Q1
Insolation can be described as the amount of energy of solar radiation received on a certain surface area and recorded in a given time. It is also known as solar irradiation and expressed as daily irradiation when recorded during a day and hourly irradiation when recorded during an hour. Throughout the year, the seasons undergo changes based on the quantity of sunlight hitting the Earth as it circles around the Sun.
Seasons occur as a result of Earth tilting on its axis, moving in a loop around the Sun every year. Summer occurs when the hemisphere is angled towards the Sun while winter takes place when the hemisphere is angled away from the Sun. When the Earth moves around the Sun, there is a change in the hemisphere, which is angled away or towards from the Sun.
The hemisphere angled towards the Sun is warmer since sunlight move more directly to the surface of the Earth and less sunlight gets dispersed in the atmosphere. This means that when the Northern Hemisphere is experiencing summer, the Southern Hemisphere is experiencing winter. The hemisphere that is angled towards the Sun experiences longer days and shorter nights. That is the reason for longer days in the summer than in the winter.
Generally, the far one travels from the equator, the cooler the temperatures in summer as well as winter become. At the equator, seasons do not occur since every day the Sun hits at around a similar angle. Each day of the year, the equator gets around 12 sunlight hours. The poles stay cool since they are never angled in a direct sunlight path. Much light is dispersed by the atmosphere prior to hitting the surface of the Earth at the poles. In midwinter, when a pole is angled away from the Sun, daylight does not occur at all. Nevertheless, in the summer, pole gets sunlight all the time and, therefore, the nights are very short or do not occur.
The atmosphere of the Earth is divided into two main zones. The homosphere is the lower zone, and it is the location where turbulent mixing pre-dominates the molecular diffusion of gases. In this zone, which happens less than 100 km, the atmospheric composition has a tendency to be independent of height. Over 100km, in the zone known as heterosphere, a number of atmospheric gases are divided by molecular mass, and the lighter gases are concentrated in the highest layers. Over a 1,000km, hydrogen and helium are the dominant species. A relatively heavy gas, diatomic nitrogen, reduces fast with height and exists just in trace quantities at 500 km and over. This reduction in the heavier gases concentration with height is largest in low Sun activity periods, when temperatures in the heterosphere are comparatively low. The transition region, which is situated at a height of 100 km between the heterosphere and homosphere, is referred to as the turbopause. Ozone is mainly concentrated in the stratosphere where solar radiations are absorbed this protects the living organisms from the harmful ultraviolet light from the sun.
Atmospheric motion is compelled by the irregular horizontal net distribution of the incoming radiation. On a universal scale, the majority of outstanding component of this irregular distribution is its dependence on latitude. The atmosphere reacts to this instability by trying to move heat from the subtropics and tropics, where insolation exceeds the infrared terrestrial radiation getting out to space, to the middle as well as high latitudes, where there is a final radiative heat loss. Convection, the vertical heat transport process together with advection, the moisture and heat transport horizontal process, accomplish this objective.
Q2
The membrane is the border between the cell’s fluids and outside. The plasma membrane or cell membrane encircles the living cells’ cytoplasm, physically dividing the intracellular constituents from the extracellular surroundings. The membrane is selectively permeable with an ability to regulate what goes into and out of the cell, therefore, enhancing the transport of materials required for survival while preventing those materials that are harmful to the cell. It comprises primarily of proteins and phospholipids. The phospholipids are organized in 2 layers with their tails of hydrophobic fatty acid situated to the membrane’s interior and their hydrophilic polar heads to the inner, as well as outer surfaces. A number of these molecules have chains of carbohydrate inhered in them making glycoprotein and glycolipids. The membrane is a fluid, and its constituents are slowly floating past each other.
Membranes play varied roles in prokaryotic and eukaryotic cells. Among the crucial roles is regulation of the motion of materials in and out of cells. The phospholipid bilayer structure that has specific membrane proteins explains the membrane’s selective permeability as well as passive and active mechanisms of transport. Additionally, prokaryotic membranes and the membranes of mitochondria and chloroplasts of eukaryotes enhance the ATP synthesis through chemiosmosis
The transport of substances across the membrane may be either passive, taking place with no cellular energy input, or active, which calls for the cell to use energy in its transport. The membrane also preserves the potential of the cell. The cell membrane, therefore, works as a selective filter, which permits only some things to go into or out of the cell.
Several mechanisms are employed for passage of some molecules across the membrane. A number of substances like carbon dioxide and oxygen can be transported across the plasma membrane through diffusion. Since the membrane serves as a barrier for some ions and molecules, they can take place in varied concentrations on the two membrane sides. A concentration gradient such as this across a semi-permeable membrane creates an osmotic flow for the water.
Nutrients, like amino acids or sugars, have to enter the cell, and some metabolism products have to leave the cell. Molecules such as these are pumped across the membrane through transmembrane transporters or diffuse through channels of protein like Aquaporins. These proteins, also referred to as permeases, are normally quite specific, acknowledging and transporting just a restricted group of chemical substances and some only one substance.
Another way through which molecules get into the cells is through endocytosis. This is the procedure through which cells take in molecules by engulfment. The plasma membrane makes a small distortion inward, known as an invagination, where the substance to be carried is captured. The distortion then pinches off from the membrane on the inside making a vesicle comprising the captured substance. Endocytosis is an internalizing solid particles’ pathway for ions and small molecules, as well as macromolecules. It needs energy and is, therefore, an example of active transport.
Other molecules move into a cell against their concentration gradients through active transport. In every cell, there is an accumulation of high molecule concentrations that the cell requires like ions, amino acids and glucose. The process may use chemical energy like adenosine triphosphate, primary active transport or may involve electrochemical gradient.
Q3
An enzyme refers to a protein molecule, which acts to catalyze biological reactions. An enzyme has three main characteristics. These include the ability to increase the reaction rate, specifically acting on one substrate in order to produce products, and finally being regulated either from a low to a high activity state and vice versa. Since most enzymes are protein in nature, the enzyme activity is dependent on a specific protein chain making the enzyme. In addition, most enzymes combine with one or more other parts known as cofactors. It is this complex that is simply known as the enzyme. The protein or polypeptide part of the enzyme is known as apoenzyme while the non-protein part is known as a cofactor. The cofactors act as helper molecules in the biochemical transformation process.
Those cofactors that are loosely bound to the apoenzyme and are organic in nature are known as coenzymes while those cofactors that are bound tightly are called prosthetic groups. Coenzymes mainly work as intermediate carriers of specific atoms, electrons or functional groups between the substrate and the product. Other cofactors that are inorganic metal ion may play a part in facilitating the activity of an enzyme. These cofactors are known as metal ion activator and include ions such as Mg+2, Zn+2, Mn+2, Fe+2, K+, Cu+2, and Na+, availability of these cofactors affect the rate of enzyme activity. Other molecules that regulate enzyme activity are the allosteric regulators. These molecules bind to a site other than the active site and this alters the enzyme configuration and hence enzyme activity. Binding of an allosteric regulator may activate some enzymes while, in other enzymes, the binding inhibits enzyme activity.
Classification of enzymes may be done depending on the type of chemical reaction that they catalyze. Those enzymes that add or remove water from other molecules are called hydrolases or hydrases. Hydrolases include enzymes such as carbohydrases, esterases, deaminases, nucleases, and proteases. Hydrases, on the other hand, include enolase, fumarase, and aconitase. Those enzymes that transfer electrons are known as oxidases or dehydrogenases. Those that transfer a radical are known as transglycosidases for monosaccharides, transaminases for amino groups, phosphomutases and transphosphorylases for a phosphate group transfer, transmethylases for a methyl group transfer, and transacetylases for an acetyl group transfer. Those enzymes that form or split a carbon-carbon bond are known as desmolases. Those enzymes that change the geometry or the structure of a molecule are known as isomerases, and those that join two different molecules via pyrophosphate bond hydrolysis in ATP or even other tri-phosphate are known as ligases.
Metabolic pathways may be classified as linear, cyclic or branched. The linear pathways are those pathways that start with one molecule and end with a different molecule such as glycolysis. Cyclic pathways are those pathways that start with one molecule and end with the same molecule, which start the cycle again such as the tricarboxylic acid cycle (TCA). Branched pathway is the pathway that has one of the intermediates acting as a branching point leading to two or more different end products. Regulation of the pathways may involve a number of mechanisms and include altering factors that affect activity of an enzyme such as pH, substrate availability, product accumulation, temperature among others. Other mechanisms through which metabolic pathways are regulated include the use of regulatory enzymes either the allosteric or covalently regulated enzymes. The mechanisms may include positive and negative feedback regulations. Negative feedback occurs when the product inhibits more production of the product. Positive feedback, on the other hand, occurs when the product leads to increased production of the product.
Q4
Glycolysis is the pathway through which, a small amount of energy is produced through the conversion of glucose into two pyruvate molecules. The glycolysis process takes place in two main parts and results, in the converting each glucose molecule into two three-carbon molecules known as pyruvate. During the glycolysis process, there is oxidation of several carbon atoms with a small amount of energy being captured and stored temporarily in ATP and NADH molecules. The total reactions in the two main parts that are involved in a glycolysis pathway are ten. The first part involves the double phosphorylation of the glucose molecule followed by a cleavage process in order to form two glyceraldehyde-3-phosphate (G-3-P) molecules. The two phosphorylation processes use up two molecules of ATP acting as an investment as this stage is the one that creates the actual substrate necessary for the oxidation process in a form that is held in the cells.
The second part of glycolysis involves the conversion of glyceraldehyde-3-phosphate to make the pyruvate molecules. Here, four ATP and two molecules of NADH are produced. Since there were two ATP molecules that were utilized in the first stage, the net ATP produced per one molecule of glucose is two ATP molecules.
The final glycolysis product is converted into acetyl-CoA, which is the molecule that enters the next stage of metabolism, the tricarboxylic acid cycle (TCA). TCA cycle is an amphibolic pathway capable of oxidizing the two acetyl carbons completely leading to the formation of carbon dioxide molecule and the reduced molecules FADH2 and NADH. The amphibolic nature of the citric acid cycle enables it to do both anabolic, as well as catabolic processes. The main objective of TCA is to reduce FAD+ and NAD+ and in producing precursors for other pathways.
The reduced molecules FADH2 and NADH are then taken to the electron transport chain (ETC). ETC is a series of reactions of reduction and oxidation and are involved in the transfer of the electrons contained in the reduced molecules to the molecule of oxygen forming water. The released during the process of electron transfer is usually coupled to a mechanism that produces ATP molecules. From the total oxidation process of one molecule of a glucose molecule forming carbon dioxide and the oxidation of all the coenzymes, there is the production of 31 molecules of ATP.
Works Cited
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