They are basically composed entirely of one type of linear protein known as actin. And one common example of the use of microfilaments is in the contraction of cells and specifically in the contraction of muscle cells, one type of cell found in our bodies. So basically during muscle contraction what happens is there is an interaction taking place between the actin found in our microfilament as well as a different type of protein known as meiosin. So myosin basically grabs the act and it pulls on it. So it walks on it and this creates our contraction of the muscle cell. Now, microfilament contain a negative end as well as a positive end.