What will be the molecular formula of a polypeptide consisting of 10 glycine residues ?

Options

A. `C_6H_(12)ON_5`
B. `C_(20)H_(32)O_(11)N_(10)`
C. `C_(30)H_(16)O_(6)N_(10)`
D. `C_(20)H_(30)O_(12)N_(10)`

Answer

To determine the molecular formula of a polypeptide consisting of 10 glycine residues, we can follow these steps:

### Step 1: Understand the structure of Glycine
Glycine is the simplest amino acid with the following molecular structure:
- **Chemical formula of Glycine (C2H5NO2)**:
- 2 Carbon (C)
- 5 Hydrogen (H)
- 1 Nitrogen (N)
- 2 Oxygen (O)

### Step 2: Calculate the total for 10 Glycine residues
When we have 10 glycine residues, we can multiply the number of each atom by 10:
- **Carbons**: 2 * 10 = 20
- **Hydrogens**: 5 * 10 = 50
- **Nitrogens**: 1 * 10 = 10
- **Oxygens**: 2 * 10 = 20

So, initially, we have:
- C = 20
- H = 50
- N = 10
- O = 20

### Step 3: Account for the formation of peptide bonds
When glycine residues are joined together to form a polypeptide, peptide bonds are formed. Each peptide bond formation results in the elimination of one water molecule (H2O).

### Step 4: Determine the number of peptide bonds
For 10 glycine residues, there will be:
- **Number of peptide bonds** = 10 - 1 = 9

### Step 5: Calculate the atoms removed due to water elimination
Each water molecule (H2O) consists of:
- 2 Hydrogen (H)
- 1 Oxygen (O)

Since 9 water molecules are eliminated during the formation of peptide bonds:
- **Hydrogens removed**: 9 * 2 = 18
- **Oxygens removed**: 9 * 1 = 9

### Step 6: Adjust the total atom count
Now we need to subtract the atoms removed from the initial total:
- **Final Carbons (C)**: 20 (no change)
- **Final Hydrogens (H)**: 50 - 18 = 32
- **Final Nitrogens (N)**: 10 (no change)
- **Final Oxygens (O)**: 20 - 9 = 11

### Step 7: Write the final molecular formula
The final molecular formula for the polypeptide consisting of 10 glycine residues is:
- **C20H32N10O11**