Chapter 3 - Water + Inorganic Ions Flashcards
What is the structure of water?
1) has one atom of oxygen and two hydrogen atoms
2) the shared negative hydrogen electrons are pulled towards the oxygen atom, so that the hydrogen atom is left with a slight positive charge.
3) this also means the oxygen will have a negative charge making water a polar molecule.
What type of bonding exists between water molecules?
Hydrogen bonding
What are the functions of water in and out of cells?
1) water is a reactant in many chemical reactions, including hydrolysis reactions.
2) water is a solvent which means substances dissolve in it. Most biological reactions take place in solution eg in the cytoplasm of cells.
3) water transports substances eg glucose and oxygen around plants and animals.
4) water helps with temperature control because it has a high specific heat capacity and a high latent heat of evaporation.
5) water is a habitat, eg for aquatic organisms.
Why does water have a high specific heat capacity + function?
The hydrogen bonds between water molecules can absorb a lot of energy, therefore water has a high specific heat capacity as it takes a lot of energy to heat up.
This means water doesn’t experience rapid temperature changes which is one of the properties that make it a good habitat.
Why does water have a good latent heat of evaporation + function?
1) it takes a lot of energy to break hydrogen bonds between water molecules, so water has a high latent heat of evaporation because a lot of energy is used up when water evaporates.
This is great for living organisms as it means water is good for cooling things. This is why we sweat when it’s too hot. When sweat evaporates, it cools the surface of the skin.
Why is water cohesive + function?
1) cohesion is the attraction between molecules of the same type. Water molecules are very cohesive because they are polar
2) this helps water to flow, making it great for transporting substances. It also helps water to be transported up plant stems in the transpiration stream.
Why is water a good solvent + function?
1) water is a good solvent because it is polar. Eg the slightly positive end of the water molecule will be attracted to a negative ion and vice versa. This means ions will get surrounded in water so they’ll dissolve.
2) waters polarity makes it a good solvent in living organisms. In humans ions can dissolve in water in blood and then be transported around the body.
Why is water less dense when solid + function?
1) a low temperatures water turns to ice. Water molecules are held further apart in ice than in water beacsye esch water molecule forms four hydrogen bonds to other water molecules making a lattice shape. This makes ice less dense than water so it floats.
2) ice forms an insulating layer on top of water so water below doesn’t freeze. This means organism that live in water don’t freeze and can still move around. The ice is also a habitat for some organisms eg polar bears.
What is an ion with a positive charge called
A cation
What is an ion with a negative charge called?
An anion
What is an inorganic ion?
An ion that doesn’t contain carbon
What are the important cations?
Ca2+ , Na+, K+, H+, NH4+
What is the function of Ca2+ ?
1) it is involved in the transmission of nerve impulses and the release of insulin from the pancreas.
2) acts as a cofactor for many enzymes eg those involved in blood clotting.
3) it is important for bone formation.
What is the function of Na+?
1) it is important for generating nerve impulses
2) important for muscle contraction
3) involved in regulating fluid balance in the body.
What is the function of K+ in the body?
1) important for generating nerve impulses
2) involved in muscle contraction
3) regulates fluid balance in the body
4) it activates essential enzymes needed for photosynthesis in plants.
