Diatom Cells are enclosed in a cell wall made up of silica or hydrated silicon dioxide namely frustule. The frustule has small walls where nutrients enter, enabling it to perform photosynthesis the same way plants do.
Answer:
Covalent bonding occurs when pairs of electrons are shared by atoms. Atoms will covalently bond with other atoms in order to gain more stability, which is gained by forming a full electron shell. By sharing their outer most (valence) electrons, atoms can fill up their outer electron shell and gain stability
The model describes how cellular membranes i.e. lipid bilayers are organized. Despite the fluidity, lipid bilayers can form certain domains with different characterisrics and compositions. The cell can use different mixtures of lipids to create a 'mosaic' or 'patchwork' of domains.
An example of such domains are so called 'lipid rafts' which are aggregates of certain lipids (mostly cholesterol and sphingomyelins). In these rafts the lateral diffusion of membrane-bound proteins is strongly reduced, thereby forming stable complexes to facilitate, for example, signal-processing and transduction.
Note that a lot about how or why a cell creates these domains is still unknown.
Inactivates certain harmful byproducts of digestion and respiration and then sends them to the plasma membrane to be ejectdd