Cohesion

Definition

Cohesion is the property of water molecules that allows them to be attracted to one another due to hydrogen bonding. This attraction results in water molecules sticking together, which is crucial for various biological processes. The high level of cohesion in water contributes to its unique characteristics, such as surface tension and the ability to form drops, which play essential roles in the movement of water in living organisms and ecosystems.

5 Must Know Facts For Your Next Test

1. Cohesion contributes to the high surface tension of water, allowing small organisms like water striders to walk on its surface.
2. In plants, cohesion helps transport water from roots to leaves through xylem vessels, crucial for photosynthesis and nutrient transport.
3. Water's cohesive properties help maintain temperature stability in organisms, as they require more energy to break the hydrogen bonds during phase changes.
4. Cohesion plays a key role in the formation of droplets and is vital in processes like precipitation and cloud formation.
5. The cohesive nature of water allows it to form a continuous column in plants, which is essential for effective water transport against gravity.

Review Questions

• How does cohesion influence water transport in plants?
  • Cohesion significantly impacts water transport in plants by enabling water molecules to stick together as they move through xylem vessels. This property creates a continuous column of water, allowing it to travel from the roots to the leaves. The cohesive forces work alongside adhesion, where water molecules also adhere to the walls of the xylem, facilitating efficient movement despite gravity.
• Discuss the relationship between cohesion and surface tension in water and its ecological implications.
  • Cohesion leads to surface tension in water, making it difficult for external forces to penetrate its surface. This property is crucial for aquatic ecosystems, as it allows small organisms to exploit the surface layer for feeding and locomotion. Additionally, surface tension helps maintain the structure of plant leaves by preventing excessive droplet formation during rain, ensuring efficient photosynthesis and transpiration.
• Evaluate the role of cohesion in maintaining homeostasis within living organisms.
  • Cohesion plays a vital role in maintaining homeostasis within living organisms by regulating temperature and ensuring efficient nutrient transport. Water's cohesive properties allow it to stabilize temperature fluctuations because more energy is required to break hydrogen bonds during phase changes. This stability is essential for metabolic processes. Additionally, cohesion aids in transporting vital substances like nutrients and hormones through bodily fluids, helping maintain internal balance and proper functioning.

Related terms

Adhesion:

The property of water that allows it to stick to other surfaces or molecules, important for processes like capillary action.

Surface Tension:

The elastic tendency of a fluid surface that makes it acquire the least surface area possible, resulting from cohesive forces between liquid molecules.

Capillary Action:

The ability of a liquid to flow in narrow spaces without the assistance of external forces, facilitated by the combined effects of cohesion and adhesion.