Cell Organelles

Cells are two types  prokaryotic cells and eukaryotic cells. Both of these types of cells have several things in common. All cells are surrounded by a plasma membrane, which is made of a double layer of phospholipids . Within this membrane which is semipermeable, is the cytoplasm which is composed of the fluid and organelles of the cell.

Plasma Membrane: The plasma membrane is composed of a phospholipid bilayer, which is two layers of phospholipids back to back. Phospholipids are lipids with a phosphate group attached to them. The phospholipids have one head and two tails. The head is polar and hydrophilic, or water loving. The tails are nonpolar and hydrophobic, or water hating.

Eukaryotic cell evolved from prokaryotes:

The theory of Endosymbosis where eukaryote cells evolved from prokaryote cells. Organelles in eukaryote cells such as mitochrondria and chloroplasts suggest eukaryote cells came from prokaryote cells. Mitochrondria and chloroplast have their own genetic material different from that of the cell. Mitochondria and Plastids have a double membrane envelope surrounding cytoplasm .

Prokaryotic cell lack membrane  bounded  organelles.

Cell organelles present in prokaryotic cell are

Cell wall: The cell wall surrounds the plasma membrane and protects the cell from changes in water pressure.

The bacterial cell wall consists of peptidoglycan (or murein), a polymer consisting of N-acetylglucosamine(NAG) and N-acetylmuramic acid ( NAM) and short chains of amino acids. N- acetylglucosamine(NAG) and N-acetylmuramic acid ( NAM) molecules are alternatively arrange with Glucose back bone and both are linked with polypeptide L-alanine, D-glutamine, L-lysine, D-alanine with a 5-glycine.

Carboxysomes : Carboxysomes are intracellular structures that contain enzymes involved in carbon fixation and found in many autotrophic bacteria. Carboxysomes are made of polyhedral protein shells filled with the enzyme Ribulose-1,5-biphosphate carboxylase/oxygenase.

Chlorosomes: chlorosomes  are light-harvesting antenna , which are oblong bodies attached to the inner side of the cytoplasmic membrane. Antennae always contain chromophores such as chlorophylls, bacteriochlorophylls, linear tetrapyrroles, or carotenoids .In  Chlorosomes  pigment, bacteriochlorophyll (BChl) .

Energy path:
carotenoid → Bchl c _chlorosome → Bchl a _baseplate → Bchl a _antenna → Bchl _{reaction center}

Mesosome:Mesosome is a convoluted membranous structure formed in a prokaryotic cell by the invagination of the plasma membrane. These extensions help in the synthesis of the cell wall and replication of DNA. They also help in the equal distribution of chromosomes into the daughter cells.It also increases the surface area of the plasma membrane to carry out various enzymatic activities.It helps in secretion processes as well as in bacterial respiration.

Ribosomes: prokaryotic ribosomes are 70S ribosomes. Ribosomes consist of two subunits, 30S and 50S. These ribosomes units are denoted by Svedberg (S) values depending on the rate of the sedimentation in the centrifugation that value is 64 and 72 .In prokaryotes, rRNA is organized into three strands in ribosomes .50s subunit contains 23s and 5s rRNA with 34 proteins,30s subunt contains 16srRNA and 21 proteins. Weight of 50s is 1.8*10⁶, 30s subunit weight is 1.0*10⁶.

Flagellum:Flagellum is made up of a monomer of globular protein called "flagellin." The flagellin is made of the "filament" which is composed of a triple helix and a hollow core. Bacterial flagella are helically shaped structures . The base of the flagellum (the hook) near the cell surface is attached to the basal body enclosed in the cell envelope. The flagellum rotates in a clockwise or counter clockwise direction, in a motion similar to that of a propeller. It drive energy from ion gradient.

Nucleoid: The nucleoid is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material. nucleoid is largely composed of about 60% DNA, plus a small amount of RNA and Protein.

Plasmid:

Plasmids are the extra chromosomal structures in the cells of bacteria which have the ability to self replicate. They do not combine with the genetic material of the host cell but stay independently.it is double stranded non-chromosomal DNA, but in some times they are circular. They make their structure circular by combining the two ends of the double stranded DNA together through covalent bonds.it carry antibiotic resistant genes , genes which are involved in metabolic activities and are helpful in digesting the pollutants from the environment.  They are also capable of producing antibacterial proteins.

Thylakoid: A thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis.

All eukaryotic cells have within them a variety of different structures called organelles. Organelles are small and function much like organs function in a large organism.  Some organelles are responsible for gathering cell energy, others for controlling cell activities.  Plant cells have different organelles and animal cells have different organelles.

Cell organelles present in Eukaryotes:

Endoplasmic Reticulum

Golgi Complex

Lysosomes

Vacuoles

Peroxisomes

Glyoxysomes

Nucleus

Mitochondria

Chloroplasts
Each of these organelles performs a specific function critical to the cell's survival. Moreover, nearly all eukaryotic organelles are separated from the rest of the cellular space by a membrane. Endoplassmic reticulum,Golgi complex,vacuoles,peroxisomes,are enclosed with single membrane . 

Nucleus,Mitochondria,chloroplast ,and lysosomes are enclosed by double membrane.