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- July 14th, 2012, 05:06 PM #681July 14th, 2012, 08:25 PM #682
the force due to gale will be zero because it is not producing acceleration in it........July 14th, 2012, 08:28 PM #683
its answer is D because the velocity and area are inversly proportional to each other....July 14th, 2012, 08:31 PM #684
its 1st chapter of second year bookJuly 14th, 2012, 08:33 PM #685July 14th, 2012, 08:38 PM #686
can u explain it is?July 14th, 2012, 08:39 PM #687
how it is in upward direction/July 14th, 2012, 09:00 PM #688
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Lysozyme may be present in
(d) all A,B,C are correctJuly 14th, 2012, 09:04 PM #689
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If the amount of DNA in human sperm cell is X/2 what will be the amount of DNA in a cell undergoing through mitosis
(d)4XJuly 14th, 2012, 09:18 PM #690
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THE RIBOSOMES ARE ATTACHED TO m-RNA THROUGH
(a)SMALLER SUB UNIT
(c)LARGER SUB UNIT
(d)ALLJuly 14th, 2012, 09:22 PM #691
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ALL OF THE FOLLOWING ARE NON POLAR MOLECULAR SOLID EXCEPT ONE
SUGARJuly 15th, 2012, 08:55 AM #692
Obviously as far as MCAT so in my opinion memorization + conceptual study go hand in hand because there are book based and knowledge based questions which could be done by memorizing the given material with different techniques like flow chart diagrams and sometimes we can also use mnemonics of our own.And also there are some conceptual questions for which we would definately have to retrieve the memorized material (e.g some formula) and then apply the concept. So this is a common question that whether concept and cramming .If one is thinking for top positions then definitely one should have command on both these things. But memorizing is always come first in my opinion then concepts #yesJuly 15th, 2012, 08:59 AM #693
1. A condensation polymerization produces a polymer andA. H2
D. H202. Which organic compound is classified as a primary alcohol?A. Ethylene glycol
3. For ethyne: C2H2
What is the total number of electrons shared between the carbon atoms?
4. Which nuclide is a radioisotope used in the study of organic reaction mechanisms?
5. Which set contains one natural polymer and one synthetic polymer?
A. Cellulose and Starch
B. Polyethylene and Nylon
C. Protein and Starch
D. Protein and Nylon
6. Aldehydes can be synthesized by the oxidation of
A. Primary alcohols
B. Secondary alcohols
C. Organic acids
D. Inorganic acids
7. Given the reaction: C2H2 + 2H2 --> C2H6
This reaction represents:
8. Which pair of names refers to the same compound?
A. Ethyne and Acetylene
B. Ethyne and Ethene
C. Ethane and Acetylene
D. Ethane and Ethene
9. A condensation polymerization reaction is best described as the
A. Joining of monomers by the removal of oxygen
B. Joining of monomers by the removal of water
C. Oxidation of a hydrocarbon by oxygen
D. Oxidation of a hydrocarbon by water
10. Which formula represents a ketone?
11. Which subatomic participle is found in all isotopes of hydrogen?
12. The bond between hydrogen and oxygen in a water molecule is classified as
A. Ionic and Nonpolar
B. Ionic and Polar
C. Covalent and Nonpolar
D. Covalent and Polar
13. What is the total number of hydrogen atoms required to form 1 molecule of C3H5(OH)3?
14. A compound that can act as an acid or a base is referred to as
A. A neutral substance
B. An amphoteric substance
C. A monomer
D. An isomer
15. Which compound is an electrolyte?
16. Which organic compound is classified as an acid?
17. The products of the fermentation of a sugar are ethanol and
C. Carbon dioxide
D. Sulfur dioxide
18. The reaction CH2CH2 + H2 --> CH3CH3 is an example of
19. In which pair of hydrocarbons does each compound contain only one double bond per molecule?
A. C2H2 and C2H6
B. C2H2 and C3H6
C. C4H8 and C2H4
D. C6H6 and C7H8
20. During fractional distillation, hydrocarbons are separated according to their
A. Boiling points
B. Melting points
C. Triple points
D. Saturation points
Last edited by jamal; July 15th, 2012 at 09:02 AM.July 15th, 2012, 09:11 AM #694
Nuclear Physics Imp#yes
Biological Effects of Radiation:-
Excessive exposure to radiation can cause damage to living tissues, cells or organism. The degree and kind of damage caused to a particular part of the body depend upon the type, energy and dose of radiation received. There is no lower limit below which radiation damages does not occur. A number of small doses received over long period of time may lead to fatal consequences.
Radiations damage to living organism is primarily due to ionization effects in the cells. The cell is the basic unit of life. Its normal metabolic function may be disrupted as a result of interaction with the ionizing radiation. Excessive radiation dose may cause death of individual cells, or produce chromosome abnormalities or genetic mutation.
The biological effects are generally of two types: somatic and genetic.
“A type of effect which affects an individual directly called somatic effect.”
The somatic effect of radiations are skin burns, loss of hair, uncertain, stiffening of lungs, contraction in eyes and drop in the white blood cells, which is followed by diarrhea, vomiting and fever known as radiation sickness. Recovery is possible from small acute doses but shortening the span of life.
“A type of effect in which genes are damaged and appear after a long time called genetic effects”
Radiations can change the chemistry of the genes and cause mutations which are changes in the genetic messages with the cells. A low radiation doses reacing the reproductive organ and chromosome may be affected by a single radiation impact. As a result, the cell may be abnormal. These effects may pass on the future generations.
Uses of Radiations:-
The nuclear radiation from radioactive sources are widely used to understand the complex reaction in biological organisms. Some of their uses are described below:
Some of the tracer techniques are as below:
The chemical properties of all the isotopes are same. The location and concentration of radioactive isotopes can be detected by measuring the radiations which these elements emit. The radioisotope thus acts as a tracer and helps us to understand the course of chemical or biological process. For example, radioactive isotope of carbon (C-14) is a useful tracer because the carbon is present in all organic molecules. The use of this isotope of carbon has made possible to understand the complex process of photosynthesis. It explains the detail of series of chemical reactions that leads from carbon dioxide to carbohydrate in the plants.
Underground location of position:-
The tracer techniques are also used to locate the particular position of an underground pipe leakage. A small quantity of radioisotope is added to the liquid flowing in the pipe. In this case radioisotopes of very short half life are used to avoid long contamination of soil or water. E.g. Na-24 and iodine-31
Path of Chemicals:-
Radioactive tracers are used to follow the path that various chemicals or food constituents take in the human body, animals and plants.
According to medical research it has been found that atoms of hydrogen and sodium present in water or food are uniformly distributed through out the body. Many other chemicals are concentrated in certain parts of the body and in some particular organs. For example, iodine tends to concentrate in thyroid, phosphorus and strontium in bones and cobalt in liver. They can serve as tracers. Small quantity of low activity substances are injected to the patients and their passages through the body and locate the diseased tissue by radiation detectors.
Cancerous tissues absorb more radioactive atoms than the healthy tissues. For example, a normal thyroid gland takes up 20% of the ingested iodine during the first hour but a hyperactive gland takes more than twice of this amount. This fact helps to locate the position of cancerous tissue by obtaining a pattern of distribution of radio iodine in gland.
v High energy radiations are capable of penetrating deep in to the body and can be used for internal selective destruction of tissues, such as cancerous tumor. High energetic x rays and γ rays are focused on cancerous tumors to destroy them.
v Artificial Co – 60 is used for treatment of various kinds of cancer. This isotope emits β particles and high energy gamma rays.
v The tumors which are not effectively attacked by gamma rays are treated with neutron therapy.
v Radioactive iodine-131 is used to treat thyroid cancer. When Iodine-131 is given to the patients, the cancerous tissues take iodine at greater rate than normal, absorb more radiations and are destroyed.
v In some cases, small pellets of radioactive isotopes are planted inside the boy close to the tumor. When the radiation emitted by them destroys the growth or tumor, the pellets are removed.
v Radioactive radon gas in small gold capsules, know as radon seeds is employed to destroy the cancerous cells.
The chemical changes going on in an animal or a plant are very complex. The tracer method has been applied to study these changes. For example, the process of photosynthesis and the incorporation of carbon atoms in the CO2 in to giant and complex protein or carbohydrate molecules have been investigated by tracer techniques. Similarly information covering the complex process of metabolism is obtained by means of radioisotopes tracers. The distribution of various elements such as hydrogen, sodium , iodine, phosphorus, strontium, iron etc in the body can be obtained by tracer technique. Genetic mutations are engineered by intense radioactivity.
The use of phosphorous or nitrogen as a tracer in fertilizers has provided the information about the best fertilizer to supply to a particular crop and soil. The technique also helps to adopt a better mode of fertilizer supply to the plants.
Through the use of radiation induced mutations, improved variety of certain crops have been developed. They have improved plant structure. The plants have shown more resistance to disease and pest, and give better yield grain quality. Food preservation time can be enhanced and improved by treating the food items with radiation. The treatment limits the microbial activity and inhibits sprouting in potato, onion, and garlic etc. radiation processes have not only isolated numerous species of fungi infesting grain and flour but also effectively used for disinfection.
July 15th, 2012, 04:57 PM #695
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when will be the entry testJuly 16th, 2012, 04:40 PM #696
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Can any one explain how to find the coordinates of gravity in the Unit 2 of UHS syllabus?July 18th, 2012, 05:12 AM #697July 18th, 2012, 05:16 AM #698July 18th, 2012, 05:17 AM #699
Biology Virus and Bacteria
VIRUS AND BACTERIA
1. Viral genes are made of
a. RNA only
b. DNA only
c. Either DNA or RNA
d. Either protein or nucleic acid
2. A virion is a
b. Viral ribosome
c. Viral lysosomes
d. Viral gene
3. An isolated virus is not considered living since it
a. Separates into tw inerts part
b. Cannot metabolize
c. Rapidly loses its genome
d. Is coated with air-tight , chemically inert sheild
4. Most RNA viruses carry a gene for an enzyme that uses viral RNA as template in the synthesis of more viral RNA this enzyme is
a. Reverse transcriptase
b. RNA polymerase
c. Viral nuclease
d. RNA replicase
5. The enzymes involved in viral replication are synthesized
a. On the viral ribosome
b. By the host cell
c. On the interior surface of the viral membrane
d. On the interior surface of the viral coat
6. Much of the research on gene expression has been done with E.coli, which inhibits the human intestine.This organism is a
7. In general bacterial genes are regulated at the time of
8. When DNA is exchanged via eytoplasmic bridges between two bacteria the process is called
9. When a bacteriophage in its lytic phase carries some of the bacterium's partially digested chromosome with it to another host cell the process is called
d. Restricted transduction
10. A bacteriophage with a lysogenic cycle must have genes that are
a. Made of RNA
b. Made of double-stranded DNA
c. Made of single-stranded RNA or DNA
d. With in a circular nucleic acid molecule
11. which of the following fungus is used to give the flavour , aroma and Characteristics colour to some cheese?
b. Ergot fungi
12. According to mode respiration which one of the following group of bacteria can grow either in the presence or absence of oxygen?
a. Facultativebacteria ( E.coli )
b. Microaeerophilic ( campylobacter )
13. which one is true for Pox-viruses?
b. DNA-non enveloped
d. DNA-naked virion
14. A disease virus in which nerves are damaged is the
a. Yellow fever
15. In some bacteria when division ocurrs in random plane it will produce an Arrangement called
16. Gram positive bacteria are usually
c. Stained pink
17. A viral disease in which brain of the host is affected is the
a. Sleeping sickness
18. Mumps and measles viruses belong to group paramyxo-viruses which are the
a. RNA enveloped viruses
b. DNA naked viruses
c. RNA non-enveloped
d. DNA enveloped viruses
19. There are about known species of bacteria that causes the diseases in man
20. Morphologically the tobacco mosaic virus is the
a. Round shape
b. Tadpole like
c. Cubical shape
d. Rod shape
21. The flavour,all of the following is due to bacterial activity, except that of
a. Butter milk
22. A scientist who established principles of immunity in "Anthrax &Rbies" was the
23. The poison, produced by bacteria during infection in host is called
24. All of the following are antibiotics, except that of
25. Bacteria ranges in size, whereas, the staphylococcus&streptococcus are in diameter
a. 0.75 to 1.25 m
b. 1.1 to 1.50 m
c. 2.0 to 6.0 m
d. 0.75 to 1.75 m
26. Which one is true for periplasmic space ,in different groups of bacteria
a. Present in all gram -negative bacteria
b. Present in all gram positive bacteraia
c. Present in few gram negative bacteria
d. Present in all gram positive&few gram negative bacteria
27. The amount of lipid in outer noundry of gtam positive bacteria is about
a. 1-4 %
28, Which one of the following antibiotics &related compounds cause permanentdiscoloration of teeth in young children
29, Antibiotics are synthesized by certain organisms such as
c. Both a%b
30. Ecological role of fungi as decomposers is parallled only by
31. Are very good bio-indicator of air quality as they are very sensitive to pollution
d. Water blooms
32. Induction is a process in which a viral DNA
a. Enters into bacterial cell and attached with bacterial DNA
b.Detached from bacterial DNA
c. Destroy the bacterial DNA
d. Multiply with bacterial DNA
1 C....2 A....3 B.....4 A.....5 B....6 C.....7 D......8 B......9 D....10 D.....11 D ...12 A....13 C....14 B..15 D...16 ?...17 B...18 A...19 C...20 D...21 C...22 D....23 A....24 C...25 B....26 A...27 A...28 A...29 A...30 B...31 C....32 B#grinJuly 19th, 2012, 04:26 PM #700
What does Diffraction of X-rays by crystals show:
A) X-rays are just like visible light
B) X-rays are electromagnetic waves
C) X-rays have very short wavelength
D) The intensity of X-rays is high?
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