2.4 - Water and its functions + inorganic ions Flashcards
Why do water molecules have unusual properties
- its diploid nature
- and the subsequent hydrogen bonding this allows
What three atoms are water molecules created from
- 2 atoms of hydrogen
- 1 atom of oxygen
Why is a water molecule described as dipolar
- the oxygen atom has a slight negative charge
- while the hydrogen atoms have a slight positive charge
—> the water molecule has both positive and negative poles = therefore described as dipolar
Explain the water and hydrogen bonding
- opposite charges attract: therefore positive poles of one molecule is attracted to the negative poles of the other
- the attractive force between these charges is called: a hydrogen bond
- each bond is fairly weak, but all together = form important forces allowing the water molecules to stick together
—> giving the water its unusual properties
Describe the specific heat capacity of water
- because water molecules stick together = takes more energy (heat) to separate them than would be needed if they didn’t bond to one another
- for this reason: boiling point is higher than expected
- without its hydrogen bonding = it would be a gas at room temp
——> water therefore has a high specific heat capacity
—> water therefore act as a buffer against sudden temp variations, making the aquatic environment a temp-stable one
—> because organisms are mostly water = it also buffers them against sudden temp changes (especially in terrestrial environments
Describe the Latent heat of vaporisation of water
- hydrogen bonding between water molecules means that it requires a lot of energy to evaporate 1g of water
- this energy is called the ‘latent heat of vaporisation’
- evaporation of water such as sweat in mammals is therefore a very effective means of cooling because body heat is used to evaporate the water
Describe the cohesion and surface tension in water
- the tendency of molecules to stick together = known as cohesion
- with its hydrogen bonding, water has large cohesive forces and these allow it to be pulled up through a tube (such as a xylem vessel in plants.)
- in the same way, where water molecules meet air they tend to be pulled back into the body of water rather than escaping it.
—> this force is called surface tension
—> it means that the water surface acts like a skin, and is strong enough to support small organisms such as pond skaters
Describe the importance of water in metabolism to living organisms
- water is used to break down many complex molecules by hydrolysis, e.g. proteins —> amino acids
- water is also produced in condensation reactions
- chemical reactions take place in an aqueous medium
- water is a major raw material in photosynthesis
Describe the importance of water as a solvent in organisms
Water readily dissolves other substances
- gases such as oxygen and carbon dioxide
- wastes such as ammonia and urea
- inorganic ions and small hydrophilic molecules such as amino acids, monosaccharides and ATP
- enzymes, whose reactions take place in solution
What are the other important features of water in an organism
- its evaporation cools organisms and allows them to control their temp
- not easily compressed, therefore provides support, e.g. the hydrostatic skeleton of animals such as the earthworm and turgor pressure in herbaceous plants
- It is transparent and therefore aquatic plants can photosynthesise and also light rays can penetrate the jelly-like fluid that fills the eye and so reach the retina
Describe the importance of water in inorganic ions
- inorganic ions are found in organisms where they occur in solution in the cytoplasm of cells and bodily fluids and apart of larger molecules. Found in varying concentrations
- inorganic ions perform a range of functions. The specific function of a particular ion performs is related to its properties
- e.g. iron ions are found in haemoglobin where they play a role in transporting oxygen
what is an electron
A stable subatomic particle with a charge of negative electricity
what is an ionic bond
A type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound
what is an Anion
A negatively charged ion (has gained 1 or more electrons)
what is a Cation
A positively charged ion (has lost 1 or more electrons)
what is the formula + use/importance of: hydrogen
- H+
- important in acid base chemistry (important for pH balance)
- establish trans-membrane electrochemical gradients (important for nerve impulses and generating ATP)
what is the formula + use/importance of: Iron
- Fe 3+ / Fe2+
- iron binding proteins are involved in redox reactions, electron transport, and in the transport of oxygen (important for respiration)
what is the formula + use/importance of: Sodium
- Na+
- transmission of nerve impulses and in fluid and electrolyte balance in plants. Involved in maintaining cell turgor and opening/closing the stomata (important for osmosis and water balance
what is the formula + use/importance of: Phosphate
- PO4 3-
- Component of phospholipids, nucleotides and ATP. Combines with calcium as calcium phosphate in bones/teeth (important for cell membranes, DNA + RNA)
Definition of adhesion
attraction between molecules of different types
Definition of cohesion
attraction between molecules of the same type (important in movement of water up a plant)
what is the definition of Latent heat of vaporisation
heat taken in by a liquid in order to transform it into vapor
what is the definition of a polar molecule
a molecule with an uneven distribution of charge as a result of electrons being more or less attracted to different atoms within the molecule
what is the definition of specific heat capacity
The amount of heat per unit mass required to raise the temp by 1’C
how does water stick to the xylem wall
using adhesion and cohesion
what is the bond between the water molecules
hydrogen bonds
- the hydrogen of one molecule forms a bond with the oxygen of another (cohesion)
- due to attraction between positive hydrogen and negative oxygen atoms
what is the bond between the hydrogen and oxygen in water molecules
covalent bonds
does water become more or less dense when frozen
it expands = less dense = hence why ice floats
electrons are in orbit more around oxygen, what’s the effect
- dipolar molecule
describe the charges of o and h
- o = -
- h = +
what does surface tension demonstrate
cohesion
- all water molecules are attracted and form bonds between each other forming cohesion, giving it surface tension
how does water support life (10)
- transparency
–> so plants and phytoplankton can photosynthesis –> oxygen - Low viscosity
–> allows blood to be pumped around the body easier - High surface tension because of cohesion
–> gives certain organisms a habitat (pond skater) - Adhesion (forming bonds with another surface)
–> xylem (uses both cohesion and adhesion) - Photosynthesis
–> its in the formula - High specific heat capacity
–> 4.184 joules to raise the temp of one gram of water by 1’C
–> so organisms have a constant environment (they wouldn’t be able to adapt quick enough to the extreme fluctuations)
–> buffers against sudden temperature variations - High latent heat of vaporisation
–> it requires a lot of energy to evaporate 1 gram of water (effective for cooling down organisms) - Insulating
–> expands as it freezes and floats on the surface, insulating the water and organisms below - universal solvent
–> many polar substances dissolve in water
–> most chemical reactions take place in an aqueous solution (e.g. cytoplasm) - condensation reactions and hydrolysis reactions
–> require water either being released or added
how do water molecules form adhesion
forming hydrogen bonds to other molecules that are charged and polar
