BIO 105-03

Class discussion Prompt #2 on WebCT!! Due Thursday 2/26!!!

Bio 105 Lecture 12 Notes

I. Eating
A. What Makes Eating So Enjoyable?
B. Taste
C. Aromas
II. Digestion
A. Basic Info
1. Definition
2. GI Tract
a. Composition
b. Functions
2. Mechanical and Chemical
3. Absorption of nutrients
4. Tasks
5. The Processes
B. Steps/Organs
1. Mouth
2. Esophagus
3. Stomach
a. Mechanical
b. Chemical
c. Stomach emptying:
4. Small Intestine
a. Anatomy
b. Mechanical and chemical digestion
5. Large Intestine (Colon)
a. Functions
b. Anatomy
c. E. coli
C. Digestion Aids
1. Chemical
a. Enzymes
b. Hormones
gastrin, secretin, cholecystokinin (CCK)
control digestive secretions, regulate enzymes
increase/decrease preistalsis
secreted by stomach, small intest., pancreas
feedback system
c. Bile
secreted by liver, stored in gall bladder
emulsifies fat in small intest.
2. Accessory Organs
not directly involved in digestion, but essential for aid
a. Mouth
teeth: mastication
tongue: mastication, swallowing
salivary glands: produce saliva
b. Liver
largest gland in the body
produces bile needed for fat digestion
metabolism of carbs, fats, proteins
stores nutrients: vits. A, D, B12, E, copper, iron, gycogen
detoxes alcohol
c. Gallbladder
concentrates and stores bile
released into GI tract when fat ingested
d. Pancreas
produces hormones: insuling & glucagon
produces sodium bicarbonate
neutralizes acidic chyme
protects enzymes in small intestine from inactivation by stomach acid
digestive enzymes for small intestine:
amyloase digests carbs
lipase digests fats
trypsin, chymotrypsin, carboxypeptidase digest proteins
D. Other Body Systems’ Influence
nervous system stimulates appetite
hormone ghrelin signals brain to eat when stomach empty
circulatory system
transports nutrients, oxygen, waste products thru blood
lymphatic system
distributes fat & fat-soluble nutrients thru lymp
excretory system
eliminates wastes from circulatory system via urine

III. Diseases of day
A. Digestive Disorders of Mouth and Esophagus
gingivitis & periodontal disease
swallowing problems: dysphagia
esophageal problems
heartburn (acid reflux) may be caused by weak LES
B. Digestive Disorders of Stomach
stomach flu: diarrhea, cramps, vomiting
usually caused by virus
peptic ulcers
erosion of mucus covering so acid eats at stomach lining
80% associated with Helicobacter pylori
C. Digestive Disorders of Small Intestine
malabsorption disorders
celiac disease: inability to digest gluten protein
short bowel syndrome: due to losing more than 65% of small intestine
less small intestine = less absorption of nutrients
duodenal ulcers
intestinal enzyme deficiencies
D. Digestive Disorders of Large Intestine
may be due to insufficient fiber and water intake, inactivity, stress, illness
need to be careful of dehydration
treatedby fluid and electrolyte replacement
special problem for children and elderly
irritable bowel syndrome (IBS)
alternating patterns of diarrhea, constipation, abdominal pain
inflammatory bowel disease (IBD)
Crohn’s disease – autoimmune, affects entire GI wall
ulcerative colitis: ulcers in colon

Clicker Questions

The process of digestion begins in the:
4.Small intestine

Why does chewing food help with digestion?
1.Chewing exercises the jaw muscles
2.Chewing is a natural reflex
3.Chewing ensures slow ingestion of food
4.Chewing increases the exposed surface area of the food

Why doesn’t the stomach digest itself?
1.Enzymes don’t work on own body
2.Not enough HCl
3.Protected by mucus
4.Protected by saliva swallowed

All absorption of nutrients occurs in the small intestine.

Which of the following is NOT a task for the large intestine?

What substance is required to break up fat globules and emulsify fats?

Which of the following is the carb-digesting enzyme produced by the pancreas?

Long-term constipation can lead to…

~~~~~ CONTINUED ~~~~

Bio 105 Lecture 13 Notes

I. Digestion of Nutrients
A. Digesting Carbs
1. Basic info
digesting a meal of pasta (starch), milk (lactose) and cherries (sucrose & fiber)
digest carbohydrates in mouth & intest.
saliva contains amylase enzyme (-ase = enzyme)
starts breaking down amylose and amylopectin in pasta into smaller starch units and maltose
2. In GI tract
in stomach – breakdown to di- and other polysaccharides
in small intest. final breakdown to monosaccharides
monosaccharides travel in blood to liver for processing to glucose
glucose travels to blood in all cells
in large intest. soluble fiber broken down by bacteria, insoluble fiber passes thru
3. Lactose Intolerance
lactose: principal carbohydrate found in dairy products
disacch: galactose & glucose
people with a deficiency of the enzyme lactase cannot digest lastose properly
lactase found in sm. intest.
lactose maldigestion is natural part of aging
as soon as baby stops nursing, body makes less lactase
lactose intolerance
lactose maldigestion resulting in nausea, cramps, bloating, diarrhea, flatulence
symptoms due to bacteria in lg intest. digesting lactose -> release H gas
B. Digesting Fat
1. In GI tract
chewing, lingual lipase
gastric lipase: triglyceride -> diglyceride (glycerol w/2 fatty acids) and one fatty acid
small intest.
when fat arrives in sm intest, 2 chemicals released
bile acids to emulsify fat
pancreatic lipase: diglyceride -> monoglyceride (glycerol w/1 fatty acid) and 1 fatty acid
small intestine (con): monoglycerides and fatty acids
packaged w/ lecithin (emulsifier from bile)
creates MICELLES for absorption into intestinal wall cells
2. Transport to body
short-chain fatty acids enter bloodstream and travel to liver directly
long-chain faty acids in intestinal cells
reformulated into fat
need transport carriers b/c too big: chylomicrons (lipoprotein)
taken to lymph first and then to blood
in blood capillaries – lipoprotein lipase
breaks down fat to fatty acids and glycerol for direct use by cells
chylomicrons w/o fats removed -> liver for processing
C. Digesting Protein
dietary proteins are digested & absorbed in stomach & small intestine
stomach acids: d
denature protein
activate pepsin – breaks down protein into shorted polypeptides
in the sm intest poplypeptides broken down into tri- dipeptides and amino acids
amino acids enter blood and travel to liver
II. Weight Management
A. Basic Info
B. Risks
1. Being overweight
2. Being underweight
C. How Do You Know If You’re at a Healthy Weight?
1. BMI
2. Body fat amount
a. Basic Info
b. Ways to measure
3. Body fat location
D. Energy Balance
E. Energy Needs
1. BMR
a. Basic info
b. Factors That Affect BMR
2. Thermic effect of food
3. Physical activity
F. Estimated Energy Expenditure (EER)

Clicker Questions

What hormone stimulates cells to take up glucose from the blood?

How many calories per gram is digested protein worth?

George has a BMI of 32. He is considered to be:
At a healthy weight

Dietary carbs and protein are converted to fat and stored when energy balance is:

For an average person, the largest portion of energy needs is determined by:
Body weight
Physical activity
Thermic effect of food

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