Nutrition, Digestion, Absorption, and Homeostasis Test Flashcards
Distinguish between essential and non-essential nutrients
Essential Nutrients: Cannot be replaced or synthesized by the body, so must be ingested in the diet
Non-Essential Nutrients: Can be synthesized by the body or have a replacement nutrient which serves same dietary purpose, so are not necessary in the diet
Outline the causes of PKU
- A genetically inherited disease (autosomal recessive) caused by a person’s chemical inability to metabolize the aa phenylalanine (into tyrosine)
-Phenylalanine builds up in tissues & bloodstream due to lack of enzyme
-Treatment: low protein diet
List the 4 major organic molecules/ macromolecules, the monomers they are broken down into in the digestive system, the specific enzymes that break them down, the part of the digestive system that makes/ secretes each enzyme, and the location of action/ optimum pH of each enzyme.
- 4 major organic molecules: proteins, carbohydrates, lipids, and nucleotides
-Pepsin: produced in gastric glands, action in the stomach, pH 1-2, products are peptides
-Amylase: produced in the pancreas, action in the lumen of the small intestine, pH 7-8, product is maltose
-Lipase: produced in the pancreas, action in the lumen of the small intestine, pH 7-8, products are fatty acids
Outline the roles of hydrochloric acid (and proton pumps) in the stomach
-hydrochloric acid lowers the pH of the stomach which denatures proteins within the stomach
-acidic conditions in the stomach are maintained by proton (H+) pumps in parietal cells in gastric pits
Outline the roles of PPI’s in the reduction of stomach acid/ ulcers
-PPI’s (proton pump inhibitors) bind irreversibly to proton pumps and prevent H+ secretion, raising pH of stomach
Outline the hormonal and nervous mechanisms that control the secretion, content, and volume of gastric juice
- The sight and smell of food triggers a response in the brain (the medulla) through the vagus nerve, which sends impulses to the gastric glands in the stomach to release gastric juice
- When food enters the stomach stretch receptors detect it
- Stretch receptors send impulses to brain, the brain then sends a signal to the stomach to trigger gastrin secretion into the bloodstream, which causes the stomach to secrete HCl
- Gastrin causes the sustained release of gastric juices
- If the pH becomes too low gastrin is inhibited by hormones
- Once digested food (chyme) passes into the small intestine, the duodenum then releases CCK hormones to stimulate the pancreas to release pancreatic juices
Be able to explain the role of the pancreas in digestion
1.Enzymes catalyze/speed up chemical reactions and lower the activation energy needed
2.Digestive enzymes are released into the gut from exocrine glands and breakdown larger molecules
3. Enzymes allow reactions to occur at body temperature
4. Amylase breaks down starch into sugars
5. Lipase breaks lipids into fatty acids
Know the general function of villi and be able to explain how the structure of a villus is adapted to its function
- Folded inner epithelial layer increases surface area for absorption
- Sealed membrane with tight junctions contain microvilli
- The Lumen is lined with villi
- Contain membrane channel proteins to aid in absorption
- Epithelial cells of each villus contain microvilli which increase the surface area FOR ABSORPTION OF NUTRIENTS
Be able to list and explain the different forms of transport
- Diffusion - fatty acids pass through hydrophobic membranes
- Osmosis - Water diffuses across epithelial membrane
- Facilitated Diffusion - Protein channels allow passage of hydrophilic food molecules
- Active transport - Glucose and amino acids pumped against a concentration gradient
- Endocytosis - cell membrane forms a vesicle around large molecules
Outline the role of the large intestine and explain why cellulose and lignin are not digested in humans
- Main function is the absorption of water
- Secretes mucus
- Moves undigested food products
- Materials that are not absorbed are egested
- Cellulose and lignin are not digested by the human body because humans do not possess the enzymes to break them down
Outline the roles of fiber in the diet
- Helps to clean out old/damaged intestinal cells
- Provides bulk to keep materials moving
- Decreases constipation
- Helps maintain bowel health
Outline how the cholera toxin can cause dehydration
- Vibrio cholerae is a bacterial pathogen that infects intestines
- V. cholerae releases a toxin that binds to a receptor on the epithelial cells in the intestine.
3.This activates ion channels in these cells so that ions (including chloride ions/ Cl-) are pumped out of these
cells and into the intestine
4.Water from the cells follows the
ion concentration gradient (by
osmosis).
5.Excess water dilutes feces =
diarrhea, and will cause
dehydration (if left untreated) as
water is continuously removed
from body tissues
Outline the cause, consequences, and treatments for stomach ulcers (and know the FULL name of the bacteria that can cause them
Stomach ulcers are caused by a bacteria called Helicobacter Pylori
Causes:
-H. Pylori survives the acidic conditions of the stomach by penetrating the mucus lining
-Secretes urease to increase pH and neutralize gastric acids
-Causes inflammation which causes damage to stomach lining
Consequences:
-May lead to stomach wall damage, and can lead to stomach cancers
Treatments:
-Treated with antibiotics and PPI’s
Outline the dual supply of blood to the liver, the reasons for the dual blood supply, and circulation of blood through the sinusoids of the liver.
-The hepatic artery (branches off
aorta) delivers oxygen-rich blood from the heart to the liver (for liver cells to use)
-The hepatic portal vein delivers nutrient-rich blood from the gut (from the capillaries of the
villi in the intestines) to the liver (blood from pancreas/ spleen/ stomach/ colon too)
Blood enters the liver through the hepatic artery and hepatic portal vein and flows into liver capillaries called sinusoids.
Outline the structure (and function) of liver sinusoids
-Sinusoids are wide blood vessels (capillaries) surrounded by a single layer of
hepatocytes (liver cells)
-Sinusoids filter, detoxify, and balance levels of nutrients in the blood (removing excess
nutrients to be stored in the liver, removing toxins, and adding nutrients
-Sinusoids also engulf and break down “old”/ damaged erythrocytes (red blood cells).
