The cell membranes are following statements is not true

Options

A. Buna-S is a copolymer of butadiene and styrene
B. Natural rubber is a 1,4-polymer of isoprene
C. In vulcanization, the formation of sulphur bridges between different chains make rubber harder and stronger
D. Natural rubber has the trans configuration at every double bond

Explanation

To determine which statement about cell membranes is not true, we will analyze each statement provided in the context of biomolecules and polymers.

### Step 1: Evaluate the First Statement
The first statement claims that buta S is a copolymer of butadiene and styrene.
- **Analysis**: Buta S is indeed a copolymer formed from the polymerization of butadiene and styrene. This statement is true.

### Step 2: Evaluate the Second Statement
The second statement states that natural rubber is a one-four polymer of isoprene.
- **Analysis**: Natural rubber, also known as polyisoprene, is indeed a polymer of isoprene with a 1,4-addition pattern. This statement is also true.

### Step 3: Evaluate the Third Statement
The third statement mentions that in vulcanization, the formation of sulfur bridges between different chains makes rubber harder and stronger.
- **Analysis**: This statement is correct as vulcanization involves the cross-linking of rubber molecules through sulfur bridges, which enhances the strength and elasticity of rubber.

### Step 4: Evaluate the Fourth Statement
The fourth statement claims that natural rubber is a trans-configuration of every double bond.
- **Analysis**: This statement is false. Natural rubber (polyisoprene) predominantly has a cis-configuration at the double bonds, not trans. Therefore, this statement is not true.

### Conclusion
The statement that is not true is the fourth one: "Natural rubber is a trans-configuration of every double bond."