Water in Biology Trivia Quiz

Answer: Hydrogen bonding

Hydrogen bonding is a strong intermolecular force that is formed between an atom of hydrogen of one molecule and an atom of either nitrogen, oxygen or fluorine. In water, the hydrogen bond is found between the partially positively charged hydrogen of one molecule and the partially negatively charged oxygen of another molecule.

This gives water its well known boiling point of one hundred degrees centigrade.

Answer: Countercurrent

This is a very important mechanism in most fish (not all fish utilise this mechanism) as the dissolved concentration of oxygen in water is very low. Thus, to maximise the absorption of the oxygen from water into the bloodstream of fish, the countercurrent mechanism is used. Essentially, the countercurrent mechanism maintains a good concentration gradient of oxygen between the blood and the water.

The larger the concentration gradient of oxygen, the more oxygen will be absorbed into the blood from the water by diffusion.

This oxygen can then be used in respiration which supplies the necessary energy for the lifestyle of many fish.

Answer: Carbonic acid

The equation for this reaction is:

CO2(g) + H2O(l) ---> H2CO3(aq)
Carbon dioxide (gas) + water (liquid) ---> carbonic acid (aqueous)

This reaction is catalysed by the enzyme carbonic anhydrase. Eventually the carbonic acid will dissociate into hydrogen ions (H+) and hydrogencarbonate ions (HCO3-). The HCO3- leaves the red blood cell and is transported by the plasma, whilst the acidic hydrogen ions need to be neutralised. Therefore, oxyhaemoglobin (HbO2) in the red blood cell dissociates into haemoglobin (Hb) and oxygen (O2). The oxygen can then diffuse out of the red blood cell to be used in respiring cells whilst the haemoglobin can act as a buffer, neutralising the acidic hydrogen ions. The reaction is as follows:

Hb + H+ ---> HHb
Haemoglobin + hydrogen ions ---> haemoglobinic acid

This, for me, is an incredible biological process that demonstrates a magnificent dual process of supplying oxygen for respiration whilst maintaining a relatively constant pH inside red blood cells.

Answer: Transpiration

In both mesophytes (plants which exist in neither really wet or really dry areas) and xerophytes (plants which exist in arid conditions) the control of transpiration is important. Transpiration provides a lot of the power needed to "pull" water from the roots to the leaves, but if too much water is lost by the process, the plant will wilt.

Therefore, when the plant has a healthy and plentiful supply of water, the guard cells which surround the stomata are turgid and the pore is opened and transpiration occurs at a relatively high rate.

However, when the plant does not have a great supply of water (particularly in xerophytes) the guard cells surrounding the stomata become flaccid and the pore is closed.

Answer: Photolysis

The reaction that illustrates the process of photolysis is:

H2O + photons (light) ---> (2)H+ + (2)e- + (1/2)O2.

As can be seen, the photons split the water into two hydrogen ions, two electrons and half a molecule of oxygen gas. The hydrogen ions are useful because they travel to the hydrogen acceptor known as NADP. The hydrogen ions reduce the NADP to form NADPH2 which is later useful in the formation of sugars and amino acids.

Furthermore, the electrons travel to a photosystem which contains many chlorophyll molecules and redresses the balance of charge that has been created from excited electrons leaving the photosystem due to incoming light. The light promotes the electrons to a higher energy level. It is when these electrons lose energy along the electron transport chain that energy in the form of ATP becomes available. This ATP is later used in the formation of sugars and amino acids in the Calvin cycle or light independent phase of photosynthesis.

Answer: Hydrolysis

Hydrolysis begins with the dissociation of water into hydrogen ions (H+) and hydroxide ions (OH-). In protein digestion the water helps to cleave the polymer along with a specific protease enzyme. Thus, due to the addition of a water molecule, the peptide bonds break and smaller polypeptides and dipeptides form. These are further hydrolysed into amino acids which can be absorbed through the walls of the small intestine.

The same sort of process occurs with carbohydrate digestion in for example starch. This time the glycosidic bond is hydrolysed (by water along with the amylase enzyme) and the polymer is broken down into maltose. The maltose is further broken down by water and the enzyme maltase into glucose.

Answer: Antidiuretic hormone

Antidiuretic hormone (ADH) is secreted from the posterior pituitary gland and regulates the amount of water present in the urine. If the body hasn't reabsorbed enough water from the nephrons' loops of Henle, then ADH is released in greater quantities.

This makes the walls of the collecting duct and the second (distal) convoluted tubule more permeable to water. The needed water is then reabsorbed into the blood by osmosis. The resulting urine will have a high urea concentration. If the body has sufficient water, then ADH will not be produced in great quantities and less water will be reabsorbed.

As a result there will be a greater volume of water in the urine.

Answer: Evaporation

The cooling of the skin comes when the sweat is evaporated. The human species is one of the sweatiest that we know of. Many other animals have no (or limited) sweat glands as they are usually of no effect due to the copious amounts of fur that coat them.

Answer: Cohesion-tension

The cohesion-tension theory is what underlies the concept of transpirational pull. When two water molecules within a xylem vessel form a hydrogen bond between them, a column of water is formed from the leaves right down to the roots. Thus, when some of the water molecules leave the leaf by transpiration, the whole column is pulled upwards, against the force of gravity.

There are other mechanisms used to transport water from the roots to the leaves of plants such as capillary action and root pressure. These contribute only a small part to the essential process, but in biological investigations it has been found that capillary action and root pressure alone aren't sufficiently powerful enough to transport water from the roots to the leaves of very tall trees. For water to successfully reach the top of tall trees, transpirational pull which uses the cohesion-tension nature of water is required.

Answer: Plasma

The fact that blood plasma consists of a lot of water makes it ideal for transporting useful nutrients such as glucose and amino acids. This is because the soluble nutrients can dissolve in the water for easy transportation through the circulatory system. The plasma also transports waste products from the cells to various parts of the body (carbon dioxide to the lungs, urea to the kidneys) so that they can be excreted.

I hope you enjoyed the quiz!