Parenchyma cells are the abundant cells that make up ground tissues in plants.They are flat at point of contact.they have thin primary cell walls and have large vacuoles for storage of food.In leaves they are called mesophyll and are sites of photosynthesis.In other parts they are sites for respiration and protein synthesis.
Sclerenchyma cells are cells with rigid secondary cell walls.Their cell walls are hardened with lignin which is the main chemical component of wood.Mature sclerenchyma cells cannot elongate and most of them are dead.
The two principal types of connective tissue in a
muscle are collagen and myofibrils. The entire muscle is wrapped in collagen to
form a fascicle. Looking at one muscle fiber, you will see that almost the
entire cross section of the muscle fiber is composed of long, cylindrical
strands of proteins called myofibrils<span>. </span>
We have been able to see more of the cell in detail. We dont have to guess about things because we can see how it works. The more we see the more theories change because we know more.
