Question

question 1-3 which of these elements may be found in a protein but not in a lipid? carbon oxygen nitrogen hydrogen

Explanation:

1. Recall the elemental composition of proteins and lipids:

• Proteins are made up of carbon, hydrogen, oxygen, and nitrogen (and sometimes sulfur, phosphorus, etc.). The basic structure of an amino acid (the building block of proteins) contains an amino group (\( -NH_2 \)) which has nitrogen.
• Lipids (like fats, oils, phospholipids) are mainly composed of carbon, hydrogen, and oxygen. Most lipids do not contain nitrogen.
• Carbon, hydrogen, and oxygen are common to both proteins and lipids. Nitrogen is present in proteins (due to amino groups in amino acids) but not typically in lipids.

Answer:

nitrogen (the option corresponding to nitrogen)