Which cell lacks a nucleus?
a. muscle cell
b. euglena
c. fungal cell
d. bacterial cell

bacterial cell (D)

Explanation: they are very simple cells.

D. Bacterial cell

Explanation:

The cells that lack a nucleus are called prokaryotic and are very simple archaic cells that lack a nucleus and have all of the DNA material is loose inside the cell, all of the other types of cells have a nucleus, Muscle cells, Fungal and Euglena all of those cells have nucleus. Nucleutic cells are part of evolution and that is why most of the cells that we can find nowadays have a nucleus.

enzyme active site and substrate specificity

enzymes bind with chemical reactants called substrates. there may be one or more substrates for each type of enzyme, depending on the particular chemical reaction. in some reactions, a single-reactant substrate is broken down into multiple products

it marks things for degradation via the proteasome. it alters there celluar location.