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.
Typically, if you lift 60%-80% of max, you could do anywhere from 10-20 reps. Lifting at 80% and above takes you down to the lower rep range, which is where you'll be if you're trying to gain size. That means keeping your reps somewhere between 8-16, if you're lifting for weight loss and fitness. Your weights are determined by the number of reps you're doing.