IB Biology - Digestion

1. Section 6.1 / Option D.1 – D.3
DIGESTION AND NUTRITION

2. 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)

3. 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 – must have connecting point.
• Not hormone produced/can be both.
• Which reaction is involved in digestion, hydrolysis or
dehydration synthesis?
• Hydrolysis

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

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

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

10. TEETH
Thank you Rebecca Lieberman!

11. 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

12. PERISTALSIS

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

16. STOMACH
• Stomach lining:
• Contains Gastric Glands:
• Has three kinds of cells:
• Parietal: Secretes HCl –
activates pepsinogen; 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.

17. CONTROL OF GASTRIC JUICE SECRETION
• Controlled by nerves and hormones:
• 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

18. SMALL INTESTINE

19. SMALL INTESTINE

20. 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.

21. 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 (maltose) (pH 7)
• Maltase - (small intestine) = (maltose into glucose). (pH 7)
• Sucrase – glucose and fructose (pH – 7)
• Lactase – glucose and galactose (pH – 7)

23. TISSUE OF THE DIGESTIVE TRACT
Mucosa
Epithelium
Longitudinal
Circular Muscle

24. MICROGRAPH OF A CROSS SECTION
– SMALL INTESTINE

26. MICROGRAPHS OF THE SMALL
INTESTINE- TRANSVERSE VIEW

29. 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
Dense capillary network Blood supply to remove water soluble
nutrients
Lacteal Removes end products of fat digestion.
Lipid soluble vitamins. Part of
lymphatic system

30. VILLUS

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

32. 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

33. THE LIVER

35. 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
• Iron, Vitamin A, Vitamin D

36. 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.

37. KUPFFER CELLS

38. BLOOD FLOW THROUGH THE LIVER

39. BLOOD FLOW (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.

42. 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)

44. 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 and MRT

45. LARGE INTESTINE

46. COLONOSCOPY

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

48. HUMAN NUTRITION

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

50. 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 – “fatty acid” essential
• Amino acids - not all
• Vitamins and Minerals – not all
Non-essential –
• Carbohydrates – energy can by made from both fats and proteins

51. 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.

52. NON-ESSENTIAL VS. ESSENTIAL

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

54. VITAMIN AND MINERALS
• Can be distinguished by their chemical nature
Minerals –
• Chemical elements; usually ionic
Vitamins –
• All organic
Cannot be made by the body - essential

55. ENERGY
IN
HUMAN
DIETS

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

57. 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

58. CALORIMETER
VITAMIN

59. SELECTED ISSUES IN NUTRITION

60. 1. NUTRITION DATABASES
• VITAMIN AND MINERAL
• NUTRIENT DATABASE
• NUTRITONAL CONTENT IN FOODS

61. 2. LIPIDS, YOUR HEALTH, AND
HEART DISEASE
Review:
1.Saturated –
• All carbon atoms are connected by single covalent bonds
• Number of hydrogen atoms bonded to carbon cannot be increased
• Non essential
1.Unsaturated –
• One or more double bonds between carbon atoms
• More hydrogen can be bonded if double bond is replaced by single
bond.

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

65. FATTY ACIDS AND HEALTH - CHOLESTEROL
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”
• High Density Lipoproteins - transports excess cholesterol and
triglycerides from body to the liver.
• “Good cholesterol”
• Triglycerides - another type of fat produced by excess calories,
alcohol, and sugar (very LDL)

68. 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:
•Most research involves total blood cholesterol levels but only
cholesterol in LDL is implicated.
•The liver synthesizes it’s own cholesterol
•Reducing dietary cholesterol…very little overall effect on CHD
Rates
•Genetic factors appear to be more important
•There is a positive correlation between intake of saturated fat
and cholesterol. Is saturated fat the issue?

69. 3. APPETITE CONTROL AND THE
BRAIN
Hypothalamus
• Appetite Control Center
Receives hormone stimuli:
• Insulin – secreted by pancreas
when Glucose levels are high
• Peptide YY - “gut hormone”
• Released by small intestine in
response to food intake
• Increases with number of calories
eaten
• Leptin –released by adipose tissue .
More secreted as more fat is stored.

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

71. VITAMIN AND MINERALS
• Can be distinguished by their chemical nature
Minerals –
• Chemical elements; usually ionic
Vitamins –
• All organic
Cannot be made by the body - essential

72. 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.
Patients develop anemia, edema,
ulcerations, lose teeth.

73. SCURVY

74. VITAMIN D – DEFICIENCY
• Calciferol
• Oily fish, eggs, milk*
• Needed for calcium absorption in
the intestines.
• Calcium: bone and teeth strength
• Symptoms of deficiency similar to
calcium deficiency
• Diseases:
• Rickets – soft bone disorder
• Osteomalacia – bone thinning
• Synthesis:
• Skin, Food, Supplement

75. PROTEIN MALNUTRITION: PHENYLKETONURIA
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

76. PHENYLKETONURIA
• Most infants are tested soon after birth.
Symptoms:
Early: seizures, small head size
Long term – severe mental retardation
Treatment: diet low in phenylalanine

77. PKU DIET

78. CONSEQUENCES OF OBESITY

79. GENERAL FACTORS THAT
LEAD TO OBESITY
• Food –
• high fat and sugar content
• Smaller quantities of high fiber
foods eaten
• Economic
• Growth – larger portions
• 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!

80. TYPE II - DIABETES

81. TYPE II - DIABETES
• Diabetes Mellitus
• Adult Onset Diabetes
• Medical Cause:
• Glucose: from Food and Liver
• Eating: pancreas secretes insulin
• Allows cells to take up sugar – Lower Blood
Glucose levels

82. TYPE II - DIABETES
Symptoms:
• Increased thirst
• Frequent Urination
• Extreme hunger
• Weight Loss
• Fatigue
• Blurred Vision
• Slow healing and more frequent infection

83. TYPE II - DIABETES
Risk Factors/ Non Physiological Causes:
• Obesity
• Inactivity
• Genetics
• Ethnic Background
• Age
• Prediabetes
• Gestational

84. TYPE II - DIABETES
Treatment
Dietary Advice:
• Avoid direct sugary foods
• Eat Complex Carbohydrates
• Digest more slowly
• High fiber – delays sugar absorption
• Lower fat -

85. COMPLICATIONS – TYPE II
DIABETES
Short Term
• Hyperglycemia
• Hypoglycemia
• Ketoacidosis
Long Term
• C.H.D.
• Circulation Issues
• Nerve Damage
• Kidney Damage
• Eye Damage
• Gum Disease
• Osteoporosis
• Alzheimer’s

86. ANOREXIA NERVOSA
• Unusual obsession with food, weight, body shape, and
excessive exercise
• Affects more women than men
Psychological disorder:
• Emotional issues
• Perfectionism
• Control
• Self worth

87. 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

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

89. DISEASES OF THE DIGESTIVE
SYSTEM

90. CHOLERA
• 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.

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

92. ACID REFLUX
• occurs when cardiac sphincter malfunctions
• Acid enters the esophagus
• Heartburn!
• Production of acid in stomach –
• proton pump (H+,K+ - ATPase Pump)
• Uses ATP to exchange 2H+ for 2K+
• Reduce Acid –
• Use of proton pump inhibitor (PPI)
• Bind to a single pump – irreversibly
• Provides temporary relief
• NEXIUM, PREVACID

95. ULCERS
• Open sore
• Partial digestion of stomach lining by pepsin/HCL
• Causes:
• Stress
• Excessive acid production
• Infection with Heliobacter pylori bacteria (80%)
• Lack of treatment can lead to stomach cancer