How are lipids carried in the bloodstream?

Correct Answer: D

Rationale: Lipids are carried in the bloodstream in the form of lipoproteins. Lipoproteins are complexes of proteins and lipids that transport fats to various parts of the body. While micelles, glycolipids, and lecithin are all related to lipid metabolism, they are not the primary carriers of lipids in the bloodstream. Micelles are small lipid clusters in the intestines, glycolipids are lipids with a carbohydrate attached, and lecithin is a type of phospholipid. Therefore, lipoproteins are the correct answer as they are specifically designed for transporting lipids through the bloodstream.

Correct Answer: D

Rationale: The correct answer is D. The stomach is protected from gastric acid by a thick mucus lining that acts as a physical barrier, preventing the acid from eroding the stomach walls. Enzymes in the stomach help with digestion but do not play a significant role in protecting the stomach from acid damage, so choice A is incorrect. While some bacteria in the stomach can be beneficial, they do not primarily protect the stomach from gastric acid, making choice B incorrect. Bicarbonate, a base, can neutralize acid, but it is not the primary defense mechanism against gastric acid in the stomach, so choice C is also incorrect.

Correct Answer: D

Rationale: The correct answer is D. Polyunsaturated fatty acids. Polyunsaturated fatty acids have two or more double bonds in their carbon chains, making them less stable and more prone to oxidation. This characteristic distinguishes them from saturated fatty acids (Choice A), which have single bonds between carbon atoms providing stability. Monounsaturated fatty acids (Choice B) contain only one double bond, and trans fatty acids (Choice C) can have varying numbers of double bonds but are not specifically defined by having two or more double bonds.

Correct Answer: C

Rationale: The correct answer is C: Chlorophyll. Chlorophyll is a pigment that is essential for photosynthesis as it absorbs light energy, allowing plants to convert carbon dioxide and water into glucose, a process crucial for plant growth. Glucose (choice A) is produced during photosynthesis and is not an ingredient necessary for the process itself. Nitrogen (choice B) is important for plant growth but is not a direct ingredient for photosynthesis. Hydrogen (choice D) is found in water, which is indeed one of the necessary ingredients for photosynthesis, but chlorophyll is specifically required to capture light energy for the process to occur.

Correct Answer: D

Rationale: Proteins, carbohydrates, and fats are macronutrients that provide energy in the form of calories when consumed and metabolized by the body. Each gram of protein or carbohydrate provides about 4 calories, and each gram of fat provides about 9 calories. On the other hand, vitamins do not provide energy or calories. They are micronutrients that are essential for various biochemical and physiological processes in the body, including the metabolism of macronutrients. However, they do not contribute directly to the energy supply. Therefore, the correct answer is 'D: Vitamins'. Choices A, B, and C (Proteins, Carbohydrates, and Fats) are incorrect because they are macronutrients that do provide energy/calories when metabolized.

Correct Answer: B

Rationale: The correct answer is B: 7 kcal/g. Alcohol provides approximately 7 kilocalories per gram, making it a significant source of energy or 'empty calories' in the diet that do not contain any nutrients. 'Empty calories' refer to the calorie content without the presence of essential nutrients. Choices A, C, and D are incorrect. The energy values of 3 kcal/g, 10 kcal/g, and 25 kcal/g are not accurate for alcohol; instead, they may pertain to other nutrients such as carbohydrates (approximately 4 kcal/g), fats (approximately 9 kcal/g), and oils (approximately 9 kcal/g).

Correct Answer: C

Rationale: The correct answer is C. Saturated fatty acids have no double bonds between carbon atoms, while unsaturated fatty acids have one or more double bonds. Therefore, the number of double bonds is the chemical feature that distinguishes a saturated fatty acid from an unsaturated fatty acid. Choices A, B, and D are incorrect because the distinguishing factor between saturated and unsaturated fatty acids lies in the presence or absence of double bonds, not in the arrangement of carbon atoms, number of oxygen molecules, or food source.

Correct Answer: A

Rationale: The correct answer is A: carbohydrates. Photosynthesis is the process by which plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy stored in glucose (a type of carbohydrate). This glucose is used by the organisms for energy production and as a building block for other organic compounds. Choice B, proteins, is incorrect because proteins are synthesized through a different process involving amino acids. Choice C, fats, are not directly synthesized through photosynthesis; they are typically formed from excess carbohydrates. Choice D, vitamins, are organic compounds that are required in small amounts for various physiological functions but are not directly synthesized through photosynthesis.

Correct Answer: B

Rationale: The correct answer is B: Supply energy. The primary function of macronutrients such as carbohydrates, fats, and proteins is to supply energy for various bodily functions. Choices A, C, and D are incorrect because while regulating metabolic processes, maintaining homeostasis, and controlling cellular activity are essential functions in the body, they are not the primary roles of macronutrients. Macronutrients mainly serve as a source of energy to support daily activities and bodily functions.