Structure and Function Flashcards

A microbiologist discovers a new species of archaea thriving in a highly acidic hot spring. Which cellular adaptation is most likely responsible for its ability to maintain homeostasis in this extreme environment?

Answer: A specialized cell membrane with unique, highly stable lipid structures.

Extremophiles, such as archaea living in acidic hot springs, possess unique cellular structures to survive. Their cell membranes contain specialized lipids that are more stable and less permeable than those found in bacteria or eukaryotes, which is crucial for maintaining a stable internal pH in a harsh external environment. Lysosomes are involved in waste breakdown, not neutralizing environmental acid. Cellulose is characteristic of plant cell walls, not archaea. While energy is needed, an overabundance of mitochondria is not the primary structural adaptation for acid tolerance; the barrier function of the membrane is key.

A patient is diagnosed with a genetic disorder that impairs the function of the smooth endoplasmic reticulum in their liver cells. Which of the following consequences is most likely?

Answer: Reduced ability to detoxify certain drugs and metabolic byproducts.

The smooth endoplasmic reticulum (ER) in liver cells is rich with enzymes, such as those from the cytochrome P450 family, that are crucial for metabolizing and detoxifying lipid-soluble drugs, alcohol, and other harmful substances. Ribosome synthesis occurs in the nucleolus, protein folding is a primary function of the rough ER, and ATP production is the main role of mitochondria.

A marathon runner's leg muscles are highly resistant to fatigue. A biopsy of their gastrocnemius muscle would likely reveal that the muscle fibers have a higher-than-average density of which organelle compared to a sprinter's equivalent muscle?

Answer: Mitochondria

Endurance activities like marathon running rely on aerobic respiration for a sustained supply of ATP. Mitochondria are the sites of aerobic respiration. Therefore, the muscle cells (fibers) of endurance athletes are adapted to have a very high density of mitochondria to meet these high, sustained energy demands. Sprinters' muscles, which rely on anaerobic metabolism for short bursts of power, have a lower mitochondrial density.

A botanist observes that a plant's new, upper leaves are showing interveinal chlorosis (yellowing between the veins) while the older, lower leaves remain green. This specific pattern suggests a deficiency in an immobile nutrient. The transport and availability of this nutrient are directly related to the function of which specialized plant tissue system?

Answer: Xylem, which is responsible for water and mineral transport.

Interveinal chlorosis in new leaves is a classic symptom of iron deficiency. Iron is an immobile nutrient, meaning the plant cannot easily move it from older tissues to new growth areas. Nutrients and minerals are absorbed from the soil by the roots and transported upwards to the rest of the plant through the xylem. Therefore, a problem with nutrient uptake or transport within the xylem would manifest symptoms in new growth first for immobile nutrients.

Which of the following correctly describes the hierarchical level of organization for the regulation of metabolism, from the most fundamental unit to the most complex system?

Answer: Islet of Langerhans cell -> Pancreas -> Endocrine System -> Organism

This option correctly shows the progression from a specialized cell to a complete system involved in metabolism. An Islet of Langerhans cell is a specialized cell that produces hormones like insulin. These cells are organized into the pancreas (an organ that is part of the endocrine gland system). The pancreas is a key gland within the endocrine system, which regulates metabolism throughout the entire organism. The other options, while showing correct hierarchies, are less specifically focused on the overall regulation of metabolism throughout the body in the same way the endocrine system is.

The sea slug *Elysia chlorotica* can incorporate chloroplasts from the algae it eats into its own digestive cells, a process called kleptoplasty. For a limited time, these sequestered chloroplasts continue to photosynthesize, providing the slug with energy. This unique adaptation represents an unusual intersection between which two levels of biological organization?

Answer: Cell and Organism

This scenario describes a single-celled organism (alga, from which the chloroplast is taken) and its functional part (organelle) being incorporated into the cells of a multicellular organism (the sea slug). The process allows the entire organism (the slug) to benefit from the function of organelles from another organism, representing a fascinating link between the cellular level (incorporating the chloroplasts) and the organismal level (providing energy for the whole slug).