Cohesion

Definition

Cohesion is the intermolecular attraction between like molecules that enables them to stick together. This property is particularly significant in water, where hydrogen bonds create strong cohesive forces, allowing water to form droplets, travel through plants, and maintain surface tension. These features are crucial for various biological processes and interactions.

5 Must Know Facts For Your Next Test

1. Cohesion in water contributes to its high surface tension, which allows small objects, like insects, to float on its surface.
2. Cohesion helps in the process of transpiration in plants, enabling water to travel from roots to leaves.
3. The unique cohesive properties of water are essential for maintaining blood circulation in organisms by ensuring smooth flow.
4. Cohesion plays a role in forming meniscus shapes in liquids when they are placed in a container.
5. Cohesion is one of the key factors that make water a versatile solvent, allowing it to support various biochemical reactions.

Review Questions

• How does cohesion contribute to the movement of water in plants?
  • Cohesion allows water molecules to stick together as they move through the plant's xylem. This creates a continuous column of water that can be pulled upward from the roots to the leaves during transpiration. The hydrogen bonds formed between water molecules provide strength to this column, enabling efficient water transport essential for photosynthesis and nutrient distribution.
• Discuss the relationship between cohesion and surface tension in water.
  • Cohesion directly leads to high surface tension in water due to the strong hydrogen bonds between water molecules. This surface tension creates a 'film' on the water's surface, allowing small objects like water striders to walk on it without sinking. The combination of these two properties is critical for various ecological interactions and behaviors in aquatic environments.
• Evaluate the role of cohesion in biological systems and its impact on homeostasis.
  • Cohesion plays a vital role in maintaining homeostasis within biological systems by ensuring stable internal conditions. For example, in thermoregulation, cohesive properties help distribute heat evenly through body fluids. Additionally, the cohesion of water supports cellular functions by facilitating nutrient transport and waste removal, illustrating how this property is fundamental to life processes and overall organism health.

Related terms

Adhesion: The attraction between different types of molecules, which allows substances like water to adhere to surfaces such as plant cell walls.

Hydrogen Bond: A weak bond formed between a hydrogen atom covalently bonded to an electronegative atom and another electronegative atom, crucial for the cohesive properties of water.

Surface Tension: The elastic tendency of a fluid surface that makes it acquire the least surface area possible, largely due to cohesion among the liquid molecules.