Structure and Function Flashcards

A scientist observes a plant cell with an unusually high number of plasmodesmata connecting it to its neighbors. Which of the following is the most likely primary function of this specialized cell, given its structure?

Answer: Rapid transport of nutrients and signaling molecules between cells.

Plasmodesmata are small channels that directly connect the cytoplasm of neighboring plant cells, allowing for communication and transport. An unusually high number of these structures strongly indicates that the cell is specialized for rapid and extensive intercellular communication and transport, such as that seen in phloem companion cells or in tissues involved in systemic signaling.

In certain neurodegenerative diseases like Parkinson's, a protein called alpha-synuclein misfolds and aggregates, leading to cell death. This process, where an improperly structured protein disrupts cellular activities, is best described as a failure in which fundamental relationship?

Answer: The relationship between protein structure and function.

Proteins must fold into a specific three-dimensional structure to perform their biological function. In protein misfolding diseases (proteinopathies), the protein's structure becomes abnormal, which in turn disrupts its normal function and can lead to toxic aggregation, causing cellular damage and disease. This directly illustrates the critical link between a protein's structure and its function.

A marathon runner is nearing the end of a race in hot weather. Their body temperature rises significantly. Which of the following represents a homeostatic negative feedback response aimed at counteracting this stimulus?

Answer: The hypothalamus triggers the dilation of blood vessels in the skin and activates sweat glands.

Homeostasis involves negative feedback loops that counteract a stimulus to return the body to a set point. When body temperature rises (the stimulus), the hypothalamus (the control center) activates cooling mechanisms. These include vasodilation (widening of blood vessels in the skin) to release heat and sweating (diaphoresis), where evaporation cools the body surface. These responses work to lower the temperature back to the normal range.

Mature mammalian red blood cells are anucleated (lack a nucleus) and have no mitochondria. This atypical structure is a specialization that directly enhances their function in what way?

Answer: It maximizes intracellular volume for hemoglobin, increasing oxygen-carrying capacity.

The primary function of a red blood cell is to transport oxygen via the protein hemoglobin. By lacking a nucleus and other organelles like mitochondria, the cell's internal volume is maximized, allowing it to carry the maximum possible amount of hemoglobin. This structural adaptation directly serves its function of efficient oxygen transport. While flexibility is important, the primary benefit of being anucleated is the increased space for hemoglobin.

In vascular plants, phloem tissue is responsible for transporting sugars. It is a complex tissue composed of several cell types, including sieve-tube elements and companion cells. Which statement best describes the structure-function relationship between these two cell types?

Answer: Sieve-tube elements lack a nucleus and other organelles to maximize flow, while companion cells perform the metabolic functions to keep them alive.

Sieve-tube elements are highly specialized for transport and have lost their nucleus, large vacuole, and ribosomes at maturity to create an open channel for sugars to flow through. Because they lack these essential organelles, they cannot sustain themselves. The adjacent companion cells, which are connected via plasmodesmata, are metabolically active and carry out the life-support functions (like protein synthesis and ATP production) for the sieve-tube elements.

A cell is found to have an extensive network of smooth endoplasmic reticulum (SER). Which of the following functions is this cell most likely specialized for?

Answer: Detoxification of drugs and synthesis of lipids.

The smooth endoplasmic reticulum (SER) has several key functions, including the synthesis of lipids, steroids, and phospholipids, as well as the detoxification of poisons and drugs. Cells with an abundance of SER, such as liver cells, are highly specialized for these roles. Protein synthesis for export occurs in the rough ER, waste breakdown in lysosomes, and ATP generation in mitochondria.