In amoeba, all functions are carried out by the single cell. Especially when amoeba ingests food through phagocytosis or pinocytosis then it makes a vacuole around the food particle. The vacuole in amoeba is contractile in nature. This contractility is important to accommodate food of various sizes and to have enough digestive enzymes. Moreover, amoeba being an aquatic animal the contractile vacuole helps in maintaining the tonocity of the cell as well.

The centrioles form the basal body of cilia or flagella, and spindle fibres that give rise to spindle apparatus during cell division in animal cells.

The centrioles form the basal body of cilia or flagella, and spindle fibres that give rise to spindle apparatus during cell division in animal cells.

An elaborate network of filamentous proteinaceous structures present in the cytoplasm is called the cytoskeleton.

When the transportation of substance takes place against concentration gradient it is called active transport.

The only cell organelle seen in a prokaryotic cell is ribosomes.

Shapes of bacteria:
i) Bacillus (rod-shaped)
ii) Coccus (spherical)
iii) Vibrio (comma shaped)
iv) Spirillum (spiral shaped)

The different types of plastids leucoplasts chromoplasts chloroplasts such as are interchangeable. The transformation from chloroplasts is observed during ripening of fruits (e.g Tomato, Chilli) when they change their color from green to reddish orange. It takes place through loss of chlorophylls and degeneration of lamellae. The most common carotenoid of the fruit is lycopene. Petals of Calendula develop orange yellow color due to the formation of chromoplasts from proplastids.
Carrot root develops it characteristic color because of the conversion of leucoplasts into chromoplasts.It is rich in carotene.

Vacuoles in plant cell contain not only unuseful substances and water but also contains pigments and toxic molecules. Tonoplast is the covering membrane of the vacuoles.

Lysosomes are the organelle known as suicide bags. They consist of a single membrane surrounding powerful digestive enzymes. If the membrane of a lysosome breaks, the enzymes released may also destroy the cell itself, giving lysosomes the name suicide bag.

The nucleolus is a ribosome factory. It combines RNAs with proteins to produce ribosome subunits. After their formation, the ribosome subunits pass out and get established in the cytoplasm. It also receives and stores ribosomal proteins formed in the cytoplasm.

Nuclear pores are the opening/pores in the nuclear envelope, formed by the fusion of its two membranes. These pores help in the exchange of materials, especially RNA, proteins, ribosomes, etc.,between the cytoplasm and nucleoplasm.

The main structures within the cell nucleus are
(i) The nucleus which is an optically dense region, spherical shaped, where there are concentrated ribosomal RNA associated to proteins.
(ii) The chromatin made up of DAN molecules dispersed in the nuclear matrix during the cell interphase.
(iii) The nuclear membrane that delimits the nucleus.

Inclusion bodies are the non-living structures present in cytoplasm not bounded by, the membrane system.They may either lie free in cytoplasm or may be covered by 2-4 nm-thick, non-protein membrane, e.g., vacuoles sulphur granules etc.

Mesosome is a special membrane structure, formed by the extension of the plasma membrane into the cell in a prokaryotic cell. It helps in cell wall formation, DNA replication and its distribution to daughter cells. It also helps in respiration, secretion process, to increase the surface area of the plasma membrane and enzymatic content.