Biochemistry Image Based Questions for NEET PG 2026

Q1. Analyse the structure of the mucopolysaccharide shown below: Which mucopolysaccharide is represented in this image?​

1. Heparan sulfate
2. Keratan sulfate
3. Chondroitin sulfate
4. Dermatan sulfate

Ans. 2) Keratan sulfate

Explanation:

The image depicts Keratan sulfate, identifiable by its unique composition of galactose and N-acetylglucosamine, along with possible sulfate groups. It is unique among glycosaminoglycans (GAGs) because it lacks uronic acid​. It is primarily found in the cornea and cartilage, contributing to their structural properties​.​

Q2. Identify the type of linkage in the given Structure.

1. ​O-linked glycoproteins
2. N- N-linked glycoproteins
3. GPI anchored Glycoproteins
4. None of the above

Answer: 1) O-linked Glycoproteins

Explanation:

O-linked glycoproteins (post-translation modification)	Carbohydrate chains are attached to the oxygen atom of serine or threonine residues. Mucins: Major components of mucus, providing lubrication and protection to epithelial surfaces. Glycoproteins in collagen
N-linked glycoproteins (Option 2)	Carbohydrate chains are attached to the nitrogen atom of asparagine residues. Immunoglobulins (IgG) & Erythropoietin
GPI anchored Glycoproteins (Option 3)	Carbohydrates are not attached to any amino acid Anchor consists of a lipid tail (phosphatidylinositol) and a glycan chain, which covalently links the protein to the membrane.

Also read: Gear Up for NEET PG 2025 with the 45-Day Challenge

Q3. Which type of isomerism is exhibited by these two compounds? ​

1. Functional Isomerism
2. Epimerism
3. Enantiomerism
4. Anomerism

​Answer: 1) Functional Isomerism

Explanation:

The given structures are that of Glucose and Fructose, which are examples of functional isomers. They have the same molecular formula but differ in their functional groups, with glucose being an aldehyde (aldohexose) and fructose being a ketone (ketohexose).

Q4. A 55-year-old female patient presents with symptoms of increased thirst, frequent urination, and weight loss. The physician suspects diabetes mellitus and decides to test the patient's urine for reducing sugars using Benedict's and Fehling's solutions. Below are images of the test results.

Image A: Benedict's Test Results ​

Image B: Fehling's Test Results​​ 

1. Based on the images provided, which of the following statements is correct?
2. ​Both tests indicate the presence of reducing sugars in the urine sample.
3. Benedict's test indicates the presence of reducing sugars, while Fehling's test indicates their absence.
4. Benedict's test indicates the absence of reducing sugars, while Fehling's test indicates their presence.

Answer: 2) Both tests indicate the presence of reducing sugars in the urine sample.

Explanation:

Image A (Benedict's Test Results):	The color changes from blue to green, yellow, and red, indicating the presence of reducing substances in the urine sample.
Image B (Fehling's Test Results)	The color changes from blue to brick-red, indicating the presence of reducing substances in the urine sample.

Q5. A child is diagnosed with essential fructosuria during a routine health check. Name the enzyme A responsible for this condition​

1. Aldolase B
2. Hexokinase
3. Fructokinase
4. Glucokinase

Answer: 3) Fructokinase

​​Explanation:

Essential fructosuria is a benign metabolic disorder caused by fructokinase deficiency. 

Fructose Metabolism :

Dietary Source	Found in fruits, honey, and high-fructose corn syrup
Structure	Ketohexose
Metabolism Site	Primarily metabolized by the liver
Fructose Metabolism :
1) Phosphorylation: Fructokinase is the primary enzyme for fructose phosphorylation. It has a high affinity (low Km) and a high Vmax for fructose. It converts fructose to fructose-1-phosphate using ATP. It is found in the liver, kidneys, and small intestine.
2) Fructose 1-Phosphate Cleavage: Aldolase B cleaves fructose 1-phosphate to dihydroxyacetone phosphate (DHAP) and glyceraldehyde. It is present in the liver, kidneys, and small intestine.  DHAP enters glycolysis or gluconeogenesis. Glyceraldehyde is metabolized through various pathways.
Disorders of Fructose Metabolism	1) Essential Fructosuria: Benign metabolic disorder Caused by fructokinase deficiency Excretion of fructose in urine Low risk of cataracts as aldose reductase does not act on fructose, and sorbitol dehydrogenase has low affinity for it. 2) Hereditary Fructose Intolerance (HFI): Caused by aldolase B deficiency. (Option A ruled out) Symptoms appear when infants consume sucrose or fructose. Effects are due to accumulation of fructose 1-phosphate. Symptoms: Vomiting, appetite loss, failure to thrive, hepatomegaly, jaundice, potential liver damage and death Diagnosis: Detection of fructose in urine, enzyme assay using liver cells or DNA-based testing. Treatment: Remove sucrose, sorbitol and fructose from the diet.

Also read: Image Based Questions in Anatomy for NEET PG

Q6. A newborn presents with bilateral lens opacities and decreased visual acuity. On examination, the characteristic "oil droplet" appearance is noted in the lens on retroillumination. Which metabolic disorder is primarily associated with developing oil-drop cataracts in newborns?​

1. ​Phenylketonuria
2. Galactosemia
3. Maple Syrup Urine Disease
4. Homocystinuria

Answer: 2) Galactosemia

​Explanation: Galactosemia is a genetic disorder that impairs the body's ability to metabolise galactose due to a defect in the enzyme galactose-1-phosphate uridyltransferase. This leads to the accumulation of galactitol, which causes osmotic stress and the characteristic “oil drop” cataracts.​

Q7. The image below shows the sites of action for different ETC inhibitors. Based on the image, which of the following is the site of action of Cyanide?

1. ​A
2. E
3. C
4. D

​Answer: 4) D

​Explanation: Cyanide is a strong inhibitor of Complex IV (cytochrome c oxidase). It blocks electron transfer to oxygen, disrupting the electron transport chain and reducing ATP production, potentially causing cellular damage.  

Q8. A 6-month-old infant has developmental delay, muscle weakness, and on eye examination, a cherry-red spot on the macula is noted. What is the most likely diagnosis, and which enzyme deficiency is responsible?​

1. ​Niemann-Pick disease, Sphingomyelinase
2. Gaucher disease, Glucocerebrosidase
3. Tay-Sachs disease, Hexosaminidase A
4. Sandhoff disease, Beta-galactosidase

Answer: 3) Tay-Sachs disease, Hexosaminidase A

Explanation:

In this scenario, the clinical features and fundoscopic image show cherry red spot in the macula are consistent with the diagnosis of Tay-Sachs disease. It is an inborn error of metabolism due to the failure of degradation of gangliosides, which is caused by a deficiency in the enzyme hexosaminidase A.

Also read: Pathology Important Topics for NEET PG

Q9. A patient presents with bone pain, fatigue and hepatosplenomegaly. Blood tests reveal anemia and thrombocytopenia. Bone marrow biopsy shows macrophages with a characteristic "wrinkled paper" appearance. Which substrate accumulates in Gaucher's disease due to the deficient enzyme activity?​

1. ​Sphingomyelin
2. Glucosylceramide
3. Ganglioside
4. Ceramide

Answer: 2) Glucosylceramide

Explanation:

Gaucher's disease is characterized by the accumulation of glucosylceramide in RBCs and platelet membranes due to a deficiency in the enzyme beta-glucosidase, leading to anemia, hepatosplenomegaly, and thrombocytopenia. Bone marrow biopsy shows macrophages with a characteristic "wrinkled paper" appearance.

Q10. A 9-year-old boy presents with episodic pain in his extremities, skin finding as shown in the image, and progressive renal dysfunction. A biopsy of the skin reveals the accumulation of ceramide trihexoside. An α-galactosidase deficiency is suspected. What is the diagnosis?

1. Tay-Sachs disease
2. Fabry disease
3. Krabbe disease
4. Gaucher disease

Answer: 2) Fabry disease

Explanation: Fabry disease is due to a deficiency of α-galactosidase, leading to the accumulation of ceramide trihexoside, resulting in symptoms such as episodic pain, angiokeratomas (as shown in the image), and renal dysfunction. 

Q11. What type of bond is primarily responsible for stabilising the structure in proteins as shown in the image?​

1. Covalent bonds between side chains
2. Ionic bonds between charged amino acids
3. ​Hydrogen bonds between backbone atoms
4. Disulfide bridges between cysteine residues

Answer: 3) Hydrogen bonds between backbone atoms

Explanation:

• The alpha-helix is stabilized primarily by hydrogen bonds between the carbonyl oxygen (C=O) of one amino acid and the amide hydrogen (N-H) of another amino acid, located four residues ahead in the chain.
• This forms a regular helical structure with 3.6 amino acids per turn.

Also read: Important Topics in Biochemistry for NEET-PG

Q12. Based on the image given below, what are the sites at which the marked steps of creatinine synthesis occur?​

1. a- brain, b- liver, c- kidney
2. a- kidney, b- liver, c- muscle
3. a- liver, b- kidney, c- muscle
4. a- muscle, b- liver, c-kidney

Answer: 2) a- kidney, b- liver, c- muscle

Explanation:

Creatinine synthesis requires the enzyme creatine kinase which is found in the liver, kidney and muscle.

Q13. Which of the following is true about the significance of technology in the following image?​ 

1. ​Used to study multiple gene expressions simultaneously
2. Not used to deciding the course of treatment
3. They have been completely replaced by next-generation sequencing.
4. Not used in proteomics and genotyping.

Answer: 1) Used to study multiple gene expressions simultaneously

Explanation:

The given image represents microarray technique, which can analyze thousands of genes at once facilitating multiple gene expression studies.

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