2.1.2 Biological Molecules – Water and Ions Flashcards
(9 cards)
What is a cation?
A positively charged ion
What are the chemical symbols for the following cations:-
a.) calcium ions
b.) sodium ions
c.) potassium ions
d.) hydrogen ions
e.) ammonium ions
a.) Ca2+
b.) Na+
c.) K+
d.) H+
e.) NH4+
What is an anion?
A negatively charged ion
What are the chemical symbols for the following anions:-
a.) nitrate ions
b.) hydrogencarbonate ions
c.) chloride ions
d.) phosphate ions
e.) hydroxide ions
a.) NO3-
b.) HCO3-
c.) Cl-
d.) PO43-
e.) OH-
Draw a diagram to show two water molecules bonded by a hydrogen bond.
How is the density of water related to its roles in organisms?
- Ice is less dense than water and so floats and therefore ice provides a habitat for some species.
- Ice floating on water insulates the water below, keeping it as an aquatic habitat for animals which can move below the ice.
- Water is a similar density to living organisms so organisms can float.
What properties of water make it an ideal habitat?
- It is a good solvent so oxygen dissolves in it, which organisms can use.
- It has high specific heat capacity so the temperature of the water stays stable.
- It has a high density so organisms can float in it.
- Ice is less dense than water and so floats providing a habitat.
Why is it important that water is a good solvent in organisms?
- It is a medium for metabolic reactions.
- It transports substances e.g. as part of plasma in blood, carries mineral ions in xylem, carries assimilates in phloem.
- Organisms can absorb minerals / ions / oxygen / food from the water.
- It is able to dilute toxic substances.
How does water act as a coolant in organisms?
Water has a high latent heat of vaporisation so it takes a lot of energy to break the hydrogen bonds that hold the water molecules together. This energy needs to come from the organism so a lot of heat energy is transferred from the organism, leading to the organism cooling down e.g. during sweating.
