Microalgae have been so far identified as the major producers of organic matter through their photosynthetic activities. In the present work, Nannochloris sp. and Amphora sp., two marine microalgae, have been investigated for proteins and lipids production. Protein fraction was quantified using Bicinchoninic acid (BCA) assay. Protein content in Nannochloris sp. was 16.69 ±4.07 % of dry mass and in Amphora sp. it was 39.89 ±2.09 % of dry mass. Enzyme assays were conducted spectrophotometrically. Nannochloris sp. had malate dehydrogenase, peroxidase and catalase activities. Amphora sp. exhibited malate dehydrogenase, catalase and cytochrome C oxidase activities. These enzymes have several valuable applications in some metabolic pathways and as antioxidant nutrition additives. Besides, lipid extraction was conducted using methanol/ chloroform solvent extraction. Crude lipid extract was analyzed using gas chromatography-mass spectrometry. Lipid contents were 8.14 ±3.67 % in Nannochloris sp. and 10.48 ±1.26% on dry basis in Amphora sp., respectively. Nannochloris sp. fatty acids were composed of C16:0 and C18:0 that are valuable for biodiesel production, and É-3 C18:3, É-6 C18:2, É-6 C16:2 having great nutritional values. In Amphora sp., the fatty acids consisted of C14:0, C16:0 and C16:1 shown to be valuable for biodiesel production and É-3 C22:6 having high nutritional values. Furthermore, a single step conversion of microalgal oil to fatty acid methyl esters was carried out starting directly from lyophilized microalgae. This promising process, in situ transesterification, led to better yields of methyl esters as compared to conventional lipid extraction followed by separate transesterification.