Physical vs. Chemical Changes in Digestion

Types of Physical Changes These changes only alter the APPEARANCE of the substance NOT their chemical composition! – Change in shape – Change is size – Change in mass – Change in the state matter (solid, liquid, gas)

Physical Changes Brainstorm some possible physical changes of an apple.

Signs of Chemical Changes NOT reversible These changes alter the substance so that a new substance with NEW properties appears and is NOT reversible: – Unexpected color change or odor – Release of heat, light, or sound – Produces gas (bubbles), or formation of a solid – NEW substance, with NEW properties

Physical vs. Chemical Changes How could you physically change a piece of paper? How could you chemically change a piece of paper? If you chemically changed the paper, what would the paper change into?

Test your real world skills! Color/dye your hair- physical or chemical? Burning down trees-physical or chemical? Bake a cake- physical or chemical? Ice cubes melting- physical or chemical? Rust on a nail- physical or chemical? Acids breaking down food in your stomach- physical or chemical?

The Digestive System Purpose of the Digestive system: Breaks down food into substances that cells can absorb and use. How is food digested? – Breaking down of food into smaller pieces by chewing Movement through the digestive tract – Chemical breakdown of the large molecules of food into smaller molecules – Chemical breakdown of the large molecules of food into smaller molecules (MACROMOLECULES TO MICROMOLECULES)

Stages of Digestion Phases Include Phases Include 1.Ingestion (taking in food) 2.Digestion (breaking food down) 3.Absorption (nutrients into bloodstream) 4.Elimination / Egestion (leftover waste removal)

Mouth Mechanical (physical) digestion – teeth Mechanical (physical) digestion – teeth Chemical digestion – saliva Chemical digestion – saliva Chewing mixes the food with saliva to make it moist and easy to swallow. Enzymes in the saliva begin digestion of carbohydrates into sugar Enzymes in the saliva begin digestion of carbohydrates into sugar.

Esophagus Muscular tube moves food by waves of muscle contraction called peristalsis It moves food by waves of muscle contraction called peristalsis. This physically moves the food along to the stomach.

Stomach The stomach lining produces strong acids but don’t worry, the stomach is also lined with mucus which keeps the acids from eating their way through enzymes and acidsbreak down and dissolve organic compounds (chemical digestion) Enzymes and acids create chemical reactions in the stomach, enzymes and acids break down and dissolve organic compounds (chemical digestion) (chemical energy-> thermal energy) When bonds are broken during digestion heat is released (chemical energy-> thermal energy)

Small Intestine organic compounds (nutrients) are broken down small enough to pass through the lining of the small intestine, and into the blood stream through villi (absorption) The organic compounds (nutrients) are broken down small enough to pass through the lining of the small intestine, and into the blood stream through villi (absorption). Enzymes continue the chemical reactions on the food. Digests proteins, fats, and carbohydrates.

Large Intestine Absorbs extra nutrients & water Absorbs extra nutrients & water Forms wastes into solid feces Forms wastes into solid feces Physical Digestion occurs, liquid to solid state

Liver Gall Bladder Produces bile to help digest fat (chemical digestion) Produces bile to help digest fat (chemical digestion) filters out toxins and waste including drugs and alcohol Stores bile from the liver, releases it into the small intestine. Stores bile from the liver, releases it into the small intestine. Fatty diets can cause gallstones

Pancreas Produces digestive enzymes to digest macromolecules (chemical digestion) Produces digestive enzymes to digest macromolecules (chemical digestion) (fats, carbohydrates and proteins) Regulates blood sugar by producing insulin

Fun Facts HOW LONG ARE YOUR INTESTINES? At least 25 feet in an adult. Be glad you're not a full-grown horse -- their coiled-up intestines are 89 feet long! Food drying up and hanging out in the large intestine can last 18 hours to 2 days! In your lifetime, your digestive system may handle about 50 tons of food!! What is a fart?!?And the big question…….. What is a fart?!? Tiny amounts of hydrogen, carbon dioxide, and methane combine with hydrogen sulfide and ammonia in the large intestine to give gas its smell. Shoooie!