Most Repeated MDCAT Biology: Bioenergetics MCQs

Explanation

Glycolysis, the first stage of cellular respiration, occurs in the cytoplasm of the cell. It is a series of biochemical reactions that break down one molecule of glucose into two molecules of pyruvate. Unlike the subsequent stages of cellular respiration (such as the citric acid cycle and oxidative phosphorylation), glycolysis does not take place in the mitochondria. Instead, it occurs in the cytoplasm, which is the gel-like substance that fills the cell and surrounds the cellular organelles.

Explanation

The process by which one molecule of glucose splits up into molecules of pyruvate is called glycolysis. Glycolysis is the first stage of cellular respiration, which occurs in the cytoplasm of the cell. During glycolysis, a molecule of glucose, a six-carbon sugar, is broken down into two molecules of pyruvate, each containing three carbon atoms.

Explanation

The end product of glycolysis is pyruvate. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, yielding a net gain of two molecules of ATP and two molecules of NADH. Pyruvate can then enter the mitochondria to be further processed in the citric acid cycle if oxygen is present, or it can undergo fermentation under anaerobic conditions. The incorrect options listed are intermediates in the glycolytic pathway, not final products.

Explanation

The main process that occurs in the dark reaction (also known as the Calvin Cycle) in photosynthesis is the synthesis of glucose. The dark reaction takes place in the stroma of chloroplasts and does not directly require light. It follows the light-dependent reactions (such as photosystem I and II) that capture and convert light energy into chemical energy in the form of ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate). In the Calvin Cycle, the primary goal is to use the ATP and NADPH produced during the light-dependent reactions to convert carbon dioxide (CO2) into glucose.

Explanation

The correct answer is the thylakoid membrane of the chloroplast. The light-dependent reactions of photosynthesis occur in these membranes, where chlorophyll absorbs light energy. This energy is then converted into chemical energy in the form of ATP and NADPH, which are essential for the subsequent light-independent reactions (Calvin cycle) in the stroma.

Explanation

The correct answer is Glycolysis. Glycolysis is a sequence of enzymatic reactions that occurs in the cytoplasm of cells, where one molecule of glucose is broken down into two molecules of pyruvic acid. This process also results in the net gain of two ATP molecules and two NADH molecules. The other options describe different stages or processes in cellular respiration or photosynthesis that do not produce pyruvic acid as an end product. The Krebs cycle further processes pyruvate, anaerobic respiration can use pyruvate but does not produce it as an end product, the electron transport chain is involved in ATP production, and photosynthesis is unrelated to pyruvate production.

Explanation

During steps 3, 4, and 8 of Krebs' cycle, 3 molecules of NADH + H+ are produced by oxidative decarboxylation of isocitrate, alpha-ketoglutarate, and malate, respectively. These NADH + H+ molecules are converted into ATP molecules by oxidative phosphorylation. Hence this option is correct.

Explanation

Ribulose bisphosphate (RuBP) is generally referred to as CO2 acceptor because it is capable of combining with carbon dioxide with the help of Ribulose bisphosphate (RuBP) carboxylase/oxygenase also known as RuBisCO.

Explanation

During anaerobic respiration, the pyruvic acid molecules are converted either to lactic acid or ethanol with the release of a very small amount of energy, i.e., just 2 ATPs.

Explanation

This is the correct answer. Glycolysis is the metabolic pathway that breaks down glucose into pyruvate, producing ATP (energy) in the process.It is the first stage of cellular respiration and can occur both in the presence (aerobic conditions) and absence (anaerobic conditions) of oxygen.

Explanation

A membrane-bound cytochrome f-b complex participates in both respiratory and photosynthetic elevtron transport.

Explanation

Carotenoids are a group of pigments that absorb light in the visible spectrum, specifically in the range of 430-470 nanometers (nm). This range corresponds to the orange to red region of the visible spectrum.

Explanation

In the non-cyclic electron transport of the light reaction, also known as the Z-scheme, the deficit of electrons occurs in the chlorophyll molecule (specifically, chlorophyll a) as it absorbs energy from light. This energy excites an electron, which is then transferred to a special molecule called an electron acceptor, leaving a deficit of two electrons in the chlorophyll molecule.

Explanation

Pyruvic acid has the molecular formula C3H4O3. It has 3 carbon atoms.you can remember it by keeping in mind the fact that one glucose molecule splits into two pyruvic acid molecules in glycolysis. As glucose has 6 C-atoms, each pyruvate should have 3 C-atoms.

Explanation

Hydrolysis of water, ATP generation, and production of reducing molecules are all part of the light-dependent phase of photosynthesis. Light independent phase involves the reaction of G3P to form energy-rich glucose so option A is correct.

Explanation

This happens because in mitochondria aerobic respiration occurs(breakdown of food in presence of oxygen)The food is glucose.Aerobic respiration:Glucose+O2=CO2 + ATPSo if the mitochondrial activity is reduced then glucose will not be used and will be excreted out through urine.

Explanation

Option C (II, I, and III) is correct because the conversion of surplus amino acids and glycerol to blood glucose and the mobilization of fat deposits (I) occurs after the breakdown of liver and muscle glycogen (II). Therefore, the correct order should be II, I and III.

Explanation

Respiration is the process by which cells generate energy from glucose and oxygen, and it is a continuous metabolic activity necessary for the plant's survival. While photosynthesis primarily occurs during the day when there is light available, respiration occurs 24/7 because plants need energy both for their daytime activities and to support basic functions like growth and maintenance during the night when there is no sunlight for photosynthesis. Therefore, plants respire both during the day and at night to maintain their life processes.

Explanation

The end products of anaerobic respiration depend on the specific type of anaerobic process involved. There are two main types of anaerobic respiration: lactic acid fermentation and alcoholic fermentation. In lactic acid fermentation, the end product is lactic acid.This process occurs in various microorganisms and in muscle cells during strenuous exercise when oxygen is not available in sufficient amounts to support aerobic respiration. The overall reaction is:Glucose → 2 Lactic Acid + Energy (in the form of ATP) In alcoholic fermentation, the end products are ethanol and carbon dioxide.

Explanation

In Anaerobic respiration only 2% of the energy present within the chemical bond of glucose is converted into ATP.