Biological Molecules (water) Flashcards
What is special about water
Water is the only molecule that can be present in all states at one time
What is the structure of water
Each hydrogen shares a pair of electrons with the oxygen
What does oxygen have a higher affinity for
The oxygen has a greater affinity for electrons than the hydrogens, so it pulls them closer.
What does oxygen having a higher affinity mean
The oxygen becomes slightly negative and the hydrogen slightly positive. This creates different charged regions making it a polar molecule.
What do the different charges in water result in
The slightly negative charged oxygen on one water molecule attracts the slightly positive hydrogen of another water molecule.
Draw 2 water molecules together
DRAW IT
What is water at room temperature
Water is a liquid at room temperature not a gas.
Why is water being a liquid at room temperature useful for organisms
It’s a habitat for aquatic organisms - oxygen/nutrients can circulate, organisms can float as water is a similar density to living organisms
It’s an effective transport medium
It’s a medium for chemical reactions
What happens when a polar molecule is dissolved in water
The water molecules form a layer around the ions and breaks the ionic substance apart.
What are lipids an example of
Non polar molecules
Why do non polar molecules not dissolve in water
They don’t dissolve in the water because they don’t attract to the water molecules.
What do the different parts of the water molecules do to the ions
The slightly positively charged hydrogen attracts to the negatively charged ions and the slightly negative charged oxygen attracts to the positively charged ions.
What does the attraction between ions and water molecules do
Separates the ions forming a solution
What does the property allow water to be
To act as a medium for chemical reactions in cells transporting dissolved molecules around living organisms.
What happens to the density of water as it freezes
It decreases
Why does the density of water decrease when it freezes
Because the hydrogen bonds fix the position of the molecules slightly further apart than the average distance in the liquid state, producing a giant open structure, with every oxygen at the centre of a tetrahedral arrangement.
Why is ice being less dense than water an important property
Animals such as polar bears can live on ice and ice forms a protective layer on ponds which insulates the water below, reducing the rate of heat loss and making the environment more stable for aquatic organisms.
What is cohesion in terms of water
At the surface the water molecules are all hydrogen bonded to the molecules below them which gives the surface of the water an ability to resist force applied to it.
What does cohesion mean for water
It means that the molecules stick together.
What does the hydrogen bonding lead to in terms of temperature
It has a high specific heat capacity.
This means that a large amount of heat energy is needed to alter its temperature.
This prevents large fluctuations in temperature.
What does this mean for aquatic organisms
It provides a constant environment allowing them to survive
What is adhesion for water molecules
Adhesion is the attraction between a water molecule and another polar molecule due to hydrogen bonding.
What do cohesion and adhesion allow for
Together with cohesion, this is what enables water to move up xylem tissue from roots to the leaves (capillary action).
What is the last property of water (liquid-gas)
It has a high latent heat of vaporisation.
This is because energy is needed to overcome the hydrogen bonding between water molecules.
What does a high latent heat of vaporisation make water
An excellent coolant
How do plants and animals make use of this
Mammals are cooled when sweat evaporates and plants are cooled when water evaporates from mesophyll cells in leaves.
