Water and its functions Flashcards
What does inorganic mean?
No carbon
What is an ion?
A charged particle
Why are inorganic ions important?
Play an important role in many essential cellular processes
Where do inorganic ions occur?
In the cytoplasm and body fluids of organisms
Define details of inorganic ions
- Some occur in high concentrations and some in low
- The concentration of certain ions can fluctuate and can be used in cell signalling and neuronal transmission
- Each type of inorganic ion has a specific role depending on its properties
What are the uses of iron ions (Fe2+/Fe3+)?
- Haemoglobin to bind with oxygen for transport for aerobic respiration
- Transfer of electrons during respiration and photosynthesis
What are phosphate ions used for (PO4^3-)?
- ATP, storing energy in bonds
- Phospholipid bilayer
- Structural role in DNA molecules (DNA and RNA)
What are magnesium ions (Mg2+) used for?
- Production of chlorophyll
What are Hydrogen ions (H+) used for?
- Optimal pH of enzymes and functioning of enzymes
- pH
- Bohr effect
- Active transport of sucrose in the phloem
What are sodium ions (Na+) used for?
- Transport of glucose and amino acids across plasma membranes
- Transmission of nerve impulses
What is the dipolar water molecule?
Although a water molecule has no overall charge, the oxygen atom has a slight negative charge, while the hydrogen atom has a slight positive one - has both positive and negative so described as dipolar
What kind of bonding occurs between water molecules?
The positive pole of one water molecule will be attracted to the negative pole of another water molecule - known as hydrogen bonds
How do hydrogen bonds help water molecules?
Each bond is fairly weak (1/10 strength of covalent bond) but together they form important forces that cause water molecules to stick together
What is the advantage of the hydrogen bonds causing water molecules to stick together?
- More energy is required to separate them than if they were not bonded so the b.p. is higher than expected
- Takes more energy to heat a given mass of water i.e. high specific heat capacity
Without its hydrogen bonding, what would water exist as at temperatures commonly found on earth?
A gas
Because of its high specific heat capacity, what does water act as?
- A buffer against sudden temperature variations, making the aquatic environment a stable one
- As organisms are mostly water, it also buffers them against sudden temperature changes especially in terrestrial environments
How does hydrogen bonding affect the latent heat of vaporisation of water?
The bonding means a lot of energy is required to evaporate 1 gram of water
How is the latent heat of vaporisation of water useful in mammals?
- Evaporation of water such as sweat in mammals is a very effective way of cooling as body heat is used to evaporate water (so a lot of energy, which is heat, is used)
- It allows organisms to control their temperature
What is cohesion?
The tendency of molecules to stick together
How is cohesion of water useful in plants?
- Water has large cohesive forces (due to hydrogen bonding) and these allow it to support columns of water in tube-like transport cells of plants
- Water can be pulled up through a tube, such as a xylem vessel, in plants
How is cohesion of water useful for water surfaces?
- Where water molecules meet air, they tend to be pulled back into the body of water
- This force is called surface tension and means that the water surface acts like a skin and is strong enough to support small organisms (pond skaters)
Why is water important?
It is the main constituent of all organisms - mammals are typically 65% water
What is water in terms of metabolism?
A metabolite
How is water used in metabolism?
- Used to break down many complex molecules by hydrolysis
- Also produced in condensation reactions
Where do chemical reactions take place?
In an aqueous medium
Why is water important in photosynthesis?
It is a major raw material
Why is water an important solvent?
It is an important solvent where metabolic reactions occur
Which substances will water readily dissolve?
- Gases such as oxygen and CO2
- Wastes such as ammonia and urea
- Inorganic ions and small hydrophilic molecules (amino acids, ATP, monosacharrides)
- Enzymes, whose reactions take place in solution
How is water useful in terms of structure?
Not easily compressed and so provides support (turgor structure in herbacceous plants)
How is water useful for aquatic plants?
Transparent so aquatic plants can photosynthesise
How is water useful for the eye?
Light rays can penetrate the jelly-like fluid that fills the eye and so reach the retina
