McDonald enjoyed scoring Celtic's second goal against Motherwell
Celtic went five points clear at the top of the Scottish Premier League as Motherwell were defeated in Glasgow.
Paul Hartley fired the home side into the lead seconds before the half-time interval with an accurate half-volley past Graeme Smith.
Well were reduced to 10 men after the break when David Clarkson was sent off for violent conduct.
Scott McDonald sealed Celtic's win with a low drive into the net from distance after 71 minutes.
Celtic had gone into the match two points clear of Old Firm rivals Rangers, who face Kilmarnock on Sunday.
Motherwell had the first serious attempt at goal when Stephen Hammell's corner found John Sutton, who bundled the ball towards goal but Shaun Maloney headed away on the line.
The Motherwell players claimed the ball had crossed the line, but referee Dougie McDonald waved play on.
Moments later, Celtic striker Scott McDonald found space on the left and cut the ball back for Scott Brown, whose left-foot shot hit the post on its way out.
Sutton then got in behind the Celtic defence to fire in a shot that was comfortably held by Mark Brown, the goalkeeper included in place of Artur Boruc, who is awaiting knee surgery.
At the other end, McDonald's powerful shot was palmed away by Smith.
Chris Porter headed wide from a corner and David Clarkson forced Brown into another save as Motherwell continued to press forward.
Paul Hartley's corner after 28 minutes was headed towards goal by McDonald, but Graeme Smith got down quickly to push the ball away from goal before the danger was cleared.
Clarkson (right) was sent off after 58 minutes at Celtic Park
Smith continued to frustrate Celtic with an excellent save from Cillian Sheridan's powerful left-foot shot.
Celtic had the ball in the net when McDonald headed Andreas Hinkel's cross past Smith, but the striker was penalised for a push on Paul Quinn.
However, the home side did take the lead in the last attack of the first half when Sheridan's cross was headed away by Marc Fitzpatrick on to the chest of Hartley, who controlled the ball before firing beyond Smith.
The visitors threatened an equaliser early in the second half when Stephen Hughes volley from the edge of the box was deflected wide.
From the resultant corner, Sutton's header was cleared off the line, but the referee had already blown the whistle for shoving.
Porter missed an excellent chance to level for Motherwell when he latched on to Sutton's header before shooting wide.
Motherwell were dealt a blow on 58 minutes when Clarkson was sent off.
The striker was fouled by Paul Caddis but then appeared to make contact with the Celtic substitute's face.
McDonald extended Celtic's lead with 19 minutes remaining, drilling the ball past Smith from outside the box.
The disparity in numbers took its toll on Motherwell in the closing stages as they struggled to create openings.
Koki Mizuno made his Celtic debut late on after coming on as a substitute for McDonald and had a shot over the bar in injury time.
Celtic manager Gordon Strachan:
"That was a terrific performance. We knew it was going to be hard. Motherwell started well in the first 20 minutes and then we got our second wind and so did the crowd.
"When you've got 10 players missing, it's a lot to handle. The lads had to get on with it.
"Paul Hartley was good and even in the sticky first 20 minutes I thought he was the best player on the pitch for us in terms of energy and understanding. The longer the game went on, the better he became.
"When the second goal went in, I could just see the players going, 'thank goodness'."
Motherwell manager Mark McGhee:
"To a degree we played well but I'm very frustrated because I think we can play better.
"We've lost today because we weren't good enough. That disappoints me because I think we are good enough to have come here and won this game.
"The results I want are the ones against the Old Firm and the performances I want are the ones against the Old Firm.
"They are the ones that get the players noticed and get them into the Scotland squad."
Celtic: Mark Brown, Hinkel, Caldwell, McManus, Wilson, Scott Brown, Hartley, Robson (Donati 78), Maloney (Caddis 49), McDonald (Mizuno 88), Sheridan.
Subs Not Used: Fox, O'Dea, Hutchinson, Naylor.
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