Which type of macromolecule regulates cell ­processes or transports material into and out of cells?

Proteins

Explanation:

Proteins perform several functions such as regulation of cellular processes and transport of materials in and out of the cells.

Some proteins serve as enzymes and catalyze the cellular processes and thereby regulate the rate of the product formation. Proteins such as transcription factors regulate the expression of several genes. Some hormones are proteins or derived proteins. Insulin is an example which in turn regulates the blood glucose levels in the body.  

Some of the proteins present in the cell membrane serve as channels and pumps to allow the transport of various substances across the cell membrane.  

any abiotic or biotic factor in an ecosystem that causes a population's size to slow or decrease is a limiting factor.