NEET 2020 NEWS
NATIONAL LEVEL OFFLINE TEST
Cytology is the branch of biology that comprises the study of cell structure and its function. The structural and functional unit of all living beings is called cell. Cell has a dense membrane-bound structure called nucleus which contains the chromosomes which further contain the genetic material, DNA.
Mycoplasmas, the smallest cells, are only 0.3 µm in length while bacteria could be 3 to 5 µm. Nerve cells are the longest cells. These are some of the important points from this section that you must remember while preparing for NEET.
Every year near about 6-7 questions are asked from this particular topic which means 10% is covered from this section. Check NEET Exam Pattern
Candidates should cover all the major topics from this section like plant cell, animal cell, Prokaryotic and Eukaryotic Cells, and much more.
There are two types of cells: plant cell and animal cell.
|Plant cell||Animal cell|
|Cell wall is present in plant cells.||Cell wall is absent in animal cells.|
|Nucleus lies near periphery.||Nucleus present near the centre.|
|Centrosome is absent from plant cells.||Centrosome is present and helps in formation of spindle fibres.|
|Plastids are present, except fungi.||Plastids are absent.|
|Mitochondria is spherical or oval in shape.||Mitochondria is tubular in shape.|
|Single large central vacuole is present.||Many vacuoles occur, which are smaller in size.|
|Number of mitochondria is from 200 – 2000.||Number of mitochondria is approximately 1600 – 16000.|
|Plant cells can form all the amino acids.||Animal cells cannot form all the amino acids.|
|No contractile vacuole.||Contractile vacuole may occur to pump excess water.|
|Lysosomes are less in number.||More Lysosomes are present.|
These are unicellular organisms, like, bacteria, blue-green algae, and mycoplasma. All prokaryotes have a cell wall that surrounds the cell membrane.
These cells include all the protists i.e. unicellular eukaryotes, plants, animals, and fungi. It contains hereditary material covered on the outside by a nuclear envelope.
All eukaryotic cells are not identical, e.g., plant and animal cells.
Difference between Prokaryotic and Eukaryotic Cells
|Prokaryotic cell||Eukaryotic cell|
|It is a single membrane system.||It is a double membrane system.|
|Cytoplasm lacks cell organelles||Cytoplasm contains various cell organelles.|
|Ribosomes are 70 S type.||Ribosomes are 80 S type.|
|There are no streaming movements of cytoplasm.||Cytoplasm show streaming movements.|
|There are no Endocytosis and exocytosis.||Endocytosis and exocytosis occur.|
|Mitotic spindle is not formed in cell division.||Mitotic spindle is formed in cell division.|
|These have small size i.e. 0.5 to 10 micrometer.||These are relatively large i.e. 10 – 15 micrometer.|
|Sexual reproduction is absent but parasexuality is present.||Sexual reproduction is present.|
Q. In prokaryotic cells, ribosomes are
(a) 70 S
(b) 80 S
(c) 60S + 40S
(d) 50S + 40S
Cell wall is the outer most, protective, non living and supportive layer found in all the plant cells. It is not found in animal cells.
Plant cells can withstand a lot of variations in the surrounding medium as compared to animal cells because of cell walls.
|Primary cell wall||Secondary cell wall|
|Primary wall is laid inner to middle lamella||Secondary wall is laid inner to primary wall.|
|It is formed in a growing cell.||It is formed when the cells have stopped growing.|
|It is capable of extension.||Extensibility is absent.|
|It is single layered.||It is three or more layered.|
|Cellulose content is comparatively low (5 – 20%).||Cellulose content is comparatively high (20 – 90%).|
|Cellulose microfibrils are shorter, wavy and loosely arranged.||They are longer, closely arranged straight and parallel.|
|Protein content is up to 5%.||Protein content is up to 1%.|
|Lipid content is present.||Lipid is absent.|
|Primary wall is thin 1 – 5 micrometer||It is thick 5 – 10 micrometer|
Protoplasm is a complex, granular, elastic colourless substance. It is selectively permeable. It is considered as “Polyphasic colloidal system”.
The substance that occurs around the nucleus and inside the plasma membrane containing various organelles and inclusions is known as cytoplasm.
It forms half of the cell’s volume and 90% of it is water. It contains ions, biomolecules, such as sugar, amino acid, nucleotide etc.
Q. The main arena of various types of activities of a cell is
a) Plasma membrane
Mitochondria are referred to as “powerhouse” of the cell and contain electron transport system. They have hollow sac like structures present in all eukaryotes except mature RBCs of mammals and sieve tubes of phloem.
The mitochondria occur singly or in groups and their shape and size vary from cell to cell depending on physiological activity of cell.
These are absent in all prokaryotes like bacteria and cyanobacteria.
Plastids, the term was first time used by Schimper and discovered by Haeckel are semiautonomous organelles having DNA, RNA, Ribosomes and double membrane envelope which store or synthesize various types of organic compounds as ATP.
These are largest cell organelles in plant cell.
Q. DNA is present in
a) chromosomes and dictyosomes
b) chloroplasts and lysomes
c) mitochondria and chloroplasts
d) mitochondria and endoplasmic reticulum
|Chl. a||Chl. b|
|Theses are bluish green in colour.||They are yellowish green.|
|Soluble in petroleum, ether.||Soluble in methyl alcohol.|
|It is present in all green plants.||It is present in all green plants except blue green, brown and red algae.|
|In chloroplast it is 75%.||In chloroplast it is 25%.|
|In reflected light it reflects blood red colour while in transmitted light, blue green colour.||In reflected light it show dull brown colour while in transmitted light, yellowish green colour.|
Golgi complex also called “traffic police” of the cell is made up of various membranous system e.g. cisternae, vesicles and vacuoles.
• Secretion is the main function of golgi body.
• It is a large sized among the secretory cells.
• Glycosidation of lipids.
• Glycosylation of proteins.
• Helps in the formation of primary lysosomes.
Q. The Golgi complex plays a major role
a) In trapping the light & transforming it into chemical energy
b) In digesting proteins & carbohydrates
c) As energy transferring organelles
d) In post translational modification of proteins & glycosidation of lipids
Lysosomes popularly called "suicidal bags" are microscopic, vesicular structures of the cytoplasm, bounded by a single membrane.
These are absent in prokaryotes but are present in all eukaryotic animal cells except mammalian RBCs.
There are four types of lysosomes recognised :
• Primary lysosomes
• Secondary lysosomes
• Tertiary lysosomes/Residual bodies
• Lysosomes of sperm provide enzyme for breaking limiting membrane of egg e.g., hyaluronidase enzyme.
• Lysosomes function as trigger of cell division or initiate cell division by digesting repressor molecules.
• They also engulf the carcinogens.
Q. Which one of the following cell organelles is enclosed by a single membrane?
The Vacuole is a non-living reservoir, bounded by a differentially or selectively permeable membrane, the tonoplast. These contain water, minerals and anthocyanin pigments.
The vacuoles may be sap vacuoles, contractile vacuoles or gas vacuoles.
Vacuole maintains the osmotic relation of cell which is helpful in the absorption of water. The turgidity and flaccid stages of a cell are due to the concentrations of sap in the vacuole.
Q. The osmotic expansion of a cell which is kept in water is regulated by
It is a double membrane structure. The space between the two membrane is known as Perinuclear Space.
The two nuclear membrane are interrupted by minute pores called Nuclear Pores, which allows only certain molecules of particular size to enter the nucleus. The nuclear matrix is known as Nucleoplasm. Nucleoplasm is composed of chromatin and nucleolus.
Chromatin is a network of DNA which is surrounded by proteins known as Histone Proteins. During no cell division, the genetic material exists in the form of chromatin.
Q. Controlling centre of cell is
Candidates must go through the topics given below before the exam to score good marks in this section.
Candidates can make a study plan. Even the revisions need to be planned so that you can cover all the topics. Candidates can follow the given below plan which will be helpful for them.
Select one to two topics daily and give 1-hour each to revise theses topics.
After revising the basics, learn or go through all the topic wise formulae and make sure you write and learn.
Try to solve at least 30-40 questions within 1 to 2 hours.
Take the previous year’s papers. Select one Topic and Identify the questions based on that topic. Try to solve these questions to improve your speed.
Give as many Mock Tests as possible daily.
Go for Last and Final Revision.
Q. A difference between eukaryotic and prokaryotic cells is in having
(b) Cell wall
(c) Nuclear membrane
(d) None of the above
Q. The two domains to which prokaryotes are classified into are:
(a) Bacteria and Protista
(b) Bacteria and Archaea
(c) Archaea and Eukarya
(d) Eukarya and Monera
Q. Which of the following has its own DNA?
Q. A cell organelle containing hydrolytic enzyme is
Q. The function of nucleolus is the synthesis of
Candidates can go through some tricks given below to study Biology while preparing for NEET 2020.