Prokaryotic and Eukaryotic Cells: Structure and Function

Integrate multiple signals through a two component phospho-relay system. The methyl-accepting chemotaxis proteins are present on the outer surface of the bacteria. They are chemical sensors that help the bacteria to sense components present in its surroundings.

Both have 70S ribosomes. Ribosomes are cellular organelles that take part in protein synthesis. They are made up of two sub units: small and large. Bacteria have 70S ribosomes. Their small subunit is called 30S and the large one is called 50S. Mitochondria have 55S ribosome: 30S and 40S.

Bacteria do not have a particular shape. Some are long-shaped called bacillus, some are round called cocci, some are spiral called spirillum, etc. Thus, they are called pleomorphic.

They use cytoplasmic ATP as their primary energy source. Bacterial flagella help the bacteria to move in its environment. It is driven by a rotary engine present at its base, by proton motive force.

Allows cytoplasmic proteins to enter the nucleus. In the nucleus, important activities as DNA replication, transcription, etc. take place. These are initiated and mediated by many enzymes that are produced inside the cell. Therefore, the enzymes are transported from cytoplasm to nuclear matrix through nuclear pore.

Assembly of subunits travelling through the hollow flagellum to the tip. The flagella of bacterium are made up of protein called flagellin. Flagellum is hollow inside and the flagellin subunits are added through the flagellum to the tip. Flagellum of Bacillus subtilis had been completely sequenced and found to be made up of 304 amino acid residues which have a molecular weight of 32600.

In the outer membrane, porin proteins make holes. Porin proteins are beta barrel proteins present in the Gram-negative bacteria that allows transport of large sized or charged molecules across the membrane by passive diffusion.

It is made up of enzymes that synthesises ATP. The F1 particle is attached to the inner membrane of mitochondria. It has a motor like structure at the base just as bacterial flagella. The motor rotates and generates ATP.

Phagocytosis and secondary lysosome fusion. Phagocytosis and lysosome fusion are engulfing of small particles by a cell, generally for its nutrition. These are generally observed in macrophages to destroy bacteria.

All of the above. Microtubules are infrastructure of a cell and give specific shape to it. Since colchicines disrupt microtubules, thus, shape of the cell will get upset resulting in the above mentioned losses.

This amino acid has a free amino group for the formation of peptide bond. Peptidoglycan of bacterial cell wall is made up of N-acetyl glucosamine (NAG)-N-acetyl muramic acid (NAM). To NAM, a tetra-peptide chain is attached consisting of L-alanine, D-glutamic acid, L-lysine and D-alanine. The L-lysine is attached to a penta-glycine chain sideways, which is further attached to D-alanine of the neighbouring NAG-NAM complex. Since L-lysine needs to form the penta-glycine chain, it should have a free amino group for peptide bond formation. This extensive cross linking gives rigid structure to the peptidoglycan moiety.

Most peptidases can only cleave L-amino acids. Peptidases are enzymes that act on short protein chains into individual amino acids. Many bacteria secrete peptidases that act on L-amino acids and help in their nutrition. But these enzymes cannot degrade their cell walls due to the presence of D-amino acids in their cell walls.

Polymerises actin filaments, causing the bacterium to move through the cytoplasm. L. monocytogenes invades the cells by polymerising actin filaments in the cytoplasm, because ActA protein is a protease enzyme and specific for actin proteins for its degradation.

Help the bacterium to survive in long period of dryness. Endospores are spores that are formed inside a bacterium. Their outer surface is hard which acts as a protective mechanism and allows the bacterium to survive during tough time as in periods of dryness and heat. During the endospore formation, it seems as a non-living thing, but inside it contains live viable bacterium.

It takes part during translation, by aligning eukaryotic mRNA on the ribosome. The mRNA is aligned to the ribosome by 7-methylguanosine cap. The 3’ poly(A) tail of mRNA is responsible for its stability and long lifespan.

G - U. According to “Wobble Hypothesis”, the codons of mRNA are degenerate, i.e. there are more codons on the mRNA than the number of amino acids. The codon–anticodon base pairing is relaxed at the third base, which allows G to pair with U, which does not generally happen.

 Na+, a charged molecule, crosses membranes through channelby active transport as it is hydrophilic.

The cell undergoes self-digestion and dies. Lysosomes contain different types of lytic enzymes. When a lysosome bursts inside a cell, lytic enzymes are released inside the cell resulting into its self-digestion and finally death. This is a usual phenomenon observed by a cell for apoptosis.

A - 4, B - 3, C - 2, D - 1: Intrinsic proteins are certain proteins embedded in lipid bilayer of cell membranes. Mesosomes are invaginations in cell membrane of certain gram positive bacteria that are responsible for their respiration. Bound ribosomes are found attached to endoplasmic reticulum in eukaryotic cells. Golgi complexes are dispersed in cytoplasm of eukaryotic cells.