Life Processes

MRS GREN Living things have certain life processes in common. There are seven things that they need to do to count as being alive. The phrase MRS GREN is a way to remember them: M-Movement-All living things move, even plantsR-Respiration-Getting energy from foodS-Sensitivity-Detecting changes in the surroundingsG-Growth-All living things growR-Reproduction-Making more living things of the same typeE-Excretion-Getting rid of wasteN-Nutrition-Taking in and using food

Respiration Respiration is a chemical reaction that happens in all living cells. It is the way that energy is released from glucose, for our cells to use to keep us functioning. Aerobic respiration The glucose and oxygen react together in the cells to produce carbon dioxide and water. The reaction is called aerobic respiration because oxygen from the air is needed for it to work. Glucose from food to cells Glucose is a type of carbohydrate, obtained through digestion of the food we eat. Digestion breaks food down into small molecules. These can be absorbed across the wall of the small intestine into the bloodstream.Glucose is carried round the body dissolved in blood plasma, the pale yellow liquid part of our blood. The dissolved glucose can diffuse into the cells of the body from the capillaries. Once in the cell glucose can be used in respiration. Oxygen from the air to cells When we breathe in oxygen enters the small air sacs, called alveoli, in the lungs. Oxygen diffuses from there into the bloodstream. Oxygen is not carried in the plasma, but is carried by the red blood cells. These contain a red substance called haemoglobin, which joins onto oxygen and carries it around the body in the blood, then lets it go when necessary. Like glucose, oxygen can diffuse into cells from the capillaries.Red blood cells carry oxygen around the body Carbon dioxide from cells to the air The carbon dioxide produced during respiration diffuses out of the cells and into the blood plasma. The blood carries it to the lungs. It then diffuses across the walls of the alveoli and into the air, ready to be exhaled.

The respiratory system and ventilation The respiratory system The human respiratory system contains the organs that allow us to get the oxygen we need and to remove the waste carbon dioxide we don't need. It contains these parts: lungs tubes leading from the lungs to the mouth and nose various structures in the chest that allow air to move in and out of the lungs. Ventilation Movements of the ribs, rib muscles and diaphragm allow air into and out of the lungs. Take care - this is called breathing or ventilation, not respiration. When we breathe in, we inhale. When we breathe out, we exhale.Air passes between the lungs and the outside of the body through the windpipe, called the trachea. The trachea divides into two bronchi, with one bronchus for each lung.Each bronchus divides further in the lungs into smaller tubes called bronchioles. At the end of each bronchiole, there is a group of tiny air sacs. These air sacs have bulges called alveoli to increase their surface area.

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