nutrition chpt 3

1. Which absorptive processes use energy? How does concentration gradient factor into this?

A concentration gradient is a difference in concentration of a solute on two sides of a membrane. A solute naturally moves from an area of high concentration to an area of low concentration (down its concentration gradient); no energy is required. However, to move a solute from an area of low concentration to an area of high concentration (against its concentration gradient), energy is required. This is called active transport, and includes absorptive processes that utilize a carrier or a vesicle (including phagocytosis and pinocytosis) to move substances across a semipermeable membrane.

1. If a person has hypothyroidism, the thyroid gland produces low levels of thyroid hormone. Will a person with hypothyroidism tend to lose weight or gain weight? Explain your answer.

A person with hypothyroidism tends to gain weight. Thyroid hormones regulate the rate of cell metabolism. If thyroid hormone levels are low, the overall rate at which nutrients are broken down for energy will be lower than usual and nutrients will be stored (e.g., as adipose tissue) instead.

1. What is the body's most efficient form of energy storage?

Adipose tissue is the most efficient form of stored energy.

Esophagus

Allows movement of food from pharynx (back of mouth) to stomach Epiglottis prevents food from entering trachea Lower esophageal sphincter (gastroesophageal sphincter or the cardiac sphincter) prevents backflow of stomach contents into esophagus No mechanical or chemical digestion

1. What is an organelle?

An organelle is a compartment, particle, or filament that performs a specialized function within a cell.

1. What is the difference between anabolic and catabolic reactions? How does ATP fit into cellular metabolism?

Anabolic reactions involve synthesis of molecules into compounds, whereas catabolic reactions involve breakdown of compounds into molecules. Energy in the form of ATP is required for anabolic reactions. Catabolic reactions release ATP.

1. What are the roles of antigens and antibodies in the immune response?

Antigens are proteins that the immune system recognizes as foreign. Antibodies (also called immunoglobulins) are proteins that are produced by certain types of white blood cells. Antibodies bind to specific antigens and signal their destruction by the cells and chemicals of the immune system.

1. Predict how nutritional genomics will affect nutrition recommendations in the future.

As we learn more about the many ways nutrition both affects and is affected by genetics, nutrient recommendations will be more and more personalized. Based on the results of a genetic test, for example, a registered dietitian may recommend megadose supplementation of folic acid for a woman of childbearing age. In addition, it will become clear who will benefit most from dietary sodium restriction for prevention or treatment of hypertension.

1. How are sodium and potassium involved in nerve impulse transmission?

At rest, ion pumps in the nerve cell membrane move sodium out of the cell and move potassium into the cell. This creates a slight electrochemical gradient across the nerve cell membrane. When the nerve cell receives a stimulus, ion channels in the nerve cell membrane open up and allow sodium to flow into the cell as potassium flows out. The change in electrical charge is transmitted along the nerve cell as additional ion channels open up. At the end of a nerve cell, the electrical signal is changed into a chemical signal as neurotransmitters are released. Neurotransmitters affect other nerve cells and surrounding tissues.

1. Discuss the levels of organization of the human body.

Atoms join together to form molecules. Molecules join together to form organelles and many organelles work together to make up a cell. A group of similar cells that works together is known as a tissue. Various tissues combine to form organs. A group of related organs forms an organ system. Many organ systems work together to make up an organism.

Food Matter Changes in Form

Bolus - moistened mass of food that moves from the mouth through the esophagus to the stomach Chyme - watery mixture of partially digested food and digestive secretions Feces - mass of water, fiber, tough connective tissues, bacterial cells, and sloughed intestinal cells formed in the large intestine and excreted through the anus

Nutritional Diseases with a Genetic Link

Cardiovascular disease Obesity Diabetes Cancer

Celiac Disease (Celiac Sprue)

Chronic, immune-mediated disease precipitated by exposure to dietary gluten in genetically predisposed people Flattens villi of small intestine Nutrient malabsorption Sources of gluten Wheat Barley Rye

Chemical Digestion in the Small Intestine

Chyme passes from stomach into small intestine (duodenum) Pancreas releases pancreatic juice Bicarbonate Pancreatic enzymes Gallbladder releases bile Small intestinal cells produce some enzymes

Inside the Large Intestine

Components of feces Water Undigested fiber Tough connective tissues (from animal foods) Bacteria Dead intestinal cells Large bacterial population (>500 different species) Probiotics - microorganisms that reside in large intestine and provide health benefits Prebiotics - substances that increase growth of probiotic microorganisms

Personalizing Nutrition Advice

Dietary advice must be tailored to personal and cultural preferences Consider family history Genetic tests available for at least 1500 diseases and conditions

Constipation

Difficult or infrequent evacuation of the bowels Common causes Ignoring the urge to defecate Muscle or nerve problems Dietary supplements (e.g., calcium, iron) Some medications Laxatives For short-term use Physician supervision Lifestyle changes Diet Increase fluid Increase fiber Increase physical activity Relaxation Regular bowel habits

1. What are enzymes? Is bile an enzyme?

Enzymes are catalysts that speed the rate of chemical reactions. Bile is not an enzyme, but it does aid digestion by emulsifying fat, thus increasing the surface area upon which enzymes can work.

1. List the four types of tissues and give an example of where you could find each in the body.

Epithelial tissue makes up the skin and lines the digestive tract. Connective tissue forms bones, tendons, and ligaments. Muscle tissue can be found in all the muscles of the body. Nervous tissue is found in the brain, spinal column, and nerve cells, which extend throughout the body.

1. What did you have for lunch today? Trace the path of your meal through the digestive system. Where is each of the nutrients broken down as it passes through the GI tract? Where is each absorbed?

Example: My lunch today was spicy chicken posole, which is a hearty soup with onions sautéed in canola oil, chicken breast, great northern beans, hominy, lime juice, and fresh herbs. The chicken and beans provide protein. Protein digestion begins in the stomach, where acid and enzymes begin to denature and break down polypeptides into smaller peptides. In the small intestine, peptides are further broken down into amino acids by enzymes from the pancreas and small intestinal cells. Amino acids are absorbed into the hepatic portal vein by the cells lining the small intestine. Very little protein escapes digestion and absorption, but any undigested protein would then pass through the large intestine and be excreted through the anus. The beans and hominy provide carbohydrates. Starch digestion begins in the mouth, where salivary amylase breaks down some starch into simple sugar units. Carbohydrates then move down the esophagus and stomach (no starch digestion here) to the small intestine. There, enzymes from the small intestine and intestinal cells break down starch into monosaccharides, which are absorbed into the cells of the small intestine and transported via the hepatic portal vein to the liver. Fiber, which is not digestible by human enzymes, then passes to the large intestine where some of it can be fermented by bacteria. Undigested carbohydrates (e.g., fiber) exit the body through the anus. Fat can be found in the chicken and the canola oil. Minor amounts of fat are digested in the mouth by salivary lipase and in the stomach by gastric lipase, but most fat will be digested in the small intestine. The gallbladder secretes bile, which emulsifies large globules of fat in the small intestine into smaller micelles, allowing more surface area for pancreatic lipase to digest triglycerides. Small fatty acids may be absorbed by the small intestinal cells directly into the hepatic portal vein, but larger fatty acids are packaged as chylomicrons and absorbed into the lymph before they enter the bloodstream.

1. List at least three hormones that tend to increase blood sugar.

Examples of hormones that increase blood sugar are glucagon, epinephrine, norepinephrine, and growth hormone.

1. When it comes to vitamins and minerals, is consuming more than the RDA or AI a good way to ensure optimal nutrition status? Why or why not?

Excesses of some vitamins and minerals are simply excreted via urine, so consuming excess nutrients has no benefit. However, for some nutrients, such as fat-soluble vitamins, excess can lead to toxicity.

Nutrient Storage Capabilities

Fat: nearly limitless storage capacity in adipose tissue Glucose: limited amount in blood Glycogen: short-term storage in muscle and liver Amino acids: limited amount in blood Vitamins and minerals: liver, adipose tissue, bones A balanced diet is the safest means to acquiring nutrients needed for optimal health

1. Why is it important to consume nutrients daily?

For most nutrients, the human body has only limited storage capabilities. Although fat-soluble vitamins and some minerals can be stored in body tissues, water-soluble vitamins are readily excreted and the short-term stores of nutrients will be rapidly turned over by metabolic processes.

Digestive System: Structures

Gastrointestinal (GI) tract Mouth Esophagus Stomach Small intestine Large intestine Accessory organs Liver Gallbladder Pancreas

Nutrition and Genetics

Genetic variations can affect Nutrient requirements Susceptibilities to diseases Responses to diet and lifestyle changes Genome - an organism's complete set of DNA Epigenome - the way that genome is marked and packaged inside the cell nucleus Epigenetics - changes in gene expression caused by mechanisms other than changes in the DNA sequence

1. Which nutrient is the brain's preferred source of fuel?

Glucose is the brain's preferred source of fuel.

Peptic Ulcers

HCl erodes the lining of the esophagus, stomach, or upper small intestine Pain Bleeding Perforation Most common causes Helicobacter Pylori NSAIDs Symptoms Stomach pain ~2 hours after eating Weight loss Lack of appetite Nausea/vomiting Bloating

1. What is hepatic portal circulation?

Hepatic portal circulation is the flow of water-soluble nutrients from the gastrointestinal tract directly to the liver.

Stomach

Holding tank for food Usual capacity = 4 cups Size may be altered by surgery Gastric secretions Water Hydrochloric acid (HCl) Enzymes Mucus Mechanical digestion Churning Chemical digestion HCl Pepsin Lipase Absorption (small amount) Water Alcohol

Diarrhea

Increased fluidity, frequency, or amount of bowel movements Causes Infections, microorganisms Malabsorption (e.g., lactose, sugar alcohols) Excessive fiber Risks Dehydration (especially among infants) Malnutrition Treatment Prevent dehydration Fluid Electrolyte replacement Dietary changes may help Fat Caffeine Fiber Poorly absorbed carbohydrates When to seek medical attention Prolonged (>7 days for adults) Dehydration Blood in stool

1. What effect does insulin have on the storage of nutrients?

Insulin increases storage of glucose, fatty acids, and amino acids within cells. For example, insulin stimulates the storage of glucose as glycogen within liver and muscle cells.

Accessory Organs

Liver Produces bile Excretion of metabolic wastes Gallbladder Stores bile Pancreas Produces enzymes Produces hormones Produces bicarbonate

1. Which nutrients are absorbed into the lymph? Why?

Long-chain fatty acids, cholesterol, and fat-soluble vitamins are absorbed into the lymph. These fat-related products are too large to enter the bloodstream directly and therefore are generally emptied into the bloodstream only after passing through the lymphatic system.

Treatment of GERD

Long-term consequences of untreated GERD Damage and inflammation Bleeding Increased risk of esophageal cancer Medical treatment for GERD Antacids H2 blockers Proton pump inhibitor Motility agents

Sphincters

Lower esophageal sphincter (gastroesophageal sphincter, cardiac sphincter) - prevents backflow of stomach contents into the esophagus Pyloric sphincter - controls flow of stomach contents into small intestine Sphincter of Oddi - controls flow of bile (from common bile duct) and pancreatic juices (from pancreatic ducts) into small intestine Ileocecal valve - prevents contents of large intestine from reentering small intestine Anal sphincters (internal and external) - control defecation

Movement of Food Through the GI Tract

Lumen - hollowing opening inside the GI tract Motility - movement of food through the GI tract Peristalsis - coordinated muscular movement that propels food along the GI tract Sphincters - muscular rings that prevent the backflow of food matter through the GI tract

treatment for ulcers

Medical treatment Antibiotics Antacids Acid-reducing medications Proton pump inhibitors H2 blockers Dietary changes are of minor importance

1. How do mucus and surface area affect absorption?

Mucus is an important lubricant and it also protects the lining of the GI tract from being destroyed by the acid and enzymes that work within its lumen. The folded lining of the small intestine, with its villi and microvilli, allows greater surface area for absorption of nutrients.

Large Intestine

No villi or enzymes Absorption of water, some minerals, vitamins Five segments Cecum Ascending colon Transverse colon Descending colon Sigmoid colon Rectum Anus

1. Contrast nonspecific (innate) and specific (adaptive) immunity.

Nonspecific (innate) immunity protects the body against invasion by any microorganism or toxin. The skin and the epithelial cells that line the GI tract, for example, block the entry of microorganisms into the body tissues. Such defenses are present at birth. After initial exposure to an antigen, specific (adaptive) immunity allows the subsequent recognition of antigens by antibodies. Specific immunity is developed after birth as the immune system is exposed to a variety of antigens.

1. List three nutrients that support the immune system.

Nutrients that support the immune system include protein, essential fatty acids, iron, copper, zinc, vitamin A, some B vitamins, vitamin C, and vitamin D.

1. What is the difference between nutrigenetics and nutrigenomics?

Nutrigenetics is the study of the ways genes affect nutritional health, whereas nutrigenomics is the study of the ways nutrients and other dietary components affect gene expression. Both nutrigenetics and nutrigenomics are part of nutritional genomics, the study of all interactions between nutrients and genetics.

Nutritional Genomics

Nutritional genomics - interactions between nutrition and genetics; includes nutrigenetics and nutrigenomics Nutrigenetics - genes influence nutritional health Nutrient requirements Responsiveness to dietary modifications Nutrigenomics - nutrition affects gene expression

Mechanisms of Nutrient Absorption

Passive diffusion - diffusion of nutrients across the absorptive cell membranes Facilitated diffusion - uses a carrier protein to move nutrients down a concentration gradient Active absorption - involves a carrier protein as well as energy to move nutrients (against a concentration gradient) into absorptive cells Phagocytosis and pinocytosis - forms of active transport in which absorptive cell membrane forms an indentation that engulfs a nutrient to bring it into cell

Saliva

Produced by salivary glands Contains enzymes for chemical digestion Amylase Lipase Contains mucus to lubricate food

bile

Produced by the liver Stored in the gallbladder Released into duodenum Necessary for digestion and absorption of dietary lipids Enterohepatic circulation - some components of bile are reabsorbed from the small intestine and return to the liver to be used again

heartburn

Relaxation of lower esophageal sphincter allows gastric contents to reflux into esophagus Obesity Pregnancy Symptoms Gnawing pain in chest ("heartburn") Nausea Gagging Coughing Hoarseness Recurrent heartburn = gastroesophageal reflux disease (GERD)

1. Choose three secretions of the digestive system. Where is each secreted? What is the role of each in the process of digestion?

Saliva is secreted by the salivary glands in the mouth. It lubricates the passage of food down the esophagus and also contains enzymes to begin the processes of carbohydrate and fat digestion. Hydrochloric acid is produced by the parietal cells of the stomach. It kills pathogens, activates enzymes, makes some minerals easier to absorb, and achieves some chemical breakdown of proteins. Enzymes are secreted by the salivary glands, the chief cells of the stomach, the absorptive cells of the small intestine, and the exocrine cells of the pancreas. In general, enzymes speed the rate of chemical reactions. Specifically in digestion, enzymes catalyze the breakdown of carbohydrates, fats, and proteins into smaller components (e.g., monosaccharides, fatty acids, and amino acids) that can be absorbed by the cells lining the intestine.

Mouth

Sense of taste Sweet Sour Salty Bitter Umami Mechanical digestion Chewing Swallowing Chemical digestion Salivary amylase Salivary lipase

Irritable Bowel Syndrome (IBS)

Symptoms Abdominal pain (relieved by bowel movement) Diarrhea, constipation, or alternating episodes of both Gas, bloating, visible abdomen distention Possible causes Altered intestinal peristalsis Inflammation Food sensitivities Depression, stress Decreased pain threshold Treatments under investigation Elimination diet (low FODMAPs) Moderate caffeine intake Low-fat, small, frequent meals Probiotics Stress reduction Cognitive behavioral therapy Antidepressants Seek help from RD to plan nutritionally-adequate diet

Care for People with Celiac Disease

Symptoms Diarrhea Cramps, bloating, flatulence Fatigue Weight loss Anemia Infertility Bone loss Accurate diagnosis prior to gluten-free diet Blood test for antibodies to gluten Small intestinal biopsy Treatment Strict dietary avoidance of wheat, rye, and barley

1. Describe how nutrients, oxygen, and wastes are exchanged between the body's internal and external environments.

The exchange of nutrients, oxygen, and wastes between the body's internal and external environments is accomplished across vessels that are one cell thick. The oxygen in inspired air crosses the cell membranes of the alveoli in the lungs to enter the capillaries of the cardiovascular system. At the same time, waste products, such as carbon dioxide, cross from the blood into the lungs to be exhaled. When food is ingested and then digested, its smallest components can be absorbed across the cells lining the intestines. Nutrients then enter the blood or lymph for transport throughout the body. Some metabolic waste products travel through the blood to the kidneys, where they are transferred across the cells lining nephrons and excreted via urine.

1. Examine Figure 3-7. How does the pancreas have both endocrine and exocrine roles?

The exocrine cells of the pancreas secrete digestive enzymes into the pancreatic duct, which are released into the small intestine to aid in digestion of carbohydrates, proteins, and lipids. The endocrine cells of the pancreas secrete hormones into the bloodstream. These hormones - insulin and glucagon - regulate blood glucose.

1. How are the kidneys involved in bone health?

The kidneys are the site for one step in the activation of vitamin D. Vitamin D (from the diet and from skin synthesis) exists in an inactive form until it is activated at the liver and kidneys. The active vitamin D hormone then assists with regulation of calcium levels in the blood.

1. Choose three organelles and explain their relevance to human nutrition.

The mitochondria are the "power houses" of the cell. These are the sites at which the chemical energy stored in carbohydrates, proteins, and fats can be converted to ATP to fuel cellular activities. The cell nucleus is the site of DNA storage in the cell. Based on the DNA instructions within the cell nucleus, new proteins can be synthesized from the amino acids that came from dietary proteins or from the breakdown of body proteins. Peroxisomes contain enzymes to detoxify harmful chemicals, including alcohol.

1. The kidneys filter wastes from the blood. Trace the path of waste products out of the body.

The nephrons of the kidneys filter wastes from the blood, secreting them into the ureters. The ureters carry wastes and excreted water to the urinary bladder, where urine is stored for short periods of time. Urine is released from the urinary bladder through the urethra to the outside of the body.

1. Examine Figure 3-2. Provide three examples of ways the organs of one system support the functions of another system.

The skin, which is part of the integumentary system, supports the immune system by blocking the entrance of pathogens into the body. The gastrointestinal tract, part of the digestive system, also assists the immune system by providing a barrier against infection. In addition, the acid produced by the stomach kills many pathogens before they can cause harm. The pancreas produces enzymes that aid the actions of the digestive system, but it also secretes hormones as part of the endocrine system.

1. List two nutrition-related diseases that are strongly affected by genetics.

There are many nutrition-related diseases that are affected by genetics. Some examples are obesity, cardiovascular disease, type 1 and type 2 diabetes, celiac disease, osteoporosis, and Alzheimer's disease.

Absorption from the Small Intestine

Villi - fingerlike protrusions that participate in digestion and absorption of food New intestinal absorptive cells are constantly produced in crypts of small intestine Microvilli - extensive folds on the mucosal surface of the absorptive cells; increase surface area x 600 Absorptive cells (enterocytes) - intestinal cells that line villi and participate in nutrient absorption

1. Describe three ways essential nutrients support cell functions.

Water serves as a medium for chemical reactions inside cells. Dietary proteins supply amino acids that will be joined together according to the genetic code to synthesize new proteins within the cell, such as hormones and enzymes. Vitamins and minerals serve as regulators of chemical reactions within the cells. Carbohydrates, proteins, and fats provide fuel for cellular activities.

1. How are signals transmitted between one neuron and the next? Why are amino acids important in this process?

When an electrical impulse reaches the end of a neuron, neurotransmitters are released into the gap between one neuron and the next. This sends a chemical signal from one neuron to another. Amino acids make up neurotransmitters. For example, tryptophan is converted to serotonin.

Digestion

process by which large ingested molecules are mechanically and chemically broken down to produce basic nutrients that can be absorbed across the wall of the GI tract

absorption

process by which substances are taken up from GI tract and enter blood or lymph system Elimination of wastes Assists immune system Under autonomic control Regulated by nervous and endocrine systems