Download Notes - Energy and Digestion

Food and Digestion Notes
19, 22, 23, 30 November; 1 December 2010
 Foods provide your body with materials for growing and for repairing tissues. Food also
provides energy for everything you do.
 nutrients: are substances in food that provide the raw materials and energy the body needs to
carry out all its essential processes (includes carbohydrates, fats, proteins, vitamins, minerals,
and water)
 calorie: amount of energy needed to raise the temperature of one gram of water by one degree
Celsius
 Calorie: the energy in food
 1 Cal = 1 kcal
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Carbohydrates
carbohydrates: a major source of energy composed of carbon, oxygen, and hydrogen
1 gram carbohydrate = 4 Calories
carbohydrates provide the raw materials to make cell parts
simple carbohydrates are sugars
glucose: major source of energy for your body’s cells
complex carbohydrates are many sugar molecules linked together in a chain
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Fats
fats: energy-containing nutrients that are composed of carbon, oxygen, and hydrogen
1 gram fat = 9 Calories
Fats form part of the cell membrane
Fatty tissue protects and supports internal organs, and insulates the body
saturated fats are usually solid at room temperature and unsaturated are usually liquid
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Proteins
proteins: contain nitrogen, carbon, hydrogen, and oxygen and play an important part in
chemical reactions within cells
needed for tissue growth and repair
amino acids: small units which are linked together chemically to form large protein molecules
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Vitamins and Minerals
vitamins: act as helper molecules in a variety of chemical reactions in the body
although vitamins are only needed in small amounts, a lack of certain vitamins can lead to health
problems
minerals: nutrients that are not made by living things and are needed in small amounts to carry out
chemical processes
know table on p.51-52, particularly the following vitamins and minerals:
o fat soluble vitamins: A, D, E, K
o water soluble vitamins: Folic acid, C, B1, B6, B12
o minerals: Calcium, Fluorine, Sodium, Potassium, Chlorine, Iodine, Iron, Magnesium, and
Phosphorus
Water
♣ water is the most important nutrient because the body’s vital processes take place in water
♣ water makes up most of the body’s fluids, including blood
♣ approx. 2 L of water are needed everyday under normal conditions
Functions of the Digestive Process
 the digestive system has three main functions:
o breaks down food into molecules the body can use
o molecules are absorbed into the blood and carried throughout the body
o wastes are eliminated from the body
 digestion: the process by which the body breaks down food into small nutrient molecules
 mechanical digestion: occurs when biting and chewing the food
 chemical digestion: occurs with saliva, HCl, bile, and other enzymes which break down food particles
into smaller chemical building blocks
 absorption: the process by which nutrient molecules pas through the wall of the digestive system
into the blood
 p.61 Diagram of Digestive System
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Mouth
both mechanical and chemical digestion begin in the mouth
saliva: provides lubrication for mechanical digestion and has enzymes for chemical digestion
enzymes: proteins that speed up chemical reactions
each enzyme has a specific shape which enables it to take part in only one kind of chemical reaction
Esophagus
epiglottis: flap of tissue which seals off the windpipe when food is swallowed
esophagus: a muscular tube that connects the mouth to the stomach
mucus: thick, slippery substance which lines the esophagus to make food easier to swallow and
move along
peristalsis: involuntary wave of muscle contractions which occurs in esophagus, stomach, and
intestines
Stomach
stomach: J-shaped, muscular pouch located in the abdomen
most mechanical digestion and some chemical digestion occur in the stomach
digestive juice contains pepsin
pepsin: chemically digests the proteins in food, breaking them down into short chains of amino acids
HCL: a very strong acid needed to create an ideal environment for pepsin and to kill many of the
bacteria swallowed with food
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Small Intestine
small intestine: where most chemical digestion takes place; about 6m long with a diameter of 2-3cm
almost all chemical digestion and absorption of nutrients takes place in the small intestine
enzymes and other secretions needed to chemically digest food come from the small intestine, live,
and pancreas
when food reaches the small intestine, starches and proteins have been partially digested, but fats
have not been digested at all
villi: tiny finger-like structures lining the small intestine which absorb nutrient molecules
villi greatly increase the surface area of the small intestine which allows for greater absorption of
nutrients
nutrients molecules pass from cells on the surface of a villus directly into the bloodstream
Liver
♣ liver: largest organ, located in upper right portion of abdomen
♣ breaks down medicines, helps eliminate nitrogen from the body, and produces bile
♣ bile: substance that breaks up fat particles (not an enzyme therefore does not chemically digest;
works like soap on grease)
♣ gallbladder, stores bile from liver and releases it into the small intestine
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Pancreas
pancreas: triangular organ between stomach and small intestine
produces enzymes that flow into the small intestine and help break down starches, proteins, and
fats
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Large Intestine
large intestine: last section of the digestive system, about 1.5 meters
contains bacteria that feed on material passing through
bacteria make certain vitamins, like vitamin K
water is absorbed into the bloodstream from the large intestine
rectum: a short tube at the end of the large intestine where waste material is compressed into
solid form
anus: muscular opening at the end of the rectum where waste material is eliminated from the
body