Nutrition

Metabolism

the use of the food by the body after digestion which results in energy

digestion

breakdown of food in the body in preparation for absorption

gastrointestinal (GI) tract

pertaining to the digestive system.

mechanical digestion

the part of digestion that requires certain mechanical movements such as chewing swallowing and peristalsis

peristalsis

rhythmical movement of the intestinal tract; moves the chyme alomg

chemical digestion

chemical changes in foods during digestion caused by hydrolysis

hydrolysis

the addition of water resulting in the breakdown of the molecule

enzymes

organic substances that cause change in other substances

catalyst

a substance that causes another substance to react

pancreas

gland that secretes enzymes essential for digestion and insulin, which is essential for glucose metabolism

bolus

food in the mouth that is ready to be swallowed

saliva

secretion of the salivary glands

salivary amylase

also called ptyalin; the enzyme secreted by the salivary glands to act on starch

esophagus

tube leading from the mouth to the stomach; part of the gastrointestinal system

cardiac sphincter

the muscle at the base of the esophagus that prevents gastric reflux from moving into the esophagus

fundus (of the stomach)

upper part of the stomach

pylorus

the end of the stomach nearest the intestine

chyme

the food mass as it has been mixed with gastric juices

gastrin

hormone released by the stomach that signals the release of gastric juices that break down food

gastric juices

the digestive secretions of the stomach that help break down food

pepsin

an enzyme secreted by the stomach that is essential for the digestion of proteins

duodenum

first (and smallest) section of the small intestine

jejunum

middle section comprising about two-fifths of the small intestine

ileum

last part of the small intestine

secretin

hormone causing the pancreas to release sodium bicarbonate to neutralize the acidity of the chyme

cholecystokinin (CKK)

hormone that triggers the gallbladder to release bile

bile

secretion of the liver, stored in the gallbladder, essential for digestion of fats

pancreatic proteases

enzymes secreted by the pancreas that is essential for the digestion of protein

pancreatic amylase

the enzyme secreted by the pancreas that is essential for the digestion of starch

pancreatic lipase

enzyme secreted by the pancreas that is essential for the digestion of fat

lactase

enzyme secreted by the small intestine essential for the digestion of lactose

maltase

enzyme secreted by the small intestine essential for the digestion of maltose

sucrase

enzyme secreted by the small intestine to aid in the digestion of sucrose

peptidases

enzymes secreted by the small intestine that are essential for the digestion of protein

colon

large intestine

absorption

passage of nutrients into the blood or lymphatic system

lymphatic system

transports fat soluble substances from the small intestine to the vascular system

villi

tiny, hairlike structures in the small intestines through which nutrients are absorbed

capillaries

tiny blood vessels connecting veins and arteries

lacteals

lymphatic vessels in the small intestine that absorb fatty acids and glycerol

aerobic metabolism

combining nutrients with oxygen within the cell; also called oxidation

anaerobic metabolism

reduces fats without use of oxygen

Krebs cycle

a series of enzymatic reactions that serve as the main source of cellular energy

anabolism

the creation of new compounds during metabolism

catabolism

the breakown of compounds during metabolism

hormones

chemical messengers secreted by a variety of glands

kilocalorie (kcal)

the unit used to measure the fuel value of food

calorie

represents the amount of heat needed to raise the temperature of 1 kilogram of water 1 degree Celsius (C)

bomb calorimeter

device used to scientifically determine the kcal value of foods

basal metabolism rate (BMR)

the rate at which energy is needed for body maintenance also referred to as resting energy expenditure

resting energy expenditure (REE)

same as basal metabolism rate (BMR)

lean body mass

percentage of muscle tissue

energy requirement

number of calories required by the body each day

adipose tissues

fatty tissues

energy balance

occurs when the caloric value of food ingested equals the calories expended

ketones

substances to which fatty acids are broken down in the liver

ketoacidosis

condition in which ketones collect in the blood; caused by insufficient glucose available for energy

monosaccharides

simplest carbohydrates; sugars that cannot be further reduced by hydrolysis; examples are glucose fructose and galactose

glucose

the simple sugar to which carbohydrate must be broken down for absorption; also known as dextrose

fructose

the simple sugar (monosaccharide) found in fruit and honey

galactose

the simple sugar (monosaccharide) to which lactose is broken down during digestion

disaccharides

double sugars that are reduced by hydrolysis to monosaccharides; examples are sucrose maltose and lactose

sucrose

a double sugar or disaccharide; examples are granulated, powdered, and brown sugar

maltose

the double sugar (disaccharide) occurring as a result of the digestion of grain

lactose

the sugar in milk; a disaccharide

polysaccharides

complex carbohydrates containing combinations of monosaccharides; examples include starch, dextrin, cellulose, and glycogen

starch

polysaccharide found in grains and vegetables

endosperm

the inner part of the kernel of grain; contains the carbohydrate

bran

outer covering of grain kernels

germ

embryo or tiny life center of each kernel of grain

glycogen

glucose and stored in the liver or muscles

glucagon

hormone from alpha cells of the pancreas; it increases blood sugar levels by trigerring the liver to release stored glucose

dietary fiber

indigestible parts of plants; absorbs water in large intestine, helping to create soft, bulky stool; some is believed to bind cholesterol in the colon, helping to rid cholesterol from the body; some is believed to lower blood glucose levels

cellulose

indigestible carbohydrates; provides fiber in the diet

hemicellulose

dietary fiber found in whole grains

lignins

dietary fiber found in the woody part of vegetables

pectin

edible thickening agent

mucilage

gel-forming dietary fiber

flatulence

gas in the intestinal tract

insulin

secretion of the islets of Langerhans in the pancreas gland; essential for the proper metabolism of glucose

islets of Langerhans

part of the pancreas from which insulin is secreted

hyperglycemia

excessive amounts of glucose in the blood

hypoglycemia

subnormal levels of blood glucose

lipids

fats

satiety

feeling of satisfaction; fullness (fats provide this)

visible fats

fats in foods that are purchased and used as fats, such as butter or margarine

invisible fats

fats that are not immediately noticeable such as those in egg yolk, cheese, cream, and salad dressings

triglycerides

three fatty acids attached to a framework of glycerol

glycerol

a component of fat; derived from water-soluble carbohydrate

fatty acids

organic compounds of carbon atoms to which hydrogen atoms are attached

linoleic

fatty acid essential for humans; cannot be synthesized by the body

linolenic

one of the three fatty acids needed by the body; cannot be synthesized by the body

saturated

fats whose carbon atoms contain all of the hydrogen atoms they can; considered a contributory factor in atherosclerosis

monounsaturated

fats that are neither saturated nor polyunsaturated and are thought to play a little part in atherosclerosis

polyunsaturated

fats whose carbon atoms contain only limited amounts of hydrogen

omega-3 fatty acids

a fatty acid that helps lower the risk of heart disease

trans-fatty acids (TFAs)

produced by adding hydrogen atoms to a liquid fat, making it solid

hydrogenation

the combining of fat with hydrogen, thereby making it a saturated fat and solid at room temperature

cholesterol

fatlike substance that is a constituent of body cells; is synthesized in the liver; also available in animal foods

hypercholesterolemia

unusually high levels for cholesterol in blood; also known as high serum cholesterol