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Nutrition Physiology EXAM 1 STUDY GUIDE Date: 10/01/24 Catabolism Breaking down compounds Releases energy Macronutrients ○ Carbohydrate: Glycogen → 2 Glucose ○ Fat: Triglycerides → Glycerol and Fatty A...

Nutrition Physiology EXAM 1 STUDY GUIDE Date: 10/01/24 Catabolism Breaking down compounds Releases energy Macronutrients ○ Carbohydrate: Glycogen → 2 Glucose ○ Fat: Triglycerides → Glycerol and Fatty Acids ○ Protein: Protein → 2 Amino Acids Anabolism Building of compounds Requires energy Macronutrients ○ Carbohydrate: Glucose + Glucose → Glycogen ○ Fat: Glycerol + Fatty Acids → Triglycerides ○ Protein: Amino Acid + Amino Acid → Protein Where in the Cell Do These Processes Occur? Glycolysis ○ Cytoplasm of nearly all types of cells (Examples: RBC, brain, muscle, liver) TCA Cycle & Electron Transport Chain (ETC) ○ Mitochondria Glucose is Broken Down to What During Glycolysis? Glucose (6-C) → 2 pyruvate molecules (3-C each) What Are The Two Pathways Pyruvate Can Take? Anaerobic Glycolysis ○ Pyruvate converted to lactate Aerobic Glycolysis ○ Pyruvate converted to Acetyl CoA to enter the TCA Cycle  2 How Many ATP Molecules are Generated via each Route? Glycolysis ○ Generates 4 ATP total, 2 net ATP ○ NAD donates and accepts electrons and hydrogen ions (H+) ○ Anaerobic Glycolysis is reversible* TCA Cycle ○ Generates 2 GTP ○ Generates NADH and FADH2 ETC ○ Produces 32 ATP WHOLE METABOLIC PATHWAY → 36 ATP YIELD What Are the Pathways Called? Gluconeogenesis (Reverse Glycolysis) ○ Creating glucose from non-carbohydrate sources ○ Pyruvate → Glucose Anaerobic Glycolysis ○ Pyruvate to Lactate Aerobic Glycolysis (Warburg Effect) ○ Happens in cancer and immune cells ○ Lactate produced in the presence of oxygen Complexes 1: NADH drops electrons at Complex 1 and FADH2 drops electrons at Complex 2 2: Complex 1 and 2 drop electrons at CoQ 3: CoQ donates electrons to Complex 3 and H+ is pushed into intermembrane space 4: Cytochrome C drops electrons at Complex 4 (produces H2O) 5: Complex 5 (ATP Synthase) → Takes ADP + Pi → ATP  3 Aerobic vs. Anaerobic Anaerobic produces gas and acid (CO2 and lactic acid) and is reversible Which Cell Types Rely Exclusively on Glycolysis and Why? Red Blood Cells (RBC) ○ Lack mitochondria so they use Glycolysis because it happens in the cytoplasm Pyruvate → Acetyl CoA (2-C) Aerobic Glycolysis Irreversible reaction* NADH is produced Occurs in the mitochondria Requires several B vitamins Which Enzyme is Involved in the Conversion of Pyruvate to Acetyl CoA and Lactic Acid? Dehydrogenase Complex ○ Pyruvate to Acetyl CoA Lactate Dehydrogenase A ○ Pyruvate to Lactic Acid Ketogenic vs. Glucogenic Amino Acids Ketogenic Amino Acids ○ Converted to Acetyl CoA ○ Can form ketones under certain conditions (ketosis)  4 Glucogenic Amino Acids ○ Converted to Pyruvate or TCA intermediates ○ Can form glucose under certain conditions (gluconeogenesis) Gastroparesis Paralysis of the stomach Affects stomach nerves and muscles Causes weaker and slower stomach contractions ○ Causes food to sit in your stomach for too long Signs & Symptoms of Gastroparesis Vomiting, nausea, abdominal bloating, pain, acid reflux, loss of appetite, weight loss, and malnutrition Most people do not have any signs or symptoms at all* Physiological Control of Gastroparesis Types of movement of through the intestine Amount of calories, protein, carbohydrates, and fats consumed affects gastric emptying Pancreatic Enzymes ○ Proteases (protein digestion) ○ Lipases (fat/lipid digestion) ○ Carbohydrase (sugar digestion) Sphincter Muscle What is the Drug Metoclopramide? Dopamine receptor antagonist that increases gastric motility (quality and ability to move) Only FDA-approved drug to treat gastroparesis General Mechanism of Action ○ Increases the movements of stomach muscles and intestines to help move food through the alimentary canal faster ○ Also treats GERD that hasn’t responded to typical treatments Metabolism of Drug  5 ○ Metabolized in the liver by Cytochrome P450 Digestive System Gastrointestinal (GI) Tract AKA Alimentary Canal ○ Long flexible muscular tube running from the mouth to the anus Lumen ○ Inside of the tube Types of Movement of Food Through the Intestine Peristalsis ○ A ring of contraction propelling material along the GI tract ○ Circular muscles: inside the small intestine ○ Longitudinal muscles: outside the small intestine Segmentation ○ A back-and-forth action that breaks apart food into particles in the small intestine Mass Movement/Propulsion ○ Peristaltic wave that contracts over a large intestine to help eliminate waste Sphincter Muscles Cardiac Sphincter ○ Top of the stomach ○ Prevents reflux of stomach content going up into the esophagus Pyloric Sphincter ○ Bottom of the stomach ○ Controls the amount of chyme released into the small intestine Sphincter of Oddi ○ Controls pancreatic and juice secretion into the duodenum Ileocecal Valve ○ Prevents large intestine bacteria from going back up into the small intestine Anal Sphincter ○ Controls elimination of feces  6 Cells of the Stomach Parietal Cells - Stimulated by Gastrin Hormone ○ Produces hydrochloric (stomach) acid (HCL) Goblet Cells ○ Produces mucus to help keep bacteria out Chief Cells - Stimulated by Gastrin Hormone ○ Produces pepsinogen (goes along with HCL) Enzyme that aids in the digestion of proteins Intestinal (Colonic) Bacteria Produces vitamins (K and Biotin) Helps metabolize fiber Produces short chain fatty acids (SCFA: acetate, butyrate) Maintains healthy colon Prevents colonization of harmful bacteria Pancreatic Secretion Produces sodium bicarbonate (Na2CO3) to neutralize stomach acid ○ Stimulated by Secretin Hormone Aids in digestion of protein Assists in calcium absorption Destroys harmful bacteria Bile Made in the liver Stored in the gallbladder Released into the small intestine (Stimulated by CCK Hormone) ○ Emulsifies fat Reabsorbed into the blood and sent back to the liver “recycled” What is Bolus and Chyme? Bolus ○ Food that is chewed up and mixed with saliva  7 Chyme ○ The pulpy acidic fluid that passes from the stomach into the small intestine Consists of gastric juices and partly digested food Digestion Hormones Gastrin ○ Stimulates the production of stomach acid (from parietal cells) and pepsinogen (from chief cells) ○ Secreted by cells in the pyloric region and upper duodenum ○ Stimulated by food entering the stomach and thoughts of food ○ Maintains narrow pH range: 1-5 to 1.7 Secretin ○ Stimulates pancreas to secrete sodium bicarbonate (Na2CO3) ○ Secreted by S cells in the duodenum and jejunum ○ Stimulated by the presence of acidic chyme and the presence of peptones in the duodenum ○ Maintains correct pH in the small intestine Cholecystokinin (CCK) ○ Stimulates gallbladder to release bile Needed for the digestion of fat ○ Stimulates the release of pancreatic enzymes (relaxes sphincter of Oddi) ○ Secreted by cells in the duodenum ○ Stimulated by food and presence of fat and protein in the duodenum Causes of Gastric Ulcers Heliobacter pylori or H. pylori ○ Bacteria that attacks stomach lining Heavy use of aspirin and/or NSAIDS Excess acid production  8 Monosaccharides Glucose ○ Primary monosaccharide in the body ○ Also known as blood sugar or dextrose ○ One of the two sugars present in every disaccharide ○ Almost all polysaccharides are composed of glucose units linked together Fructose ○ Also known as levulose ○ Occurs naturally in fruit and honey ○ Present in high fructose corn syrup Galactose ○ When combined with glucose through a condensation reaction, the result is disaccharide lactose ○ The hydrolysis of lactose to glucose and galactose is catalyzed by the enzymes lactase and B-galactosidase Portal Vein Travel ○ End product of carbohydrate digestion Monosaccharides enter the capillaries of the intestinal wall ○ Travel to the liver via the portal vein ○ In the liver: galactose and fructose are converted to glucose Disaccharides Maltose (Glucose + Glucose) ○ Breakdown product of starch ○ Produced during fermentation of alcohol Sucrose (Glucose + Fructose) ○ Table sugar ○ Found in sugar cane, sugar beets, maple syrup Lactose (Glucose + Galactose) ○ Found in milk and dairy All disaccharides have the same chemical formula (C6H12O2)2*  9 Complex Carbohydrates Oligosaccharides ○ 3 to 10 monosaccharides ○ Maltotriose ○ Found in beans and legumes ○ Not digested but metabolized by bacteria in the large intestine Results in gas ○ Beano ® Enzyme that breaks down oligosaccharides Alpha - galactosidase Polysaccharides ○ > 10 monosaccharides ○ Glycogen Major storage form of carbohydrates in humans and animals Found in liver and muscle Structure ○ More highly branched ○ More sites for enzyme action ○ Similar to amylopectin* ○ Starch Major storage form of carbohydrates in plants Amylose: straight chain polymer Amylopectin: branched ○ Dietary Fiber Humans can not digest or absorb fiber Provides no energy (kcals) Metabolized by colonic bacteria Characterized By Chemical composition Physical properties (soluble vs. insoluble)  10 Condensation and Hydrolysis Reaction and What is Formed From What Condensation ○ Taking two monosaccharides and creating a disaccharide Glucose + Glucose = Maltose and Water Water is released by the two glucose Hydrolysis ○ Breaking down bonds by adding water to it Water comes into Maltose and creates two glucose molecules Soluble vs. Insoluble Fiber Soluble ○ Fruits ○ Beans ○ Oats ○ Barley Insoluble ○ Vegetables ○ Whole grains Cellulose vs. Hemicellulose Cellulose ○ Found in plant cell wall ○ Homogenous: linear molecule of glucose units ○ Neutrally charged ○ Water insoluble ○ Poorly fermented by colonic bacteria Hemicellulose ○ Found in plant cell wall ○ Heterogenous: polymer with side chains ○ Charge, solubility, and fermentability depends on side chains  11 Dietary Fiber Recommendations Women: 25 grams per day Men: 38 grams per day 14g per 1,000 kcals DV: 25g/day Average intake in US is 13 to 17 grams per day Excessive Fiber Intake ○ > 60 grams per day ○ Require extra intake of fluid ○ Binds to some minerals ○ Develop phytobezoars (undigested fiber) ○ Fills the stomach of a child quickly Carbohydrate Digestion 1. Mouth a. Mechanical digestion of chewing 2. Salivary Gland a. Starch is broken down by salivary amylase to maltose b. Breaks down alpha 1-4 bonds and leaves 1-6 bonds intact 3. Stomach a. Cardiac sphincter allows food into stomach b. Gastrin is secreted i. Stimulates production of stomach acid from parietal cells c. Food becomes chyme i. Pyloric sphincter to duodenum 4. Pancreas a. Enzymes (amylase) break down starch into maltose b. Cholecystokinin (CCK) stimulates the release of sodium bicarbonate to neutralize stomach acid 5. Small Intestine a. Enzymes in the wall of the small intestine break down disaccharides into monosaccharides b. Villi and Microvilli (Brush Borders)  12 i. Aid in the absorption of nutrients and digested food c. Enzymes cut 1-4 linkage to 2 Glucose i. Isomaltase acts on dextrin* 6. Hepatic Portal Vein a. Blood vessel where glucose, fructose, and galactose enter capillaries of intestinal villi through transporters b. GLUT5 i. Where fructose goes from small intestine → microvilli → enterocyte c. SGLT Transporter i. Pumps sodium from the cell to the lumen ii. Potassium travels back into the enterocyte iii. Sodium concentration drops in the enterocyte d. GLUT2 i. Where fructose, galactose, and glucose are taken from the enterocyte cells to the hepatic portal vein 7. Liver a. Absorption of glucose, fructose, and galactose 8. Large Intestine a. Some soluble fiber (viscous) is fermented into various acids and gasses by bacteria in the large intestine 9. Anus a. Insoluble fiber is excreted in feces and little other dietary carbohydrates are present Glycemic Response How quickly glucose is absorbed after consuming How highly blood glucose rises and returns to normal Glycemic Index Blood glucose response to a given food compared to a standard (white bread) Influenced by the amount of starch, fiber, processing, structure, and presence of other macronutrients  13 Glycemic Load Better reflection of a food’s effects on blood glucose* Carbohydrate Intake Recommendations RDA ○ 130 grams per day for adults ○ 50 to 100 grams per day to prevent ketosis ○ 45% to 65% of total energy Current Intake ○ 180 to 330 grams per day ○ Worldwide intake is ~70% of total energy Protein Sparing Effect Protein is not used or burned for energy Allow protein to do its body building activities Gluconeogenesis Producing glucose from non-carbohydrate based sources Occurs in liver and kidneys and activates cortisol ○ NOT in muscles because it lacks the G-6-P (can happen indirectly) LACTATE STEPS ○ 1: Lactate From Muscle → Liver (Cori Cycle) ○ 2: Lactate → Pyruvate Enzyme: Lactate Dehydrogenase B ○ 3: Pyruvate → OAA (4C oxaloacetate) Enzyme: Pyruvate Carboxylase ○ 4: OAA → Malate → OAA ○ 5: OAA → Phosphoenolpyruvate (PEP) Enzyme: PEPCK ○ 6: PEP → Fructo-1-6–Bisphosphate (F16B) Enzyme: Fructo-1-6–Bisphosphatase ○ 7: F16B → G-6-P ○ 8: G-6-P → ER → Free Glucose  14 GLYCEROL STEPS ○ 1: Lipolysis (Splits Triglycerides aka Lipids to Glycerol and Fatty acids) ○ 2: Glycerol → Glycerol-3-Phosphate Enzyme: Glycerol Kinase ○ 3: G-3-P to Dihydroxyacetone Phosphate (DHAP) Happens in fasted states (low blood glucose) ○ Body needs to increase blood glucose levels Pancreas releases Glucagon (hormone that helps regulate blood sugar levels by raising it) Excess gluconeogenesis causes hyperglycemia Low gluconeogenesis causes fetal hypoglycemia 3 Irreversible Steps of Glycolysis Phosphoenolpyruvate to pyruvate Fructose-1-6-bisphosphate to fructose-6-phosphate G-6-P to Glucose Steps of Glucose Homeostasis STEP 1 ○ When a person eats, blood glucose rises STEP 2 ○ High blood glucose stimulates the pancreas to release insulin STEP 3 ○ Insulin stimulates the uptake of glucose into cells and storage as glycogen in the liver and muscles Also stimulates the conversion of excess glucose into fat for storage Insulin helps lower blood sugar levels STEP 4 ○ As the body’s cells use glucose, blood levels decline STEP 5 ○ Low blood glucose stimulates the pancreas to release glucagon into the bloodstream  15 STEP 6 ○ Glucagon stimulates liver cells to break down glycogen and release glucose into the blood STEP 7 ○ Blood glucose begins to rise  16 What Are The Glucose Transporters? GLUT2 ○ Pancreas, liver, intestine (regulated by insulin) ○ Fructose, galactose, and glucose are taken from enterocyte cells to hepatic portal vein GLUT3 ○ Activated by Cortisol ○ Kidneys GLUT4 ○ Transports glucose into muscles (can be regulated without insulin) GLUT5 ○ Enterocyte (Fructose Transport) Fructose goes from the small intestine to microvilli to enterocyte cells SGLT (Sodium Glucose Transporter) ○ Active transport: Brings glucose, galactose, and sodium into the enterocyte ○ Pumps sodium from the cell to the lumen ○ Potassium travels back into the enterocyte ○ Sodium concentration drops in the enterocyte Pancreas & ATP Gated Calcium Channels 1: Glucose enters Pancreatic Beta Cell ○ Alpha Cell makes Glucagon ○ Beta Cell makes Insulin 2: GLUT2 pulls in the glucose to the pancreas ○ Makes ATP 3: ATP allows Calcium Channel to open up 4: Calcium enters the cell and stimulates the ER to create insulin 5: Insulin secreted into blood and taken to every cell 6: Glucose binds with insulin receptors in the cell (in the liver) 7: Insulin allows GLUT2 to let glucose in  17 Glycogen Synthesis (Glycogenesis) Blood glucose is high and insulin is released Occurs in muscles and liver STEPS ○ Glucose from hepatic portal vein enters liver cell via GLUT2 Glucokinase (enzyme) “rips” off ATP from glucose to form ADP + phosphate in the liver (G-6-P) Phospho-gluco-mutase is the enzyme that moves phosphates around Phosphate is put on the 6th position of glucose Then moved to the 1st position: G-1-P ○ Uridine Triphosphate (UTP) Provides energy Phosphatase cuts the bond of the phosphate group on UTP to release 2 Leads to Uridine Monophosphate (UMP) and 2 phosphate groups known as pyrophosphate ○ Pyrophosphate Provides energy to fuel reaction ○ UMP Links to phosphate of G-1-P Becomes UDP-Glucose ○ Priming Reaction (PRIMER) Glycogenin (protein enzyme) floats around the cell Has OH groups which interact with UDP-Glucose Autocatalytic Reaction No enzyme involved Carbon 1 of UDP-Glucose attaches to OH of Glycogenin UDP leaves after this bond ○ Repeating UDP released and glucose chains put together ○ Presence of Priming Reaction Activates Glycogen Synthase Critical for synthesis of glucose  18 ○ Glycogen Synthase Continually connect glucose molecules together Creates 1-4 linkage Releases UDP Only glucose is attached ○ Branching Enzyme Cuts alpha 1-4 bonds in glucose bond Makes 1-6 bond Glycogen links is how liver and muscle store glycogen Enzyme: Glycogen Phosphorylase Takes phosphate from pyridoxal phosphate - coenzyme (active form of vitamin B6 and coenzyme of Glycogen Phosphorylase) ○ Sticks it between 1-4 bonds to regenerate/release G-1-P Enzyme: Debranching (Glycogenolysis) Can transfer 6 glucose ○ Cuts a group of 3 glucose and sticks it to another bond ○ Cuts 1-4 linkage, makes new 1-4 bond, cuts 1-6 linkage ○ Releases a glucose molecule which floats into the bloodstream Glucose-6-Phosphate (G-6-P) Muscle and liver cells Created when phosphate is put on the 6th position Glycogen Synthesis (Creating Glycogen) ○ G-6-P takes phosphate and puts in on the 1st position (G-1-P) Glycogenolysis (Breakdown of Glycogen) ○ G-1-P creates G-6-P Enzyme: Glucose-6-Phosphatase Liver Transporter 1 brings G-1-P into the endoplasmic reticulum (ER) Transporter 2 takes G-6-P phosphate and removes a phosphate ○ Becomes glucose to go into the bloodstream  19 Pathways That Are Not Reversible Oxaloacetate converted to malate in the mitochondria ○ Malate is pushed out into the cytoplasm and becomes Oxaloacetate again Acts on PEPCK to make phosphoenolpyruvate HBA1C Classification Percentage of RBC attached with sugar Normal ○ < 5.7% Pre-Diabetes ○ 5.7 to 6.4% Diabetes ○ 6.5% +  20 Practice Questions What are the end products of cellular respiration? Water CO2 ATP (energy) Where is lactose absorbed? Small intestine Glucose to pyruvate is called? Substrate phosphorylation Pyruvate to Acetyl CoA begins in the? TCA Cycle What are the products of fermentation? CO2 and lactic acid (lactate) AKA gas and acid What are the primary products of carbohydrate digestion in the duodenum? Maltose units Maltotriose Dextrins What enzymes are released in the lumen of the small intestine? Maltase Sucrase Lactase Isomaltase (acts on dextrin) What is the movement of the intestine that shears and breaks down ingested material? Segmentation What is stomach acid neutralized by? Sodium bicarbonate (Na2CO3) - pancreatic secretion  21 What sphincter controls the amount of chyme released into the small intestine? Pyloric sphincter Where are most drugs metabolized? Liver What increases the surface area of nutrient absorption? Villi True or Fale: Metoclopramide is a dopamine receptor agonist False - Metoclopramide is a dopamine receptor antagonist What do parietal cells produce? Hydrochloric (stomach) acid - HCL What emulsifies fat globules? Bile True or Fale: After digestion, amino acids enter the lymphatic system and get distributed to different organs False - Amino Acids enter blood vessels True or False: Infections cannot be a cause of stomach ulcers False - Infections can cause stomach ulcers What slows gastric (stomach) emptying? Gastric inhibitory peptide (GIP) Colonic bacteria are a good source of what? Biotin True or False: Gastroparesis can be caused by surgical procedures True What is the primary site of absorption of sodium? Large intestine  22 True or False: Secretin stimulates the stomach to produce HCL and maintain the pH of the stomach False - Secretin stimulates the pancreas to secrete sodium bicarbonate Which complex plays a role in the ETC and the TCA Cycle? Complex 2 Which complex does NOT pump H into the intermembrane space? Complex 2 Which is shuttled between the complexes? Electrons What complexes pump protons out? Complex 1, 3, and 4 Complex 2 and 5 do NOT The enzyme that converts G-6-P to G-1-P is? Phosphoglucomutase Ture or False: Linear and non-branching bonds between C1 and C4 of glucose molecules are alpha glycosidic bonds True What reaction converts glucose to maltose? Condensation What hormone stimulates the production of bicarbonate? Secretin What does the breakdown of lactose produce? Glucose and Galactose True or False: Three free glucose molecules are released into the bloodstream by the action of the debranching enzyme False - one glucose muscle is released into the bloodstream  23 True or False: The enzyme that adds a phosphate group to other proteins or enzymes is phosphatase False - Phosphatase cuts the bond of phosphate groups What are energy-rich molecules that power glycogen synthesis? Pyrophosphates True or False: The sugar molecule Glycogenin serves as the initial primer for beginning glycogen synthesis False - Glycogenin is a protein molecule that has OH groups and interacts with UDP What is the major storage site of Glycogen? Muscle What enzyme is essential for the breakdown of Glycogen? Pyridoxal phosphate True or False: Pancreatic amylase de-branches dextrin False - Amylase breaks down starch into maltose What does a drop in blood glucose levels stimulate? Production of Glucagon What is an example of an Oligosaccharide? Maltotriose