Free NEET Biology Questions and Answers — Questions and Answers

Question 1: The carbon dioxide produced during cellular respiration is

taken out (Correct answer)
absorbed
consumed
stored

Correct answer: taken out

During cellular respiration, glucose is oxidized to produce energy (ATP), and carbon dioxide (CO2) is generated as a metabolic waste product. This CO2 is transported by the blood to the lungs, where it is subsequently expelled from the body through the process of exhalation. Therefore, the carbon dioxide produced is taken out.

Question 2: Which process produces oxidative phosphorylation?

NADH in respiration
NADPH in photosynthesis
ATP in photosynthesis
ATP in respiration (Correct answer)

Correct answer: ATP in respiration

Oxidative phosphorylation is the metabolic pathway that generates the vast majority of ATP during aerobic respiration. This process occurs in the mitochondria, where energy released from the electron transport chain is used to power the synthesis of ATP from ADP and inorganic phosphate. It is the most efficient method of ATP production in cells.

Question 3: What is glycolysis' final result?

Pyruvic acid (Correct answer)
Fructose I – phosphate
Glucose I – phosphate
Acetyl CoA

Correct answer: Pyruvic acid

Glycolysis is the initial metabolic pathway in cellular respiration, occurring in the cytoplasm. During this process, one molecule of glucose, a six-carbon sugar, is broken down into two molecules of pyruvic acid, a three-carbon compound. Therefore, pyruvic acid is the final result of glycolysis.

Question 4: The connection between the Krebs cycle and glycolysis is modified before pyruvate enters the cycle to

Oxaloacetate
PEP
Acetyl CoA (Correct answer)
Pyruvate

Correct answer: Acetyl CoA

Before pyruvate, the end product of glycolysis, can enter the Krebs cycle (also known as the citric acid cycle), it undergoes an intermediate step called pyruvate oxidation. In this step, pyruvate is converted into Acetyl CoA, a two-carbon molecule that then condenses with oxaloacetate to begin the Krebs cycle. Acetyl CoA thus serves as the crucial link between glycolysis and the Krebs cycle.

Question 5: NADP+ conversion to NADPH is reduced in

Calvin cycle (Correct answer)
HMP

Correct answer: Calvin cycle

The Calvin cycle is the set of light-independent reactions in photosynthesis where carbon dioxide is fixed and converted into glucose. This process requires reducing power, which is supplied by NADPH. Specifically, NADPH is utilized to reduce 3-phosphoglycerate to glyceraldehyde-3-phosphate, providing the electrons necessary for carbohydrate synthesis within the cycle.

Question 6: Select the false statement about the Krebs cycle.

during the conversion of succinyl Co-A to succinic acid, synthesis of a molecule of GTP occurs
cycle starts with condensation of acetyl group with pyruvic acid to produce citric acid (Correct answer)
the cycle has three points where reduction of NAD+ to NADH + H+ occurs
at a point, reduction of FAD+ to FADH2. occurs

Correct answer: cycle starts with condensation of acetyl group with pyruvic acid to produce citric acid

The Krebs cycle begins with the condensation of a two-carbon acetyl group from Acetyl CoA with a four-carbon oxaloacetate molecule to form a six-carbon citric acid. The statement incorrectly claims the cycle starts with pyruvic acid; pyruvic acid is first converted to Acetyl CoA in an intermediate step before entering the cycle. Therefore, this statement is false.

Question 7: For every glucose molecule that enters the cell, 38 ATP molecules are used to store ________ of energy.

277 Kcal
654 Kcal
456 Kcal
686 Kcal (Correct answer)

Correct answer: 686 Kcal

The complete oxidation of one mole of glucose during cellular respiration releases a total of approximately 686 Kcal of energy. While not all of this energy is captured in the form of ATP, the formation of 38 ATP molecules represents the cell's efficient mechanism for storing a significant portion of this released energy for various cellular activities.

Question 8: Which of these is the ultimate respiratory substrate and produces the most ATP molecules?

Ketogenic amino acid
Glycogen
Glucose (Correct answer)

Correct answer: Glucose

Glucose is considered the ultimate and most common respiratory substrate for cellular respiration in most organisms. It is efficiently broken down through glycolysis, the Krebs cycle, and oxidative phosphorylation to produce the largest number of ATP molecules compared to other substrates. This makes it the primary and most efficient energy source for cells.

Question 9: In cellular respiration, the CH bond of food is broken down by

catalysis
oxidation (Correct answer)
reduction
metabolism

Correct answer: oxidation

Cellular respiration is fundamentally an oxidative process where the energy stored in the C-H bonds of food molecules, such as glucose, is released. During this process, electrons are progressively removed from glucose through a series of oxidation reactions and transferred to electron carriers, ultimately leading to the synthesis of ATP. The breaking of C-H bonds and removal of electrons define this oxidation.

Question 10: The incomplete oxidation of glucose into pyruvic acid, which involves numerous intermediate processes, is known as .

HMS-pathway
Glycolysis (Correct answer)
TCA-pathway
Krebs cycle

Correct answer: Glycolysis

Glycolysis is the metabolic pathway that initiates cellular respiration by breaking down one molecule of glucose (a six-carbon sugar) into two molecules of pyruvic acid (a three-carbon compound). This process involves a series of ten enzyme-catalyzed reactions and represents the incomplete oxidation of glucose, occurring in the cytoplasm without the need for oxygen.

Question 11: This trait of a hormone prevents it from exerting its full action in the absence of another hormone.

synergism
permissiveness (Correct answer)
antagonism
self-assertive

Correct answer: permissiveness

Permissiveness describes a hormonal interaction where one hormone cannot exert its full biological effects without the prior or concurrent presence of another hormone. For instance, thyroid hormone is permissive to the actions of epinephrine, enhancing its ability to stimulate fat breakdown, even though thyroid hormone itself doesn't directly cause significant fat breakdown.

Question 12: Where is the "hormone response element" located on the cell?

DNA (Correct answer)
membrane
enzymes
RNA

Correct answer: DNA

Hormone response elements (HREs) are specific DNA sequences located in the promoter regions of target genes. Intracellular hormone receptors, typically activated by lipid-soluble hormones like steroids or thyroid hormones, bind to these HREs. This binding then directly regulates the transcription of the associated gene, either activating or repressing its expression.

Question 13: This organ is neuroendocrine.

pituitary
pancreas
hypothalamus (Correct answer)
adrenal cortex

Correct answer: hypothalamus

The hypothalamus is a critical neuroendocrine organ because it serves as the primary link between the nervous and endocrine systems. It receives neural signals and, in response, produces and secretes various releasing and inhibiting hormones that control the secretion of hormones from the anterior pituitary gland. It also produces ADH and oxytocin, which are stored and released by the posterior pituitary.

Question 14: Which of these does the hormone classification by their chemical makeup not include?

protein based hormones
glucose containing hormones (Correct answer)
amino-acid based hormones
steroid hormones

Correct answer: glucose containing hormones

Hormones are chemically classified into major groups based on their structure, including steroid hormones (derived from cholesterol), amino acid-derived hormones (like catecholamines and thyroid hormones), and peptide/protein hormones (chains of amino acids). 'Glucose containing hormones' is not a recognized chemical classification for hormones.

Question 15: The responsibility for new messenger RNA transcription is taken up by .

catecholamines
pituitary gland hormones
pancreatic hormones
steroid hormones (Correct answer)

Correct answer: steroid hormones

Steroid hormones are lipid-soluble and can readily diffuse across the cell membrane to bind with specific intracellular receptors. The hormone-receptor complex then translocates to the nucleus, where it binds to specific DNA sequences (hormone response elements). This binding directly regulates gene expression by initiating or repressing the transcription of new messenger RNA (mRNA), thereby altering protein synthesis within the cell.

Question 16: The release of the sympathetic nerve impulses

estrogen
insulin
epinephrine (Correct answer)
aldosterone

Correct answer: epinephrine

Sympathetic nerve impulses are part of the 'fight or flight' response, which prepares the body for immediate action. This response involves the release of hormones from the adrenal medulla, primarily epinephrine (also known as adrenaline) and norepinephrine. These hormones increase heart rate, blood pressure, and glucose levels to mobilize energy and enhance alertness.

Free NEET Biology Questions and Answers

The carbon dioxide produced during cellular respiration is