Strange as it may seem, a few Christian teachers assert that 'confessing Jesus as Lord' (e.g., Rom. 10:9) doesn't mean acknowledging and submitting to his authority, but only means believing in his Deity. But I think it's clear that Jesus' own words contradict such a notion, for he himself asked, "Why do you call me, 'Lord, Lord,' and do not do what I say?" (Luke 6:46, compare verses 47-49). So, for yet another reason, we affirm once again, to be a Christian is to be a person committed to comprehensive obedience to Jesus, via his Word.
One more point worth making: I'm not sure why affirming that Jesus is God wouldn't also entail acknowledging/submitting to his authority!