C2 - The Importance of Water Flashcards
Why is water necessary?
All life forms depend on water.
Water is the major constituent of most organisms.
Two thirds of this water is found within cells and the rest is found in extra cellular bio fluids e.g. plasma in animals and phloem sap in plants.
Most biochemical reactions take place in water so without it there would be no life on planet Earth.
What is the structure of water?
Water is a polar molecule made up of an oxygen atom and two hydrogen atoms.
There’s a covalent bond between to O and H.
The water molecule is a bent molecule rather than linear (104.5°)
What is the charge of water?
Water has a slight charge so is called polar.
The oxygen atom has a slight negative charge and the hydrogen atoms have a slight positive charge.
Having opposite charges in two places makes it dipolar.
The water molecule is a bent molecule rather than linear and so the hydrogen atoms are on one side of the molecule and form a positive pole.
Meanwhile the oxygen atom is on the other forming the negative pole
What are hydrogen bonds?
Within water
Hydrogen bonds are the forces of attraction when water molecules are attracted to each other as the slight positive charges (of the H atoms) are attracted to the slight negative charges (of the oxygen atoms).
Hydrogen bonds are actually weak intermolecular forces rather than actual bonds.
Individually they are very weak but if there are a lot of hydrogen bonds in a given volume they are collectively quite strong
What is cohesion?
The attraction between two water molecules
The sticking of particles of the same substance
What is adhesion?
The attraction between water and another polar molecule
Sticking of particles of different substances
Why is water a good solvent?
What are molecules are attracted to other polar and charged particles which makes water a good solvent for substances with these properties.
The water molecules from a ‘shell’ around charged ions and other molecules that possess a slight charge on their surface
This prevents the ions and molecules from clumping together and so causes the ions to dissolve.
Nonpolar molecules cannot dissolve in water therefore cannot be transported in the plasma (instead they have to be combined with soluble molecules)
How is water being a solvent an important property?
It’s important:
For transporting substances around the body in the plasma such as glucose, insulin and lymph
In removing metabolic waste such as urea in urine
In allowing chemical reactions to take place within cells such as respiration and protein synthesis
Why does water have a high specific heat capacity?
There are many hydrogen bonds which restricts the movement of water molecules.
This increases the amount of energy needed to break the hydrogen bonds.
A large amount of energy is needed to make bodies of water change temperature and so water must lose a large amount of energy in order to cool down
(this means the temperature of water is relatively stable in comparison to air and land and so is an ideal habitat for aquatic organisms)
Why is water having a high specific heat capacity an important property?
It prevents our internal body temperature changing quickly as a result of changes in the environment
What is the latent heat of vaporisation?
The amount of heat needed to turn a substance to a gas.
Why does water have a high latent heat of vaporisation?
It’s molecules need a high amount of heat to enable a molecule to separate from other molecules in a liquid to become a vapour.
As it requires a large amount of heat to break the hydrogen bonds, this means that when water evaporates, it has a cooling effect.
Why is water having a high latent heat of vaporisation an important property?
It allows our bodies to lose heat through sweating
Why is water viscous?
Due to its cohesive and adhesive properties.
Why is the cohesion and adhesion of water an important property?
It allows water to be used as a lubricant in the form of pleural fluid (minimising friction between the lungs and rib cage) and mucus (e.g. To allow passage of faeces down the colon).
It’s critical to transport in xylem vessels in plants.
What is cytosol?
The liquid part of cytoplasm in an intact cell, excluding any part that is contained within organelles.
The less water in the cell, the slower the metabolic rate.
What are body/biofluids?
Liquids produced within the body.
Fluids secreted or excreted from the body e.g. Bile, semen, breast milk, amniotic fluid, cerebrospinal fluid.
They can be placed into 2 groups:
Intracellular fluids
Extracellular fluids
What are intracellular fluids?
Fluid found within cells e.g. Cytosol
What are extracellular fluids?
Fluids found outside of cells e.g. Plasma and tissue fluid
What are the three main body fluids (in terms of volume)?
Blood plasma
Tissue fluid
Lymph
What is blood plasma?
Approx 55% of blood is (pal yellow) liquid (plasma). The remaining 45% is made up of cells
NO cells in plasma
What does plasma contain?
Plasma proteins (albumin, antibodies, clotting factors)
Absorbed nutrients (glucose, amino acids, fatty acids)
Excretory waste (urea, CO2)
Hormones (insulin, adrenaline)
Electrolytes (sodium and chlorine ions)
Heat
What is tissue fluid?
Fluid produced due to hydrostatic pressure which forces fluid out of the plasma and into the spaces between the cells.
The capillary walls are permeable to most components of the blood except most blood cells and large plasma proteins.
What’s hydrostatic pressure?
Pressure created by water within cells.
Tissue fluid forms as a result of HP due to the force created by the heart pumping blood from the left ventricle around the body in the arteries, arterioles and capillaries.
The pressure forces fluid out of the plasma carrying nutrients and oxygen.
What does tissue fluid enable?
It allows capillaries to exchange substances with every cell in the body.
Tissue fluid returns to the bloodstream via capillaries and the lymphatic system.
What’s lymph?
A colourless fluid containing leucocytes that bathes the tissues and drains through the lymphatic system into the bloodstream.
White blood cells and other substances that are continually exchanged with substances from the blood plasma.
1/10th of tissue fluid drains into lymphatic capillaries which drain into larger lymph vessels containing valves.
It drains back into the bloodstream in the subclavian vein.
It’s important for our immune systems.
What moves lymph?
The contraction of skeletal muscles and hydrostatic pressure of the tissue fluid left in the capillaries.
What’s urine?
A fluid stored in the bladder and discharged through the urethra.
It is one of the body’s chief means of eliminating excess water and salt, and also contains nitrogen compounds such as urea and other waste substances removed from the blood by the kidneys.
How is urine produced?
Metabolic reactions within the body produce waste products, some of which contain nitrogenous-high substances which are toxic and must be removed from the bloodstream.
Soluble waste, excess water, ions and sugars are excreted mainly by the urinary system and perspiration.
The urinary system consists of 2 kidneys with a ureter each that leads to the bladder and urethra.
Urine is the end result of filtration and reabsorption of the substances in the blood stream. (And has high concentration of toxic substances and urea)
What is serum?
The blood plasma which has had it’s clotting factors removed from it.
What does serum contain?
Electrolytes Antibodies Antigens Hormones Soluble proteins (which aren't involved in blood coagulation/clotting)
How’s serum obtained?
By allowing whole blood to clot at room temp for 15-30.
Clots and cells are removed by centrifuging it for 10 mins.
The serum is immediately collected and stored at 2-8°C
What’s serum used for?
Blood typing
Diagnostic tests
Testing for IgG
What biofluids are in plants?
Cytosol or cell sap (intra) Vacuole contents (intra) Contents of specialised cells e.g. Phloem and xylem (intra) Fluid in cell walls (intra) Fluid between cell walls (extra)
Xylem fluid is very dilute compared to phloem sap and cytoplasm.
Unlike phloem sap, xylem fluid contains no sucrose otherwise they’re similar. (Ions, molecules and auxins)
What are the charges of the hydrogen and oxygen within water?
The oxygen has a slight negative charge
The hydrogen has a slight positive charge
Oxygen has a greater affinity than hydrogen as it has more protons so has a greater positive charge overall.
This charge makes water dipolar
What’s the symbol for a slightly positive or negative dipole?
δ
The symbol δ indicates the partial charge of an individual atom.
What happens when a charged plastic rod is held alongside a stream of water?
The water bends towards or away from the rod based on their charges (attracted or repelled)
Why does water have so many properties?
Because of its ability to form hydrogen bonds.
Why is water a good solvent?
Water molecules form a layer around the ions and break the ionic substances apart.
Non-polar molecules e.g. Lipids are insoluble because they do not attract the water molecules.
What is surface tension?
The tension of the surface film of a liquid caused by the attraction of the particles in the surface layer by the bulk of the liquid, which tends to minimize surface area.
Surface tension is the elastic tendency of a fluid surface which makes it acquire the least surface area possible. Surface tension allows insects (e.g. water striders), usually denser than water, to float and stride on a water surface.
At liquid-air interfaces, surface tension results from the greater attraction of liquid molecules to each other (due to cohesion) than to the molecules in the air (due to adhesion).
