Question

Describe the structure, composition, function and importance of the major prokaryotic and

eukaryotic structures below.

Structures common to all cells:

Cell wall

Cell membrane

Cytoplasm

Ribosome

Nucleus/nucleoid region (genome)

Flagella

Structures unique to prokaryotic cells:

Endospore

Pilus

Capsule

plasmid

Structures unique to eukaryotic cells:

Mitochondria

Chloroplast

Vesicle

Cytoskeleton

Answer 1

Cell wall- surrounds the cell membrane of a cell.  It can be tough, flexible, and sometimes rigid. It provides the cell with both structural support and protection, and also acts as a filtering mechanism. It can be made up of cellulose in plant cell and of chitin in fungi and of peptidoglycan in certain bacteria. So its composition is varied. It is absent in the animal cells.

Cell membrane-  is a biological membrane that separates the interior of all cells from the outside environment. It is kind of semipermeable i.e allowing certain substances to pass through it and certain substances are not passed depending on their charge and size. It is made up of phospholipids and proteins and it can be explained best by fluid mosaic model.

Cytoplasm- is mainly composed of water, salts, and proteins. In eukaryotic cells, the cytoplasm includes all of the material inside the cell and outside of the nucleus.

Ribosomes-  is a complex molecule made of ribosomal RNA molecules and proteins. It is a structure responsible for protein synthesis. It can be found free in the cytoplasm or attached to the endoplasmic reticulum making them rough.

Nucleus- The nucleus is an organelle found in eukaryotic cells and absent in prokaryotic cells. Inside its fully enclosed nuclear membrane, it contains the majority of the cell's genetic material. This material is organized as DNA molecules, along with a variety of proteins, to form chromosomes.

Flagella- is a locomotory organelle.  They help propel cells and organisms in a whip-like motion. The flagellum of eukaryotes usually moves with an “S” motion and is surrounded by the cell membrane.

Endospore- is the structure restricted to bacteria. It is a tough and non-reproductive structure which is used for the protection in adverse conditions. Thus the primary function of most endospores is to ensure the survival of a bacterium through periods of environmental stress.

Pilus- present n the surface of many bacteria that helps its attachment to the host or other cells.

Capsule- It is a polysaccharide layer that lies outside the cell envelope and is not easily washed off, and it can be the cause of various diseases.

PlaSmid- is the extrachromosomal material which can either integrate to the main chromosome to form episome or lie independently in the bacterial cell. It contains many important genes such as antibiotic-resistant genes that can save bacteria from various antibiotics.

Mitochondria- is cause the powerhouse of the cell as it is the primary site of ATP production in the aerobic metabolism of the eukaryotic cell. It is a double membrane structure. The outer membrane covers the organelle and contains it like skin. The inner membrane folds over many times and creates layered structures called cristae. Various metabolic processes take place here such as Kreb`s cycle, pyruvate oxidation, electron transport chain and oxidative phosphorylation. All these reactions are ultimately important for the generation of energy in the form of ATP.

Chlorop[last- exclusively found in the plant cells. The chloroplast has an inner and outer membrane with an empty intermediate space in between. Inside the chloroplast are stacks of thylakoids, called grana, as well as stroma which is the ground substance. Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells. The entire process is called photosynthesis and it all depends on the little green chlorophyll molecules in each chloroplast.

Vesicle-  A vesicle is a small structure within a cell, consisting of fluid enclosed by a lipid bilayer. Vesicles form naturally during the processes of secretion (exocytosis), uptake (phagocytosis) and transport of materials within the cytoplasm.

Cytoskeleton- is the skeleton of the cell. It gives shape to the cell. It is made up of three types of structures- microtubules, intermediate filaments and microfilaments. It also helps in the cell division.