Head And Neck- Biochemistry

Head and Neck

Head and Neck -Biochemistry

Compiled Topical Questions of Head and Neck – Biochemistry

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In the dark, you need to rewind the movie reel —
But not by just playing it backward. You need a special twist to bring the light-sensing molecule back to its original frame.

1 / 25

Category: Head and Neck – Biochemistry

Tags: 2024

Which enzyme is responsible for converting all-trans retinal back to 11-cis retinal in the visual cycle?

Retinal oxidase

Retinal kinase

Retinal reductase

Retinal dehydrogenase

Retinal isomerase

Keratomalacia is not an early sign of vitamin A deficiency. It’s a destructive, advanced stage that affects the integrity of the cornea. Which option reflects structural damage and loss of transparency, not just early symptoms?

2 / 25

Category: Head and Neck – Biochemistry

Tags: 2021

In the case of vitamin A deficiency, keratomalacia occurs. Which of the following characterizes this condition?

Dryness of conjunctiva and cornea

Patient cannot see in low light or in near dark condition

Unable to see in light or dark condition

Localized thickening of conjunctiva

Dryness and clouding of cornea

The moment light hits rhodopsin, a chain reaction begins, producing intermediate unstable forms until the active signaling molecule is formed. Which one leads to activation of transducin and kicks off the visual signal?

3 / 25

Category: Head and Neck – Biochemistry

Tags: 2020

Which of the following is the correct change in the photochemical process occurring due to absorption of light by rhodopsin?

Metarhodopsin to bathorhodopsin

Lumirhodopsin to metarhodopsin

Lumirhodopsin to bathorhodopsin

Bathorhodopsin to rhodopsin

All-trans retinol to all-trans retinal

Think of rhodopsin like a loaded mousetrap—ready to spring when hit by light. It’s the light-sensitive form of vitamin A that binds to scotopsin. Which form is perfectly shaped to activate the visual cycle before light hits?

4 / 25

Category: Head and Neck – Biochemistry

Tags: 2020

What substance combines with scotopsin to form rhodopsin?

11-cis retinal

All-trans retinol

13-cis retinol

All-trans retinal

11-cis retinol

Vitamin A helps maintain the health of surface tissues and photoreceptors. What happens when those tissues lose their protective, nourishing support? Think beyond just vision—what happens to the structure of the eye itself?

5 / 25

Category: Head and Neck – Biochemistry

Tags: 2020

In the case of vitamin A deficiency, keratomalacia occurs. Which of the following characterizes this condition?

Localized thickening of conjunctiva

Dryness and clouding of cornea

Unable to see in light or dark condition

Patient cannot see in low light or in near dark condition

Dryness of conjunctiva and cornea

Think about the nutrient essential for both the health of epithelial cells and the photoreceptors in your eyes—its deficiency dries out surfaces that should stay moist and can lead to serious vision complications.

6 / 25

Category: Head and Neck – Biochemistry

Tags: 2023

What disease is caused by the deficiency of vitamin A?

Xeropthalmia

Strabismus

Pernicious anemia

Amblyopia

Glaucoma

Think about the form of vitamin A that changes shape when light hits it—this molecular twist sets off the chain reaction that allows you to see. Which form has a structure suited for light-triggered isomerization?

7 / 25

Category: Head and Neck – Biochemistry

Tags: 2023

Which biochemical form of vitamin A is found in the visual cycle?

Retinol

Retinone

Retinyl ester

Retinaldehyde

Retinoic acid

Think about the specialized molecule in the eye that acts like a trigger for vision—it’s not just present in the eye but is biochemically activated when struck by photons, setting off the cascade that lets you “see.”

8 / 25

Category: Head and Neck – Biochemistry

Tags: 2023

Which protein is responsible for absorbing light in the retina and for vision?

Rhodopsin

Keratin

Fibrin

Collagen

Melanin

One component gives the protein its shape, the other its sight. Ask yourself: What combination of structure and sensitivity allows rods to detect even a whisper of light?

9 / 25

Category: Head and Neck – Biochemistry

Tags: 2022

Rhodopsin is a conjugated protein present in the rods of the retina. What is its composition?

Keratin and 11-cis-retinal

Opsin and 11-cis-retinal

Crystalline and 11-cis-retinal

Crystalline and retinoic acid

Opsin and retinoic acid

Option	Why It’s Incorrect
Opsin and retinoic acid	Retinoic acid is involved in gene transcription, not in phototransduction
Keratin and 11-cis-retinal	Keratin is a structural protein, not found in photoreceptors
Crystalline and retinoic acid	Crystalline is in the lens, not part of photopigments
Crystalline and 11-cis-retinal	Again, crystalline is lens-related, not found in rods

When considering reversibility, focus on redox reactions involving alcohols and aldehydes. Ask yourself: which transformations involve oxidation, and which can go both ways with minimal biochemical effort?

10 / 25

Category: Head and Neck – Biochemistry

Tags: 2020

Which of the following forms are most easily interconvertible?

Retinol and retinoic acid

Retinol and retinyl esters

Retinal and retinoic acid

Retinal and retinol

Retinoic acid and beta-carotene

When light dims and dryness takes over the eyes, think of the nutrient that’s not just about vision but about keeping barriers hydrated and protective.

11 / 25

Category: Head and Neck – Biochemistry

Tags: 2021

Which of the following diseases is caused by the deficiency of vitamin A?

Exophthalmos

Hemorrhage

Xerophthalmia

Megaloblastic anemia

Hair loss

“Which form of vitamin A is chemically altered when light strikes the photoreceptors in the retina, leading to the signal that allows you to see?”

12 / 25

Category: Head and Neck – Biochemistry

Tags: 2021

Which of the following is an active metabolite of vitamin A present in the eye?

Retinoic acid

Retinol

Carotenoid

Retinal

Beta carotene

Which vitamin is crucial for gene expression and differentiation of cells, especially in embryonic development?

13 / 25

Category: Head and Neck – Biochemistry

Tags: 2019

All trans-retinoic acid and 9-cis-retinoic acids are responsible for which of the following?

Iron metabolism

Growth hormones

Growth and cellular differentiation

Cholesterol synthesis

Bone development

This visual pigment helps you see in the dark and undergoes a crucial transformation when exposed to light.

14 / 25

Category: Head and Neck – Biochemistry

Tags: 2019

What is the composition of rhodopsin?

scotopsin + 11-cis-retinal

iodopsin + 11-cis-retinal

scotopsin + 11-trans-retinal

iodopsin + 11-trans-retinal

opsin + 11-cis-retinal

This vitamin is crucial for maintaining healthy eyesight and is stored in the liver before being converted into its active forms.

15 / 25

Category: Head and Neck – Biochemistry

Tags: 2019

11-cis-retinal is derived from which vitamin?

Vitamin B9

Vitamin A

Vitamin C

Vitamin K

Vitamin B12

This functional group is commonly found in compounds that can interact with water and can be oxidized into other biologically active forms.

16 / 25

Category: Head and Neck – Biochemistry

Tags: 2019

Retinol falls under which of the following functional groups?

Alcohols

Ketones

Esters

Aldehydes

Ethers

Think about what happens when light is absorbed by rhodopsin—what form does retinal change into, and what needs to happen to restore its functional state?

17 / 25

Category: Head and Neck – Biochemistry

Tags: 2019

What is the first step in the resynthesis of rhodopsin?

All cis retinal conversion to 11-trans retinal

All trans retinol conversion to 11-cis retinol

All trans retinal conversion to 11-cis retinal

All trans retinal conversion to 10-cis retinal

All cis retinol conversion to 11-trans retinol

“Rhodopsin is formed by opsin + a specific retinal form that is bent in darkness but straightens in light—what is it?”

18 / 25

Category: Head and Neck – Biochemistry

Tags: 2018

What substance combines with scotopsin to form rhodopsin?

13-cis retinol

11-cis retinal

All-trans retinol

11-cis retinol

All-trans retinal

Consider an enzyme that facilitates the oxidation of retinol to its active aldehyde form, with the help of a common coenzyme found in many metabolic processes

19 / 25

Category: Head and Neck – Biochemistry

Tags: 2017

Which of the following enzymes is involved in the conversion of retinol to retinal?

Retinol isomerase

Retinol translocase

Retinol synthase

Retinol oxidase

Retinol dehydrogenase in presence of NAD

Think about the process in which the visual pigment is replenished in the retina after it has been exposed to light.

20 / 25

Category: Head and Neck – Biochemistry

Tags: 2017

Vitamin A is involved in which of the following process?

Breakdown of rhodopsin

Resynthesis of rhodopsin

Synthesis of rhodopsin

None of them

Storage of iodopsin

Focus on what structures vitamin A maintains on the surface of the eye, and consider how epithelial changes might manifest when that support is lost.

21 / 25

Category: Head and Neck – Biochemistry

Tags: 2020

The deficiency of vitamin A causes a pathological condition called xerophthalmia. Which of the following correctly describes it?

Dryness of cornea along with cloudy appearance

Poor vision in dim light

Poor vision at night

Dryness of the cornea and conjuctiva

Thickening of a part of cornea

This molecular combo is like the light switch of your visual world — flip it with a photon, and it launches a cascade that lets your brain form images. So what do we call this photoreceptor-bound duo?

22 / 25

Category: Head and Neck – Biochemistry

Tags: 2021

11-cis retinal bound to a specific protein is classified as which of the following?

None of these

Intermediates

Photo-transducer

Retinoid acid binding protein

Visual pigment

“Think about which form of vitamin A is directly absorbable into the intestinal lymphatics and what must be removed from the ester before absorption.”

23 / 25

Category: Head and Neck – Biochemistry

Tags: 2021

Which of the following are the end products of hydrolysis of retinyl esters in intestinal mucosa?

Retinal and free fatty acids

Retinoic acid and free fatty acids

Retinol and free fatty acids

Retinoic acid and retinol

Retinal and retinol

Consider the condition that leads to reduced tear production and dryness in the eyes, which is caused by a vitamin deficiency affecting the tissues that line the eye.

24 / 25

Category: Head and Neck – Biochemistry

Tags: 2019

The deficiency of vitamin A causes a pathological condition called xerophthalmia. Which of the following correctly describes it?

Dryness of the cornea and conjuctiva

Poor vision in dim light

Thickening of a part of cornea

Poor vision at night

Dryness of cornea along with cloudy appearance

“What vitamin is essential for maintaining a smooth, transparent corneal surface?”

25 / 25

Category: Head and Neck – Biochemistry

Tags: 2018

What can cause xeropthalmia?

Corneal infection

Pleomorphic adenoma

Keratinization of cornea

Decreased keratinization of skin

Conjunctival inflammation

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Head And Neck- Biochemistry

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🔁 Visual Cycle Summary:

❌ Why the Other Options Are Incorrect:

❌ Why the Other Options Are Incorrect:

❌ Why the Other Options Are Incorrect:

11-cis Retinal is Correct:

❌ Why the Others Are Incorrect:

❌ Why the Other Options Are Incorrect:

🔍 What is Xerophthalmia?

How is vitamin A involved?

❌ Why the Other Options Are Incorrect:

✅ Correct Answer: Retinaldehyde

🔍 What is the Visual Cycle?

→ 11-cis-retinal (a form of retinaldehyde)

❌ Why the Other Options Are Incorrect:

✅ Correct Answer: Rhodopsin

🔍 What is Rhodopsin?

❌ Why the Other Options Are Incorrect:

🔬 Composition of Rhodopsin:

❌ Why the Other Options Are Wrong:

🔄 Interconversion:

❌ Why the Other Options Are Incorrect:

✅ Why Xerophthalmia is Correct:

❌ Why the Other Options Are Incorrect:

❌ Megaloblastic anemia

❌ Exophthalmos

❌ Hair loss

❌ Hemorrhage

1️⃣ Retinal:

2️⃣ Beta carotene:

3️⃣ Carotenoid:

4️⃣ Retinoic acid:

5️⃣ Retinol:

📝 Key takeaway:

Why the Other Options Are Incorrect:

❌ Why the Other Options Are Incorrect:

❌ Let’s examine the incorrect options:

✅ Correct Answer: Retinol and free fatty acids

🔍 What are retinyl esters?

🧪 Enzymatic hydrolysis:

🧐 Why other options are incorrect:

📝 Key takeaway:

Pathophysiology of Xerophthalmia:

Why the Other Options Are Incorrect: