Nutrition：练习题

What is the primary biological function of proteins in the human body?

In the human alimentary canal, the pancreas secretes a digestive juice into the duodenum. Which of the following correctly identifies an enzyme present in this juice and the specific substrate it breaks down in the small intestine?

A graph shows the rate of photosynthesis plotted against light intensity for a plant at two different carbon dioxide concentrations: \(0.04\%\) and \(0.1\%\). If the temperature is kept constant, both curves eventually plateau. What is the limiting factor for the plant at the plateau when the \(CO_2\) concentration is \(0.04\%\)?

Which of the following chemical elements are found in all lipids (fats and oils) but are generally absent from carbohydrates?

The upper epidermis of a leaf is a specialized layer of cells. Which feature of this layer is an adaptation that directly supports a high rate of photosynthesis in the layers below?

Name the specific enzyme responsible for the chemical digestion of lipids and state the two types of molecules produced by this reaction.

Describe how the stomata are involved in the process of photosynthesis and explain how their location on the leaf helps prevent excessive water loss.

Explain how palisade mesophyll cells are structurally adapted to ensure a high rate of photosynthesis occurs in the leaf.

(a) Identify the three chemical elements that are found in all lipid molecules. (1 point)
(b) Name the two types of smaller basic units that combine to form a single lipid molecule. (1 point)
(c) Explain why a manual labourer generally requires a higher daily intake of carbohydrates than a person with a sedentary office job. (2 points)

(a) Write the word equation for the process of photosynthesis. (1 point)
(b) A student wants to investigate the effect of carbon dioxide concentration on the rate of photosynthesis in an aquatic plant. Describe how the student could vary the concentration of carbon dioxide in the water. (2 points)
(c) Explain why the rate of photosynthesis eventually plateaus (reaches a maximum) when carbon dioxide concentration is increased, even if light intensity and temperature are kept constant and optimal. (2 points)