The answer to this is totally different depending on your pace and personal fitness level.
Most people who'd call themselves a long distance runner can run at least a 5k at a moderate pace without breathing hard. However, if you run a 5k at sub-5 minute mile pace, you're going to be very tired unless you're a very good runner. It all depends on how hard you push yourself and how fit you are to begin with.
If you're exhausted by running a short distance like 1km, you probably just need to work on building up your aerobic fitness. Try running until you're slightly out of breath/tired, then walk a little, then start up and run 1km again. Do this for a while, slowly lengthening the interval you run.
It's also important to not try and go too fast right away. For example, running 1km in five minutes is a fairly fast pace for a total beginner. You might try running up to one minute slower and try to go longer, in order to build up endurance.
The answer to this is totally different depending on your pace and personal fitness level.
Most people who'd call themselves a long distance runner can run at least a 5k at a moderate pace without breathing hard. However, if you run a 5k at sub-5 minute mile pace, you're going to be very tired unless you're a very good runner. It all depends on how hard you push yourself and how fit you are to begin with.
If you're exhausted by running a short distance like 1km, you probably just need to work on building up your aerobic fitness. Try running until you're slightly out of breath/tired, then walk a little, then start up and run 1km again. Do this for a while, slowly lengthening the interval you run.
It's also important to not try and go too fast right away. For example, running 1km in five minutes is a fairly fast pace for a total beginner. You might try running up to one minute slower and try to go longer, in order to build up endurance.