Nutrients are absorbed directly into the cell from the external environment. Most animals obtain nutrients by ingestion, taking food into their bodies where it is digested and absorbed. Plants, being autotrophs, produce their food internally. A few fungi, such as yeasts and chytrids, may be single-celled, but these represent a very small percentage of the estimated 1.5 million species. Plant cell walls contain cellulose, not chitin.
Animals lack cell walls altogether.
Although fungi may seem to be as unlike ourselves as any organism can be, there are many things we have in common. In common with all living things fungi must obtain energy and they must obtain foods to be used as the building blocks for their own bodies. They must reproduce and they must be able to travel through space and time. Like humans, fungi utilize organic sources of carbon for the energy to power their life functions. Most of the sources of energy used by humans are also used by fungi.