3.1 Food Becomes Us Flashcards
What are the most abundant elements in our bodies?
Carbon, hydrogen, oxygen, and nitrogen
What is the chemistry of all life on Earth based on?
Organic molecules - those which contain carbon bonded to hydrogen
Which nutrient classes are made of organic molecules? Which are not?
- carbohydrates, lipids, proteins, and vitamins are made up of organic molecules
- water and minerals are inorganic nutrients because they do not contain carbon-hydrogen bonds
What are atoms?
The smallest units of an element that still retain the properties of that element.
What are elements?
Substances that cannot be broken down into products with different properties.
What are chemical bonds?
Forces that hold atoms together.
What are molecules?
Units of two or more atoms of the same or different elements bonded together.
What are cells?
The basic structural and functional units of plant and animal life.
What are organs?
Discrete structures composed of more than one tissue that perform a specialized function.
Describe the organization of life.
What is digestion?
The process of breaking food into components small enough to be absorbed into the body.
What is absorption?
The process of taking substances into the interior of the body.
What types of tissue does the human body contain?
Muscle, nerve, epithelial, and connective
Do most organs function alone?
No, they are part of a group of co-operative organs called an organ system.
What are the organ systems in humans?
There are 11 organ systems in humans: nervous, respiratory, urinary, reproductive, cardiovascular, lymphatic/immune, muscular, skeletal, endocrine, integumentary, and digestive.
Describe the nervous system.
What are the two main functions of the digestive system?
Digestion and Absorption
Why is digestion important?
Most food must be digested in order for the nutrients it contains to be absorbed into the body.
What is the main part of the digestive system?
the gastrointestinal tract, gut, digestive tract, intestinal tract, or alimentary canal.
Describe the gastrointestinal tract.
hollow tube, 10 meters in length, from mouth to anus.
What are the organs of the gastrointestinal tract?
The mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.
What counts as food being “inside” the body?
The inside of the tube that the organs of the gastrointestinal tract form are called the lumen. Food that is still inside the “lumen” is technically still outside the body. Food that has been transferred into the cells that line the intestine by the process of absorption is actually “inside” the body.
What is the pharynx?
Swallows chewed food mixed with saliva.
What is the esophagus?
Moves food to the stomach.
What does the stomach do?
churns and mixes food; secretes acid and a protein-digesting enzyme
What does the liver do?
makes bile, which aids in the digestion and absorption of fat
What does the pancreas do?
releases bicarbonate to neutralize intestinal contents; produces enzymes that digest carbohydrates, protein and fat
What does the gallbladder do?
stores bile and releases it into the small intestine when needed.
What does the small intestine do?
completes digestion; absorbs nutrients into blood or lymph
What does the large intestine do?
absorbs water and some vitamins and minerals; home to intestinal bacteria; passes waste material
What do the salivary glands do?
produce saliva, which contains a starch-digesting enzyme
What does the mouth do?
Chews food and mixes it with saliva
What does the anus do?
Opens to allow waste to leave the body.
What is the transit time?
The time between the ingestion of food and the elimination of the solid waste from that food.
The amount of time it takes for food to pass the length of the GI tract from mouth to anus
What is the transit time in a healthy adult?
24–72 hours
It is affected by the composition of the diet, physical activity, emotions, medications, and illnesses.
How many layers of tissue does the wall of the GI tract contain?
Four layers of tissue.
What is the mucosa?
The layer of tissue lining the GI tract and other body cavities. It is responsible for the absorption of the end products of digestion.
What is the lifespan of the cells of the mucosa? Why?
2-5 days
They come into direct contact with churning food and harsh digestive secretions.
What is one of the first parts of the body to be affected by nutrient deficiencies?
The mucosa
What aids digestion inside the lumen of the GI tract?
Digestive secretions
What is mucus?
A viscous fluid secreted by glands in the GI tract and other parts of the body, which acts to lubricate, moisten, and protect cells from harsh environments.
What are enzymes?
Protein molecules that accelerate the rate of specific chemical reactions without being changed themselves.
Salivary amylase
Mouth
Breaks starch (a large carbohydrate molecule) into smaller carbohydrate molecules.
Rennin
Stomach
Causes the milk protein casein to curdle.
Pepsin
Breaks proteins into polypeptides and amino acids.
Trypsin
Pancreas
Breaks proteins and polypeptides into shorter polypeptides.
Chymotrypsin
Breaks proteins and polypeptides into shorter polypeptides.
Carboxypeptidase
Breaks polypeptides into amino acids.
Pancreatic lipase
Breaks triglycerides into monoglycerides, fatty acids, and glycerol.
Pancreatic amylase
Breaks starch into shorter glucose chains and maltose.
Carboxypeptidase, aminopeptidase, and dipeptidase
Small intestine
Breaks polypeptides into amino acids.
Lipase
Breaks monoglycerides into fatty acids and glycerol.
Sucrase
Breaks sucrose into glucose and fructose.
Lactase
Breaks lactose into glucose and galactose.
Maltase
Breaks maltose into glucose.
Dextrinase
Breaks short chains of glucose into individual glucose molecules.
What is the function/role of nerve signals in gastrointestinal function?
They help regulate activity in the GI tract. The sight and smell of food, as well as the presence of food in the gut, stimulate nerves throughout the GI tract. Nerve signals cause muscle contractions, and they also stimulate or inhibit digestive secretions.
What are hormones?
Chemical messengers that are produced in one location, released into the blood, and elicit responses at other locations in the body.
How do hormones help regulate activity in the GI tract?
Hormones are released into the bloodstream and help prepare different parts of the gut for the arrival of food. They help regulate the digestion of nutrients and the rate at which food moves through the system.
Gastrin
Stomach mucosa
Stimulates secretion of hydrochloric acid (HCl) and pepsinogen by gastric glands in the stomach and increases gastric motility and emptying.
Somatostatin
Stomach and duodenal mucosa
Inhibits the following: stomach secretion, motility, and emptying; pancreatic secretion; absorption in the small intestine; gallbladder contraction; and bile release.
Secretin
Duodenal mucosa
Inhibits gastric secretion and motility; increases output of water and bicarbonate from the pancreas; increases bile output from the liver.
Cholecystokinin (CCK)
Stimulates contraction of the gallbladder to expel bile; increases output of enzyme-rich pancreatic juice.
Gastric inhibitory peptide
Inhibits gastric secretion and motility.
What is barrier function?
The protective role that gastrointestinal cells have in limiting the absorption of harmful substances and disease-causing organisms.
What is an antigen?
A foreign substance (almost always a protein) that, when introduced into the body, stimulates an immune response.
What are antibodies?
Proteins produced by cells of the immune system that destroy or inactivate foreign substances in the body.
What is an allergen?
A substance, usually a protein, that stimulates an immune response.
How many Canadian children report having allergies?
Approx. 7.1%
How many Canadian adults report having allergies?
Approx. 6.6%
What foods most commonly cause allergies?
eggs, milk, mustard, peanuts, seafood (fish, crustaceans, and shellfish), sesame, soy, sulphites, tree nuts, and wheat
Describe Barrier Function.
How do phagocytes and lymphocytes differ?
Phagocytes target an invader, engulf it, and destroy it by breaking it up so that antigens are “presented” at the surface of the phagocytes.
Lymphocytes then detect these antigens and react by producing and secreting protein molecules called antibodies.
