Every living thing on Earth needs water for survival. Water has several unique chemical properties, most of which result from the fact that water is a polar molecule (which have positively and negatively charged ends) and the ability of water molecules to form hydrogen bonds with adjacent water molecules. Hydrogen bonds are bonds between negatively charged ends of polar molecules (electronegative elements) and the positively charged end of adjacent polar molecules (hydrogen atoms). The weak attractions between water molecules due to hydrogen bonds give water the properties of cohesion (water sticks to water) and adhesion (water sticks to many surfaces). Cohesion results in water beading, forming droplets, and having surface tension (which allows water striders to walk on water). Adhesion is the reason surfaces stay wet after coming in contact with water. Cohesion and adhesion together result in capillary action, which is in part responsible for water rising up through the vascular systems of plants. Because of hydrogen bonds forming a crystal lattice upon freezing, water is less dense as a solid than as a liquid, which is very unusual among substances. This means that ice floats, which keeps lakes insulated during winter, allowing life to thrive beneath even when the surface of the water is frozen solid. Water has a high specific heat, which means it can store a lot of heat energy. This allows for the oceans to regulate the climate of earth for one thing. Water has a high heat of vaporization, which means it takes lots of energy to make it evaporate. This makes water a great coolant and helps humans regulate their temperature by sweating. Finally, water is an excellent solvent for many substances. This allows organisms to dissolve the nutrients and minerals needed to maintain function. Photorespiration is when oxygen binds to RuBP in the Calvin cyle, reducing photosynthetic efficiency because this oxygen must then be removed before the RuBP molecule can be used again for carbon fixation. This generally occurs on hot, dry, bright days, when stomata close and the oxygen concentration in the leaf exceeds that of carbon dioxide. Basically oxygen poisons the Calvin cycle.
C4 and CAM Plants have adapted and developed a strategy to address this inefficiency in hot dry climates. In addition to reducing photorespiration, these strategies also improve water use efficiency because stomata can remained less open without reducing photosynthetic yield.
C4 Plants- Address this problem by separating photosynthesis into different cells. Outer layer of leaf cells called mesophyll cells absorb CO2 and bind it into a 4 carbon molecule of malate. This molecule is then pumped into an inner layer of cells called bundle sheath cells, where the CO2 is then released. The Calvin cycle part of photosynthesis only occurs here. This effectively keeps CO2 levels continually high in these cells, reducing the amount of photorespiration by displacing oxygen. Because of the stored carbon these plants don't need to open their stomata all the way, reducing water loss.
CAM Plants- Accomplish the same process by separating calvin cycle by time, not location. During the day, stomata remain closed, reducing water loss in hot dry climates. During the night, stomata of the plant open and CO2 is stored in a series of 4 carbon molecules. During the day, these C4 compounds release the stored CO2 for the Calvin cycle.
Cells do cellular respiration to harness the energy they need to stay alive. In the process of cellular respiration, the energy that is stored in the chemical bonds of food molecules, such as glucose, is released and used to store energy in the chemical bonds of ATP, which is the main energy carrying molecule used to carry out all cellular functions. Cells cannot use the energy in the bonds of glucose directly so this process is necessary to be able to transform the stored energy into a usable form of stored energy (ATP).
In glycolysis, the first phase of respiration, glucose (6 carbon sugar) is broken down to two, 3 carbon molecules; the energy released is used to reduce a small amount of ADP to ATP. These 3 carbon molecules (called Pyruvate) are further oxidized (releasing carbon dioxide) and combined with coenzyme A to become 2 carbon Acetyl-CoA molecules. During the krebs cycle, the Acetyl CoA is combined with a 4 carbon molecule to form the 6 carbon molecule Citrate, allowing further energy (and CO2) to be released from oxidation as citrate is broken down back to the 4 carbon starting point in the cycle. This energy is stored in energy carrying molecules (NADH and FADH2), which will be used to power the electron transport chain (ETC). The ETC utilized the energy stored in high energy electrons of NADH and FADH2 to pump protons across the membranes inside the mitochondria of te cell. The protons flow back with the gradient via the channels in ATP-synthase. This enzyme complex harnesses the energy from the flow of protons to crank out a large quantity of ATP. At the end of the chain, the electrons must be deposited onto oxygen (forming water as a biproduct) so that the ETC does not become backed up and stop working. When oxygen is not available cells cannot harness the ATP from the ETC, meaning they rely on glycolysis, which has a much lower net output of ATP.
Biotechnology has several potential benefits and risks. The use of biotechnology has led to many advancements in the medical field, including new medicines, therapies, and diagnostic tools. Food production could potentially see a benefit from biotechnology because this may allow us to develop crops that are able to grow in places that currently do not support crop production. In the face of changing climate, having the capability to engineer plants with particular traits may help us to offset some of the loss in productivity due to changing climate. There are also many risks. There is a risk for engineered genes to escape into wild populations, which could cause ecological disruptions. There have not been many long term studies to evaluate whether GMO foods pose risks to human consumers. Ethical issues also emerge around the patents and ownership of engineered organisms. For instance, if a farmer downwind of a GMO farm has crops pollinated by the upwind neighbors' GMO pollen, this can result in the downwind neighbor having seeds that contain the engineered genes. If these are patented, the downwind farmer could be sued for patent violations even though the pollination of his crops was outside of his/her control. In the realm of medicine, there are also ethical issues that emerge. Where do we draw the line? For instance, is it ethical to clone individuals or to alter their genes. Is it ethical to sequence the genomes of the unborn prior to deciding whether or not to continue the pregnancy?...these and many other questions present potential costs to the use of biotechnology.