Water

Definition

Water is a vital polar molecule made up of two hydrogen atoms and one oxygen atom (H2O), which plays a crucial role in biological processes. Its unique properties, such as cohesion, adhesion, and its ability to dissolve many substances, make it essential for maintaining homeostasis within cells. Additionally, water is the medium through which passive transport processes like diffusion and osmosis occur, facilitating the movement of molecules across cell membranes.

5 Must Know Facts For Your Next Test

1. Water makes up about 70% of the human body and is a key component of cellular structure and function.
2. Due to its polar nature, water can form hydrogen bonds, which contribute to its high surface tension and the ability to dissolve many ionic and polar substances.
3. In the context of osmosis, water moves across cell membranes to balance solute concentrations, which can influence cell shape and function.
4. The movement of water via osmosis can create osmotic pressure, which is important for processes like nutrient absorption in plant roots.
5. Water's role as a solvent allows for biochemical reactions to occur efficiently, facilitating metabolic processes necessary for life.

Review Questions

• How does the polarity of water contribute to its role in diffusion and osmosis?
  • The polarity of water molecules leads to their ability to form hydrogen bonds with other polar molecules and ions. This property is significant in diffusion and osmosis as it enables water to interact with solutes effectively. During osmosis, water moves across semipermeable membranes to equalize solute concentrations, utilizing its unique properties to maintain cellular homeostasis.
• Discuss how water's properties impact cell structure and function in relation to passive transport mechanisms.
  • Water's cohesive and adhesive properties contribute significantly to maintaining cell structure by providing turgor pressure in plant cells. This pressure is crucial for keeping cells rigid and functional. Additionally, because water acts as a solvent, it facilitates passive transport mechanisms like diffusion and osmosis, allowing essential nutrients and waste products to move in and out of cells efficiently. Without these properties of water, cells would struggle to maintain their internal environments.
• Evaluate the implications of osmotic pressure on cell health and survival in varying environmental conditions.
  • Osmotic pressure plays a critical role in determining cell health and survival, particularly when cells are exposed to hypotonic or hypertonic environments. In hypotonic conditions, cells may swell and potentially burst due to excessive water intake, while in hypertonic environments, cells can lose water and shrink, leading to dehydration. Understanding how osmotic pressure influences these changes is vital for grasping how organisms adapt or fail in different environments, ultimately affecting their overall survival.

Related terms

Diffusion:

The process by which molecules move from an area of higher concentration to an area of lower concentration, driven by their kinetic energy.

Osmosis:

The specific type of diffusion that involves the movement of water molecules across a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.

Semipermeable Membrane: A membrane that allows certain molecules or ions to pass through while blocking others, critical for maintaining the internal environment of cells.