Energy stores/transfers, work, renewable/non-renewable resources, and efficiency.

Mass/weight, density, Newton’s laws, friction, moments, circular motion, momentum, and pressure.

Measurement tools, scalars/vectors, resultant vectors, and motion kinematics (graphs, acceleration, free fall).

Respiration Energy from respiration Respiration is the chemical process in cells that releases energy from glucose. Cells use this energy for: muscle contraction; protein synthesis; cell division; active transport; growth; nerve impulses; and maintaining body temperature. Respiration is not the same as breathing. Breathing moves air into and out of the lungs; respiration releases energy in cells. Aerobic respiration Aerobic respiration uses oxygen to break down glucose and releases a large amount of energy. ...

Gas exchange in humans Gas-exchange surfaces A gas-exchange surface needs: a large surface area, providing many sites for diffusion; a thin surface, giving a short diffusion distance; a good blood supply, maintaining concentration gradients; and good ventilation, replacing air and maintaining concentration gradients. Alveoli provide these features. Their large total surface area gives many diffusion sites, their walls are one cell thick, capillaries carry away oxygen and bring carbon dioxide, and ventilation continually refreshes the air. ...