Download Integrated Science Chapter 13 Notes Section 1: Nutrients and Diet

Integrated Science
Chapter 13 Notes
Section 1: Nutrients and Diet
Nutrient – a chemical substance required for the life and growth of an organism. Nutrients are a
variety of chemical substances found in food that your body needs for energy to do everything from
breathing to walking. Nutrients also contain raw materials that form structures such as bones,
muscles, and hair
1. What Nutrients Are in Your Food
• Carbohydrates provide quick energy
Æ Carbohydrates – a class of nutrients containing carbon, hydrogen, and oxygen that can
be used by living organisms as an energy source
Æ Some carbohydrates are simple sugars, glucose and fructose, found in fruits. Other
sugars include lactose, found in milk, and sucrose, which is used as a sweetener in
coffee or tea and in some baked foods
Æ Complex carbohydrates are larger molecules made of many sugar molecules linked
together. A common complex carbohydrate is starch.
• Fats store energy
Æ Fats – a class of compounds containing long hydrocarbon chains that are bonded to a
glycerin molecule
Æ Fats are very concentrated sources of energy that your body can use to meet your
energy needs if you do not eat enough carbohydrates. Excess fat is stored under your
skin and around your internal organs
Æ Saturated fats have the maximum possible number of hydrogen atoms in the chains and
are usually solid at room temperature. Most animal fats, including the fat in butter, are
saturated fat. A diet high in saturated fats can increase your chances of getting heat
disease
Æ Unsaturated fats have fewer hydrogen atoms in their chains and are usually liquid at
room temperature. Most plant fats are mostly unsaturated
• Proteins form the main structures of the body
Æ Protein – a nutrient that is a polymer of amino acids, containing carbon, hydrogen,
oxygen, and nitrogen
Æ Your body uses some of the protein in food to rebuild structures that wear out and to
make new structures as you grow
Æ Proteins are made of many amino acid molecules linked together. There are 20 amino
acids found in your body. However, the body can make only 12 twelve of the amino
acids, the remaining 8, called essential amino acids, must be obtained from the food you
eat
• Vitamins help promote chemical reactions in the body
Æ Vitamin – an organic compound needed in trace amounts by the body
Æ Vitamins help the enzymes in your body function properly
• Minerals are inorganic nutrients
Æ Mineral – an inorganic compound found on Earth
2. Choosing Foods for Your Health
Balanced diet – a selection of foods that provides all of the nutrients needed for healthy living
• Using the food pyramid to build a balanced diet
Æ Using the USDA Food Guide Pyramid can help ensure that you eat a healthy, balanced
diet
Section 2: Energy and Food
1. The Role of Energy in Your Body
• Dieticians and nutrition
scientists can measure the
amount energy contain in a
particular food by burning a
small sample in a sealed
container surrounded by water.
As the food burns, the energy is
released into the water
• Food energy measured in this
way is given the units of
Calories
Æ Calorie – a unit of energy
describing the amount of
energy needed to warm 1
kg of water by1OC
Æ 1 gram of carbohydrates
and 1 gram of protein each
contain about 4 Calories,
while 1 gram of fat contains about 9 Calories
Food energy is transferred as heat and work
Measuring your energy use for activities
Æ Your body expends the energy in foods in thousands of different chemical reactions,
which are known collectively as metabolism
Æ Metabolic rate – the amount of energy consumed by the body in a given time period
Æ The amount of energy you use during an average day depends on how active you are
and your age. Typically, children and adolescents use more energy than teenagers and
adults
• Basal metabolic rate
Æ Basal metabolic rate – the rate of energy use for a living body that is not performing
other activities
2. Dietary Problems
• Consuming too many calories leads to obesity
Æ When you consume mote energy than you use, you store the extra energy as gat and
gain weight.
Æ Obesity – a condition in which too much of a body’s weight is stored as fat
• Consuming too few calories causes undernourishment
Æ Undernourishment – the breakdown of the body and its organs as a result of
inadequate food intake
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Section 3: Digestion
Digestion – the process of breaking down food into usable molecules
1. Mechanical and Chemical Digestion
• Mechanical digestion is a physical change
Æ The chewing, mixing, and churning of your food are processes called mechanical
digestion. The molecules of the chewed up mixture are identical to the original food
• Chemical digestion is a chemical change
Æ While mechanical digestion is occurring, enzymes and other chemicals are being mixed
with the food. Once mixed in the food, each enzyme targets a specific type of nutrient
and breaks it down into smaller molecules
2. The Start of Digestion
• Digestion begins in the mouth
Æ Mechanical digestion is aided by saliva, a watery substance
Æ Salivary glands – the glands located in the bottom and top of the mouth that secrete
watery saliva
Æ Saliva contains an enzyme that breaks down starch into sugar, so both mechanical and
chemical digestions occur in your mouth
• The esophagus moves food to the stomach
Æ Esophagus – the muscular tube connecting the mouth and stomach
• Food is broken down by acid and pepsin in the stomach
Æ Cells lining the stomach wall release two substances. One is hydrochloric acid, which can
kill many of the bacteria that is in your food, and the other is pepsin, an enzyme the
breaks down proteins into amino acids
• Chemical digestion is completed in the small intestine
Æ Small intestine – an organ that breaks down food and absorbs nutrients
• The pancreas and liver make product used for digestion
Æ Pancreas – a large gland behind the stomach that makes digestive juices
Æ These digestive juices are enzymes that break down carbohydrates, fats, and proteins
Æ Liver – a large organ that makes bile and modifies substances in the blood
Æ Bile is a bitter, alkaline fluid that acts to break large drops of fat into smaller droplets that
are more easily digested
3. Absorption of Nutrients
• The small intestine is the site of nutrient absorption
Æ The inner surface of the intestinal wall is covered with millions of tiny fingerlike
projections called villi. Because of the villi, the area of the small intestine’s inner surface
is very large, so the small intestine can absorb most of the nutrient molecules in the food
you eat.
• The large intestine absorbs water from indigestible food
Æ Large intestine – an organ that stores, compacts, and eliminates indigestible material