Extra Questions

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 cataboilc reactions involve breakdown of compounds into molecules. Energy in the form of ATP is required for anabolic reactions. Catabolic reaction releases ATP.

In what form are carbohydrates absorbed, and what happens to these compounds after absorption?

Carbohydrate digestion is the process of breaking down larger carbohydrates into smaller units, and eventually to monosaccharide forms, which are absorbed. Following primarily an active absorption process, glucose and galatose are taken up by absorptive cells in the intestine. Fructose undergoes facilitated absorption. All of the monsaccharides then enter the portal vein that goes directly to the liver. The liver finally excersizes its metabolic options, producing glucose, glycogen, and even fat if carbohydrates are consumed in great excess and overall calorie needs are exceeded.

What are some compounds that are made from cholesterol in the body?

Cholesterol forms part of cell membranes, hormones, and bile acids. If sufficent amounts are not consumed, the body makes what phospholipids and cholesterol it needs.

What is the main difference between a chylomicron and lipoproteins?

Chylomicrons are made in the intestine as a result of the consumption of fat, lipoproteins are made in the liver as a result for the need for fats/cholesterol inside the body

How does the body respond when too little carbohydrate is consumed?

Eating too little carbohydrates forces the body to make glucose using primarily amino acids from proteins found in muscles and other vital organs. A low glucose supply in cells also inhibits efficent metabolism of fats. Ketosis can then result.

What are enzymes? Where is bile produced?

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. Bile is produced in the liver.

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?

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

In what ways do fatty acids differ from one another?

Fatty acids can be distinguished from one another by the length of the carbon skeleton and the number and position of double bonds along that skeleton.

What makes fiber a very different kind of carbohydrate, and what is the difference between nonfermentable, viscous, and functional fiber?

Fiber is essentially the portion of plant food that remains undigested as it enters the large intestine. There are two general classes of fiber: nonfermentable and viscous. Nonfermentable (insoluable) fibers are mostly made up of cellulose, hemicelluloses, and lignins. Viscuous (soluable) fibers are made up mostly of pectins, gums, and mucilages. Both nonfermentable and viscous fibers are resistant to human digestive enzymes, but bacteria in the large intestine can break down viscous fibers.

What are some of the important functions of fiber?

Fiber-rich foods also help in weight control and reduce the risk of developing obesity and cardiovascular disease, and possibly colon cancer. Soluable fiber can also be useful for controlling blood glucose in patients with diabetes and in lowering blood cholesterol. Whole-grain breads and cereals, vegtables, beans, and fruits are excellent sources of fiber.

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 nutrition will be rapidly turned over by metabolic processes.

What is the difference between glucagon, glycogen, glucose, gluconeogenesis, and glycogenolysis?

Glucagon - the pancreas releases this hormone when the levels of glucose in the blood fall too low. Glucagon causes the liver to convert stored glycogen into glucose, which is released into the bloodstream. High blood-glucose levels stimulate the release of insulin Glycogen - multibranched polysaccharide of glucose that serves as a form of energy stored in animals Glucose - main source of energy for most cells in the body Gluconeogenesis - metabolic pathway that results in the generation of glucose from non-carbohydrate carbon substrates Glycogenolysis - biochemical breakdown of glycogen to glucose

Why are HDLs considererd good cholesterol

HDL picks up cholesterol from cells and transports it primarily to other lipoproteins for eventual transport back to the liver. Risk factors for cardiovascular disease include an elevated level of LDL and/or low amounts of HDL in the blood

What is hepatic circulation?

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

What is the function of insulin

Hormone produced by the pancreas to control blood glucose levels. When glucose levels are elevated, insulin delivers glucose to the cell and allows it to enter so it can be used for fuel.

How do hunger and appetite differ in the way they influence our desire to eat?

Hunger is the primarily physical or internal desire to find and eat food. Fulfilling it creates satiety-no further desire to eat exists. Food intake is also affected by appetite-realted (external) forces like social cusoms, time of day, and being with others.

What happens to unsaturated fats during the process of hydrogenation?

Hydrogenation of unsaturated fatty acids is the process of adding hydrogen to carbon-carbon double bonds to produce single bonds. This results in the creation of some transfatty acids. Hydrogenation changes vegetable oil to solid fat.

What enzyme is responsible for digestion of triglycerides?

In the SI, a lipiase enzyme released from the pancreas digests dietary triglycerides.

Why do some individuals feel discomfort after they consume large amounts of lactose? How can they avoid these symtoms?

Lactose maldigestion is a condtion that results when cells of the intestine do not make sufficent lactase, the enzyme necessary to digest lactose, resulting in symptoms such as abdominal gas, pain, and diarrhea. Most people with lactose maldigestion can tolerate cheeses and yougurt, as well as moderate amounts of milk. When significant symptoms develop after lacose intake, it is called lactose intolerance.

What are the end products of fat digestion?

Lipase digests dietary triglycerides into monoglycerides and fatty acids. These endpoints of fat digestion then diffuse into the absorptive cells of the SI

How do lipids move through the bloodstream?

Lipids generally move through the bloodstream as part of lipoproteins.

Where are VLDLs made and what do they contain?

Lipids synthesized in the liver are packaged as very-low-density lipoproteins (VLDL)

Where do the LDLs originate and what is their destination?

Lipoprotein lipase removes triglycerides from the interiors of both chylomicrons and VLDL, breaking the triglycerides down into glycerol and fatty acids, which are taken up by tissues for energy needs or storage. What remains after the action of lipoprotein lipase are chylomicron remnants, the components of which are recycled by the liver, or LDL, rich in cholesterol. LDL is picked up by receptors on body cells, especially liver cells. Scavenger cells in the arteries may do the same, speeding the development of atherosclerosis.

What are the differences between the absorption of long- versus short-chain fatty acids?

Long chain are transported through the lymphatic system, whereas short are absorbed directly into the portal vein that connects directly to the liver. Other lipids are prepared for absorption by different enzymes.

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.

Trace the path of fat through the digestive system. Where is each of the nutrients broken down as it passes through the GI tract? Where is each absorbed?

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 secreets bile, which emulsifies large globules of fat in the small intestine into smaller micells, allowing moer surface are afor 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.

How do nutrient density and energy density differ?

Nutrient density of a food is determined by comparing its protein, vitamin, or material content with the amount of calories it provides. Nutrient-dense foods, such as fat-free milk, fruits, vegetables, and whole-grain breads and cereals, supply many nutrients without contributing excessive calories. Energy density is a measurement that best describes the calorie content of a food. Energy density of a food is determined by comparing the calorie content with the weight of the food. Consuming foods of low energy density, such as fruits and vegetables, may also help in weight energy density, such as fruits and vegetables, may also help in weight control, because they promote satiety with relatively few calories.

What are the ABCDE steps of assessign nutritional status? Give an example.

Nutritional state can be assessed by using anthropometric, biochemical, clinical, dietary, and economic assessments A - measuring body weight B - enzyme activities in urine C - examination of eyes D - a record of previous few days' food intake E - ability to purchase and prepare foods needed to maintain health

Where are phospholipids found in the body?

Phosplolipidsare emulsifiers - compounds that can suspend fat in water. Phospholipids also form parts of cell membranes and various compounds in the body.

Trace the path of protein through the digestive system. Where is each of the nutrients broken down as it passes through the GI tract? Where is each absorbed?

Protein digestion begins in the stomach, where acid and enzymes begin to denature and break down polypeptides into smaller peptides. In the SI, peptides are further broken down into amino acids by enzymes from the pancreas and SI cells. Amino acids are absorbed into the hepatic portal vein by the cells lining in 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

How do the definitions of RDA and AI differ? Which DRI category includes the highest amounts of a nutrient unlikely to cause adverse effects?

RDA are the amounts of each nutrient that will meet the needs of healthy individuals within specific gender and age categories. If not enough information is avalible to set an RDA, the AI value is used. UL's are the highest amounts of a nutrient unlikely to cause adverse health effects. UL's have been set for some vitamins and minerals.

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 lubricated the passage of food down the esophogas and also contains enzymes to begin the process 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 calls 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 digestio, enzymes catalyze the breakdown of carbohydrates, fats, and proteins into smaller components that can be absorbed by the cells lining the intestine.

What is the difference between saturated and unsaturated fatty acid, and between an omega-3 and omega-6 fatty acid?

Saturated fatty acids contain no double bonds within their carbon skeleton. That is, they are fully saturated with hydrogens. Monounsaturated fatty acids contain one carbon-carbon double bond, and polyunsaturated fatty acids contain two or more of these bonds. The location of the first double bond on an unsaturated fatty acid is an important feature and will either 3,6, or 9 carbons from the methyl end. If the first double bond starts three carbons from the methyl (omega) end of the fatty acid, it is an omega-3 fatty acid. If the first double bond is located six carbons from the omega end, it is an omega 6 fatty acid.

Trace the path of carbohydrates through the digestive system. Where is each of the nutrients broken down as it passes through the GI tract? Where is each absorbed?

Starch digestion begins in the mouth, where salivary amylase breaks down some starch into simple sugars units. Carbohydrates then move down the esophagus and stomach to the SI. There, enzymes from the SI and intestinal cells break down starch into monosaccharides, which are absorbed into the cells of the SI 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 exit the body through the anus.

What is the recommended intake of total carbohydrate per day, and how do typical dietary intakes compare?

The RDA for carbohydrate is 130 grams per day. The typical North American diet provides 180 to 330 grams per day. A reasonable goal is to have about half our calorie intake coming from starch and our total carbohydrate intake making up about 60% of our calorie intake, with a range of 45% to 65%

How do fats become rancid and how can this be prevented?

The carbon-carbon double bonds in polyunsaturated fatty acids are easily broken, yielding products responsible for rancidity. The presence of antioxidants, such as vitamin E in oils, naturally protects unsaturated fatty acids against oxidative destruction. Manufacturers can use hydrogenated fats and add natural or synthetic antioxidants to reduce the likelihood of rancidity.

What are the characteristics of the Mediterranean diet?

The major sources of fat in the Mediterranean diet include liberal amounts of olive oil compared to a small amount of animal fat (from animal flesh and dairy products). The Mediterranean diet also allows a moderate alcohol consumption and plenty of whole grains and few refined carbohydrates.

How much fiber is recommended each day? Give examples of high fiber foods, including fermentable and nonfermentable.

The recommended intake of fiber is 25 to 38 grams per day for woman and men, respectively. High fiber diets must be accompanied by adequate fluid intakes to avoid constipate and should be followed only under a physician's guidance.

How do triglycerides differ from phospholipids?

Triglycerides are the major form of fat in the body and in foods. These consist of three fatty acids bonded to a glycerol backbone. Phospholipids are similar to triglycerides in structure, but at least one fatty acid is replaced by another compound containing phosphorus. Phospholipids play an important structural role in cell membranes.

What are the functions of triglycerides in the body?

Triglycerides are the major form of fat in the body. They are used for energy stored in a tissue, they insulate and protect body organs, and they transport fat-soluable vitamins

What are the mechanisms by which blood glucose levels are maintained within a narrow range?

When blood glucose rises after a meal, the hormone insulin is released in great amounts from the pancreas. Insulin acts to lower blood glucose by increasing glucose storage in the liver and glucose up-take by other body cells. If blood glucose fails during fasting, glucagon and other hormones increase the liver's release of glucose into the bloodstream to restore normal blood glucose concentrations. In a similar way, the hormone epinephrine can make more glucose available in response to stress. This balance in hormone activity helps maintain blood glucose within a healthy range.

How are dietary fats packaged in the small intestine and transported?

chylomicrons