Digestive System: Chemical Digestion
What is the difference between a food and a nutrient?
1. a food is what we eat: it can contain millions of nutrients 2. a nutrient is a small molecule that our cells need; cells need 6 classes of nutrients
There are 2 types of digestive processes. What are they?
1. chemical digestion 2. mechanical digestion
What are the 6 major classes of nutrients that are needed by body cells?
1. monosaccharides 2. amino acids 3. triglycerides 4. vitamins 5. minerals 6. water
What is the difference between an enzyme and mucus?
1. mucus is secreted throughout the entire GI tract (goblet cells); mucus moistens and lubricates food during digestion 2. different enzymes are made by different organs, and they break the chemical bonds between foods
What enzymes are produced by the mouth?
1. salivary amylase 2. lingual lipase
What 3 nutrients are ingested but NOT digested?
1. vitamins 2. minerals 3. water (are ingested but not digested)
What is the pH of pancreatic juice?
8-9; to neutralize acid chyme from the stomach
What turns pepsinogen into pepsin?
HCl
What is bile?
a molecule produced by the liver, which is stored and concentrated in the gallbladder....
What is pancreatic juice?
a variety of enzymes, including: 1. trypsinogen, chymotrypsinogen, elastase, carboxypeptidase (break down proteins), 2. pancreatic lipase (breaks down lipids), 3. nucleases (break down nucleic acids) and 4. amylase (breaks down starches.) 5. bicarbonate ions in the enzyme mix help to raise the pH of chyme.
What are the final products of chemical digestion (assuming one ate a balanced meal?)
amino acids (from proteins) monosaccharides (from starches) triglycerides and monoglycerides (from fats/ lipids)
Why is pepsin made in an inactive form?
because it digests proteins and would attack the cells that made it
What is the function of the pancreas in digestion?
chemical digestion of foods in the small intestine
Which stomach cells produce gastric lipase?
chief cells
Which stomach cells produce pepsinogen?
chief cells
What is bile made from?
cholesterol
What is intestinal juice?
digestive enzymes that include peptidase, sucrase, maltase, lactase and intestinal lipase
What does salivary amylase do?
digests ingested starches (pasta, corn, potatoes, taro, sweet potato, french fries, breads, bagels, etc. )
What are "brush border" enzymes?
enzymes made in the final step in digestion of dietary carbohydrates and proteins; this occurs right on the face of microvilli found on small intestinal cells
What nutrient, in excess, can cause excess bile production and gallstones?
fats: especially saturated fats from animals because they are solid
Is the pancreas a part of the GI tract?
no, it is an accessory organ, like the liver
What digestive enzymes are found in the pharynx and esophagus?
none; they are involved in swallowing and food transport to stomach
Which stomach cells produce Cl- ions?
parietal cells
Which stomach cells produce H+ ions?
parietal cells
Which stomach cells produce intrinsic factor?
parietal cells
What is the major enzyme produced by the stomach?
pepsin
What is the inactive form of pepsin called?
pepsinogen
What are digestive enzymes?
proteins secreted by the GI tract that break down food into nutrients by breaking the chemical bonds in foods
What does lingual lipase do?
starts to break down fats
Where is pancreatic juice secreted?
the duodenum of the small intestine
What is chemical digestion?
the enzymatic breakdown of food
What is mechanical digestion?
the physical tearing and maceration of food in the mouth; the churning of the stomach, and segmentation by the small intestine
Where does salivary amylase come from?
the salivary glands
Why do cells in the small intestine have "brush borders?"
these are microvilli, which: 1. contain the final enzymes of digestion 2. provide a huge surface area for absorption
The function of chemical digestion is:
to break down foods into smaller and smaller pieces by breaking the chemical bonds between the food molecules until they become nutrients
What is the function of digestion?
to break food down into nutrients that cells can use
What is the function of bile?
to emulsify fats