A1.1 WATER Flashcards
Where do we see water in metabolism?
- Is a solvent; acts as a medium for metabolic reactions.
Water in nutrition?
- Is an aqueous medium for respiration and photosynthesis.
Water in growth:
Cells absorb water by osmosis to grow.
Water in reproduction?
- Sperm swim to the ovum through water, supports mammalian fetuses in the womb.
Water in response to stimuli?
- Water dissolved Na+ and K+ ions, which generate nerve impulses.
- Hormones are transported through water.
Water in movement?
- Its viscosity allows many aquatic organisms to swim through it.
Water in Excretion?
- Is a solvent for toxins to be excreted in the form of urine.
- Excretion of gases requires a moist surface.
Water in homeostasis?
- High SHC creates a moderating effect for aquatic environments.
- Water in Blood plasma and tissue fluid maintains a stable internal environment for cells.
Cohesion
Water molecules being attracted to each other via H-bonds
How is cohesion an important property?
- It allows for strong tensions to be exerted in pulling water up xylem vessels.
- Creates surface tension which provides an aquatic habitat for some organisms.
Adhesion
The attraction between water and hydrophilic substances via intermolecular forces (H-bonding).
How is adhesion an important property?
- Cellulose forms H-bond with water and keeps cell walls saturated with water during transpiration in leaves.
- Adheres to xylem walls so that water is transported upwards via capillary action.
Why is a water a good solvent?
- It’s polar due to partial negative and positive charges, creates intermolecular forces with other polar substances.
Why are water’s solvent properties important?
- Allows for movement and more substrate-active site collisions in chemical reactions.
- Is present in blood plasma to transfer nutrients as solvents.
- Phloem saps use water to transport solvents.
Why is it important that water is not attracted to hydrophobic substances?
- Waxy cuticle on leafs prevents water loss and dehydration.
- ## oils on human skin prevent dehydration.
Buoyancy
The upward force a substance exerts on an object, water is more buoyant than air.
Viscosity
Resistance to flow, water is more viscous than air.
Thermal Conductivity
The ability of a material to transfer heat, water has better thermal conductivity than air.
Specific heat capacity
The amount of heat needed to to raise the temperature of a gram of substance by one degree celsius، higher than air.
Discuss the adaptations of organisms to the different physical properties of water:
- Buoyancy: The ringed seal’s density is close to that of water and remains afloat. Arctic loon is less dense than air and has wings to remain airborne.
- Viscosity: The ringed seal has to overcome more resistance when swimming than the artic loon through air.
- Thermal conductivity: The ringed seal has a layer of blubber underneath its skin as it is more vulnerable to hypothermia.
Explain the theory of the origins of water:
- Asteroids containing ice collided with earth.
- Ice melts, increasing the volume of water on earth.
- Water is retained due to gravity and temperature.
