TEST - Nutrition, Digestion, Absorption & Homeostasis Flashcards
Distinguish between essential and non-essential nutrients.
Essential - CANNOT be synthesized by the body(must be consumed through the diet).
Non-Essential - CAN be synthesized by the body.
Outline the causes and treatments of PKU.
Cause - genetic, lack of enzyme that breaks phenylalanine into tyrosine, causes buildup of phenylalanine
Treatment for PKU - low protein diet, limit intake of protein sources that contain phenylalanine; supplemented with formula containing essential aa’s/ tyrosine
Outline WHY food needs to be digested.
Food macromolecules need to be hydrolyzed into smaller molecules in order to be absorbed.
Pepsin / endopeptidase
- Hydrolyzes protein into amino acids
- Pepsin secreted by the gastric glands in the stomach (acidic pH)
- Endopeptidase secreted by pancreas into the lumen of the small intestine (neutral pH)
Amylase
- Hydrolyzes carbs (starch) into maltose
- Salivary produced in salivary glands and acts in mouth (neutral pH)
- Pancreatic produced in pancreas and acts in lumen of small intestine (neutral pH)
Lipase
- Hydrolyzes lipids into di- / mono-glycerides / fatty acids / glycerol
- Produced by pancreas and acts in the lumen of the small intestine (neutral pH)
Nuclease
- Hydrolyzes nucleotides (nucleic acids) into nucleosides
- Produced by pancreas and acts in the lumen of the small intestine (neutral pH)
If IB simply states “digestion” in a question without stating which type they mean, what do they mean?
“Chemical Digestion”
Outline the roles of hydrochloric acid in the stomach.
- Lowers the pH, which initially denatures proteins
- Activates pepsinogen into pepsin
- Kill pathogenic bacteria and fungi in ingested foods
Outline the roles of proton pumps in the stomach.
- Maintain acidic conditions (low pH) by actively pumping protons into the stomach
- Cl combines to form HCL
Outline the roles of PPI’s in the reduction of stomach acid/ ulcers.
- Proton pumps maintain acidity
- PPI’s bind irreversibly to proton pumps
- Lowers the amount of acid produced
Outline the hormonal and nervous mechanisms that control the secretion, content, and volume of gastric juice.
- Sight/smell of food triggers medulla to send signal to stomach to secrete gastric juice via vagus nerve
- Impulses from stretch receptors send signals to medulla via vagus nerve which sends signals to stomach to trigger production of gastrin
- Gastrin causes sustained release of gastric juices (HCL)
Which cells in the gastric pits secrete which components of gastric juice?
- HCl secreted by parietal cells
- Pepsinogen secreted by chief cells
Where does chemical digestion and most absorption happen?
Small intestine
Where does protein digestion begin?
Stomach
What enzymes does the pancreas secrete?
Amylase, Lipase, Endopeptidase(Protease), Nuclease
Function of the villi.
Maximum absorption of nutrients by increasing surface area.
Explain how the structure of a villus is adapted to its function.
Epithelial cells - surround each villus (decreases diffusion distance of nutrients into bloodstream)
Rich Capillary Network - large concentration gradient (between blood and fluid in small intestine) allows for rapid absorption of nutrients
Lacteals - Absorb lipids (into lymphatic system – transports fats, drains tissues of excess fluids)
Intestinal crypts - release juices that act as ‘carrier fluids’ for nutrients
List and explain the different forms of transport used by the small intestine to absorb different nutrients.
Diffusion - fatty acids absorbed through conc. gradient
Facilitated Diffusion - fructose pumped through protein channels in the epithelial cell membrane
Active transport (uses ATP) - glucose/amino acids pumped through protein channels against conc. gradient
Endocytosis - cholesterol in lipoprotein particles transported by means of vesicles.
Outline the role of the large intestine.
- Absorbs water / minerals / vitamins / ions
- Peristalsis (contraction of muscles) to move food undigested food
- Secretes mucous (lubrication)
Explain why cellulose and lignin are not digested in humans.
Humans do not possess the enzymes needed to break them down.
Outline the roles of fiber in the diet.
- More fiber = faster rate of material movement through the intestine
- Decreases hunger (prevents obesity)
- Absorbs water to keep faces soft to pass (reduces constipation)
- “Works out” microflora
State the other substances that are egested (excreted) by the body.
BELCH
- Bile pigments
- Epithelial Cells
- Lignin
- Cellulose
- Human Microflora / bacteria
Outline how the cholera toxin can cause dehydration.
- Vibrio cholerae produces toxin
- Toxin causes ions to be pumped into small intestine
- Water follows gradient by osmosis, diluting faces (diarrhea) causing dehydration because water is being constantly removed from body
Outline the cause, consequences, and treatments for stomach ulcers.
Cause - Helicobacter pylori infection, increases pH to neutralize stomach acid that kills it (urease), degrades mucous lining (mucinase)
Consequences - Inflammation, digestion of stomach lining by pepsin & HCL, pain
Treatments - Proton pump inhibitors reduce stomach acid production (bind irreversibly to proton pumps), lower acidity (high pH) helps ulcers to heal, antibiotics
Outline the dual supply of blood to the liver and reasons why it is necessary.
- Dual blood supply is blood entering liver form Haptic Artery and Hepatic Portal Vein.
- Hepatic Portal Vein delivers nutrient-rich blood from the gut to liver
- Hepatic Artery delivers oxygen-rich blood from the heart to liver
Outline the circulation of blood through the sinusoids of the liver.
- Blood enters thru the hepatic artery and hepatic portal vein and flows into sinusoids
- Sinusoids surrounded by single layer of hepatocytes
- Sinusoids remove excess nutrients to be stored in the liver, toxins, and add stored nutrients to the blood when needed (filter, detoxify, balance)
- Prevents osmotic imbalance in blood
- Clean & balanced blood exits liver thru HPV back into the heart
Outline the structure and function of liver sinusoids.
- Sinusoids remove excess nutrients to be stored in the liver, toxins, and add nutrients (stored in the liver) to the blood when needed.
- Each sinusoid is lined with a single layer of hepatocytes, which detoxify, & store vitamins, minerals and molecules so they are available at ALL times. (carb and protein metabolism)
- Contains Kupffer cells which engulf bacteria and break down old / damaged red blood cells (erythrocytes)
Outline the role of the liver in the regulation of nutrient levels in the blood.
- Liver stores glucose as glycogen (under influence of insulin/ glucagon (depending on blood glucose lvls): carbohydrate metabolism)
- Kupffer cells in liver break down hemoglobin into heme and globin
- Iron (from heme) is carried to bone marrow to produce new hemoglobin for new red blood cells
- Some excess nutrients (Vitamins A/D, Iron) stored in liver
- Liver detoxifies blood
- Excess cholesterol covered into bile salts for bile which is secreted by liver (lipid metabolism)
Explain how erythrocytes (red blood cells) are broken down and the recycling of their components by the liver.
- Erythrocytes rupture after 120 days
- Kupffer cells ingest erythrocytes in sinusoids of liver
- Hemoglobin split into heme and globin groups
- Heme broken down into iron group
- Globin provides amino acids
- Iron stored and transferred to bone marrow
- Bilirubin becomes part of bile
Outline the roles/ functions of hepatocytes in the sinusoids of the liver.
- Excess glucose is stored as glycogen in hepatocytes
- Hepatocytes break down globin into amino acids
- Hepatocytes stores essential vitamins, minerals and molecules so they are available to the body at ALL times (to maintain homeostasis)
- Hepatocytes synthesize and regulate cholesterol (for bile salt production)
Outline the production of bile by the liver.
- Bile is made of bile salts and bilirubin(bile pigment)
- Hepatocytes convert heme into bilirubin
- Bilirubin transferred to bile and normally excreted
Outline the causes and consequences of jaundice.
Cause - blockage of bile ducts / disease in liver
Consequence - Bilirubin accumulates in blood, yellowing skin,
Explain how the pancreas is able to act as an endocrine gland to regulate blood glucose levels.
- Pancreas produces hormones that control levels of glucose
- Beta cells produce insulin when blood-glucose is high
- Alpha cells produce glucagon when blood-glucose is low
- Insulin causes calls to take up glucose (increases muscle mass)
- Glucagon causes liver to break down glycogen into glucose (increases glucose lvls in blood / decrease muscle mass)
- ## Negative feedback control
Explain the causes, symptoms, and treatments of type I diabetes.
- Early onset
Cause: Beta cells damaged/ destroyed by body’s own immune system: autoimmune disease (not enough insulin produced)
Symptoms: High blood glucose levels, glucose in urine, increased thirst, fatigue.
Treatments: Insulin injections which regulate blood-glucose levels
Explain the causes, symptoms, and treatments of type II diabetes.
Adult onset
Cause: Insulin receptors on cells less sensitive to insulin, poor diet, obesity, genetics
Symptoms: High blood glucose levels, glucose in urine, thirst, fatigue
Treatments: High fiber foods satisfy appetite but aren’t broken down /
small meals to avoid rapid rise in glucose /
complex carbs w low glycemic index digested & absorbed slower
Outline the role of leptin in the body.
- Leptin secreted by adipose tissue
- Acts on cells in the hypothalamus (appetite control center) to inhibit appetite
- More adipose tissue = more leptin (means reduced appetite/eating)
- Obese people can develop resistance to leptin
