During photosynthesis, light energy is used to produce ATP molecules which are then used to construct sugar molecules from carbon dioxide and hydrogen obtained from water. Chloroplasts have two outer membranes and several stacks of small disc-shaped membranes called thylakoids (also spelled thylacoids) inside.
Scheduling a week off will give your body time to do this and will also help you return to your workout stronger and ready to challenge your body once again. Many endurance athletes end their season with a week off and many weightlifters will take a week off from their program every four to eight weeks.
A toning style core routine can be performed 4-6 days per week once you have built up your tolerance for those exercises, but if you become overly sore you may need to take a 48 hour break to allow muscles to properly heal. Just make sure you take at least one day off each week, even if you never get sore.