Question

The body temperature of cold-blooded animals varies with the ambient temperature. From the point of view of reaction rates, explain why cold- blooded animals are more sluggish at cold temperatures.

Short answer

Cold-blooded animals are more sluggish at cold temperatures because their body temperature, and thereby the rate of their biochemical reactions, are directly influenced by the ambient temperature, leading to slower metabolism and reduced physical activity at lower temperatures.

Step-by-step solution

Understanding Thermodynamics

Recognize that the rate of chemical reactions depends on the temperature. As temperature increases, molecules move faster, increasing the number of collisions per second and the energy of those collisions, thus increasing the rate of reaction.

Relating Temperature to Cold-Blooded Animals

Understand that cold-blooded animals, or ectotherms, do not regulate their body temperature internally. Their body temperature is dependent on the ambient temperature, which means their internal biochemical reactions are likewise dependent on the external temperature.

Correlating Sluggishness with Biochemical Reactions

Connect the dependence on external temperature with reaction rates in cold-blooded animals. At low temperatures, their body temperature drops, leading to slower molecular movement, reduced collision rates, and less energy for collisions. This results in slower biochemical reactions, which manifest as sluggishness in the animal's physical activities.

Key concepts

Thermodynamics in Biology

Thermodynamics plays a crucial role in understanding the biological processes that drive life on a molecular level. In biology, thermodynamics refers to the study of energy transformations that occur during chemical and physical processes within living organisms. The laws of thermodynamics dictate that energy cannot be created or destroyed, only transformed, and that during any energy transfer or transformation, some energy is lost as heat. This is particularly relevant to biochemical reactions, which are governed by the same physical laws that apply to non-living systems.

For example, the metabolic processes that occur within an organism involve the conversion of energy from food into forms that cells can use to perform work. Temperature is a key factor in this conversion; it influences the kinetic energy of molecules, affecting how they react with each other. In essence, higher temperatures increase molecular movement, thereby enhancing the likelihood of successful collisions between reactant molecules, and ultimately speeding up the rate of biochemical reactions.

Ectotherms Temperature Regulation

Ectotherms are organisms that rely on environmental heat sources to regulate their body temperature instead of generating significant internal heat. This group includes many reptiles, amphibians, fish, and invertebrates. Unlike endotherms (warm-blooded animals), ectotherms do not have the same degree of control over their internal temperature and are subject to the ambient conditions of their surroundings. For these creatures, behavioral strategies are often employed to maintain optimal body temperature for physiological functions.

Examples of these strategies include basking in the sun to raise body temperature, seeking shade or burrowing to avoid overheating, and changing posture or orientation to control exposure to heat sources. These behaviors are vital because the enzyme-catalyzed reactions that facilitate metabolism, digestion, and other life-sustaining processes are temperature-sensitive. By adjusting their behaviors, ectotherms can influence their body temperature to optimize the rate at which these biochemical reactions occur.

Effects of Temperature on Reaction Rates

Temperature exerts a significant influence on the rate at which chemical reactions occur, and this is governed by the collision theory and the Arrhenius equation. The collision theory states that for a reaction to proceed, reactant particles must collide with sufficient energy and an appropriate orientation. As temperature increases, particles move more rapidly and collide more frequently and with greater energy, which increases the chances of reaction. In biological systems, this means that enzymes, which are biological catalysts, will facilitate more reaction events at higher temperatures, speeding up the metabolic processes.

Conversely, a decrease in temperature leads to a reduction in molecular motion, resulting in fewer and less energetic collisions. This effect explains why cold-blooded animals become sluggish when the temperature drops: their biochemical reactions slow down, leading to decreased nerve transmission, muscle contraction, and overall body function. The relationship between temperature and reaction rates is typically modeled by the Arrhenius equation, which mathematically describes how reaction rate constants change with temperature. By understanding this relationship, scientists can predict how changes in temperature will affect the biological function of organisms.