A DNA molecule consists of two stands of nucleotides that wind around each other like a twisted ladder with a phosphate and sugar backbone. The nitrogenous bases are divided into two groups called the pyrimidines and the purines. The pyrimidines include the thymine and cytosine, the purines are adenine and guanine. The nitrogenous bases in the double helix are bound together according to the base pairing rule. Adenine pairs with thymine (A-T) and guanine pairs with cytosine (G-C). The student either drew the base pairing showing adenine and thymine or guanine pairing with cytosine.
Answer:
chloroplasts
Explanation:
this is fourth grade level stuff.
Answer:
They keep toxic substances out of the cell
Explanation:
They contain receptors and channels that allow specific molecules, such as ions, nutrients, wastes, and metabolic products, that mediate cellular and extracellular activities to pass between organelles
