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)

Carbohydrates cont.Types

Monosaccharide (single sugar unit) Glucose (human blood), fructose (plant), ribose (DNA)

Disaccharides (2 single sugar unit bonded together) Maltose (malt sugar), lactose(milk sugar), sucrose

(table sugar) Polysaccharides (more than 2 single sugar units

bonded together) Starch(plants store energy), cellulose (plant cell walls),

glycogen (animals store energy)

Monosaccharide

Disaccharide

Polysaccharide

Proteins (249-251)Function

Not a primary energy source Structural components of cell

Cell organelles Part of muscles, nerves, skin and hair Antibodies and enzymes

Building Blocks amino acids Made up elements Carbon, Hydrogen and Oxygen,

Nitrogen and Sulfur

Proteins cont.Source

Once you ingest and digest they are broken back down into amino acids and carried away in blood

8 essential amino acids we have to ingestTypes

histidine, isoleucine, leucine, methionine, phenylalanine, threonine, tryptophan, valine

Polypeptides

Amino AcidsPrimary

Secondary

Tertiary Quaternary

Lipids (Fats) (pg 246-249)

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

which breaks proteins down into polypeptides 

AbsorptionWaterSpecific vitaminsCertain medicines Alcohol

Small Intestine and Pancreas (pg 264-265)

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