Biology Test 358

The process of transferring energy from food molecules to each living cell is called respiration. It is of two types i.e.,

(1) Aerobic respiration which requires oxygen.

(2) Anaerobic respiration which does not require oxygen.

(3) Aerobic respiration: In this process, glucose is broken down in the presence of oxygen to water and carbon dioxide. The energy that is liberated through this process is used to synthesize ATP, which transfers energy from chemical bonds to cells in the body.

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy

In Z-scheme, the movement of electrons is downhill in terms of an oxidation reduction or redox potential scale.

Fermentation is referred to as the decomposition of organic compounds, anaerobically by enzymes yielding alcohol, organic acids; gases etc... In fermentation the only energy extraction pathway is glycolysis pathway.

A is correct.

Aerobic respiration involves the complete oxidation of glucose to 6CO₂ + 6H₂O in the mitochondria, producing the largest amount of usable cellular energy as ATP - typically about 30-38 ATP per glucose molecule.

Fermentation, such as alcoholic fermentation by yeast, is a partial oxidation that yields only about 2 ATP per glucose and serves mainly to regenerate NAD+. Anaerobic glycolysis in muscle during a short sprint also gives about 2 ATP per glucose and produces lactic acid.

Microbial anaerobic transformations that produce methanol or other reduced products generate far less usable cellular ATP than complete aerobic oxidation and do not exceed the energy yield of aerobic respiration.

Therefore, A is the correct choice.

In rhodophyceae (red algae) food is stored in the form floridean starch. Whereas mannitol and laminarin are stored food material of class phaeophyceae (brown algae). In the diplontic life cycle, sporophyte represents the dominant phase.

Respiration is a catabolic and exergonic cellular process. Respiration, which is also known as cellular respiration, is an enzymatic process of biological oxidation of food materials in a living cell, using molecular O₂, producing CO₂, H₂O and releasing energy in small steps and then storing it in the form of ATP. When required, this ATP is utilised by the cell. Chemically it is a catabolic process and brings about the oxidation and decomposition of organic compounds like carbohydrate, fat, protein in the cells of plants and animals with the release of energy. But all the energy present in respiratory substrate is not released free into the cell.

The chemiosmotic theory postulated by the British biochemist Peter Mitchell (1920− 22) to explain the formation of ATP in the mitochondrial electron transport chain. As electrons are transferred along with the electron carrier system in the inner mitochondrial membrane, hydrogen ions (protons) are actively transported into the space between the inner and outer mitochondrial membranes, thus containing a higher concentration of protons than the matrix. This creates an electrochemical gradient across the inner membrane, through which protons move back into the matrix.

Pyruvic acid is the end product of glycolysis. This pyruvic acid forms acetyl CoA. Acetyl CoA is an initial compound of Kreb's cycle. Glycolysis is the first step in the process of respiration, in which one glucose molecule is broken down into two molecules of pyruvate. Under aerobic conditions, the two pyruvates undergo oxidative decarboxylation to form 2 molecules of acetyl CoA that enter the Krebs cycle.

Under anaerobic conditions, pyruvates are either converted to lactic acid or ethanol. During aerobic respiration, glucose in the cytosol is converted into two moles of Pyruvic acid (a three-carbon compound). This pyruvic acid cannot enter the TCA immediately in the mitochondria. The pyruvate must be transported inside the mitochondria via a special transporter.

The PA is decarboxylated oxidatively (the process is called oxidative decarboxylation) to produce one molecule (for each PA) of CO₂ and NADH, under the influence of the enzyme pyruvate dehydrogenase. The product combines with an S-containing molecule, called CoA or co-enzyme-A to form Acetyl CoA. Thus, Acetyl Co-A is the connecting link between glycolysis and Krebs cycle

In geometrical growth, both the progeny cells following mitotic cell division retain the ability to divide and continue to do so. However, with a limited supply of nutrients, the growth becomes slow which leads to the stationary stage. A sigmoid curve is the characteristic of organisms living in the natural environment.

Respiration is the metabolic process during which organic compounds, like glucose, break down into simpler substances and liberate carbon dioxide and ATP. The compounds like fats, proteins, carbohydrates, or organic acids are oxidized during the process.

The respiration rate increases with an increase in temperature from 0°C to 30°C. The rate of respiration doubles for every 10°C rise in temperature, thus the temperature coefficient (Q₁₀) for respiration is 2. At very high temperatures such as 50°C or more, the rate of respiration decreases due to enzymatic denaturation.

So, at the optimum temperature, the rate of respiration shows an initial increase for a short duration but later declines.