IB Bio

1. Section 6.1 / Option D.1 – D.3
DIGESTION AND NUTRITION
Selected diagrams: Credit to:
Cornell, B. 2016. Referencing. [ONLINE] Available at: http://ib.bioninja.com.au.

2. Section 6.1 and D.2
THE DIGESTIVE SYSTEM

3. ESSENTIALS
• The structure of the walls of the stomach and
small intestine allow them to move, digest, and
absorb food (CORE)
• Digestion is controlled by nervous and
hormonal mechanisms. (D2)
• The chemical composition of the blood is
regulated by the liver. (D3)
• A balanced diet is essential to human health.
(D1)

4. DIGESTION
• What is digestion?
• Breaking food down into smaller molecules.
• This can be done by physically pounding the molecules, or chemically
breaking the molecules apart.
• What is the medical term for anything digestive?
• GASTRO
• What sort of molecules help with chemical digestion?
• Enzymes
• What kind of gland aids in digestion?
• Exocrine –
• Produces enzyme
• Connected to target organ – DUCT
• Glands in DS can be both Exocrine and Endocrine
• Which reaction is involved in digestion, hydrolysis or dehydration
synthesis?
• Hydrolysis

5. FIVE STAGES OF FOOD
PROCESSING
1. Ingestion
2. Digestion (enzymatic hydrolysis)
3. Absorption – into the blood
4. Assimilation – into the body
5. Egestion

6. MAMMALIAN DIGESTION
• Physical digestion – caused by movement
• Chemical Digestion – enzymes, water, acids
• Accessory glands:
• Salivary glands
• Pancreas
• Liver / Gall bladder

9. ORAL CAVITY
• Organs Includes:
• Tongue – mixes/moves chewed food
• Teeth – breaks food down
• Enzymes:
• Salivary Amylase – begins digestion of
polysaccharides. Starch to smaller polysaccharides
(pH – 7)
• Chewed and swallowed food: Bolus

11. TEETH
Thank you Rebecca Lieberman!

12. ESOPHAGUS
• Muscular tube…connects mouth to stomach.
(epiglottis)
• No chemical action. No digestion.
PERISTALSIS – (rhythmic) muscular movement of
food thru the digestive tract after swallowing.
Longitudinal – lengthen
Circular - squeeze

13. PERISTALSIS

15. STOMACH
The Basics:
• J – shaped muscular
organ. Thick walled
• Chemical and physical
digestion
• Sphincter – cardiac and
pyloric
• Stores food
• Begins protein
digestion….

17. STOMACH
• Stomach lining:
• Contains Gastric Glands:
• Has three kinds of cells:
• Parietal: Secretes HCl –
activates pepsinogen; denatures
protein; kills pathogen.
• Chief: Secretes Pepsinogen;
activates to PEPSIN (gastric
protease) begins protein
digestion. pH – 2.
• Neck: Releases mucous;
provides protection
• Stomach processes food in 2-
6 hours
• Semisolid food: chyme.

18. CONTROL OF GASTRIC JUICE SECRETION
• Controlled by nerves and hormones (727-728)
• Sight and smell of food sends nerve impulses to Parietal
cells – secretes acid (REFLEX)
• Na and Cl ions secreted. Water moves into stomach by
osmosis. Forms Gastric Juice.
• Chemoreceptors detect amino acids – move stomach wall.
• Impulses are sent to brain. Brain sends impulses to
endocrine glands via VAGUS NERVE to secrete Gastrin.
• Gastrin stimulates further secretion of acid and
pepsinogen.
• Secretin and Somatostatin - inhibit gastrin secretion

19. SMALL INTESTINE

20. SMALL INTESTINE

21. SMALL INTESTINE
• Small diameter….7 meters long/ 23 ft (appx)
• Some physical; mostly chemical digestion.
• Receives secretions from the liver and
pancreas.
• 3 sections: duodenum (digestion), jejunum
(digestion and absorption) and ileum (for
absorption)
• Absorption of nutrients begins in the lining of
the small intestine.

22. SMALL INTESTINE - ENZYMES
• Bicarbonate – from pancreas to neutralize acid (not an enzyme)
• Protein –
• Trypsin - (pancreas) continues protein digestion. (pH 8)
• Endopeptidase - (small intestine) completes protein digestion to
amino acids (pH – 7.5)
• Fat –
• Bile – (liver) not an enzyme. Breaks down large fat molecules
• Lipase – (pancreas) digests fats. (pH – 8)
• Carbohydrates
• Amylase (pancreas) continues starch digestion (disaccharides)
(pH 7)
• Maltase - (small intestine) = (maltose into glucose). (pH 7)
• Sucrase – glucose and fructose (pH – 7)
• Lactase – glucose and galactose (pH – 7)

25. VILLUS

26. SMALL INTESTINE - FOOD ABSORPTION
• Absorbed food travels to the liver for assimilation.
Structure Function
Finger-like shape Large surface area
Surface cell with – microvilli Huge increase in surface area
Surface cells with – enzymes Digestion
Surface cells with – large number of
mitochondria
Active transport and Pinocytosis
Tight Junction Membrane to membrane proteins.
Seals to prevent molecules from passing
between villus
Dense capillary network Blood supply to remove water soluble
nutrients
Lacteal Removes end products of fat digestion.
Lipid soluble vitamins. Part of
lymphatic system

27. METHODS OF ABSORPTION
• Simple Diffusion – hydrophobic nutrients – fatty acids
• Facilitated Diffusion – hydrophilic nutrients (fructose)
• Active Transport – mineral ions….Na, Ca, Fe
• Endocytosis – Triglycerides, cholesterols

28. SUMMARY OF ABSORPTION METHODS

29. STARCH DIGESTION - APPLICATION

30. TISSUE OF SMALL INTESTINE
Serosa
Longitudinal Muscle
Circular Muscle
Submucosa
Mucosa

31. MICROGRAPH OF A CROSS SECTION
– SMALL INTESTINE

37. MICROGRAPHS OF THE SMALL
INTESTINE- LONGITUDINAL VIEW

39. ASSIMILATION
• Taking molecules to cells to become part of
the body:
• Carbohydrates: produce ATP, DNA, RNA,
Cell membrane
• Fat: Adipose tissue, phospholipids,
mitochondrial membranes, hormones
• Amino acids: cells=proteins. Excessive
amino acids are deaminated by the liver to
form urea

40. LARGE INTESTINE
• Larger diameter…shorter tube (1.5m)
• Sections: cecum, colon (main), rectum
• Functions:
• Reabsorbs water.
• Mutualistic bacteria (E. coli): synthesize
vitamin K
• Elimination (egestion) of Waste (Feces)

42. MAIN COMPONENTS OF FECES
• CELLULOSE - dietary fiber
• LIGNIN - - dietary fiber
• BILE PIGMENTS
• BACTERIA
• INTESTINAL CELLS
• MEAN RESIDENCE TIME –
• average time undigested “food” remains in the Lg. Intestine.
• Positive correlation between the amount of dietary fiber in a person’s diet
the rate of movement through the large intestine.

43. LARGE INTESTINE

44. COLONOSCOPY

45. I THINK THIS SELECTION WILL
JUST ABOUT SAY IT ALL!

46. •DRAW

47. THE LIVER – D.3

49. BLOOD FLOW THROUGH THE LIVER

50. BLOOD FLOW THROUGH THE LIVER
• LIVER CELL = HEPATOCYTE
• Blood is supplied by these vessels:
• HEPATIC PORTAL VEIN – blood from stomach, sm. Int. &
spleen directly to liver. Not a true vein. Bring nutrients to liver.
• HEPATIC VEIN – blood -- no Oxygen to heart from liver
• HEPATIC ARTERY – blood supplies Oxygen from heart
• HPV separates into SINUSOIDS
• Capillary- like (wider), thin celled, many pores: allows blood
flowing through it to come in close contact to liver cells.
• HA branches to form capillaries that join sinusoids: provides
Oxygen to liver cells.

52. FUNCTIONS
• Composed of hepatocytes (Liver cells):
1. Detox: removes toxins from blood. Converts them to less
toxic/non-toxic.
2. Conversion of Cholesterol to Bile Salts: part of BILE. Bile
helps to emulsify fats in small intestine.
3. Production of Plasma proteins: rER of liver cells produce
90% of plasma proteins (Albumin & Fibrinogen). Processed
by Golgi in liver cells
4. Nutrient Storage and Regulation:
• GLUCOSE STORAGE – as Glycogen
• Storage; Iron, Vitamin A, Vitamin D
• Removal of the Amino Group
• Conversion of excess Carb & Protein into Fatty Acids
& Triglycerides
• Assimilates phospholipids & Cholesterol

53. FAT METABOLISM

54. 5. BREAKDOWN OF ERYTHROCYTES (RBC)

55. FUNCTIONS
5. Breakdown of Erythrocytes (RBC)
• Kupffer Cells – walls of sinusoids.
• Specialized macrophages that absorb and
breakdown RBC by phagocytosis.
• Recycle the components:
• Hemoglobin split
• Globins hydrolyzed
• Iron separates from heme – taken to
bone marrow
• Remainder of the heme forms BILIRUBIN
– used to form bile.

58. HUMAN NUTRITION D.1

59. 1. ESSENTIAL VS. NON
ESSENTIAL

60. DIET
• THE TOTAL FOOD INTAKE BY AN
ORGANISM.
• Nutrition – the supply of nutrients.

61. NUTRIENTS
Essential Nutrients – must be consumed as part of your diet. Cannot
be synthesized by the body.
These four nutrients are essential:
• Water - essential
• Lipids – some types of fatty acid - essential
• Amino acids - ½ are essential
• Vitamins and Minerals – All minerals & most vitamins
Non-essential –
• Carbohydrates – energy can be made from both fats and proteins

62. AMINO ACIDS
• 20 amino acids
Essential - lacking any a.a not made by the
body
Non essential – any that the body can make
by conversion of other nutrients.

63. NON-ESSENTIAL VS. ESSENTIAL

64. FATS
• Storage of energy
• Insulation of body against temperature changes
• Fat around some organs provides shock
absorbers
• Cell membrane - phospholipid

65. VITAMIN AND MINERALS
• Can be distinguished by their chemical nature
Minerals –
• Chemical elements; usually ionic
Vitamins –
• All organic
• Vitamin K and D – non essential

66. 2. ENERGY
IN
HUMAN
DIETS

67. COMPARISON OF ENERGY
IN NUTRIENTS.
• Measured in kilojoules (kJ)
CARBOHYDRATES: 1760
kJ/100g
PROTEIN – 1720 kJ/100g
FAT – 4000 kJ/100g

68. MEASURING ENERGY CONTENT
• To heat one mL of water 1°celcius – 4.2J of energy is needed
= 1 calorie
• SO:
Energy content = temp change(ºC) x water volume(mL) x 4.2
of a food mass of food (g)
Calorimeter – instrument used to measure energy content

69. CALORIMETER

70. 3. READING NUTRITIONAL DATABASES
• VITAMIN AND MINERAL
• NUTRIENT DATABASE
• NUTRITONAL CONTENT IN FOODS

71. 4. MINERALS

72. MINERALS

73. 5. LIPIDS, YOUR HEALTH, AND
HEART DISEASE
Humans can synthesize most fatty acids from carbohydrates
Some Fatty Acids are ESSENTIAL:
• Omega 3 – Fatty Acids
• Omega 6 – Fatty Acids
Evidence exists linking deficiencies to:
• Brain impairments
• Maintenance of cardiac tissue
•Good sources: Fish, Leafy Vegetables, Walnuts

75. • SATURATED
• CHOLESTEROL
• TRANS FATS
• UNSATURATED
• MONOUNSATURATED
• POLYUNSATURATED
• CIS: OMEGA 3 & 7
GOOD FATS VS. BAD FATS
GOOD BAD

76. CHOLESTEROL LEVEL AS A C.H.D. INDICATOR
HDL vs. LDL – produced in the liver
CHOLESTEROL travels in the blood attached to a protein
• Low Density Lipoprotein – transports cholesterol and triglycerides from
the liver around the body…tends to deposit on artery walls.
• “Bad cholesterol” “Lousy”
• High Density Lipoproteins - transports excess cholesterol and
triglycerides from body to the liver.
• “Good cholesterol” “Happy”
Other source of FAT:
• Triglycerides - another type of fat produced by excess calories, alcohol,
and sugar (very LDL)

78. CHOLESTEROL AND CORONARY HEART DISEASE
• Cholesterol = steroid
Research has shown a positive correlation between high levels of
cholesterol and an increased risk of CHD, but it is not certain that lowering
cholesterol intake reduces the risk of CHD. WHY?
•Most research involves total blood cholesterol levels but only
cholesterol in LDL is implicated:
• The liver synthesizes its own cholesterol
• Saturated and Trans Fat raise cholesterol level
•Reducing dietary cholesterol…very little overall effect on CHD
Rates
•Genetic factors appear to be more important (less understood)

79. • When you’re HUNGRY:
• Stomach releases GHRELIN
• Pancreas release GLUCAGON
• When you’re FULL (satiety):
• Stretch receptors in stomach &
intestine activated
• Adipose tissue releases LEPTIN
• Sm. Intestine releases CCK
• Pancreas releases INSULIN
6. APPETITE CONTROL - HYPOTHALAMUS
Controlled by Hormones Produced:
•Pancreas
•Stomach
•Intestines
•FAT (Adipose) Tissue

80. 7. NUTRIENT DEFICIENCY DISEASES/DISORDERS
Malnutrition – a deficiency, imbalance,
or excess of specific nutrients in the
diet.
Starvation – severe lack of intake of both essential and non-
essential nutrients.
• Results in breakdown of body tissue

81. FORMS OF MALNUTRITION

82. VITAMIN C
• Vitamin C = Ascorbic Acid
• Needed for synthesis of collagen fibers in:
• Skin
• Blood vessel walls
• Humans cannot synthesize
• Not exclusive to humans
SCURVY – Vit. C deficiency disease.
Deficiency symptoms:
• Bruising & skin discoloration
• Hemorrhaging
• Anemia
• Dental
• Edema

83. SCURVY

84. SCURVY

85. VITAMIN D – DEFICIENCY
• Calciferol
Needed for calcium absorption in the
intestines.
Symptoms of deficiency similar to calcium
deficiency:
• Rickets – soft bone disorder
• Bone Fracturing
• Muscle atrophy
• Dental
• Delayed bone growth
• Enlargement of liver/spleen
• Osteomalacia – bone thinning
• Synthesis:
• Skin, Food, Supplement

86. PROTEIN MALNUTRITION: PHENYLKETONURIA
PKU CAUSES:
• Autosomal recessive – causes a mutation of the
gene for the enzyme PAH
• Condition where a baby is unable to breakdown
the a.a. phenylalanine into tyrosine.
• Deficiency in the enzyme PAH
• Levels of phenylalanine accumulate

87. PKU

88. PHENYLKETONURIA
• Most infants are tested soon after birth.
Symptoms:
Early: seizures, small head size
Long term – severe cognitive impairment
Treatment: DIET low in protein
Supplement of essential Amino Acids

89. Pku diet

90. 8. CONSEQUENCES OF OBESITY:
HYPERTENSION
AND
TYPE II DIABETES

91. GENERAL FACTORS THAT CAN
LEAD TO OBESITY (NONMEDICAL)
• Food –
• high fat and sugar content
• Smaller quantities of high fiber
foods eaten
• Economic
• More unhealthy food is cheaper
• Transport
• More cars ---- less walking
• Jobs
• Physically undemanding
• Technology
• Tasks done by hand
--- now done by
machine.
•Video games and
television watching =
“couch potato”
generation!

92. HYPERTENSION
• Excess weight:
• Places more strain on heart – higher heart rate
• Atherosclerosis – narrow blood vessels – higher
heart rate
Precursor to C.H.D.

93. TYPE II - DIABETES

94. TYPE II - DIABETES
•Medical Cause:
• Decreased responsiveness of
LIVER, FAT, & MUSCLE
cells to insulin

95. TYPE II - DIABETES
Risk Factors:
• Obesity due to overeating
• Diets rich in fat/low in fibre
• Inactivity
• Genetics – parent? Sibling?
• Age
• Ethnic background

96. TYPE II - DIABETES
Symptoms:
• Elevated blood/urine glucose
• Frequent Urination
• Dehydration/Increased thirst
• Extreme hunger
• Weight Loss
• Fatigue
• Slow healing and more frequent infection

97. COMPLICATIONS – TYPE II
DIABETES
If not carefully managed:
• Atherosclerosis/circulation issues
• Hypertension
• CHD

98. 9. ANOREXIA NERVOSA

99. • Unusual obsession with food, weight, body shape, and
excessive exercise
• Self-imposed starvation
• Affects more women than men (as reported)
Psychiatric Condition based on :
• Emotional issues
• Perfectionism
• Control
• Self worth

100. PHYSICAL CONSEQUENCES
• Circulatory
• Anemia - bruising
• Low blood cell count & electrolyte balance
• Heart failure
• Respiratory – lung tissue
• Skeletal – bone loss; osteoporosis
• Muscle – loss of muscle mass, weaker
• Hair Loss
• Women – interruption of ovulation
• Men – low testosterone

101. PSYCHOLOGICAL CONSEQUENCES
• Depression
• Obsessive Compulsive
Disorder
• Drug Abuse
• Personality Changes

102. DISEASES OF THE DIGESTIVE
SYSTEM D.2 – D.3

103. JAUNDICE (D3)
• Condition in which the skin and eyes become
yellow
• Due to accumulation of BILIRUBIN in blood
plasma
• Causes: Liver (Hepatitis or Cancer), Gall
Bladder (gall stones), Bile duct disease
• Result: could damage the brain, in infants –
cerebralpalsy

104. CHOLERA (D2)
• Infection of the intestines
• Source: Vibria cholerae (bacteria)
• Bacteria releases a toxin that binds to receptors in
the intestines.
• Toxin enters cells: endocytosis
• Toxin triggers release of Cl & HCO3 Water follows
leading to acute diarrhea.
• Fluid loss can cause death within hours
if untreated.

105. STOMACH ACID SECRETION AND ULCERS(D2)
Stomach Acid
•secreted by parietal cells
•Disrupts ability of cells to be held
together in tissue
•Leads to denaturing of proteins
(except pepsin)

106. ACID REFLUX (D2)
• occurs when cardiac sphincter malfunctions
• Acid enters the esophagus
• Production of acid in stomach –
• Proton Pump: H+/K+ ATPase
• Uses ATP to exchange 2H+ for 2K+ with H+ secreted.
• Reduce Acid –
• Use of proton pump inhibitor (PPI)
• Bind to a single pump – irreversibly – blocks activity – raises
stomach pH
• Provides temporary relief
• PRILOSEC, PREVACID

109. ULCERS (D2)
• Open sore
• Partial digestion of stomach lining by pepsin/HCL
• Possible Causes:
• Infection with Heliobacter pylori bacteria (80%)
• Overuse of OTC pain medicine:
NSAID/Aspirin/Ibuprofen
• Lack of treatment can lead to stomach cancer