Which factors should be considered to promote longevity? Select all that apply.

A. The gallbladder does not produce bile. Its primary function is to store and concentrate bile that the liver produces, releasing it into the small intestine through the common bile duct when fat-containing food enters the duodenum. While the gallbladder is essential for regulating bile flow, it does not synthesize it.

B. The liver is the accessory organ responsible for producing bile, a yellow-green fluid composed of bile salts, cholesterol, phospholipids, and waste products like bilirubin. Bile plays a critical role in emulsifying fats, breaking them into smaller droplets so pancreatic lipase can effectively digest them. Additionally, bile aids in the absorption of fat-soluble vitamins (A, D, E, and K) and facilitates the excretion of certain waste products, such as excess cholesterol and bilirubin, helping maintain metabolic balance. Bile is continuously produced by the liver and transported via the hepatic ducts to either the gallbladder for storage or directly to the duodenum for immediate digestive use.

C. The spleen is primarily involved in filtering the blood, recycling red blood cells, and supporting immune function. It has no role in bile production or fat digestion.

D. The pancreas produces digestive enzymes (such as amylase, lipase, and proteases) and hormones (including insulin and glucagon) but does not produce bile. It contributes to digestion by releasing enzymes into the small intestine, complementing bile’s function in fat digestion.

A. The cell nucleus contains genetic material (DNA) and is surrounded by a nuclear envelope, which also has a double lipid bilayer. However, the question refers to the general structural component of the cell, and the nucleus is not considered the primary barrier separating the cell from its environment.

B. The cell membrane, also called the plasma membrane, is composed of a phospholipid bilayer. This structure has hydrophilic (water-attracting) heads facing outward and hydrophobic (water-repelling) tails facing inward, creating a semi-permeable barrier that regulates the entry and exit of substances. The cell membrane also contains proteins, cholesterol, and carbohydrates that support signaling, transport, and structural stability.

C. The endoplasmic reticulum (ER) is a membrane-bound organelle involved in protein and lipid synthesis. While it contains lipid membranes, the ER is an internal structure, not the primary boundary of the cell, and its membrane is continuous with the nuclear envelope.

D. Mitochondria are double-membrane organelles responsible for energy production via ATP synthesis. Although they have an inner and outer membrane, the question refers to the cell component composed of a phospholipid bilayer that serves as the main barrier of the cell, which is the plasma membrane.