Examination Preparation

Archive for March, 2008

There are two types of cells: eukaryotic and prokaryotic. Prokaryotic cells are usually independent, while eukaryotic cells are often found in multicellular organisms.

Eukaryotic cells

Eukaryotic cells are about 10 times the size of a typical prokaryote and can be as much as 1000 times greater in volume. The major difference between prokaryotes and eukaryotes is that eukaryotic cells contain membrane-bound compartments in which specific metabolic activities take place. Most important among these is the presence of a cell nucleus, a membrane-delineated compartment that houses the eukaryotic cell’s DNA. It is this nucleus that gives the eukaryote its name, which means “true nucleus”. Other differences include:

• The plasma membrane resembles that of prokaryotes in function, with minor differences in the setup. Cell walls may or may not be present.
• The eukaryotic DNA is organized in one or more linear molecules, called chromosomes, which are associated with histone proteins. All chromosomal DNA is stored in the cell nucleus, separated from the cytoplasm by a membrane. Some eukaryotic organelles also contain some DNA.
• Eukaryotes can move using cilia or flagella. The flagella are more complex than those of prokaryotes.

Prokaryotic cells

Prokaryotes differ from eukaryotes since they lack of a nuclear membrane and a cell nucleus. Prokaryotes also lack most of the intracellular organelles and structures that are seen in eukaryotic cells. There are

two kinds of prokaryotes, bacteria and archaea, but these are similar in the overall structures of their cells. Most functions of organelles, such as mitochondria, chloroplasts, and the Golgi apparatus, are taken over by the prokaryotic cell’s plasma membrane. Prokaryotic cells have three architectural regions: appendages called flagella — proteins attached to the cell surface; a and pilicell envelope – consisting of a capsule, a cell wall, and a plasma membrane; and a cytoplasmic region that contains the cell genome (DNA) and ribosomes and various sorts of inclusions. Other differences include:

• The plasma membrane (a phospholipid bilayer) separates the interior of the cell from its environment and serves as a filter and communications beacon.
• Most prokaryotes have a cell wall (some exceptions are Mycoplasma (bacteria) and Thermoplasma (archaea)). This wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from “exploding” (cytolysis) from osmotic pressure against a hypotonic environment. A cell wall is also present in some eukaryotes like plants (cellulose) and fungi, but has a different chemical composition.
• A prokaryotic chromosome is usually a circular molecule (an exception is that of the bacterium Borrelia burgdorferi, which causes Lyme disease). Even without a real nucleus, the DNA is condensed in a nucleoid. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular. Plasmids can carry additional functions, such as antibiotic resistance.

Souce : wikipedia

CSIR Life Science Sample Questions

Cell Biology

Q. Phragmoplast is formed during

A) cell plate formation in animal cells

B) protein synthesis in animal cells

C) lysis in animal cells

D) cell plate formation in plant cells

Bio Chemistry

Q. Which bond in B DNA have to be rotated to convert it to syn G to anti confirmation?

A) Hydrogen Bond

B) Glycosidic bond

C) Phosphodiester

D) Hydrophobic

Genetics

Q. 9:3:3:1 ratio is modified in complementary genes as

A) 5:1

B) 9:7

C) 13:1

D) 12:3:1

Physiology

Q. An orthotropous ovule is one, in which micropyle and chalaza are

A) at right angles to funicle

B) parallel to funicle

C) in straight line to funicle

D) parallel along with to ovule

Q. Excessive stimulation of vagus nerve in humans may lead to

A) hoarse voice

B) peptic ulcers

C) efficient digestion of proteins

D) irregular contractions of diaphragm

Evolution

During the course of evolution the protherians have evolved from

A) Birds

B) Reptiles

C) Eutherians

D) Amphibians

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Earth,Atmospheric, Ocean & Planetary Sciences Syllabus

Paper 1 Section A

Paper 1 Section B

Paper 2 – Geology

Paper 2 – Physical Geography

Paper 2 – Geophysics

Paper 2 – Oceanography

Paper 2 – Meteorology

Paper I :

An objective-type test of duration 2 hours and 15 minutes, in 2 sections, A and B. All the questions are compulsory with the cut-off mark in Paper I deciding whether Paper II is to be evaluated or not. Negative marks are assigned to wrong answers in this paper where a maximum of 200 marks can be scored.

Section A - In 30 general questions, the candidate’s knowledge on general information pertaining to Science, aptitude for Scientific Research, Quantitative Reasoning and Computer Science are tested.
Section B - Focusses on the candidate’s chosen subject. There are 70 objective-type questions, each carrying a maximum of 2 marks.

Paper II:

A paper of duration 2 hours and 30 minutes, it consists of descriptive-type questions for a maximum of 200 marks. Candidates are expected to answer 10 to 15 questions.

Use of calculators / logarithm tables (other than those provided in the answer books) is not permitted.