Cohesion

Definition

Cohesion is the property of water that causes molecules to be attracted to each other, resulting in the formation of hydrogen bonds. This unique characteristic allows water to exhibit high surface tension and contributes to its ability to transport nutrients and other substances in biological systems. Cohesion plays a crucial role in various biological processes, making it essential for life as we know it.

5 Must Know Facts For Your Next Test

1. Cohesion is responsible for the high surface tension of water, allowing small insects like water striders to walk on its surface without sinking.
2. In plants, cohesion helps facilitate the movement of water from the roots to the leaves through a process known as transpiration.
3. Cohesion contributes to water's unique properties, such as its high boiling and freezing points compared to other similar-sized molecules.
4. This property is vital for the formation of droplets, which is why rainwater collects into beads on surfaces instead of spreading out flat.
5. Cohesion also plays a significant role in maintaining the structure of cells, influencing how cells interact with their environment.

Review Questions

• How does cohesion contribute to the process of transpiration in plants?
  • Cohesion allows water molecules to stick together as they move through plant vessels. When water evaporates from the leaves during transpiration, it creates a negative pressure that pulls more water upward from the roots through the xylem. This continuous column of water relies on cohesion to maintain its integrity, ensuring efficient nutrient and water transport throughout the plant.
• Discuss how cohesion influences the unique properties of water that are essential for biological systems.
  • Cohesion leads to high surface tension and allows water to have a relatively high boiling and freezing point. These properties are crucial for maintaining stable temperatures in living organisms and for allowing various biological processes, such as digestion and nutrient transport, to occur effectively. The ability of water molecules to form hydrogen bonds due to cohesion means that they can also dissolve many substances necessary for life, supporting cellular functions.
• Evaluate the implications of cohesion on ecosystems, particularly regarding water availability and species interactions.
  • Cohesion has significant implications for ecosystems, particularly in how water behaves in different environments. For instance, high surface tension due to cohesion enables certain organisms, like pond skaters, to exploit surface habitats efficiently. Additionally, cohesion helps maintain water availability in plants and contributes to their growth, which in turn supports diverse animal populations. Disruptions in these cohesive properties could lead to altered water cycles and affect species interactions within ecosystems.

Related terms

adhesion:

The attraction between water molecules and different substances, which helps water to stick to surfaces.

surface tension:

The force that causes the surface of a liquid to behave like a stretched elastic membrane, largely due to the cohesive forces between liquid molecules.

hydrogen bonding:

The weak attractive force between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom, critical for the cohesive properties of water.