Nutrition 120

• Explain why cholesterol is not an essential nutrient

  Because the liver manufactures it
• What are the functions of cholesterol in the body?

  Found in cell membranes

  Part of myelin- the coating on many nerve cells

  Needed to synthesize vitamin D in the skin, cholic a component of bile acid, estrogen, testosterone, cortisol
• How are the polar and non-polar parts of a phospholipid molecule organized to form a lipid bilayer?


  The phosphoglycerate ends (soluble in fat) face outwards while the lipid (soluble in water) face inwards

  Tails together
• How does a phospholipid differ from a triglyceride?


  Triglyceride- the major form of lipid in food and in the body. They consist of three fatty acids attached to a glycerol molecule

  Phospholipid- types of lipids containing phosphorus. The most common are the phosphoglycerates, which are composed of a glycerol backbone with two fatty acids and a phosphate group attached
• What are some common food sources of each of the following:


  Saturated fat- no double bonds, full of hydrogen

  Omega-6- a fatty acid containing a carbon- carbon double bond between the sixth and seventh carbons from the omega end

  Omega-3 Fatty acid- a fatty acid containing a carbon-carbon double bond between the third and fourth carbons from the omega end

  Monosaturated fatty acid

  Oleic acid- monounsaturated fatty acid which is prevalent in olive and canola oils
• State the similarities and differences between omega-3 and omega-6 fatty acids with respect to chemical structure.

  Omega 6- a double bond between the sixth and seventh carbons, found in corn and safflower oils

  Both are used to synthesize regulatory molecules in the body

  Omega-3- a double bond between the third and fourth bonds
• What type of processing results in the formation of trans fatty acids in a vegetable oil? In what foods are trans fatty acids naturally occurring?


  Hydrogenation

  Naturally occurring in beef and dairy products
• What chemical properties of fatty acids determine whether a lipid is solid or liquid?

  Triglycerides which are a combination of fatty acids
• What distinguishes a saturated fat from a monounsaturated fat? From a polyunsaturated fat?

  Saturated fat- a fatty acid in which the carbon atoms are bound to as many hydrogens as possible and which, therefore, contains no carbon-carbon double bonds

  Monounsaturated fat- a fatty acid that contains 1 carbon-carbon double bond

  Polyunsaturated fat- a fatty acid that contains 2 or more carbon-carbon double bonds
• The quantity of trans fat in the Canadian food supply has declined since the 1990s. Describe the policy changes that are responsible for this decline


  The use of them are now prohibited in Canada
• Which foods should be excluded in a dietary pattern intended to lower saturated fat intake?

  Fast foods
• According to the CCHS, which food groups and individual foods most contribute to the fat intake of Canadian adults? Are these sources considered healthy fats?

  Meat and milk were major contributors

  ¼ of the fat intake was due to pizza, sandwiches, subs, hamburgers, hotdogs, baked goods
• Which types of fat and food sources are associated with a decreased risk of chronic disease?

  Unsaturated fats from fish, nuts, soybean, canola, flaxseed, and olive oils are associated with a lower risk for disease

  Foods with high fibre, fruits, vegetables
• Which types of fat and food sources are associated with an increased risk of chronic disease?

  Saturated fats are associated with an increased risk of cardiovascular disease

  Fast food and snacks are often high in saturated fat

  Trans fat
• Why are fat intakes about 35% calorie of concern?

  It is difficult to avoid saturated fats when the fat consumption is that high even those high in polyunsaturated fat contain some saturated fat
• In terms of kcalories percentage. How has the fat intake of Canadians changed since the 1970s?

  Has declined
• What are the main functions of the kidneys?

  primary site for excretion of water, nitrogen- containing wastes from protein, and other metabolic waste
• What are four routes for eliminating waste form the body?

  Lungs

  Skin

  Kidneys
• What are some potential benefits of healthy microflora?

  Minimize inflammation and promote immune function or barrier function of the GI tract
• how do prebiotic and probiotics differ?

  Probiotics- specific types of live bacteria found in foods that are believed to have beneficial effects on human health

  Prebiotics- indigestible carbs that pass the colon where they serve as a food supply for bacteria, stimulating the growth or activity for certain type of beneficial bacteria
• What are the functions of intestinal microflora?

  Microorganisms that inhibit the large intestine
• How are facilitated diffusion and active transport different?

  Facilitated diffusion- the movement of substances across a cell membrane from an area of higher concentration to an area of lower concentration with the aid of a carrier molecule. No energy is required

  Active transport diffusion- the transport of substances across a cell membrane with the aid of a carrier molecule and the expenditure of energy. This may occur against a concentration gradient
• How are osmosis and diffusion different?

  Osmosis- the passive movement of water across semipermeable membrane in direction that will equalize the concentration of dissolved substances on both sides

  Diffusion-the movement of substances from an area of higher concentration to an area of lower concentration. No energy is required
• How do functions of secretin and cholecystokinin differ?

  Secretin- signals the pancreas to secrete pancreatic juice rich in bicarbonate ions and stimulates the liver to secrete bile into the gallbladder

  Cholecystokinin- signals the pancreas to secrete digestive enzymes and causes the gallbladder to contract and release bile into the duodenum
• What are the functions of the pancreas and gallbladder?

  Pancreas- an organ that secretes enzymes and bicarbonate ions into the small intestine during digestion

  Gallbladder- an organ of the digestive system that stores bile, which is produced by the liver
• What is the purpose of segmentation?

  Three segments duodenum, jejunum, ileum

  Allows the maximum surface area for nutrients to be absorbed

  Enhances absorption by repeatedly moving chyme over the surface of the intestinal mucosa
• How do villi and microvilli differ?

  Villi- finger like protrusions of the lining of the small intestine that participate in the digestion and absorption of nutrients

  Microvilli- bush like projections on the mucosal cell membrane that increase the absorptive surface area in the small intestine
• Why is the small intestines structure to have a high surface area?

  Main site of digestion of food and absorption of nutrients

  6m in length and divided into three segments

  Allows for maximal absorption of the nutrients
• What is the composition of chyme? How is it formed?


  It is a mixture of partially digested food and stomach secretions

  When food is mixed with highly acidic stomach secretions it forms a semiliquid food mass called chyme
• What is the composition of gastric juices? What are the functions of each component of gastric juice?

  hydrochloric acid produced by parietal cells- acidifies the stomach contents and as a result kills most of the bacteria present in food

  Pepsinogen produced by chief cells- inactive form of the enzyme pepsin. Breaks down proteins into shorter chains of amino acids called polypeptides. The acidic environment of the stomach stops the function of salivary amylases.
• What is peristalsis?

  Coordinated muscular contractions that move food through the GI tract
• Why is the epiglottis important for proper swallowing?

  Ensures that the bolus of food passes through the stomach not the lungs

  It is a piece of elastic connective tissue at the back of the throat that covers the opening of the passageways to the lungs during swallowing
• How does saliva contribute to digestion?

  It moistens the food so that can be easily tasted and swallowed

  It begins the enzymatic digestion of starch

  It cleanses the mouth and protects teeth from decay

  It lubricates the upper GI tract
• How do phagocytes and lymphocytes differ?

  Phagocytes- the first immune cells to respond. They target any invader. Engulf it, and destroy it by breaking it up so that antigens are presented at the surface of the phagocyte

  Lymphocyte- react by producing and secreting protein molecules called antibodies
• What is meant by barrier function?

  The protective role that gastrointestinal cells have in limiting the absorption of harmful substances and disease causing organisms
• How do hormones regulate the GI tract?

  They are released into the bloodstream

  Signals help prepare different parts of the gut for the arrival of food and thus regulates the digestion of nutrients and the rate at which food moves through the system
• What is the function of amylase? Trypsin and chymotrypsin? Lipase? Lactase?


  Salivary amylase- breaks starch into smaller carb molecules

  Trypsin- breaks proteins and polypeptides into short polypeptides

  Chymotrypsin- breaks proteins and polypeptides into short polypeptides

  Lipase- breaks monoglycerides into fatty acids and glycerol

  Lactase- breaks lactose into glucose and fructose
• What are the similarities and differences between mucus and enzymes?

  Mucus- a viscous fluid secreted by glands in the GI tract and other parts of the body, which acts to lubricate, moisten and protect cells from harsh environments

  Enzymes- protein molecules that accelerate the rate of specific chemical reactions without being changed themselves.
• What are the functions of the four layers of the wall of the GI tract?


  Lumen- where some of the components are digested and absorbed and the remainder are excreted in the feces

  connective tissue- surrounds the mucosa, it contains nerves and blood vessels. This layer provides support, delivers nutrients to the mucosa, and provides the nerve signals that control secretions and muscle contractions

  Layers of smooth muscle- surround the connective tissue, the contractions mixes food, breaks it into smaller particles, and propels it through the digestive tract

  External layer of connective tissue- provides support and protection
• What is mucosa? Why does it have a short lifespan? What is mucosa? Why does it have a short lifespan?

  The layer of tissue lining the GI tract and other body cavities

  They are in direct contact with churning food and harsh digestive secretions