Chapter 27 Nutrition

Nutrition

• nutrition is the study of how living organisms obtain and utilize nutrients needed to grow and sustain life.
• nutrients are biomolecules, vitamins, and minerals.
  • nutrients are required for synthesis of new molecules, energy maintenance, growth, and repair
  • nutrients are obtained through food
  • water is also considered a nutrient
• Nutrient levels are regulated during and following meals.
• RDA is the recommended daily allowance
  • recommend daily allowance is the amount of each nutrient that must be obtained each day.

Nutrient Categories

• macronutrients, micronutrients, essential, and nonessential.
• macronutrients must be consumed in relatively large quantities and are needed in daily amounts
  • organic molecules: carbohydrates, lipids, and proteins.
  • all macronutrients provide fuel for cellular respiration to form ATP (i.e., they provide energy)
• micronutrients must be consumed in small quantities
  • vitamins and minerals are considered micronutrients and can be obtained through supplements or plants (variety).
• essential nutrients must be obtained and absorbed via digestive system from diet.
• Deficiency if intake or absorption is impaired
• nonessential nutrients are Provided by biochemical body processes, NOT REQUIRED IN DIET,
  • Cofactors body produces and recycles as needed

Measuring Energy

• Calorie = the amount of heat required to raise the temperature of 1 g of water by 1ºC.
• 1 kilocalorie = 1000 calories
• body weight is maintained when calories consumed and calories expended are in balance.
• Calorie density of 500cal in stomach:
  • oil → cheese, nuts, butter → potatoes, rice, beans → lean meat, fish → fruits, veggies.

Carbohydrates

• carbohydrates include disaccharides, monosaccharides, polysaccharides.
• sugars are monosaccharides, disaccharides, other sugars
  • monosaccharides: glucose, fructose, galactose.
  • disaccharides: sucrose, lactose, maltose
  • other sugars: dextrose, brown sugar, honey, molasses
• Starch includes polysaccharides
  • polysaccharides: tubers, grains, beans, peas
  • refined starches are thickness and stabilizers.
• sugars and starch are usually converted to glucose as primary energy, not an essential nutrient.
• Fibers are molecules of both plants and animals & Cannot be chemically digested and absorbed by GI tract.
  • fiber adds bulk, peristalsis, keeps you regular, and lowers cholesterol.
  • Lentils, peas, beans, whole grains, oatmeal, berries, nuts are good sources of fiber.

Fatty Acids

• triglycerides fatty acids are composed of glycerol & fatty acids, have 3 categories.
• saturated fatty acids have no double bond, solid at room temp.
  • meat fat, milk, cheese, coconut oil, palm oil
• unsaturated fatty acids have one double bond, liquid at room temp
  • nuts, canola oil, olive oil, sunflower oil
• polyunsaturated fatty acids have two or more double bonds, liquid at room temp
  • soybean oil, corn oil, safflower oil

Proteins

• proteins are the most MOST DIVERSE MOLECULES, Needed in adequate quantities to replace worn out protein structures
  • the amount of proteins depends on age and sex
  • higher amount of proteins are needed to fight and infection, injury, stress, pregnancy, cancer
  • They body DOES NOT store excess proteins
• complete proteins are all essential amino acids (animal proteins)
• incomplete proteins are not all essential amino acids (plant proteins), combinations of dishes containing plant proteins can provide all essential a.a.
• Amino acids are the building blocks for proteins, Used to make ATP, amine group removed by DEAMINATION
  • amine group → urea → kidney → urine elimination
  • some amino acids can be converted to glucose
• there are 8 essential amino acids and the other 12 can be synthesized in body.

Nitrogen

• nitrogen is formed from protein amino group
• synthesize nitrogen-containing molecule (DNA, RNA, porphyrin)
• positive nitrogen balace absorbs more nitrogen than excreted (during growth, pregnancy, recovering from injury)
• negative nitrogen balance is when more nitrogen excreted than absorbed (during blood loss, malnutrition, Can be fatal)

Vegans & Vegetarians

• vegetarians do not eat meat, poultry, or fish
• lacto-ovo vegetarians do not eat animal flesh but eat milk, eggs, cheese
• vegans do not eat any animal products
• plant-based proteins sources are often individually incomplete therefore one must obtain essential amino acids through complementary protein sources, Not necessarily eaten at the same meal, but regularly

Vitamins

• vitamins are Organic molecules needed for metabolism, present in small amounts, h2o/fat soluble, essential/nonessential.
• water-soluble vitamins dissolve in h2o, Vit. B & C, easily absorbed into blood from GI tract, excess excreted in urine, some coenzymes assist w/ norm. enzyme function.
• fat-soluble vitamins dissolve in fat, Vit. A D E & K, absorbed from GI tract in micelles, excess stored in fat, toxic if overdosed,
• Vitamin A: precursor of visual pigment retinal
• Vitamin D: forms calcitriol, increases calcium absorption from GI tract
• Vitamin E: stabilizes and prevents damage to cell membranes
• Vitamin K: required for synthesis of blood clotting proteins.

Minerals

• minerals are inorganic ions obtained from diet (required in daily amounts).
• Fe3+ in hemoglobin binds to O2, In mitochondria electron transport system binds electrons
• Ca2+ Required for formation and maintenance of skeleton and muscle contraction, blood clotting, and exocytosis of neurotransmitters.
• Na+/K+ Maintain resting membrane potential in excitable cells, Required to generate action potential.
• I3+ Needed to produce thyroid hormone.
• Zn Roles in protein synthesis and wound healing.
• major minerals: Ca, Cl, K, P, Mg, >100g/day required
• trace minerals: Cr, CU, I, Fe, Zn, <100mg/day required
• stored to varying degrees in body.

Iron Deficiency

• iron is needed in hemoglobin & myoglobin, part of e- transport proteins to
• most common nutrition deficiency synthesize hormones, neurotransmitters, and amino acids.
• Symptoms of iron deficiency include fatigue, weakness, pale skin, cold sensitivity, usually from bleeding.
• Sources of iron include meat, poultry, fish, dark leafy veggies, nuts, whole grains.

Food Stuff

• foods can be fortified by adding one or more essential nutrients
• nutritional food labels provide details on composition of prepackaged items
  • food labels promote health in well individuals, for those w/ special dietary needs.
  • Serving size, calories, total fat, cholesterol, Na+

Digestion States

• post absorptive state is the time between meals where body relies on storing nutrients and works to maintain homeostatic nutrient levels.
• absorptive state is time during eating, digesting, absorbing nutrients, (4hr after meal)
  • GI tract absorbs glucose, triglycerides, amino acids
  • blood glucose levels are between 70-110 mg/dL

Hormones

• insulin is a major regulatory hormone, released from pancreas to increase blood glucose, stimulates liver & muscles cells
  • glucose is converted into glycogen
  • increased triglyceride uptake
  • stimulates lipogenesis and inhibits lipolysis
  • stimulates cell results in an increase of amino acids uptake resulting in increase of protein synthesis
• glucagon is a major regulatory hormone released during postabsorptive state and released in response to decreasing blood glucose levels.
  • Stimulates liver to increase breakdown of glycogen to glucose
  • Stimulates gluconeogenesis from noncarbohydrate sources
  • Causes adipose tissue to break down triglycerides

Blood Cholesterol Levels

• high levels of LDL’s, total cholesterol level above 200mg/dL, and low HDL levels are risk factors for cardiovascular disease.
• LDL’s are considered bad cholesterol because excess cholesterol is deposited on inner arterial walls.
• HDL’s are considered good cholesterol because they transport lipid from arterial wall to liver.
• High cholesterol occurs from high saturated fat intake, cigarette smoking, caffeine intake, and stress.
• Statin drugs lower blood cholesterol
  • statin is an inhibitor for HMG-CoA that is needed for cholesterol synthesis.
• Cholesterol synthesis occurs in the liver were fatty acids are transported in blood to the enter hepatocytes
  • beta oxidation occurs where fatty acids are broken down into two-carbon units, acetyl CoA.
  • 2 acetyl CoA molecules synthesize cholesterol to produce it at basal level.
  • ==Higher== amounts of cholesterol intake ==decrease== cholesterol synthesis.
  • %%Lower%% amount amount of cholesterol intake %%increase%% cholesterol synthesis.
• blood analysis 60% LDL and 40% HDL, does a person have high or low cholesterol?
  • if 80%, the person has HIGH cholesterol level.

Lipoproteins

• lipoproteins are lipids with proteins that are wrapped for transport.
• chylomicrons are lipids that are absorbed from the small intestine.
• very-low-density lipoproteins (VLDL) have the most lipid.
  • Various types of lipids with protein, Assembled within liver and released into blood.
  • Circulate in blood, release triglycerides to peripheral tissues (Primarily adipose tissue),
  • With release of triglycerides, becomes low-density lipoprotein
• low-density lipoproteins (LDL) have less lipid
  • Contain high amounts of cholesterol,
  • Deliver cholesterol to cells,
  • Bind to LDL receptors in plasma membrane of cell, Engulfed by endocytosis, Cholesterol incorporated into plasma membrane, Used by certain tissues %%to produce steroid hormones.%%
• high-density lipoproteins (HDL) have the least amount of lipid and are considered the healthiest.
• Lipids are transported from liver to peripheral tissues.

Liver

• liver is the largest internal organ
• liver lobule is the functional liver unit, the hepatocyte cords radiation out from central vein.
• liver functions: Plasma protein formation, bilirubin removal, bile formation, bile release
• the liver is responsible for Carbohydrate metabolism, Protein metabolism, Lipid metabolism, Transport of lipids, Other functions (storage and drug detoxification).

Metabolism

• metabolic rate is the rate of energy used in a period of time (BMR & TMR)
• basal metabolic rate (BMR) is the amount of energy used at rest
  • Individual not eaten for 12 hours, relaxed, temperature about 20°C, Measured by calorimeter or respirometer
  • BMR varies do to age, lean body mass, sex, blood hormones levels.
  • BMR decreases with age (3% each decade around age of 30)
  • more body mass means higher BMR
• Thyroid hormone increases BMR
  • hypothyroidism means lower than normal BMR
  • hyperthyroidism means higher than normal BMR
• Body surface area has a big impact on BMR
  • greater skin surface area means more heat loss, more heat loss means more active body cells must be to maintain temperature
• total metabolic rate (TMR) is the BMR + metabolism associated with physical activity
  • TMR depends on amount of skeletal muscle activity (increase during vigorous exercise), food intake (increase after meal, but decrease after absorption), changes in environmental conditions (increase in cold temperature)
• calorimeter is used when a person placed in water-filled chamber, Heat released from body alters temperature of water, Change in temperature measured
• respirometer is an instrument that measures oxygen consumption, Indirect measure BMR.
  • oxygen is used to produce ATP which is utilized to produce heat.
• nutrient interconversion are biochemical pathways associated with cellular respiration where one nutrient bio molecule changes into another.
  • glucose → acetyl CoA → triglycerides
  • protein or fat → glucose
• lysis means splitting or breaking down a molecules into smaller components.

Temperature

• temperature homeostasis: Variable heat produced due to variable metabolic rate, Body temperatures maintained within certain physiological limits
  • normal body temperature of 98.8F (37.C)
• core body temperature: Temperature of vital portions of body—head and torso, Temperature kept relatively constant, Maintained by allowing fluctuations in peripheral regions
• hormonal control is mediated by Thyroid, epinephrine, norepinephrine, growth hormone, and testosterone
  • thyroid hormone establishes metabolic rate, raises body temp. by increasing rate of all cells.
  • If temperature drops, hypothalamus releases thyrotropin-releasing hormone, which stimulates thyroid-stimulating hormone from anterior pituitary, which stimulates thyroid gland to release thyroid hormones.

Clinical Views:

• frostbite is damage to superficial cells due to extreme cold, Skin white with possible loss of sensation
• dry gangrene may be caused by severe frostbite, Body part dry, distinct in color, shriveled, Due to extensive vasoconstriction of blood vessels in response to cold, Oxygen deprivation and tissue death.