Fluid mosaic model of membrane structure was proposed by:

 # Fluid mosaic model of membrane structure was proposed by:

A. Watson and Crick

B. Edward H. Angle

C. G.V. Black

D. Singer and Nicolson

The correct answer is D. Singer and Nicolson.

The fluid mosaic model explains various observations regarding the structure of functional cell membranes. According to this biological model, there is a lipid bilayer (two molecules thick layer consisting primarily of amphipathic phospholipids) in which protein molecules are embedded. The phospholipid bilayer gives fluidity and elasticity to the membrane. Small amounts of carbohydrates are also found in the cell membrane. The biological model, which was devised by SJ Singer and G. L. Nicolson in 1972, describes the cell membrane as a two-dimensional liquid that restricts the lateral diffusion of membrane components. 

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Which of the following does not occur in mitochondria?

 # Which of the following does not occur in mitochondria?

A. TCA

B. HMP shunt

C. Urea cycle

D. Beta oxidation of fatty acids

The correct answer is B. HMP shunt.

HMP shunt or hexose monophosphate pathway or pentose phosphate pathway (PPP) or phosphogluconate pathway : for oxidation of glucose as an alternative pathway to glycolysis and TCA cycle. Enzymes for HMO shunt are located in cytosol/cytoplasm.

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Muller’s muscle is seen in:

 # Muller’s muscle is seen in:

A. Nose tip

B. Upper eye lid

C. Lower eye lid

D. Mid canthus

The correct answer is B. Upper eyelid.

Posterior to the levator aponeurosis is the underlying Muller's muscle complex- Orbitalis muscle or the circular fibres of the ciliary muscle, both of which are also known as Muller's muscle. 

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Why is morphine contraindicated in maxillofacial injury or head injury?

 # In patients with maxillofacial injury, narcotics like morphine are contraindicated because:

A. Morphine causes miosis

B. Morphine causes mydriasis

C. Morphine is respiratory irritant

D. Morphine is circulatory depressant

The correct answer is A. Morphine causes miosis.

Miosis masks the neurological signs of cerebral hemorrhage.

  Morphine is a phenanthrene derivative opioid analgesic. It is contraindicated in head injuries due to:

- Retention of carbondioxide leading to increased intracranial pressure

- exaggerated depression of respiration and the potential need to control ventillation of the patient must be considered

- vomitting, miosis (miosis will interrupt in monitoring the eye signs in case of probable head injury in the patients of maxillofacial injury), and altered mental state interfere with assessment of prognosis in patients with head injury

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‘Chicken-wire’ appearance of enlarged bone marrow spaces is seen in:

 # ‘Chicken-wire’ appearance of enlarged bone marrow spaces is seen in:

A. Fetal alcohol syndrome

B. Sickle cell anemia

C. Hemophilia A

D. Beta thalassemia major

The correct answer is D. Beta thalassemia major.

Radiographic changes of thalassemia include generalized rarefaction of alveolar bone, chicken-wire appearance of enlarged marrow spaces and coarse trabeculation. In the skull, proliferation of marrow may completely erode the cortex, leaving only periosteum, and produce a ‘hair-on-end’ radiographic appearance.

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Enamel can act in a sense like a:

# Enamel can act in a sense like a:

A. Permeable membrane

B. Impermeable membrane

C. Semipermeable membrane

D. Infrapermeable membrane

 

The correct answer is C. Semipermeable membrane.

Another physical property of enamel is its permeability. It has been found with radioactive tracers that the enamel can act in a sense like a semipermeable membrane, permitting complete or partial passage of certain molecules: 14C-labeled urea, I, etc. The same phenomenon has also been demonstrated by means of dyes.

Reference: Orban's

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All primary teeth would have begun to calcify by:

 # All primary teeth would have begun to calcify by:

A. 14 weeks of intrauterine life

B. 18-20 weeks of intrauterine life

C. 6 months of gestation

D. 6 months of age

The correct answer is B. 18-20 weeks of intrauterine life.

Calcification of the primary teeth begins in utero from 13 to 16 weeks postfertilization. By 18 to 20 weeks, all the primary teeth have begun to calcify. Primary tooth crown formation takes only about 2 to 3 years from initial calcification to root completion. However, mineralization of the permanent dentition is entirely postnatal, and the formation of each tooth takes about 8 to 12 years.

Reference: Wheeler's

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