Nutrition and metabolism
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Nutrition and Metabolism - PowerPoint PPT Presentation

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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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  • 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

Major digestive enzymes cont d3
Major Digestive enzymes cont’d.

  • Table 14.3

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


  • 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

Recognizing bulemia
Recognizing Bulemia

  • Fig. 14.19

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