Options price is dependent on underlying or buy/sell orders? Irrespective of available buy/sell orders in options, will the options price increase/decrease automatically if underlying increases/decreases?
Most of option movement is by algos, rather than manual traders.
So you can expect option to efficiently price in the move which happened in underlying
Options Prices are derived from Black Scholes Formula.
The Black Scholes model requires five input variables: the strike price of an option, the current stock price, the time to expiration, the risk-free rate, and the volatility.
Based on the above variable prices are determined.