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Nutrition & Digestion. Objectives: Define and Comprehend. Food processing Human digestion Know words on term list (available on web site) Nutrition 3 needs Chemical energy Vitamins and minerals. Food Processing. Food Processing . Most food consists of what macromolecules?

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objectives define and comprehend
Objectives: Define and Comprehend
  • Food processing
  • Human digestion
    • Know words on term list (available on web site)
  • Nutrition
    • 3 needs
    • Chemical energy
    • Vitamins and minerals
food processing4
Food Processing
  • Most food consists of what macromolecules?
    • Carbohydrates, lipids, and proteins
  • Why is food chemically broken down?
    • The macromolecules are too large to pass through cell membranes
    • The polymers must be broken down into monomers, so that the organism can make their own polymers
human digestion oral cavity
Human Digestion: Oral Cavity
  • At sight or smell of food, salivary glands secrete saliva
    • Glycoprotein protects & lubricates lining of mouth
    • Antibacterial agents
    • Amylase to hydrolyze starch
  • Why do you chew your food?
    • Easier to swallow
    • Expose more surface area to enzymes
  • Tongue pushes bolus to back of oral cavity & into pharynx
human digestion the epiglottis
Human Digestion: the epiglottis

How does the epiglottis prevent food from moving into the trachea?

human digestion the tum tum10
Human Digestion: the tum tum
  • Why don’t we need to eat constantly?
    • Besides breaking down food, the stomach stores food –enough to satisfy our body for many hours
  • What prevents gastric juice from digesting away the stomach lining?
    • Pepsin, an enzyme which begins the chemical digestion of protein, is secreted in the inactive form pepsinogen
      • Protects the gastric gland cells
    • Mucus helps protect the stomach lining from both pepsin and acid
    • However, the stomach lining must be replaced about every 3 days
human digestion small intestine12
Human Digestion: small intestine
  • Nutrients are absorbed into the blood from the small intestine
  • All 4 types of macromolecules (carbohydrates, lipids, proteins, & nucleic acids) are digested in the duodenum
  • Carbohydrate digestion completed in rest of the small intestine
    • Hydrolytic enzymes breakdown polymer into monomers
human digestion small intestine13
Human Digestion: small intestine
  • Protein digestion
    • Pancreas and duodenum secrete hydrolytic enzymes that break polymer into monomers (amino acids)
  • Nucleic acid digestion
    • Pancreas and duodenum secrete hydrolytic enzymes which breakdown DNA & RNA polymers into
      • Nitrogenous bases, sugars, phosphates
human digestion small intestine14
Human Digestion: small intestine
  • Lipid digestion
    • Lipids reach stomach almost completely undigested
      • Why?
        • Fats are hydrophobic
    • Bile salts from gallbladder coat tiny fat droplets that keep them separated from each other
      • Why is the separation of fats into small droplets beneficial for digestion?
        • More surface area is exposed, which allows the enzyme to breakdown the fats quickly
human digestion small intestine15
Human Digestion: small intestine
  • Majority of chemical digestion has been completed by the time chyme mixture passes through duodenum
  • Rest of small intestine is adapted for the absorption of nutrients
  • Small intestine has high surface area
    • This allows for greater…
      • Absorption
  • Also has many folds and projections
human digestion small intestine17
Human Digestion: small intestine
  • Capillaries that drain away from the villi converge into larger blood vessels and eventually into a main vessel that leads directly to liver
    • Converts many of nutrients into new substances the body needs
    • Liver removes excess glucose and stores it as?
      • Glycogen in liver cells
  • Blood is then transported to heart, which pumps blood and nutrients to all parts of the body
human digestion large intestine19
Human Digestion: large intestine
  • Colon absorbs water –approximately 90% of the 7 liters of fluid that enters the canal a day are reclaimed (most in small intestine)
  • Remains of undigested food become more solid as water is absorbed
    • Feces
      • Consists mainly of plant fibers and prokaryotes
      • Diarrhea occurs when the colon is irritated and is less effective at reclaiming water
      • Constipation occurs when peristalsis moves the feces too slowly
        • Colon reabsorbs too much water and feces becomes too compacted
          • Diet low in plant fiber or lack of exercise
nutrition
Nutrition
  • There are 3 needs which demand a healthy diet
    • Fuel to power our bodies
    • Organic raw materials needed to make our own molecules
    • Essential nutrients that we cannot make ourselves and must obtain in a prefabricated form
nutrition why we need chemical energy
Nutrition: why we need chemical energy
  • The chemical processes of our bodies are fueled by?
    • ATP
      • Cellular metabolism produces ATP by oxidizing small molecules that are digested from food
        • Usually use carbohydrates and fats, but when required, will use proteins too
  • Cellular metabolism must continue or we die
    • Our basal metabolic rate (BMR) is approximately 1,300 to 1,800 kcal per day
nutrition too many kcal
Nutrition: too many kcal
  • We burn more kcal when we “move”
  • What happens when we take in more kcal than we use?
    • Muscle and liver store it as glycogen
    • Also stored as fat
      • Liver can convert excess carbohydrates and proteins into fat
nutrition too many kcal23
Nutrition: too many kcal
  • Extremely low-carb diets
    • Initial weight loss is mostly WATER
    • Can cause fatigue and headaches, and in the long-term –muscle loss
  • Extremely low-fat diets
    • Inadequate provision of essential fatty acids, proteins, and certain minerals
    • Decrease absorption of fat-soluble vitamins and can cause irregular menstrual periods
  • Formula diets –if very low in kcal
    • Result in loss of body protein, may cause dry skin, thinning hair, constipation, and salt imbalance
nutrition what works
Nutrition: what works?
  • Scientists find that the best diet to maintain a healthy body weight is…
    • There is no best diet
    • What works is the following equation
      • Calories in – calories out
nutrition vitamins
Nutrition: Vitamins
  • If one eats a balanced diet, one does not need to take vitamins
    • Most serve as coenzymes or are parts of coenzymes
    • Used over and over again in metabolic processes
    • Deficiencies and excessive use can cause serious problems
    • Water-soluble vitamins are not harmful as excess can pass in urine and feces
    • Excessive fat-soluble vitamins are deposited in fat and can have toxic effects
nutrition minerals
Nutrition: Minerals
  • Must obtain minerals through dietary sources
  • Ex: calcium needed for normal functioning of nerves and muscles
  • Ex: phosphorous is an ingredient of ATP and nucleic acids
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