Question

what is the primary function of enzymes in the digestive system?* 1 point
transport nutrients through the bloodstream
break down large food molecules into smaller pieces
store excess energy as fat
produce stomach acid

in the enzyme model shown in the document, what does the shape of the enzyme demonstrate? * 1 point
random molecular movement
chemical bonding patterns
specific substrate binding
energy transfer processes

where does protein digestion begin in the digestive system?* 1 point
small intestine
mouth
stomach
large intestine

what is the relationship between enzymes and their substrates?* 1 point
enzymes work on any available substrate
substrates change the shape of enzymes permanently

Explanation:

• For the first question: Enzymes in the digestive system act as biological catalysts. Their main role is to break down large, complex food molecules (like proteins, carbohydrates, and fats) into smaller, absorbable units. For example, amylase breaks down starch (a complex carbohydrate) into simpler sugars. Transport of nutrients is mainly done by the circulatory system (not enzymes), storing energy as fat is a function related to adipose tissue and metabolic processes beyond just enzyme action in digestion, and producing stomach acid (like hydrochloric acid) is a secretion of stomach cells (not the primary function of digestive enzymes).
• For the second question: In the lock - and - key model (a common enzyme - substrate model), the shape of the enzyme is complementary to the shape of its specific substrate. This is called specific substrate binding. Just like a specific key fits into a specific lock, a specific enzyme binds to a specific substrate. Random molecular movement is more related to Brownian motion in general solution dynamics, chemical bonding patterns are about how atoms bond in molecules (not directly about enzyme - substrate interaction shape), and energy transfer processes in cells involve things like ATP but not the shape - related aspect of enzyme - substrate interaction.
• For the third question: Protein digestion begins in the stomach. The stomach secretes pepsinogen (which is activated to pepsin by hydrochloric acid). Pepsin starts the breakdown of proteins into smaller polypeptides. In the mouth, carbohydrate digestion (by amylase) mainly occurs. The small intestine is where further digestion (including of proteins, by enzymes like trypsin and chymotrypsin) and absorption take place. The large intestine is mainly for water absorption and feces formation.
• For the fourth question: Enzymes are highly specific to their substrates. This is due to the complementary shape (as per the lock - and - key or induced - fit model). Enzymes do not work on any available substrate (they are specific). Substrates do not change the shape of enzymes permanently (in the induced - fit model, there is a temporary shape change, but the enzyme returns to its original form after the reaction).

Answer:

• First question: Break down large food molecules into smaller pieces
• Second question: Specific substrate binding
• Third question: Stomach
• Fourth question: Enzymes are specific to their substrates (the un - listed correct option based on the concept of enzyme - substrate specificity)