只要是生物，一定是由细胞构成的．（判断对错）

按教材填空

（1）有些蛋白质起____ 作用，能够调节机体的生命活动，如胰岛素．

（2）核酸是细胞内____ 的物质，在生物体的遗传、变异和蛋白质的生物合成中具有极其重要的作用．

（3）功能越复杂的细胞膜，____ 越多．

（4）____ 染液是将活细胞中线粒体染色的专一性染料，可以使活细胞中的线粒体呈现蓝绿色，细胞质接近无色．

（5）这些____ 等结构，共同构成细胞的生物膜系统．

（6）____ 称为原生质层．

    Finding out what kind and how much physical activity you need

    How do I do it?

    It's your choice. Pick an activity that's easy to fit into your life. Do at least 10 minutes of physical activity at a time. Choose aerobic activities that work for you. These make your heart beat faster and can make your heart, lungs, and blood vessels fitter. Also, do strengthening activities which make your muscles do more work than usual.

    Why should I be physically active?

    Physical activity can make you feel stronger and more alive. It is a fun way to be with your family or friends. It also helps you improve your health.

    How many times a week should I keep physically active?

    It is up to you, but it is better to spread your activity throughout the week and to be active at least 3 days a week.

    How do I build up more physical activity?

    Do a little more each time. Once you feel comfortable, do it more often. Then you can trade activities at a moderate level for vigorous ones that take more effort. You can do moderate and vigorous activities in the same week.