Photosynthesis and Respiration

Plants also respire. 

Photosynthesis and respiration occur together.

In photosynthesis, we require carbon dioxide. The waste product is oxygen. In aerobic respiration, we need oxygen and release carbon dioxide as a waste product. However, these chemical processes do not always balance out as respiration occurs all the time. The leaf will always be respiring. The rate of photosynthesis will change depending on limiting factors such as light, temperature and carbon dioxide availability. As the sun continues to rise, the rate of photosynthesis will increase. At one point in the morning, the amount of oxygen released will equal the amount of oxygen absorbed. This point is called the compensation point. 

As the day continues, there tends to be more photosynthesis as more carbon, from carbon dioxide is absorbed. 

Enzymes in Biology: The Good Guys

Enzymes benefit chemical reactions but allowing them to happen, they are biological catalysts. However and interestingly, they are not necessarily used up. So, enzymes help large molecules separate in the intended fashion or join in the intended fashion. Enzymes are composed of proteins in amino acids - folded into complex shapes. Smaller molecules can fit into the enzymes like a jigsaw: these are called substrate molecules. The product molecule has to separate from the the enzyme thus it becomes free to join up with substrate molecule. This process is repeated. The place on the enzymes where the molecules go into are called the active sight. The shape of the enzyme is important.

In short, enzymes are: a chain of amino acids, thence proteins coded for by a gene. They are catalysts used for protein synthesis, DNA replication, for breaking big things into small things.

This is usually understood through a lock and key diagram as shown below:

Denatured enzymes by pH or temperature

If the shape of the enzyme changes, the substrate molecules can not fit into it. This is referred to as the enzyme becoming denatured usually do to extreme pH levels or high temperatures.

The enzyme has not been killed. They are just proteins - not living things. High temperatures increase the frequency of collisions between enzymes and other molecules thus the rate of reaction has increased. For most enzymes, body temperature is idealistic for them to work appropriately (about 37 degrees). The wrong pH can denature enzymes. Different enzymes work best at different pH levels. For instance, in our stomach the enzymes called pepsin work best at pH 2 (optimal).

As mentioned, when you increased temperature there will be more kinetic energy which the molecules have thus meaning more successful collisions hence an increased rate of reaction. On a graph, there would be a bell shape as the peak of the bell represents the optimum temperature.
If the molecules do not 'lock' into the enzyme, they will bounce off. If the temperature of pH is not favoured by the enzyme, its substrate complex does not form for the molecule. The bonds break.

The active site is complimentary shape to the substrate. It is a specific shape. One enzyme has a certain shape that will only fit in the active zone; the substrate will no longer fits in the enzyme if it denatured so the chemical reaction will not occur.

If you gradually increase the pH and decrease slightly from the optimal pH - the rate of the reaction decreases - the rate of reaction does not result to zero completely.

When are enzymes involved in our world?

Enzymes take part in photosynthesis of plants; they join amino acids together to form proteins; they take part in aerobic respiration. Aerobic respiration is not the same as breathing which is important to consider; it is the chemical reaction that releases energy from glucose. Enzymes catalyse the reaction, usually in the cytoplasm of cells, in tiny objects called mitochondria. The energy tends to be used for contracting muscles joined to molecules forming proteins. Enzymes maintain body temperature in many birds and mammals.

Some microorganisms release enzymes into the environment which we can use for several industries to improve standards of living.

Are they in products we use today?

Well, why are they referred to as 'biological'? This is because the detergents contain enzymes that digest proteins and fats in order to make water-soluble products, as this helps to remove stains hence enzymes are biological catalysts.

How does our body stop the denaturing of enzymes? 

You might come across a 'buffer', it is a solution that stops the pH from changing so much. We have buffers in our body so the chemical reactions will continue to happen at the optimal level. For instance, in aerobic respiration, the carbon dioxide formed causes carbolic acid. This will lower the pH of blood if you breathe more often. When one breathes more often, more respiration occurs, so more carbon dioxide is released as a product of that reaction hence carbolic acid.
It is so important for the pH to remain constant in our bodies - for our well-being.

Nuclear Wastes and the Levels

Nuclear power stations release huge amounts of energy when the nuclei of two radioactive elemts such as those from uranium and plutonium, split apart. The process is called nuclear fission and starts when neutrons are fired towards the fuel causing some of the large unstable nuclei to split into small nuclei which is roughly of equal sixes. Each split nucleus also releases two or three more neutrons and a bountiful of energy.

Nuclear reactions release more energy than those of chemical reactions e.g combustion. You can calculate just how much energy is released using the famous e=mc^2 discovered by Albert Einstein. 

The following picture is just a nutshell worth of information as to what occurs in a nuclear power plant:

http://www.revisescience.co.uk/2011/schools/albany/pp66.asp

The waste from nuclear power stations are incredibly hard to dispose of and this process has to be done very carefully. Nuclear power stations do not release any gas meaning we will stop the production of pollutants that contribute to acid rain and global warming. However, these power stations release radioactive waste.

Most waste from power stations or by medical use is considered 'low level' (slightly radioactive) like paper and gloves. This waste can be disposed of by burying it in secure landfill sites.

Intermediate level waste is usually quite radioactive and lots of them will stay that way for tens of thousands of years. Examples of intermediate level waste are metal cases of used fuel rods and some waste from hospitals. These tend to be put into concrete blocks then into steel canisters for storage thus being buried underground though it is not easy to find places where to store them. The site has to be geologically appropriate because big movements could break the canisters and the radioactive material could be released. This would increase the dosage levels for people near-by on ground and underground. Those who live nearby often rebuke having canisters near-by for fear of being harmed. Hence, most intermediate to high level waste is kept at nuclear power stations where they are moderated by those who work there. 

High level waste is so radioactive that they generate a great deal of heat. These forms of waste are stored in glass and steel, then cooled for about fifty years before it's moved to more permanent storage. The uses of a lot of time and effort by workers. 

Remember high level waste decays to form intermediate level waste and so on... It seems the process of very costly. 

The Uses of Radiation (PET Scans)

Ionising radiation can be useful for treating cancer. Since high doses of gamma rays will kill all living cells, it can be carefully directed at just the right dosage to kill cancer cells, without damaging too many normal cells. However, a fair bit of damage is done to normal cells which makes the patient feel incredibly ill. If the cancer is killed off in the end, the treatment was therefore worthy. A capsule which emits beta radiation can be given to the person to swallow. You would need the element to have a long half-life so that the radioactivity lasts enough to kill lots of cancer cells despite the risk of killing or mutating lots of normal cells. This is called radiotherapy.

Another advantage of radioactivity is for medical equipment. Gamma rays are used to sterilise medical instruments through killing all the microbes on them. This is better than trying to boil the equipment which can damage them. You would require a strongly radioactive source that has a long half-life so that is doesn't need replacing too often.

You can even sterilise food. The gamma rays can kill of all microbes. This keeps the food fresh longer without having to freeze or cook it. The food is not radioactive afterwards so you can eat it.

Lastly, you could detect diseases by using tracers. Tracers are radioactive molecules that be be injected into people; they progress around the body and it is followed using an external detector. They can detect cancer or if an organ is working properly or not. They should have a short half-life so that the radioactivity inside the patient is gone before it could cause damage to the living cells.

So, what about PET scans?

Well, the process is very similar to using tracers.

BBC Bitesize goes into depth with PET scans and says the following:
"PET (Positron Emission Tomography) scanning uses radioisotope tracer drugs such as fluorine-18. The tracer is usually injected into the patient’s blood. Gamma rays emitted by the tracer are detected by the PET scanner and multiple images are taken and then analysed by computers. The half-lives of radioisotopes used in PET scans are very short. This means that they often have to be produced in hospitals or at a nearby location." If you think about it, they need short half-lives so that the radioactive material is gone before it causes damage to normal cells, as mentioned with tracers.

Background Radiation and the Dangers of Radiation

Examples of elements that emit ionising radiation all the time are: radon, uranium, astatine (halogen), plutonium and francium. The behaviour of radioactive materials cannot be changed by chemical or physical processes because radioactivity occurs due to an unstable nucleus, there is no involvement of electrons here. After the radioactivity has ended within an element, it should change to another element. For instance with carbon atoms, they randomly give out radiation once and what is left afterwards is a different element, usually referred to as a 'daughter product' or a 'decay product' element. It is a change inside of the atom, not a chemical change.

There are three types of energetic radiation that causes the nucleus to change once it is emitted. The following image shows their penetration properties:

http://pediaa.com/difference-between-alpha-beta-and-gamma-radiation/

Most of the background radiation we hear on a Geiger counter, is from natural sources. In fact, 84% is natural:

• 12% from cosmic rays which is ionising radiation from out space.
• 50% radon gas from the ground.
• 13% gamma rays from the ground and buildings.
• 9.5% from food and drink.

Some background radiation comes from artificial radiation:

• nuclear discharges
• medical reasons.

Radiation dose measures the possible harm the radiation can do to the body. It is measured in millisieverts (mSv). Sieverts show how radiation could be hazardous to humans. Sieverts take account the type and amount of radiation you've been exposed to. In addition, the damage to the body will also depend on the type of tissue affected. If Radon gas in inhaled, it is very likely to cause a great deal of harm to the lung tissue if they come in contact with each other, for lung tissue is easily prone to damage.

2 - 2.5 msV/year is the typical amount of background radiation experienced by all people. 100 msV is the lowest level at which the probability of cancer occurrence and the increase in cancer is evident.

Moreover, ionising radiation can be incredibly threatening to our health. It has the energy to knock of an electron from an atom, or it could make an atom gain an electron to thus become a positive or negative ion. The ionising radiation has the energy to break molecules in the cells in the body into ions. The ions can then take part is chemical reactions that are likely to damage the body. If the ionising radiation effects the DNA of the human body, this may lead to the cell being mutated or killed. If the cells mutate, then this could cause cancer.

There is no such thing as a 'safe dose' because just one radon atom could cause cancer. The chances are low, but there is always a risk. Radiation exposes humans to risk by either irradiation or/and contamination.

Exposure to a radiation source outside of the body is could irradiation. Alpha irradiation does not usually cause harm to the human cellular structure. This is because alpha particles only travel a few centimeters in the air, and they are easily absorbed. Irradiation by beta particles is more risky because they can penetrate a few centimeters into the body. Most gamma rays pass through the body but if they are absorbed, their high energy retention can cause some huge threats towards cells within the body whether it be skin, or heart cells. 

If a radiation source enters your body, or gets on skin or clothes, it is called contamination. If you swallow or breathe in any radioactive material, your vital organs will be exposed to continuous radiation for a long time. Alpha particles are the most ionising so contamination can cause cancer very quickly or kill cells. Contamination by gamma is less threatening because it could just pass through the body due to its high penetration. So, irradiation and contamination occurs to most if not all humans because of background radiation. 

Categories of people at higher risks of being exposed to radiation include those who work in a nuclear power plant or miners. Uranium minders and processors workers in nuclear power plants are constantly being exposed to the radioactivity of uranium. Airline staff usually are in contact with cosmic rays and miners suffer from radioactive rocks. Nuclear researches also find themselves near the constant nuclear waste, releasing radiation and medical staff like radiographers find themselves being exposed to x-rays, which is a form of ionising radiation that is apart of the electromagnetic (EM) spectrum.

In the UK, people who tend to have higher doses of radiation are carefully monitored and have regular health check-ups to make sure they are not becoming ill as a result of radiation they are exposed to whilst working.