Which one of the following structures between two adjacent cells is an effective transport pathway?
Plasmodesmata are the structure between two adjacent cells that permits the transport and communication between them. They are the fine cytoplasmic strands that connect the protoplasts of adjacent plant cells by passing through the cell walls.
Which one of the following has its own DNA?
Mitochondria has its own DNA. It is as structure within cytoplasm of eukaryotic cells that carries out aerobic respiration. It is the site of Kreb’s cycle and ETS.
Therefore, it is also called as cell’s energy production site.
The main arena of various types of activities of a cell is:
The main arena of various types of activities of a cell is cytoplasm. It forms the living protoplasm of a cell excluding the nucleus. It consists of proteins, fats, carbohydrates, nucleic acids, vitamins, waste metabolites and all organelles.
The plasma membrane consists mainly of:
Plasma membrane comprises mainly proteins embedded in a phospholipid bilayer. Protein molecules occur at places both inside and outer side of the lipid bilayer.
Given below is a sample of a portion of DNA strand. What is so special shown in it?
5’ —— GAATTC —— 3’
3’ —— CTTAAG —— 5’
The sample of a portion of DNA strand shown in the figure is palindromic sequence of base pairs.
Important site for formation of glycoproteins and glycolipids is
Golgi apparatus is the important site for formation of glycoprotein and glycolipid.
Peptide synthesis inside a cell takes place in:
Peptide synthesis takes place in ribosome inside a cell.
What are those structures that appear as beads - on- string in the chromosomes when viewed under electron microscope ?
Under electron microscope the nucleosomes appear as beads on string in chromosome, due to a short length of DNA wrapped around a core of histone proteins.
The figure below shows the structure of a mitochondrion with its four parts labelled (A), (B), (C) and (D).
Select the part correctly matched with its function.
The mitochondrial inner membrane forms infoldings known as cristae, which allow greater surface area for protein such as cytochrome to function properly and efficiently.
In mitochondria, proteins accumulate in the
The inner membrane of mitochondria contains more than 151 different polypeptides, and has a very high protein-to- phospholipid ration.
Which one of the following is not considered as a part of the endomembrane system ?
Cell organelles, whose functions are coordinated, are considered together as an endomembrane system. The endomembrane system includes endoplasmic reticulum (ER), Golgi complex, lysosomes and vacuoles. Since the functions of the mitochondria, chloroplast and peroxisomes are not coordinated with the above components, these are not considered as part of the endomembrane system.
Ribosomal RNA is actively synthesized in
The nucleolus is the largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesisRibosomal RNA is actively synthesized in the nucleolus. The nucleolus is also known as the ribosomal factory.Hence Ribosomal RNA is actively synthesized in Nucleolus.
So, the correct answer is 'Nucleolus'.
Which one of the following does not differ in E.coli and Chlamydomonas
Cell membrane of prokaryotes is structurally similar to that of eukaryotes. So, it does not differ in E. coli and Chlamydomonas.
E.coli (bacteria) is a prokaryote while Chlamydomonas (algae) is a eukaryote. Ribosomes of both groups differ being 70S in prokaryotes and 80S in eukaryotes. Prokaryotic chromosomes lack histone protein unlike eukaryotic ones. Cell wall organization also differs as bacterial cell wall is rich in muramic acid while algal cell wall is cellulosic. It is the cell membrane which has similar organization in both the groups.
What is true about ribosomes
Ribosomes are amembraneous (ie. without membrane) cell organelle composed of rRNA and protein. These are found in both prokaryotic and eukaryotic cells. In prokaryotes, ribosomes are 70S type while in eukaryotes, it is 80S type.
Nuclear mebrane is absent in
Nostoc is prokaryote while rest are eukaryotes. Nuclear membrane is absent in prokaryotes.
Select the correct statement from the following regarding cell membrane.
Fluid mosaic membrane model was proposed by Singer and Nicholson in 1972. It is most accepted model of structure of biomembrane.
Which one of the following structures is an organelle within an organelle?
Ribosome are small naked (non membrane bound) particles made of r-RNA and proteins. Ribosomes are also seen in the organelles like mitochondria and chloroplasts. They are the cell’s protein factories and are found on RER and scattered in the cytoplasm as polyribosomes. Ribosomes are the sites at which information carried in the genetic code is converted into protein molecules.
Which one of the following cellular parts is correctly described?
Centrioles serve as basal bodies for cilia and flagella. They are concerned with spindle formation during cell division. Lysosomes are membrane-bound organelles containing many hydrolytic enzymes, which are optimally active at an acid pH (near pH 5). Thylakoids are membrane-bound organelles found within chloroplasts. The thylakoid membrane, forms many flattened, fluid-filled tubules that enclose a single convoluted compartment. These tubules tend to stack on top of each other to forma structure called a granum
Which one of the following organelle in the figure correctly matches with its function ?
Rough endoplasmic reticulum is a network or reticulum of tiny tubular structures scattered in the cytoplasm and bear ribosomes on their outer surface. These are involved in protein synthesis and secretion. They are extensive and continuous with the outer membrane of the nucleus.
The Golgi complex plays a major role
Golgi apparatus plays a major role in post translational modification of proteins forming glycoprotein and glycosidation of lipid forming glycolipids. A number of proteins and lipids synthesised on endoplasmic reticulum (rough and smooth respectively) are modified in the cisternae of the Golgi apparatus before they are released from it trans face.
A major site for synthesis of lipids is :
The smooth endoplasmic reticulum is the major site for synthesis of lipid. In animal cells lipid like steroidal hormones are synthesised in SER.
The term ‘glycocalyx’ is used for
[NEET Kar. 2013]
Glycocalyx or mucilage is the outermost coating of bacterial cells/cell wall which is rich in polysaccharides. A thick and tougher mucilage is called capsule which gives gummy or sticky trait to cells. It protects the cells from dessication, toxins and preventing attachment to foreign invaders.
Which of the following type of plastids does not contain stored food material?
[NEET Kar. 2013]
Chromoplasts are non-photosynthetic coloured plastides which synthesise and stored carotenoid pigmentes. They, therefore, appear orange red and yellow where as amyloplast (store starch), aleuroplast (store proteins) and elaioplast (store oil droplets and fats) are leucoplasts, colourless plastids.
Select the alternative giving correct identification and function of the organelle ‘A’ in the diagram
[NEET Kar. 2013]
In fig., (A) shows the cell organelle mitochondria. The mitochondria are bounded by two membranes, i.e., outer membrane and inner membrane. Mitochondria are referred as “powerhouse” of the cell as they produce 95% of ATP. This energy is produced during the break down of food molecules which involve glycolysis, oxidative decarboxylation and oxidative phosphorylation (krebs cycle and respiratory chain).
Why is a capsule advantageous to abacterium?
[NEET Kar. 2013]
Capsule is a layer that lies outside the cell wall of bacteria. The capsule can protect cells from engulfment by eukaryotic cells, such as macrophages. They also exclude bacterial viruses and most hydrophobic toxic materials such as detergents.