Name one element invariably found in proteins but not in all carbohydrates and lipids.

Explanation

To answer the question, "Name one element invariably found in proteins but not in all carbohydrates and lipids," we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Basic Biomolecules**: Understand that the three main types of biomolecules are proteins, carbohydrates, and lipids.

2. **List Common Elements**: Recognize that proteins, carbohydrates, and lipids are primarily composed of carbon (C), hydrogen (H), and oxygen (O).

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