Cell Biology and Structure

Plastids, responsible for photosynthesis, possess numerous internal membrane layers called thylakoids. These are the sites of light absorption and ATP synthesis, and contain many proteins, including those involved in the electron transport chain. Photosynthetic pigments such as chlorophylls a, b and c, and some others like xanthophylls, carotenoids and phycobilins are also embedded within this membrane, thus plastids are responsible for photosynthesis containing numerous internal membranes.

Amyloplasts are the largest leucoplasts. They function in storage of starch.

Elaioplasts are the leucoplasts which store fats.

The rod-shaped bacteria are called bacilli, round shaped are called cocci, spiral shaped are called spirilla, and comma-shaped are called vibrious. 

Some bacteria survive adverse conditions by forming a spore or a cyst (a protective coating). When the environment improves, they come to life again, and begin multiplying.   

Besides being selectively permeable, plasma membrane of eukaryotes also functions in synthesis of ATP through chemiosmosis.

Caveolae are the small invaginations of plasma membrane of many vertebrate cell types, especially in endothelial cells and adipocytes. These are rich in proteins and lipids.

Podosomes are connected to cellular motility and invasion. Therefore, they serve as sites of attachment and degradation along the extracellular matrix.

Lipid rafts and caveolae microdomains of the cell membrane are rich in cholesterol.

The actin-based filaments formed by cytoskeleton in order to sense the external environment are called filopodia. They are rich in actin-binding proteins, e.g. fascin and fimbrin. Filopodia are slender cytoplasmic projections that form focal adhesion with the substrate linking it to the cell surface.

Cell membrane of myocytes is known as sarcolemma. It consists of a plasma membrane, which is a lipid bilayer, and an outer coat consisting of a thin layer of polysaccharide material (glycocalyx) that contacts the basement membrane, which contains numerous thin collagen fibrils and specialized proteins such as laminin that provide a scaffold for the muscle fiber to adhere to it.

G-proteins are an example of lipid-anchored proteins. G-proteins act as molecular switches inside the cell and are involved in transmitting signals from a variety of stimuli outside a cell to its interior.

The inner mitochondrial membrane is very rich in proteins. It contains proteins in the form of enzymes required for electron transport chain.

Sphingolipids are not found in cell membrane.

In yeast and plant cells, long fatty acids are converted to medium chain fatty acids, which are eventually broken down to carbon dioxide and water exclusively in the peroxisomes.