influenced by various factors including pH.

The pH level affects the ionization state of amino acid residues within the enzyme's active site. This, in turn, can affect the enzyme's ability to bind substrate molecules and catalyze reactions.

Different enzymes have different optimal pH ranges at which they exhibit maximum activity. This optimal pH range is determined by the specific environment in which the enzyme typically functions. For example, pepsin, which is involved in digesting proteins in the stomach, works optimally at an acidic pH around 2, whereas enzymes in the small intestine function optimally at a slightly alkaline pH around 7 to 8.

Extreme deviations from the optimal pH can denature enzymes, causing them to lose their structure and function. Therefore, maintaining the appropriate pH level is crucial for ensuring the proper functioning of enzymes in biochemical reactions.

Answer Explanation

D) vitamins and minerals

- Correct: Vitamins and minerals are nutrients that can be absorbed without first being digested in the human gastrointestinal tract. Unlike carbohydrates, proteins, and fats, which require enzymatic digestion to break them down into smaller molecules for absorption, vitamins and minerals are already in a form that can be readily absorbed by the body. Once absorbed, vitamins and minerals play essential roles in various physiological processes, such as metabolism, immune function, and bone health.

A) carbohydrates and polypeptides

- Incorrect: Carbohydrates and polypeptides (large protein molecules) require enzymatic digestion to break them down into simpler molecules (such as glucose from carbohydrates and amino acids from polypeptides) before they can be absorbed by the gastrointestinal tract.

B) proteins and vitamins

- Incorrect: Proteins require enzymatic digestion to break them down into amino acids before they can be absorbed by the gastrointestinal tract. While vitamins do not require digestion and can be directly absorbed, proteins do not fall into this category.

C) minerals and polysaccharides

- Incorrect: Minerals, such as calcium, iron, and zinc, can be directly absorbed without prior digestion in the gastrointestinal tract. However, polysaccharides (complex carbohydrates) require enzymatic digestion into simpler sugars before they can be absorbed.

Answer Explanation

C) absorbed food is the raw material for metabolism

- Correct: The digestion of food and subsequent absorption into the bloodstream are essential processes because absorbed food molecules serve as the raw material for metabolism. Once nutrients from food are absorbed into the bloodstream, they are transported to cells throughout the body where they are used for various metabolic processes. Carbohydrates are broken down into glucose, which is used for energy production. Proteins are broken down into amino acids, which are used for building and repairing tissues, as well as for synthesizing enzymes and hormones. Fats are broken down into fatty acids and glycerol, which are used for energy production and for building cell membranes and certain hormones. Overall, absorbed food molecules provide the necessary energy and building blocks for cellular activities, growth, and maintenance of the body.

A) absorbed food is toxic to the body

- Incorrect: Absorbed food is not inherently toxic to the body. In fact, nutrients obtained from food are essential for the body's survival and proper functioning. However, certain substances in food may be harmful if absorbed in excessive amounts, such as certain vitamins or minerals. Generally, the body has mechanisms to regulate nutrient absorption and maintain homeostasis.

B) absorbed food stimulates reproduction

- Incorrect: While proper nutrition is important for overall health and fertility, absorbed food does not directly stimulate reproduction. Reproduction is regulated by various hormones and physiological processes within the body.

D) absorbed food aids in respiration

- Incorrect: While nutrients obtained from food are used by cells for energy production through respiration, absorbed food itself does not directly aid in respiration. Respiration is a complex physiological process that involves the exchange of gases (oxygen and carbon dioxide) in the lungs and cellular respiration within cells to produce energy.