2.2 Water Flashcards
What to the hydrogen and oxygen share?
Each hydrogen shares a pair of electrons with the oxygen
Why does the oxygen pull the electrons closer?
It has a greater affinity for the electrons than the hydrogen
What is the the charge of the oxygen?
Slightly negative
What is the charge of the hydrogens?
Slightly positive
What type of molecule is water?
The different charged regions makes it a POLAR MOLECULE. Because it has two charged regions it is DIPOLAR.
How do water molecules bond?
HYDROGEN BONDING. The slightly negative charge on the oxygen atom makes it attract to the slightly positive hydrogen atom of another water molecule.
What do the numerous hydrogen bonds do to waters structure?
They make it very stable
What is the biological importance of water?
Water is necessary for transport, chemical reactions, temperature control, support, movement and reproduction
What is the structure of water?
H2O
Two hydrogen atoms covalently bonded to one oxygen atom
Give an example of how water is used in transport:
- All transport fluids in mammals are water based (e.g: cytoplasm, blood, plasma, tissue fluid)
- uptake of minerals in soil by plants occurs in solution (in water)
Give an example of how water is used in chemical reactions:
- water is the ideal environment for reactions, photosynthesis, respiration and excretion occur in solution
- water also acts as a reactant in hydrolytic reactions (e.g digestive enzymes)
Give an example of how water is used in temperature control:
- water remains liquid over a huge temperature range, essential for metabolism and for aquatic organisms to avoid freezing
- when water evaporates energy is released, this is involved in cooling mechanisms
Give and example of how water is used for support:
- in plants water confers turgidity essential in maintaining maximum leaf surface area, which increases light absorption in photosynthesis
- in animals water filled tissues contribute to skeletal support
Give an example of how water is used in movement:
- water is involved in nastic movements, for instance the opening and closing of plants
- earthworms use their hydrostatic skeletons to move, their muscles are able to contract against the watery fluid of the coelom for them to move
Give and example of how water is used in reproduction:
- organisms use water to bring make and female gametes together in the process of fertilisation
- in mammals the foetus develops in a water filled sac providing physical and thermal stability
What are nastic movements?
Those not involving growth in a particular direction
The non directional response to stimulus
What is turgidity?
It refers to something swollen, giving it structure. Hence why plant cells are full of water, if not they would wilt
Why does salt (NaCl) dissolve in water?
The positive sodium is attracted to the negative oxygen atom in a water molecule, whilst the negative chlorine is attracted to the positive hydrogen atoms. The salt is then pulled apart (it dissolves)
What molecules are insoluble in water?
Non polar molecules like lipids because they do not attract to the atoms within the water molecule
What does it mean that water has high latent heat evaporation, what is this used in?
It takes a lot of energy to break the hydrogen bonds between water molecules. So a lot of energy is used up when water evaporates (high latent heat of evaporation).
Used in cooling mechanisms
What is cohesion?
Attraction between molecules of the same type
Why are water molecules very cohesive?
Because of their polarity - water molecules tend to stick together
What does waters polarity help it do?
- flow
- making it good for transport
- all transport fluids in animals are water based (cytoplasm, blood, plasma)
What else does waters polarity make it?
A good solvent
