Nutrition

1
Nutrition Digestion
2
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

3
Food Processing
4
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

5
Human Digestion System
6
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

7
Human Digestion the epiglottis
How does the epiglottis prevent food from moving
into the trachea?
8
Human Digestion into the esophagus
9
Human Digestion the tum tum
10
Human Digestion the tum tum

• Why dont 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

11
Human Digestion small intestine
12
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

13
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

14
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

15
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

16
Human Digestion small intestine
17
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

18
Human Digestion large intestine
19
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

20
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

21
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

22
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

23
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

24
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

25
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

26
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