In this review, we elucidate the mechanisms of A beta oligomer toxicity which may contribute to Alzheimer's disease (AD). In particular, we discuss on the interaction of A beta oligomers with the membrane through the process of adsorption and insertion. Such interaction gives rises to phase transitions in the sub-structures of the A beta peptide from alpha-helical to beta-sheet structure. By means of a coarse-grained model, we exhibit the tendency of beta-sheet structures to aggregate, thus providing further insights to the process of membrane induced aggregation. We show that the aggregated oligomer causes membrane invagination, which is a precursor to the formation of pore structures and ion channels. Other pathological progressions to AD due to A beta oligomers are also covered, such as their interaction with the membrane receptors, and their direct versus indirect effects on oxidative stress and intraneuronal accumulation. We further illustrate that the molecule curcumin is a potential A beta toxicity inhibitor as a beta-sheet breaker by having a high propensity to interact with certain A beta residues without binding to them. The comprehensive understanding gained from these current researches on the various toxicity mechanisms show promises in the provision of better therapeutics and treatment strategies in the near future.