Which is correct statement?

Options

A. Starch is a polymer of `alpha`-glucose
B. Amylose is a component of cellulose
C. Proteins are composed of only one type of amino acids
D. In cyclic structure of pyranose, there are five carbons and one oxygen atom

Answer

To determine which statement is correct among the provided options, let's analyze each statement step by step.

### Step 1: Analyze the first statement
**Statement:** Starch is a polymer of alpha-glucose.

**Analysis:**
- Starch is not just a single polymer; it is a mixture of two polymers: amylose and amylopectin.
- Amylose is a linear polymer that constitutes about 10-15% of starch, while amylopectin is a branched polymer that makes up about 80-85% of starch.
- Therefore, this statement is **incorrect**.

### Step 2: Analyze the second statement
**Statement:** Amylose is a component of cellulose.

**Analysis:**
- Amylose is actually a component of starch, not cellulose.
- Cellulose is made up of beta-glucose units, while amylose consists of alpha-glucose units.
- Thus, this statement is also **incorrect**.

### Step 3: Analyze the third statement
**Statement:** Proteins are composed of only one type of amino acid.

**Analysis:**
- Proteins are composed of 20 different amino acids, which can combine in various sequences to form different proteins.
- Therefore, this statement is **incorrect**.

### Step 4: Analyze the fourth statement
**Statement:** In the cyclic structure of pyranose, there are 5 carbon atoms and 1 oxygen atom.

**Analysis:**
- The cyclic structure of pyranose (a six-membered ring) actually contains 5 carbon atoms and 1 oxygen atom.
- The structure consists of 5 carbon atoms and 1 oxygen atom forming a hexagonal ring.
- Thus, this statement is **correct**.

### Conclusion
The correct statement among the options provided is: **In the cyclic structure of pyranose, there are 5 carbon atoms and 1 oxygen atom.**

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