Digestive System pg 240-280. Process of breaking down food so its small enough to absorb Digestive Tract (alimentary canal) Open ended, mostly one way tube Approximately 6 ½ - 9 m long in an adult Consists of accessory glands that secrete digestive juices as well 4 stages - PowerPoint PPT Presentation
Digestive System pg 240-280 Process of breaking down food so its small enough to absorb Digestive Tract (alimentary canal) Open ended, mostly one way tube Approximately 6 ½ - 9 m long in an adult Consists of accessory glands that secrete digestive juices as well 4 stages 1. Ingestion-taking nutrients in 2. Digestion- physical and chemical breakdown of nutrients 3. Absorption-Transport of nutrients to the tissues of body 4. Egestion- removal of indigestible
Transcript
Digestive System pg 240-280
Process of breaking down food so its small enough to absorb
Digestive Tract (alimentary canal) Open ended, mostly one way tube Approximately 6 ½ - 9 m long in an adult Consists of accessory glands that secrete digestive juices
as well4 stages
1. Ingestion-taking nutrients in2. Digestion- physical and chemical breakdown of
nutrients3. Absorption-Transport of nutrients to the tissues of body4. Egestion- removal of indigestible
Principle StructuresAdd the structures of the digestive system
to Digestive Dave(pg 259)
Pathway of Digestion
Food travels through mouth down esophagus, to stomach into small intestine to large intestine through rectum and out anus
Not all organs actually “see” food, accessory organs secrete enzymes to aid in chemical digestion (liver, gall bladder, salivary glands, appendix, pancreas)
Nutrients digested (Chemical’s of Life) Carbohydrates, Lipids (Fats) and Proteins
Peristalsis (series of wave like movements) moves the food
Essential Nutrients: Chemicals for Life
CarbohydratesProteinsLipids (Fats)
Carbohydrates (242-244)
Function Primary source of energy for cells Structural material for plant cell walls
Source Can’t make so must eat PLANTS (photosynthesis) Test for Carbs in food by adding Benedicts or Iodine
solution Make up the bulk of our diets
Building Blocks Monosaccharide (sugar units) Carbon, Hydrogen, Oxygen (1:2:1 ratio)
Function Energy storage Structural component of cell Cushions delicate organs Carries vitamins such as A D E K Raw materials for hormones and other body
chemicals Insulation
Building Blocks Glycerol and fatty acids Made with elements of Carbon, Hydrogen, Oxygen
Lipids (Fats) cont. Source
Get lipids through plant oils and animal fatsTypes
3 Types1. Triglyceride
- Glycerol and three fatty acids- Animal fat (Saturated=hard to break down) solid at room
temp- Plant oil (Unsaturated = easy to break down) liquid at room
temp2. Phospholipids
- Glycerol and phosphate group3. Waxes
- long chain of fatty acid and long chain of alcohols or carbon rings
Animal fat vs Plant oil
Triglycerides
Phospholipids
Enzymes (pg 254-258)What are they?
Proteins that play a vital role in production of chemicals during complex, multistep reactions in the human body (metabolic pathways)
Approximately 200,000 different reactions in that 20 different enzymes assist with
Names of enzymes end in –ASE 3 major groups of enzymes each responsible for
breaking down a specific nutrient Carbohydrates-Carbohydrases (Maltose-Maltase) Proteins-Proteases Lipids-Lipases
Has two important sites for binding: an active and regulatory site
Enzyme Structure (pg 254 or 257)
REGULATORY SITE
ACTIVE SITE
Enzyme
Substrate
EnzymesWhat do they do?
Interact with substrate to lower amount of energy needed for the reaction to occur (activation energy)
Increase chance reactions occur by bringing molecules together in the “right” way
Substrates (carbs, lipids, proteins) bind to active site and then enzyme helps the substrate line up and bind with other molecules
Lock and Key-specific substrates only combine with specific enzymes
Factors that affect enzymes
If enzyme is altered in any way then will not function properly due to change in shape
Factors that affect Enzymes
pH 3 D shape of enzyme is altered because bonds
between amino acids that make it up are changed Some enzymes work better in acidic conditions (0-7)
and other better in basic (7-14)
Factors that affect Enzymes
Substrate concentration If there is too much substrate and not enough
enzyme then the rate at which reaction will occur will slow down
Substrate has to wait until enzymes are available for use
Factors that affect Enzymes
Temperature Heat up molecules they move faster and collide
more therefore more products will be formed Too hot can cause permanent damage to the shape
of the enzyme and its active site
Factors that affect Enzymes
Competitive Inhibition Other molecules that are similar to substrate “beat”
the substrate to the active site and prohibit the substrate from binding to enzyme
Regulating Enzyme Activity
Allosteric activity is way the body controls reactions to avoid accumulation of unneeded chemicals, controlled by body’s demand for chemicals
Two process involved Feedback inhibition (turn production off) Precursor activity (turn production on)
Feedback InhibitionTOO MUCH final product Excess final product will bind to initial
enzymes regulatory site therefore changing shape and function of enzyme
Reaction will be “shut off”
Precursor ActivityTOO MUCH initial reactant Excess initial reactant will bind with last
enzyme’s regulatory site, change its shape and its function
“turn up” the reaction
DIGESTION: LETS GET SPECIFICOutcome:
Describe the chemical and physical processing of matter through the digestive
system.
Mouth (pg 260)Physical digestionTeeth chew, grind and rip food Increase food surface area for chemical digestion “Bolus”
Chemical digestionTaste, smell and sight of food promotes secretion of saliva
produced by the salivary glands (3 sets)Saliva contains:
1. Mucin- protects the mouth and dissolves food2. Buffer- neutralize acids3. Antibacterial agents- kill pathogens4. SALIVARY AMYLASE- breaks polysaccharides (starches) into
midsize sugar unit chains AbsorptionNothing is absorb in the mouth
Pharynx and EsophagusPathway to stomach Air and food travel down the pharynx but
then directed by epiglottis
Stomach (pg 261) Food storage and initial protein digestion
Physical digestionThe lower esophageal sphincter relaxes to
allow bolus into the 3 layers of contracting muscle before it passes highly acidic chyme through the pyloric sphincter to the small intestine
Chemical digestionThe presence of the bolus promotes the
secretion of gastric juices from cells in the stomach
Gastric Juice contains:1. Protective coating/alkaline mucus- stops the HCl
from digesting the stomach2. HCl- pH of 2.0, kills pathogens, dismantles tissues
holding food together3. PEPSINOGENS-converted by HCL into PEPSIN
Food does not pass through the pancreas but it works closely with the small intestine to help it digest food
Physical digestionBy the time chyme reaches the 7 m long
intestine there is no longer any need for the physical breakdown of the food
Small Intestine and Pancreas
Chemical digestionMost chemical digestion occurs here and is triggered
by the arrival of the extremely low pH of the chyme
The small intestine secretes a number of different chemicals1. SECRETIN- converted from prosecretin this chemical travels via the bloodstream to the pancreas to promote release of pancreatic fluid4. EREPSIN- this protein digesting enzyme breaks short chain polypeptides into amino acids6. DISACCARDIESASES (e.g. maltase, surceases, lactases)- finish the what the mouth and pancreas started and breaks disaccharides (lactose, maltose, sucrose) into monosaccharide (glucose, fructose, galactose)
SECRETIN arrives via the blood stream from the small intestine and stimulates the pancreas to release pancreatic fluid Pancreatic fluid contains:5. PANCREATIC AMYLASE- continues the mouths digestion of mid size sugar chains and breaks them down to disaccharides2. BICARBONATE IONS (HCO3)- neutralize the acid from the stomach3. TRYPSINOGEN- protein digesting enzyme that is converted to TRYPSIN to finish what the stomach started and gets protein from long polypeptides to short polypeptides7. LIPASE – enzymes that break down lipids
Small Intestine and Pancreas
Small Intestine and Pancreas
AbsorptionMost absorption of nutrients occurs hereFinger-like projections called villi increase
the highly folded small intestine up to 10 fold
Capillary networks transport amino acids and monosaccharides and Lacteals transport the fatty acids and glycerol
Small Intestine
Liver and Gallbladder (pg 267-268)
Food does not travel here but aid in fat digestion
Liver has many functions (see handout)
Physical digestionLiver produces bile which is stored in the
gallbladder Bile released when fats are present in
small intestine Bile physically breaks down fat droplets
Large Intestine (pg 268)Indigestible material (cellulose, fibre etc) wait, bulk
and build up before excreted
Physical digestionNo more digestion
Chemical digestionNo more digestion
AbsorptionWaterInorganic saltsVitamins
Review what we know!
Digestive DisordersDeficiencies can severely affect our ability
to functionMost disorders either affect the nutritional
state of the body or its salt and water content
Examples include ulcers, inflammatory bowel disease (IBS), hepatitis, cirrhosis and gallstones
