physical and chemical changes in the digestive system notes - 2011
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Physical and Chemical Changes in the Digestive System
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Digestion and Nutrients Digestion: is the process where food is broken down by the digestive system into small nutrients to be absorbed by the body
Nutrients: are very tiny molecules that are broken down from large molecules to be absorbed and used by body cells.
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DigestionThere are two types of digestion:
� Mechanical digestion: Changes the physical form of food (physical changes)
� Chemical digestion: Changes the chemical composition of food into a new substance with the aid of digestive enzymes ( chemical changes)
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It takes place inside the mouth where teeth and tongue breakdown food. (Physical Changes)
� Chew
� Tear
� Grind
� Mash
� Mix
� Crush
Mechanical Digestion = Physical Change
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Chemical Digestion = Chemical Change� The salivary glands secrete mucus and an
enzyme called saliva that breaks down carbohydrates in to sugar.
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Esophagus� The esophagus is a muscular tube. As we
swallow, we push food along the tube until the food reaches our stomach. This process of pushing down the food is called peristalsis
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Stomach� The stomach mixes the Food with gastric
juices called pepsin to form chyme. � The chemical digestion of proteins begins in
the stomach.
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Which type of digestion?
� Chewing a saltine?
� Saliva breaking the saltine down into molecules of glucose?
� Your tongue breaking pieces of a hamburger apart?
� Pepsin (an enzyme) in your stomach breaking the hamburger into amino acids?
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Small Intestines
� Here where fat molecules are broken down into smaller molecules. Which is an example of chemical digestion
� The remaining food is pushed down (peristalsis) to exit the digestive system.Which is an example of physical digestion.
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Digestion Video
�http://www.youtube.com/watch?v=AEsQxzeAry8&feature=related
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Why Do We Eat?
� The food we eat has chemical energy stored in it.
� This energy is released by breaking the food down by the digestive system.
� The law of conservation of energy states: Energy can’t be destroyed or created. Energy changes forms.
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Why Do We Eat?
Body uses this released energy to:
Walk, Jump, Talk, Breath by changing
� Chemical energy Mechanical energy.
Also to generate body heat by changing.
� Chemical energy Heat energy.