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Nutrition and Metabolism. Metabolism. All of the chemical reactions that occur in cells Reactants substances that participate in chemical reactions Products substances that are formed in a chemical reaction Metabolic pathways A series of reactions

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metabolism
Metabolism
  • All of the chemical reactions that occur in cells
    • Reactants
      • substances that participate in chemical reactions
    • Products
      • substances that are formed in a chemical reaction
  • Metabolic pathways
    • A series of reactions
      • Begins with a specific reactant and through multiple steps, produces an end product
      • Each step is catalyzed by a specific enzyme
      • More efficient for capturing metabolic energy
        • Rather than releasing it all in one step
metabolism cont d
Metabolism cont’d
  • Enzymes
    • Protein molecule which functions as a catalyst to speed up rate of chemical reaction
    • Reactants in an enzymatic reaction are called substrates
digestive enzymes overview
Digestive Enzymes - Overview
  • Hydrolytic Reactions
    • Substrate interacts with water and results in the decomposition of that substrate.
    • Break macromolecules to monomers
  • Must have optimum pH for activity
    • Maintains shape of molecule
    • Specific for substrate
major digestive enzymes
Major Digestive enzymes
  • Salivary amylase
    • Catalyzes the reaction starch + H2O  maltose
      • Starch hydrolyzed to dissaccharides
      • Occurs in the mouth
  • Pepsin
    • Catalyzes the reaction protein + H2O  peptides
      • Pepsinogen activated to pepsin by pH<2
      • Occurs in the stomach in presence of HCl
major digestive enzymes cont d
Major Digestive enzymes cont’d.
  • Pancreatic amylase
    • Catalyzes the reaction starch + H2O  maltose
      • Occurs in duodenum
        • pH in duodenum is slightly basic from sodium bicarbonate
        • Optimal pH for pancreatic amylase
      • Completes digestion of starches to dissaccharides
major digestive enzymes cont d1
Major Digestive enzymes cont’d.
  • Trypsin
    • Catalyzes the reaction protein + H2O  peptides
      • Occurs in duodenum
      • Produced by pancreas as trypsinogen- inactive
      • Activated in duodenum by enterokinase
  • Lipase
    • Catalyzes the reaction fats + H2O  glycerol + 3 fatty acids
    • Emulsification by bile salts occurs first
    • Occurs in duodenum
    • Glycerol and fatty acids absorbed into villi
    • Rejoined and packaged as lipoproteins
      • absorbed into lacteals
major digestive enzymes cont d2
Major Digestive enzymes cont’d.
  • Peptidases
    • Catalyze reaction peptides + H2O  amino acids
      • Occurs in small intestine
      • Absorbed into villi
  • Maltase
    • Catalyzes reaction maltose + H2O  2 Glucose
      • Occurs in small intestine
      • Each dissaccharide has its own enzyme
      • Lack of any one of these can cause illness
        • Lactose intolerance - lack of lactase enzyme
digestive enzymes conditions required
Digestive Enzymes – Conditions Required
  • Environmental conditions must be optimum
  • Warm temperature
    • Most function well at normal body temperature
  • Correct pH
    • Each enzyme has its own optimal pH
      • Most function at near neutral pH
      • Some exceptions
        • Ex: pepsinogen requires acidic pH
nutrition
Nutrition
  • Science of foods and nutrients
    • Nutrient- component of food that performs physiological function
  • All body functions depend on proper nutrition
  • Food Guide
    • Guides food choices to fulfill nutritional needs
    • Guidelines change as nutritionists gain information… not a pyramid anymore!
nutrition guidelines
Nutrition - Guidelines
  • Its just chemistry!
    • Balance energy input with energy output to maintain weight
  • Eat a variety of foods
    • Our bodies require ALL the different types of nutrients for different things!
    • A balanced healthy diet provides all the nutrients and vitamins you need!
    • Drink lots of water!
      • All those enzyme pathways need water… DRINK IT!
      • Cells are 70-80% water
nutrition guidelines1
Nutrition - Guidelines
  • A healthy diet
    • You still need fat!
      • A moderate total fat intake low in saturated fats and cholesterol
    • Protein!!!
      • Vegetarians need to be especially careful!
      • Sources include poultry, fish, plants
    • Choose whole foods
      • Fresh fruits and veggies, whole grains, legumes,
      • Provides fiber and complex carbs
    • Avoid Processed foods
      • “white” breads and pasta’s refined carbs
      • Canned goods - salt and sodium
nutrients carbohydrates
Nutrients: Carbohydrates
  • Primary energy source
  • Glucose
    • Most readily available energy source
    • Body cells can use fatty acids for energy
      • Brain cells can ONLY use glucose
  • Complex carbohydrates
    • Gradually broken down to glucose
    • Contain fiber
      • Insoluble fiber-may protect against cancer
      • Soluble fiber-combines with bile acids and cholesterol
nutrients carbohydrates cont d
Nutrients: Carbohydrates cont’d
  • Simple sugars
    • High glycemic index-elevate blood sugar rapidly
    • Pancreas releases overload of insulin
    • Sugar taken up rapidly- hunger returns
    • Could lead to insulin resistance
nutrients proteins
Nutrients: Proteins
  • Functions
    • Growth and development
    • Regulate metabolism
    • Can be energy source
  • Used to make structural proteins
    • Muscle, hair, skin, nails
nutrients proteins cont d
Nutrients: Proteins cont’d
  • Synthesis of other proteins
    • Hemoglobin
    • Plasma proteins
    • Enzymes
    • Hormones
  • Synthesis of body proteins
    • Requires all 20 amino acids
    • 8 must be supplied in diet-essential amino acids
    • Remaining 12 can be synthesized by the body
nutrients proteins cont d1
Nutrients: Proteins cont’d.
  • Complete proteins
    • Contain all 20 amino acids
    • Eggs, meat, milk
  • Incomplete proteins
    • Proteins of plant origin
    • Each lacks at least essential amino acids
    • Vegetarians must combine plant protein sources
      • Complementary Proteins
      • Legumes with grains-provides all 20 amino acids
nutrients proteins cont d2
Nutrients: Proteins cont’d.
  • Amino acids are not stored
    • Must take in daily supply
  • Too high intake of protein can be harmful
    • Deamination of amino acids produces urea
    • Urea excretion requires water
    • Dehydration especially if individual is exercising
    • Can also cause calcium loss
  • Some protein foods also are high in saturated fats
      • Red meat
      • Can lead to cardiovascular disease
nutrients lipids
Nutrients: Lipids
  • Energy storage
  • Saturated fats
    • Solids at room temperature
    • Animal origin
      • Exceptions: palm oil, coconut oil
    • Associated with cardiovascular disease
    • Trans fatty acids are worst
      • Hydrogenated unsaturated fatty acids
      • May reduce ability to clear cholesterol
nutrition lipids cont d
Nutrition: Lipids cont’d
  • Unsaturated fats
    • Oils have percentage of mono- and polyunsaturated fats
    • Polyunsaturated oils contain essential fatty acids
      • Linoleic and linolenic acid
  • Omega-3 fatty acids
    • Double bond in third position
    • Especially protective against heart disease
    • Cold water fish, flax seed oil
nutrition lipids cont d1
Nutrition: Lipids cont’d.
  • Fats that cause disease
    • Plaques- form in arteries
      • Contain cholesterol and saturated fats
    • Cholesterol
      • Carried in blood by low density lipoprotein (LDL) and high density lipoprotein (HDL)
      • LDL-”bad” cholesterol- transports from liver to cells
      • HDL- “good” cholesterol-transports to liver to make bile salts
    • Trans-fats
      • In commercially packaged foods
      • Linked to diabetes melitis and heart disease
nutrition vitamins
Nutrition: Vitamins
  • Coenzymes
    • organic molecules that are required by certain enzymes to carry out catalysis
    • Deficiencies produce specific symptoms
  • Cofactors
    • inorganic substances that are required for, or increase the rate of, catalysis
  • 13 vitamins
    • Fat soluble- A,D,E,K
    • Water soluble- remaining 9
nutrition vitamins cont d
Nutrition: Vitamins cont’d
  • Antioxidants
    • Vitamins C,E, and A
    • Defend against free radicals
      • Molecules responsible for aging and tissue damage
    • Cell metabolism generates free radicals
      • O2- and OH-
      • Bind to DNA, proteins to stabilize
      • Cause cell damage
nutrition vitamins cont d1
Nutrition: Vitamins cont’d
  • Vitamin D
    • Converted in skin to active form by UV light
    • Further modification in kidneys and liver
      • Becomes calcitrol
      • Promotes calcium absorption from intestines
    • Deficiency causes ricketts
nutrition minerals
Nutrition: Minerals
  • Major minerals
    • Body contains more than 5 grams
    • Constituents of cells
    • Structural components
  • Trace minerals
    • Body contains less than 5 grams
    • Components of larger molecules
      • Iron- part of hemoglobin
      • Iodine- part of thyroxine
      • Zinc, copper, selenium-components of enzymes
nutrition minerals cont d
Nutrition: Minerals cont’d.
  • Calcium
    • Deficiency causes osteoporosis
      • Osteoclasts more active than osteoblasts
      • Bones become porous
      • Fracture easily
    • Calcium intake can slow bone loss
    • Requirements
      • Men and premenopausal women-1000 mg/day
      • Postmenopausal women-1300 mg/day
      • Smoking, excess caffeine increase risk
    • Vitamin D is essential companion to calcium
nutrition minerals cont d1
Nutrition: Minerals cont’d.
  • Sodium
    • Requirement is 500 mg/day
    • Average intake in US is 4000-5000 mg/day
      • May be linked to hypertension
    • Only is naturally occurring in diet
      • added in processing
      • added as table salt
nutrition eating disorders
Nutrition: Eating Disorders
  • Obesity
    • Body weight 20% above normal
    • 28% women and 10% men in US are obese
    • Hormonal, metabolic, and social factors
      • May be linked to lack of leptin- satiety hormone
    • Behavior modification is usual treatment
    • Avoid cycle of gaining and losing weight
nutrition eating disorders cont d
Nutrition: Eating Disorders cont’d
  • Bulimia Nervosa
    • Can coexist with obesity or anorexia
    • Binging and purging-damage from vomiting
    • Overly concerned about body shape and weight
    • Can damage kidneys and cause fatal arrhythmias
    • Psychotherapy and medication are treatments
nutrition eating disorders cont d1
Nutrition: Eating Disorders cont’d
  • Anorexia Nervosa
    • Morbid fear of gaining weight
    • Athletes at risk
    • Distorted self-image
    • All symptoms of starvation
      • Low blood pressure
      • Constant chilliness
      • Irregular heartbeat
    • Can result in death
    • Force-feeding and psychotherapy are critical
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