Cohesion

Definition

Cohesion is the property of water that causes its molecules to stick together due to hydrogen bonding. This tendency of water molecules to be attracted to each other plays a crucial role in various biological processes, influencing phenomena like surface tension, water transport in plants, and the formation of water droplets. It highlights how water's unique molecular structure contributes to its essential functions in living organisms.

5 Must Know Facts For Your Next Test

1. Cohesion is responsible for the high surface tension of water, enabling small objects, like water striders, to float on its surface.
2. In plants, cohesion helps in the transport of water from the roots to the leaves through xylem vessels, a process called transpiration.
3. The cohesive nature of water also plays a critical role in maintaining the structure and stability of cellular membranes.
4. Cohesion contributes to the formation of droplets, which is essential for processes like rain formation and various biological functions.
5. Changes in temperature or pressure can affect cohesion; for instance, heating water decreases its cohesive properties, influencing its behavior in biological systems.

Review Questions

• How does cohesion contribute to the unique properties of water that are vital for life?
  • Cohesion significantly contributes to water's unique properties by enabling high surface tension and allowing it to effectively transport nutrients within organisms. This property ensures that water molecules can stick together as they move through plant vessels, supporting processes like transpiration. Without cohesion, many biological functions reliant on water's ability to remain a liquid would be compromised, impacting living organisms' survival.
• In what ways does cohesion interact with adhesion in biological systems?
  • Cohesion and adhesion work together in biological systems to facilitate processes like capillary action. In this process, adhesion allows water to stick to the walls of xylem vessels while cohesion keeps the water molecules together as they ascend against gravity. This interaction is crucial for transporting water and nutrients from the roots of plants to their leaves, showcasing how both properties are essential for plant health and growth.
• Evaluate the implications of altered cohesion due to environmental changes on ecosystems and biological functions.
  • Altered cohesion due to environmental changes such as pollution or climate change can significantly impact ecosystems and biological functions. For example, if increased temperatures lead to reduced cohesion in water, it can affect plant transpiration rates and nutrient transport, ultimately threatening plant health and food supply. This disruption can cascade through food webs, affecting entire ecosystems and highlighting the delicate balance maintained by properties like cohesion in supporting life.

Related terms

Hydrogen Bonding: A weak bond formed between a hydrogen atom, which is covalently bonded to a more electronegative atom, and another electronegative atom.

Surface Tension:

The cohesive force at the surface of a liquid that allows it to resist an external force, resulting from the attraction between liquid molecules.

Adhesion: The property of water that allows it to stick to other substances, which is important for processes such as capillary action.