Bear in mind that the Arduino digital and anlog read/write abstractions that make this platform so easy to use, do reduce the execution time over what could be achieved if one used low level code to directly access these functions. The arduino functions will be slower than the timings quoted above.
For example, the Arduino digitalRead function first does a lookup to convert the Arduino pin number to an actual port and pin. It then disables any PWM function that could be running on this pin. And finally, it executes another dozen instructions or so to actually read the port. I would think it would take well over twenty times longer for each digitalRead compared to directly accessing a specific low level port pin.
AnalogRead also does the Arduino pin mapping lookup and it sets the analog reference bits each time analogRead is called, although this probably represents a small fraction of the total ADC conversion time.
If your application does need digital read times under a microsecond, you can read more about direct port manipulation here: Arduino Reference - Arduino Reference