Channel Mediated Facilitated diffusion | Cellular Transport : Click Here
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]]>Check out about the Structure and Function of Plasma Membrane in below mention lecture
Other proteins can act as signal receptors or adhesion molecules Cholesterol molecules are weakly amphipathic and are interspersed among the other lipids in both layers of the membrane. The tiny —OH group is the only polar region of cholesterol, and it forms hydrogen bonds with the polar heads of phospholipids and glycolipids. The stiff steroid rings and hydrocarbon tail of cholesterol are nonpolar; they fit among the fatty acid tails of the phospholipids and glycolipids.
The carbohydrate groups of glycolipids form a polar “head”; their fatty acid “tails” are nonpolar. Glycolipids appear only in the membrane layer that faces the extracellular fluid, which is one reason the two sides of the bilayer are asymmetric, or different.
The Lipid Bilayer
The basic structural framework of the plasma membrane is the lipid bilayer, two back-to-back layers made up of three types of lipid molecules—phospholipids, cholesterol, and glycolipids. About 75% of the membrane lipids are phospholipids, lipids that contain phosphorus. Present in smaller amounts are cholesterol (about 20%), a steroid with an attached !OH (hydroxyl) group, and various glycolipids (about
5%), lipids with attached carbohydrate groups.
Image credit from www.pw.live , for educational purpose only.
The bilayer arrangement occurs because the lipids are amphipathic molecules, which means that they have both polar and nonpolar parts. In phospholipids, the polar part is the phosphate containing “head,” which is hydrophilic. The nonpolar parts are the two long fatty acid “tails,” which are hydrophobic hydrocarbon chains. Because “like seeks like,” the phospholipid molecules orient themselves in the bilayer with their hydrophilic heads facing outward. In this way, the heads face a watery fluid on either side—cytosol on the inside and extracellular fluid on the outside. The hydrophobic fatty acid tails in each half of the bilayer point toward one another, forming a nonpolar, hydrophobic region in the membrane’s interior.
Find below more articles on transport across the cell membrane
Carrier Mediated Facilitated diffusion explained: Lecture and notes of Transport across the cell membrane : Click here
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]]>The post Top 5 Big Mistakes of Students for Exam Preparation, Competitive Exam Tips for UPSC, GPAT, SSC, GATE, NEET, IIT, CUET appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>1. Beginning the Revision Process Too Late
May exams are in May, so I should have plenty of time to prepare, right? Not at all! In order to be prepared when April finally sticks its terrible snout out, you must begin as early as November. By the time the examinations begin in two weeks, do you think you will have enough money saved up to have many chapters set aside? They come more quickly than you might think, which makes pupils resort to drastic means like missing entire chapters or subjects.
2. Ignoring a section or topic
Each year, a few students believe they have figured out what will and won’t be tested. They fall short every year. You have no idea whether or not a particular chapter will be skipped. Therefore, omitting a lesson is the last thing you should do. The only time you will be certain of the subjects the teachers selected is when the exam paper is in front of you.
3. Allowing previous outcomes to impair your judgement
By motivating oneself, you can get into the proper frame of mind for studying and achieve achievement. Positive affirmations are an effective technique for developing strong confidence and self-belief. A few instances of exam affirmations are:
I work hard, I’m capable, intelligent, and exam-ready.
I’ll ace this test and then accomplish my objectives.
4. Allowing anything to divert your attention
Even though it appears simple, most individuals fail to do it. Your phone must be on “Do not Disturb” mode. Fair enough, you need it to make research. While you’re doing it, though, you don’t really need to view message notifications, and others run the risk of distracting you from the original reason you opened your phone.
5.Not getting enough sleep the previous evening
In order to maximise your chances of passing an exam, you must get enough sleep. To function at your best, you must obtain the appropriate quantity of sleep. You can’t stay up late studying in the hopes of passing your exam the next day. Both neurologically and physiologically, it is not conceivable. Your brain need a lot of sleep in order to restore information. It organizes everything and stores it in the appropriate folder so you can access it at a later time during your downtime. Thus, it’s essential that you take a nap.
Get full lecture series of exam preparation Tips : Click Here
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]]>The post Thyroid Gland | Thyroid Hormone Synthesis | Steps of T3 and T4 synthesis | Endocrine System Notes for NEET, GPAT, UPSC, SSC, NET appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>The butterfly-shaped thyroid gland is located just inferior to the larynx (voice box). It is composed of right and left lateral lobes, one on either side of the trachea, that are connected by an isthmus anterior to the trachea . A small, pyramidal-shaped lobe sometimes extends upward from the isthmus. The normal mass of the thyroid is about 30 g (1 oz). It is highly vascularized and receives 80–120 mL of blood per minute.
Microscopic spherical sacs called thyroid follicles make up most of the thyroid gland. The wall of each follicle consists primarily of cells called follicular cells,
most of which extend to the lumen (internal space) of the follicle. A basement membrane surrounds each follicle.
When the follicular cells are inactive, their shape is low cuboidal to squamous, but under the influence of TSH they become active in secretion and range from cuboidal to low columnar in shape. The follicular cells produce two hormones: thyroxine , which is also called tetraiodothyronine or T4 because it contains four atoms of iodine, and triiodothyronine or T3, which contains three atoms of iodine.
T3 and T4 together are also known as thyroid hormones. A few cells called parafollicular cells or C cells lie between follicles. They produce the hormone calcitonin , which helps regulate calcium homeostasis.
Synthesis of Thyroid Hormone (T3 and T4)
The thyroid gland is the only endocrine gland that stores its secretory product in large quantities—normally about a 100-day supply. Synthesis and secretion of T3 and T4 occurs as follows
1. Iodide trapping: Thyroid follicular cells trap iodide ions (I-) by actively transporting them from the blood into the cytosol. As a result, the thyroid gland normally contains
most of the iodide in the body.
2 Synthesis of thyroglobulin: While the follicular cells are trapping I-, they are also synthesizing thyroglobulin (TGB), a large glycoprotein that is produced in the rough endoplasmic reticulum, modified in the Golgi complex, and packaged into secretory vesicles. The vesicles then undergo exocytosis, which releases TGB into the lumen of the follicle.
●3 Oxidation of iodide: Some of the amino acids in TGB are tyrosines that will become iodinated. However, negatively charged iodide ions cannot bind to tyrosine until
they undergo oxidation (removal of electrons) to iodine: I- to I2. As the iodide ions are being oxidized, they pass through the membrane into the lumen of the follicle.
●4 Iodination of tyrosine: As iodine molecules (I2) form, they react with tyrosines that are part of thyroglobulin molecules. Binding of one iodine atom yields monoiodotyrosine (T1), and a second iodination produces diiodotyrosine (T2). The TGB with attached iodine atoms, a sticky material that accumulates and is stored in the lumen of the thyroid follicle, is termed colloid.
●5 Coupling of T1 and T2: During the last step in the synthesis of thyroid hormone, two T2 molecules join to form T4 or one T1 and one T2 join to form T3.
●6 Pinocytosis and digestion of colloid: Droplets of colloid reenter follicular cells by pinocytosis and merge with lysosomes. Digestive enzymes in the lysosomes break down TGB, cleaving off molecules of T3 and T4.
●7 Secretion of thyroid hormones: Because T3 and T4 are lipid soluble, they diffuse through the plasma membrane into interstitial fluid and then into the blood. T4 normally is secreted in greater quantity than T3, but T3 is several times more potent. Moreover, after T4 enters a body cell, most of it is converted to T3 by removal of one iodine.
●8 Transport of T3 and T4 in the blood: More than 99% of both the T3 and the T4 combine with transport proteins in the blood, mainly thyroxine-binding globulin (TBG)
MCQ on Thyroid Hormone:
1. The main hormone secreted by the Thyroid gland
(a) T4
(b) T3
(c) (a) and (b) Both
(d) TSH
2. Which of the following is steps of synthesis of T3 and the T4
(a) Iodide trapping
(b) Synthesis of thyroglobulin
(c) Coupling of T1 and T2
(d) All
3. Which of the following hormone is involved in stimulation of Iodide trapping
(a) TRH
(b) TSH
(c) (a) and (b) Both
(d) None
4. Which of the following Transporter is involved in Iodide trapping
(a) Sodium Iodide Transporter
(b) Potassium Iodide Transporter
(c) Calcium Iodide Transporter
(d) None
5. Which of the following Transporter is involved putting iodide into lumen
(a) Pendrin
(b) Megalin
(c) Dendrin
(d) None
Correct Answer
1 -c
2 -d
3 -b
4 -a
5 -a
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]]>The post Physical Pharmacy Study Material, Notes and MCQ for NEET, GPAT, NIPER, Pharmacist, Drug Inspector, Paramedical Staff Recruitment appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>Here you can find free study material related to Physical Pharmacy.
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]]>The post Pharmaceutical Aerosols: General formulation and MCQs for GPAT, NIPER, Pharmacist and Drug Inspector exam appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>Solution aerosols – Topical aerosols consist of a solution of active ingredients in pure propellant or a mixture of propellant and solvents. The solvent is used to dissolve the active ingredients and/or retard the evaporation of the propellant. Solution aerosols are relatively easy to formulate, provided the ingredients are soluble in the propellant. However, the propellants are non-polar in nature and in most cases are poor solvents for some of the commonly used medicinal ingredients. Through use of a solvent that is miscible with the propellant, one can achieve varying degrees of solubility of the active ingredient. For topicals (isopropyl alcohol, isopropyl myristate, polyethylene glycols, etc.), ethyl alcohol has found the greatest use, although some other solvents may be of limited value. For those substances that are insoluble in the propellant or propellant/solvent system, a dispersion or suspension can be produced. In this case the drug must be micronized so that the particles are less than 10 micrometers in average diameter. Topical pharmaceutical solutions are formulated using the hydrocarbon propellants, butane, isobutene, and propane. Although butane and isobutene can be used individually, the hydrocarbons are generally used as a blend. Other non-MDIs are formulated as aqueous solutions (eye care, etc.) and utilize nitrogen as the propellant. These are packaged as a conventional aerosol or utilize a barrier system.
Dispersions (powder aerosols) – These aerosols are similar to solution aerosols except that the active ingredients are suspended or dispersed throughout the propellant or propellant and solvent phase. This system is useful with antibiotics, steroids, and other poorly soluble compounds. Problems associated with the formulation of this system include agglomeration, caking, particle size growth, and valve clogging. Some of these problems have been overcome through use of lubricants such as isopropyl myristate, sorbitan trioleate, oleic acid, or other substances that provide slippage between particles of the compound as well as lubricating component parts of the valve. Surfactants also have been used to disperse the particles. The use of dispersing agents such as sorbitan trioleate, oleic acid, or lecithin is useful in keeping the suspended particles from agglomerating. Thought also should be given to both the particle size and the moisture content of the powder. The moisture content should be kept between 100 and 300 ppm or less, depending upon the type of product, and the propellants and solvents must be dried by passing them through a drying agent. The particle size for metered-dose inhalants should remain in the micrometer range and should be between 2 and 8 micrometers or less, with a mass median diameter of between 3 and 6 micrometers.
Emulsions – An emulsion system is useful for a great variety of topical pharmaceutical products. Since these systems contain a relatively small amount of propellant (4 to 10 percent), there is little, if any, chilling effect. Active ingredients that may be irritating if inhaled can be used as a foam. Depending on the nature of the formulation and the manner in which the product is to be used, the foam is aqueous or nonaqueous and can be stable or quickbreaking.
Emulsions can be dispensed from an aerosol container as a spray, stable foam, or quick-breaking foam, depending on the type of valve used and the formulation. Two types of emulsions can be formulated for use in an aerosol. A W/O emulsion is one in which the water phase is dispersed throughout the oil phase; an O/W emulsion is one in which the water is the continuous phase. If the product concentrate is dispersed throughout a propellant, the system behaves similarly to a W/O emulsion. However, since the propellant is in the external phase, the product is dispersed as a wet stream rather than as a foam. When the propellant is in the internal phase (O/W), a foam will be produced. The consistency and stability of the foam can be modified by choice of surfactants and solvents used. Many water-based aerosols are of the W/O type, in which the propellant is in the external phase. Stable shave-cream foams, on the other hand, are produced by keeping the propellant in the internal phase.
The stable foam is similar to a shaving-cream formulation, into which therapeutically active ingredients are incorporated. The foam is dispensed and rubbed into the skin or affected area. By substituting glycols and glycol derivatives for the water in an emulsion, a nonaqueous foam is obtained. The foam stability can be varied by the choice of surfactant, solvent, and propellant. It has been suggested that these foams are applicable to ointment bases, rectal and vaginal medication, and burn preparations.
A quick-breaking foam allows convenient and efficient application of medication. In certain instances the product was dispensed as a foam that quickly collapsed. This was useful in covering large areas with no rubbing necessary to disperse the medication. These quick-breaking foams consist of alcohol, surfactant, water, and propellant.
Table 1 – Metered-dose Inhalants (solution and suspensions): prototype formulation
| Solution (CFC, HFC):
Active ingredient(s): solubilized antioxidants: ascorbic acid Solvent blends: water, ethanol, glycols Propellants: 12/11, 12/114 or 12 alone; 134a, 227, 134a/227 |
| Suspensions (CFC):
Active ingredient(s): micronized and suspended Dispersing agent(s): sorbitan trioleate, oleyl alcohol, oleic acid, lecithin, etc. Propellants: 12/11, 12/114, 12 or 12/114/11 suspensions(HFC) Active ingredient(s): micronized and suspended solvent:ethanol Dispersing agent(s): sorbitan trioleate, oleyl alcohol, oleic acid, lecithin, etc. Propellants: 134a, 227, 134a/227 Or Active ingredient(s): micronized and suspended propellants: 134a, 227, 134a/227 |
Formulation factors – Included among formulation factors are the physicochemical characteristics of the active ingredients, the particle size and shape of the drug, the type and concentration of surface-active agent used, and, to some extent, the vapor pressure and the metered volume of propellants. In terms of physicochemical properties, the lipoidal solubility and pulmonary absorption rates of the active ingredient are of utmost importance. Another physicochemical factor governing the biopharmaceutics of a drug is its dissolution characteristics in pulmonary fluids. Drugs having a rapid dissolution rate in pulmonary fluids predictably produce much more intense and rapid onset of action, having a shorter duration than their less soluble derivatives. Therapeutic agents that exhibit very poor solubility in pulmonary fluids are to be avoided since they are likely to serve as irritants and precipitate bronchial spasms. The selection of the appropriate surface-active agent (required in most pressurized inhalation suspension aerosols) is another important consideration, since the surfactant will influence droplet evaporation, particle size, and overall hydrophobicity of the particles reaching the respiratory passageways and pulmonary fluids. Solubility of these dispersing agents or surfactants is limited when formulating with an HFC propellant. Ethyl alcohol has been added to increase their solubility.
Multiple choice questions:
1.Topical pharmaceuticals may be formulated as aerosols using
a)emulsions
b)powders
c)semisolid
d)all of these
2.MDIs are formulated as
a)solutions
b)suspensions
c)powders
d)a and b
3.For topical aerosols which of the following solvents are used?
a)isopropyl alcohol
b)isopropyl myristate
c)polyethylene glycols
d)all of these
4.For those substances that are insoluble in the propellant or propellant/solvent system, a dispersion or suspension can be produced.
a)true
b)false
5.In this case the drug must be micronized so that the particles are ______ in average diameter.
a)<10 micrometer
b)>10 micrometer
c)= 10 micrometer
d)none of these
6.Topical pharmaceutical solutions are formulated using
a)butane
b)isobutene
c)propane
d)all of these
7.Dispersion aerosols are useful with
a)antibiotics
b)steroids
c)poorly soluble compounds
d)all of these
8.Problems associated with the formulation of dispersions include
a)agglomeration
b)caking
c)particle size growth
d)all of these
9.Which of the following lubricants is/are used in dispersion aerosols?
a)isopropyl myristate
b)sorbitan trioleate
c)oleic acid
d)all of these
10.The particle size for metered-dose inhalants should remain in the micrometer range and should be
a)2-8 micrometers
b)5-10 micrometers
c)10-15 micrometers
d)2-10 micrometers
11.An emulsion aerosol system contain what percent of propellant?
a)4-10%
b)10-12%
c)50%
d)95%
12. Active ingredients that may be irritating if inhaled can be used as
a)spray
b)foam
c)wet stream
d)all of these
13.Quick-breaking foams consist of
a)alcohol
b)surfactant
c)water
d)all of these
14.In Metered-dose Inhalants(solutions) solvent blends used is/are
a)water
b)ethanol
c)glycols
d)all of these
15.In Metered-dose Inhalants(Suspensions) solvent used is/are
a)water
b)ethanol
c)glycols
d)all of these
Solutions:
- d)all of these
- d)a and b
- d)all of these
- a)true
- a)<10 micrometer
- d)all of these
- d)all of these
- d)all of these
- d)all of these
- a)2-8 micrometers
- a)4-10%
- b)foam
- d)all of these
- d)all of these
- b)ethanol
References:
- Remington Essential of Pharmaceutics, 1st edition 2013, page no. 644-648.
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]]>The post Oogenesis Process, Phases of Oogenesis, Notes of Oogenesis for Class 12, BPharma, BSc, Nursing, Medical and Paramedical exams appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>Oogenesis Complete in three Phases
A. Multiplication Phase
B. Growth Phase
C. Maturation Phase
1. Primordial germ cell undergoes mitosis to produce Oogonia (occurs Pre-natally). Oogonia are diploid (2n) stem cells that divide mitotically to produce millions of germ cells. Even before birth, most of these germ cells degenerate in a process known as atresia.
2. A few oogonia, however, develop into larger cells called primary oocytes (2n).
3. Each Primary Oocyte starts to undergo meiosis I replicating their DNA, but they are arrested at the first Meiotic Prophase. During this arrested stage of development, each primary oocyte is surrounded by a single layer of flat follicular cells, and the entire structure is called a primordial follicle. The ovarian cortex surrounding the primordial follicles consists of collagen fibers and fibroblast-like stromal cells. At birth, approximately 200,000 to 2,000,000 primary oocytes remain in each ovary. Of these, about 40,000 are still present at puberty, and around 400 will mature and ovulate during a woman’s reproductive lifetime. The remainder of the primary oocytes undergo atresia.
4. Each month after puberty until menopause, gonadotropins (FSH and LH) secreted by the anterior pituitary further stimulate the development of several primordial follicles, although only one will typically reach the maturity needed for ovulation. A few primordial follicles start to grow, developing into primary follicles. Each primary follicle consists of a primary oocyte that is surrounded in a later stage of development by several layers of cuboidal and low columnar cells called granulosa cells. The outermost granulosa cells rest on a basement membrane. As the primary follicle grows, it forms a clear glycoprotein layer called the zona pellucida between the primary oocyte and the granulosa cells. In addition, stromal cells surrounding the basement membrane begin to form an organized layer called the theca folliculi.
5. With continuing maturation, a primary follicle develops into a secondary follicle. In a secondary follicle, the theca differentiates into two layers: (1) the theca interna, a highly vascularized internal layer of cuboidal secretory cells that secrete estrogens and (2) the theca externa, an outer layer of stromal cells and collagen fibers. In addition, the granulosa cells begin to secrete follicular fluid, which builds up in a cavity called the antrum in the center of the secondary follicle. The innermost layer of granulosa cells becomes firmly attached to the zona pellucida and is now called the corona radiate.
6. The secondary follicle eventually becomes larger, turning into a mature (graafian) follicle. While in this follicle, and just before ovulation, the diploid primary oocyte completes meiosis I, producing two haploid (n) cells of unequal size—each with 23 chromosomes. The smaller cell produced by meiosis I, called the first polar body, is essentially a packet of discarded nuclear material. The larger cell, known as the secondary oocyte, receives most of the cytoplasm. Once a secondary oocyte is formed, it begins meiosis II but then stops in metaphase.
7. The mature (graafian) follicle soon ruptures and releases its secondary oocyte, a process known as ovulation. At ovulation, the secondary oocyte is expelled into the pelvic cavity together with the first polar body and corona radiata. Normally these cells are swept into the uterine tube. If fertilization does not occur, the cells degenerate. If sperm are present in the uterine tube and one penetrates the secondary oocyte, however, meiosis II resumes. The secondary oocyte splits into two haploid cells, again of unequal size. The larger cell is the ovum, or mature egg; the smaller one is the second polar body. The nuclei of the sperm cell and the ovum then unite, forming a diploid zygote. If the first polar body undergoes another division to produce two polar bodies, then the primary oocyte ultimately gives rise to three haploid polar bodies, which all degenerate, and a single haploid ovum. Thus, one primary oocyte gives rise to a single gamete (an ovum).
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]]>The post Ball Mill Principle, Construction, Uses, Advantage, Disadvantage, and Question Answer for GPAT, GATE, Pharmacist, Drug Inspector & NIPER JEE Exam appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>The ball mill operates on the principle of impact and attrition. In this, impact occurs between fast moving balls and the powder material while the attrition mode comes in action when the hollow cylinder rotates on its longitudinal axis. All is occurs at low speed and the balls roll over each other.
Construction
Ball mill consist of a hollow cylinder mounted/fitted on a metallic frame and rotates around its longitudinal axis. The cylinder is made up of metal and lined with chrome but in most of the pharmaceutical industries, cylinder is lined with rubber and porcelain. The balls occupy about 30-50% of mill volume. These balls are made of steel, iron or stoneware. They act as grinding medium and their weight is kept constant.
Working
- The feed material is introduced in the cylinder in such a quantity that it occupies 60% of the volume of cylinder.
- A fixed no of balls are introduced and the cylinder is closed and the mill starts rotating
- The speed of the rotation is important. At low speed, the balls will roll over each other and mostly only attrition will occur.
- At high speed, balls are kind of thrown out to the walls due to the centrifugal force and hence grinding will not occur. And in this case, only compression by the balls against the wall will takes place which is not sufficient for size reduction.
- At critical/ optimum speed, the centrifugal force will occur and as the result of this, the balls are picked by the walls and carried to the top and then they fall to the bottom. In this way both impact and attrition occur and size reduction hence becomes more efficient.
Uses
- Fine grinding with particle size 100-5 micro-meters or less
- Can be used particularly for hard and abrasive materials
- Stainless steel balls are preferred for the production of ophthalmic and parental products
- At low speed, ball mill is used for milling dyes, pigments and insecticides
Advantages
- It produces very fine powder
- It is suitable for both wet and dry grinding
- Since it is a close system, toxic substances can be ground
- Sterility is achieved due to closed cylinder
- The milling process can be done in an inert atmosphere if the oxygen sensitive substances are to be milled.
Disadvantages
- It is a very noisy machine
- It is a slow process
- Soft, tacky, fibrous material cannot be milled by ball mill
Multiple Choice Questions (MCQs)
1. Pebble mill works on which of the following mechanism?
A. Compression
B. Attrition
C. Impact
D. Both B and C
2. At which speed centrifugal force occurs in ball mill?
A. Low speed
B. High speed
C. Optimum Speed
D. All of the above
3. The cylindrical part of the ball mill rotates around which axis?
A. Latitudinal axis
B. Longitudinal axis
C. Diagonal axis
D. Both A and C
4. Which of the following material lines the metallic hollow cylinder of the mill?
A. Rubber
B. Chrome
C. Both
D. None of the above
5. Match the following-
A. At high speed 1. Ball mill can be used for milling
B. At low speed 2. Ball mill cannot be used for milling
C. Sticky material 3. Only compression by balls occur
D. Brittle drugs 4. Only attrition takes place
6. The balls used in pebble mill are made up of which type of material?
A. Steel
B. Iron
C. Stoneware
D. All of the above
7. Which type of grinding can tumbling mill perform?
A. Dry grinding
B. Wet grinding
C. Both
D. None
8. Which type of balls is preferred for the production of ophthalmic and parental products?
A. Rubber
B. Iron
C. Porcelain
D. None of the above
9. Which of the following statement is NOT true?
A. Hardinge mill, the variant of ball mill consist of a hollow cylinder with conical end
B. Rods and bars can also be used in place of balls as grinding medium in ball mill
C. Ball mill is an open system, hence sterility is a question
D. Fibrous materials cannot be milled by ball mill
10. What particle size can be obtained through ball mill?
A. 20 to 80 mesh
B. 4 to 325 mesh
C. 20 to 200 mesh
D. 1 to 30 mm
ANSWERS:-
1. Both B and C
2. Optimum speed
3. Longitudinal axis
4. Both
5. A – 3 B – 4 C – 2 D – 1
6. All of the above
7. Both
8. None of the above
9. Ball mill is an open system, hence sterility is a question
10. 20 to 200 mesh
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]]>The post Rotary Cutter Mill and Roller Mill Principle, Construction, Uses, Advantage, Disadvantage, Question Answer for GPAT, GATE, Pharmacist, Drug Inspector & NIPER JEE Exam appeared first on Gpatindia: Pharmacy Jobs, Admissions, Scholarships, Conference,Grants, Exam Alerts.
]]>Principle
In Rotary cutter mill, feed material is size reduced by continuous cutting and shearing by the help of sharp knives
Construction
In this mill, the milling chamber contains 2 types of knives: stationary knives and rotating knives. A rotor disc is mounted horizontally which consist of 2 to 12 knives placed at equal distance. The casing contains several stationary knives and the hopper is placed above it. The screen which controls the size of the particle is present below the casing. A receiver is placed at the bottom of the mill where the product is collected.
Working
The rotor disc rotates at a speed of 200-900 rotations per minute. The feed is loaded and it comes down due to gravity. Due to the rotations made by the rotator disc, the feed material comes in close contact between the stationary and rotating knives which results in size reduction. Small particles pass through the screen while the coarser particles are held again by the rotating knives and the same procedure is repeated till the desired size is obtained. The shape and size of the particles depends on the size of rotor, gap between rotating and stationary knives and the opening of sieve.
Uses
- It results in particle size 80-100 mesh
- Used for tough and fibrous material
- Size reduction of drugs extracted from medicinal plants and animal tissues
- It is also used for the production of rubber, plastics and recycling of paper
Variants
Double runner disc mill- It consist of two vertical discs which rotates in opposite direction. Else all the parts are and working is similar to the cutter mill.
Roller Mill
Principle
This mill works on the principle of compression by applying stress. Stress is applied by rotating heavy wheels or rollers.
Construction
Roller mill consist of two cylindrical rollers made up of stone or metal where rollers have diameter ranging from few mm to a meter. Rollers rotate on their longitudinal axis where one of the rollers is subjected to motor while the other one run freely. The size of the particle depends on the gap between the rollers.
Working
The material is fed from the hopper into the gap between the rollers and rollers are also allowed to rotate at the same time. Size reduction occur when the feed pass through the rollers under high pressure. The product is then collected in the receiver at the bottom of the mill.
Uses
- Used for crushing and cracking of seeds before extraction of fixed oils.
- To crush soft tissues to help in penetration of solvent during extraction process
Multiple Choice Questions (MCQs)
1. Which mode of stress is applied in roller mill?
A. Impact
B. Attrition
C. Compression
D. Cutting
2. Which part of the cutter mill controls the size of particle?
A. Rotor disc
B. Screen
C. Receiver
D. Both B and C
3. What is the speed of rotor disc in cutter mill?
A. 1000 rotations per min
B. 2000 Rotations per min
C. 500 Rotations per min
D. None of the above
4. Which type of materials is size reduced by cutter mill?
A. Fibrous material
B. Abrasive material
C. Hard material
D. Soft material
5. Match the following-
A. Use of roller mill 1. Compression
B. Use of cutter mill 2. Cutting
C. Principle of roller mill 3. Used for cracking seeds
D. Principle of cutter mill 4. Used for tough and fibrous materials
6. How is the stress applied in roller mill?
A. Hammers
B. Rollers
C. Wheels
D. Both B and C
7. What is the only difference in the cutter mill and double runner disc mill?
A. Rotor disc performs more rotations per min in double runner disc mill
B. 2 screens are present in double runner disc mill
C. Two discs are present which rotates in opposite direction in double runner disc mill
D. No. of knives are more in double runner disc mill
8. Which of the following statement is NOT true?
A. Cutter mill consist of 14-20 knives placed at unequal distance
B. In roller mill, Size reduction occur when the feed pass through the rollers under high pressure
C. Cutter mill results in particle size 80-100 mesh
D. The rotor disc rotates at a speed of 200-900 rotations per minute
9. Particle size depends on which of the following factor in the cutter mill?
A. Size of rotor
B. Gap between rotating and stationary knives
C. Opening of sieve
D. All of the above
10. Which of the following mill is engaged in the manufacturing of rubber?
A. Hammer mill
B. Roller mill
C. Ball mill
D. None of the above
ANSWERS:
1. Compression
2. Screen
3. 500 rotations per min
4. Fibrous material
5. A – 3 B – 4 C – 1 D – 2
6. Both B and C
7. Two discs are present which rotates in opposite direction in double runner disc mill
8. Cutter mill consist of 14-20 knives placed at unequal distance
9. All of the above
10. None of the above
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]]>The hammer mill works on the principle of impact. Here impact occurs between the fast moving hammers which are fitted on a rotor and the feed material.
Construction
The hammer mill is of two types: either vertically shafted type or horizontally shafted type. The surface of mill where impact occurs is made of abrasive resistant material like haystellite or curably. Hammer is made up of hard steel or stainless steel. In pharmaceutical industries, mainly hammers of stainless steel are used.
Hammers are of various shapes, but the two widely used hammers are stirrup shaped or bar shaped. Bar shaped hammers are majorly used for tablet granulation. The blades attached to the hammers may be with flat edges or sharp edges or both according to the need. Hammers may be either rigid or swing type. The main advantage of using swing-type hammer is that there will be increase in clearance between the hammers and screen when excess of bulk occurs in mill.
The mill is enclosed with a chamber containing removable screen through which materials must pass. These screens are made of metal sheets and are not woven type. The thickness of metal sheet varies with perforated holes or slots.
Working
The hammers are in constant motion with a speed of 8000-15000 rotations per minute. When these hammers are in continuous motion, the feed is placed in the hopper which then flows vertically downwards due to gravity and then horizontally. Impact occurs when the rotating hammers beat the feed to get smaller particles. These size reduced particles then pass through the screen. And due to the tangential shaped exit, the size of particles is comparatively smaller.
The screens are interchangeable. This helps to achieve any grade of fineness as required. Large amount of air is drawn through the mill since the hammers work as centrifugal fans. In some cases, the air drawn is sufficient to counter act the heat generated during the process. The size of particle depend on the following-
- Feed rate
- Rotor velocity
- Clearance between hammers and screen
- No and type of hammer used
- Size of screen
Uses
- On depending on the speed of hammer, fine to moderate grinding can be done through this mill.
- The expected particle size varies from 10-400 micro-meters.
- Non-abrasive to moderately abrasive, brittle materials can be size reduced
- Ointments, slurries, wet-filter press cakes can be milled.
Advantages
- Hammer mill is easy to install and clean
- Different types of feed material can be size reduced using different size of screens
- It occupies less space
- It is a versatile mill
- Since it is operated in close container so possibility of degradation is less.
Disadvantages
- The screen may get clogged
- Excessive heat is generated, therefore product may get degraded
- It cannot be used for sticky, fibrous and hard materials
Variants
- Fitzpatrick comminuting machine (Fitz mill):- used for drugs, roots, herbs, glands, liver and soaps.
- Stokes tornado mill
- Micro-pulveriser:- it is used for sugars, chemicals and cosmetics.
Multiple Choice Questions (MCQs)
1. Hammer mill works on the principle which mode of stress?
A. Impact
B. Attrition
C. Compression
D. Both A and B
2. The mode of stress is applied between which two components in Hammer Mill?
A. Hammer and rotor
B. Hammer and feed
C. Rotor and Feed
D. None of the above
3. Hammers are made of which type of material in Hammer Mill?
A. Haystellite
B. Curably
C. zinc
D. None of the above
4. Which shaped hammers are used for tablet granulation?
A. Bar
B. Stirrup
C. Bell
D. None of the above
5. Match the following-
A. Milling surface is made of 1. No. of rotations per minute
B. Hammers are made of 2. Feed rate
C. particle size depends on 3. Stainless steel
D. Flow of particles depends on 4. Curably
6. Which of the following factor affect the particle size of feed material?
A. Rotor speed
B. No. of hammer
C. Size of screen
D. All of the above
7. What is the benefit of interchangeable screens in hammer mill?
A. Speed of hammer can be changed
B. Any grade of fine particle can be achieved
C. Both
D. None
8. Which type of material is size reduced by hammer mill?
A. Fibrous
B. Soft
C. Brittle
D. All of the above
9. Which of the following statement is NOT true in Hammer Mill?
A. Only one type of hammer is used in hammer mill
B. Size reduction depends on rotor velocity
C. Fitz mill is used for roots and soaps
D. None
10. Why is hammer mill called as a versatile mill?
A. Screens can be changed rapidly
B. Speed can be changed easily
C. Both
D. None
ANSWERS:-
- Impact
- Rotor and feed
- None of the above
- Bar
- A – 4 B – 3 C – 2 D – 1
- All of the above
- Both
- Brittle
- Only one type of hammer is used in hammer mill
- BothFor More Standard and Quality Question Bank you can Join Our Test Series Programme for GPAT, NIPER JEE, Pharmacist Recruitment Exam, Drug Inspector Recruitment Exams, PhD Entrance Exam for Pharmacy
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]]>IVIVC refers to a relationship between a physicochemical characteristic of the dosage form, as determined by in vitro dissolution and biological property and as determined by in vivo pharmacokinetics. The objectives of IVIVC are to use the rate of dissolution as a discriminating parameter with respect to minor changes including changes in equipment, manufacturing process, formulation, batch size and manufacturing site. IVIVC also helps in setting dissolution specifications. For successful IVIVC, in vitro dissolution has to be the rate-limiting step in the absorption of the drug to the systemic circulation. Levels of IVIVC generally recognized are described below:
Level A – It represents a point to-point relationship between in vitro dissolution and the in vivo pharmacokinetics. In this case, the in vitro dissolution curve can be superimposed to the in vivo pharmacokinetic curve and can serve as a surrogate for in vivo performance. A correlation of this type is the best predictor of bioavailability from the dosage form.
Level B – Based on the principle of statistical moment analysis, the mean in vitro dissolution time is compared either with the mean in vivo dissolution time or with the mean residence time.
Level C – It establishes a single-point relationship between one of the dissolution parameters (e.g. time for specific amount dissolved) and one pharmacokinetic parameter (e.g. AUC or Cmax). Level C correlation is the weakest IVIVC and does not reflect the complete shape of the plasma concentration–time curve of the dissolution profile.
Multiple level C – It relates to the amount of drug dissolved at several time points of the dissolution profile to one or several pharmacokinetic parameters.
BIOPHARMACEUTICAL CLASSIFICATION SYSTEM:
The Biopharmaceutical Classification System (BCS) is the scientific basis for classifying drugs based on the key determinants of the rate and extent of drug absorption from immediate release solid orals—aqueous solubility, intestinal permeability and dissolution. The BCS classifies the drug substance into four distinct classes.
Table no. 1 – Classification of drugs based on the biopharmaceutical classification system
| Class | Properties |
| Class 1 | High solubility High permeability Examples: diltiazem, metoprolol, propranolol, verapamil |
| Class 2 | Low solubility High permeability Examples: danazol, ketoconazole, mefenamic acid, nifedipine, phenytoin |
| Class 3 | High solubility Low permeability Examples: acyclovir, captopril, cimetidine, neomycin B |
| Class 4 | Low solubility Low permeability Examples: taxol |
Solubility – The drug is considered highly soluble when the highest dose strength is soluble in 250 mL (approximately 8 ounces) or less of aqueous media over the pH range of 1–7.5.
Permeability – The drug is considered highly permeable when the extent of drug absorption in humans is 90% or more of an administered dose based on a mass balance determination or in comparison to an intravenous reference dose.
Dissolution – The drug is considered rapidly dissolving when the immediate-release product of the drug releases 85% or greater of the labelled amount of the drug within 30 min, using USP Apparatus I at 100 rpm or USP Apparatus II at 50 rpm in a d900 mL of acidic media such as 0.1 N HCl or Simulated Gastric Fluid USP without enzymes, a pH 4.5 buffer and a pH 6.8 buffer or Simulated Intestinal Fluid USP without enzymes.
To develop immediate-release generic products, the FDA requires demonstration of bioequivalence of the potential generic version with the innovator product. In addition to routine quality control tests, in vitro dissolution tests have been used to grant biowaivers (waive bioequivalence studies) for lower strengths of a dosage form. The BCS characteristics (aqueous solubility and intestinal permeability), together with the dissolution of the drug from the dosage form, supports in vivo bioavailability and bioequivalence waivers for immediate release solid dosage form of drugs.
Conditions to obtain biowaiver for immediate-release solid oral dosage forms are as follows:
- Based on an adequate dissolution test, biowaivers are provided for lower strengths after it has been demonstrated that the highest strength is bioequivalent to the innovators.
- The drug products containing the lower dose strengths should be compositionally proportional or qualitatively the same as the higher dose strengths and have the same release mechanism.
- The drug substances should belong to BCS Class 1, with rapid in vitro dissolution and with the caveat that excipients in the dosage form must not significantly affect absorption of the drug substance.
- The drug product should meet the profile comparison criteria, and the test and reference products should have similar dissolution profile.
Multiple choice questions:
1.IVIVC refers to a relationship between a physicochemical characteristic of the dosage form, as determined by in vitro dissolution and biological property and as determined by in vivo pharmacokinetics.
a)true
b)false
2.The objectives of IVIVC are to use the rate of dissolution as a discriminating parameter with respect to minor changes including changes in
a)equipment
b)manufacturing process
c)formulation
d)all of these
3.For successful IVIVC, _____ has to be the rate-limiting step in the absorption of the drug to the systemic circulation.
a)in vivo dissolution
b)in vitro dissolution
c)intrinsic dissolution
d)intrinsic solubility
4.How many Levels of IVIVC are?
a)1
b)2
c)3
d)4
5.Which of the following represents a point to-point relationship between in vitro dissolution and the in vivo pharmacokinetics?
a)Level A
b)Level B
c)Level C
d)Multiple level C
6.Which of the following is based on the principle of statistical moment analysis, the mean in vitro dissolution time is compared either with the mean in vivo dissolution time or with the mean residence time?
a)Level A
b)Level B
c)Level C
d)Multiple level C
7.Which of the following establishes a single-point relationship between one of the dissolution parameters (e.g. time for specific amount dissolved) and one pharmacokinetic parameter (e.g. AUC or Cmax)?
a)Level A
b)Level B
c)Level C
d)Multiple level C
8.Which of the following is the weakest IVIVC and does not reflect the complete shape of the plasma concentration–time curve of the dissolution profile?
a)Level A
b)Level B
c)Level C
d)Multiple level C
9.Which of the following relates to the amount of drug dissolved at several time points of the dissolution profile to one or several pharmacokinetic parameters?
a)Level A
b)Level B
c)Level C
d)Multiple level C
10.BCS stands for
a)Biopharmaceutical Classification System
b)Biological Classification System
c)Biopharmaceutical Classification Standard
d)Biochemical Classification System
11.The BCS classifies the drug substance into _____ distinct classes.
a)1
b)2
c)3
d)4
12.According to BCS system which of the following is example of Class 1?
a)diltiazem
b)neomycin B
c)taxol
d)phenytoin
13.Class 4 is associated with
a)High solubility High permeability
b)Low solubility High permeability
c)High solubility Low permeability
d)Low solubility Low permeability
14.The drug is considered highly permeable when the extent of drug absorption in humans is _____ or more of an administered dose based on a mass balance determination or in comparison to an intravenous reference dose.
a)10%
b)50%
c)90%
d)100%
15.Which of the following conditions obtain biowaiver for immediate-release solid oral dosage forms?
a)Based on an adequate dissolution test, biowaivers are provided for lower strengths after it has been demonstrated that the highest strength is bioequivalent to the innovators.
b)The drug products containing the lower dose strengths should be compositionally proportional or qualitatively the same as the higher dose strengths and have the same release mechanism.
c)The drug substances should belong to BCS Class 1, with rapid in vitro dissolution and with the caveat that excipients in the dosage form must not significantly affect absorption of the drug substance.
d)all of these
Solutions:
- a)true
- d)all of these
- b)in vitro dissolution
- d)4
- a)Level A
- b)Level B
- c)Level C
- c)Level C
- d)Multiple level C
- a)Biopharmaceutical Classification System
- d)4
- a)diltiazem
- d)Low solubility Low permeability
- c)90%
- d)all of these
References:
- Gaurav K. Jain Theory and Practise of Physical Pharmacy, 1st edition 2012 Elsevier, page no. 297-299.
- Martins Physical Pharmacy, 6th edition 2011, page no. 576-577.
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