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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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Nutrition & Digestion

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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?

    • 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 System


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

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


Human Digestion: into the esophagus


Human Digestion: the tum tum


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 intestine


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 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 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 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 intestine


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 intestine


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

  • 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

  • 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

  • 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 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?

  • 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

  • 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

  • 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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