Digestion, absorption and sources of energy Flashcards
Review: What is Digestion
- Mechanical
- Chemical
GI tract review
mouth -> pharynx -> epiglottis -> esophagus -> esophageal sphincter -> stomach -> pyloric sphincter -> gallbladder -> pancreas -> duodenum -> jejunum -> ileum -> ileocecal valve -> colon -> appendix -> rectum -> anus
Mouth
- Saliva lubricates
- Amylase starts starch digestion
- Chewing breaks down food
Pharynx
Epiglottis keeps food from airway
Esophagus
Peristalsis starts
Stomach
- Food storage
- Acid kills bacteria, unfolds proteins, activates pepsin (breaks down protein)
Small intestines
- Most digestion & absorption
- Pancreatic enzymes digest food & bicarbonate neutralizes acid
- Bile breaks fat
Large Intestine
- absorb water
- bacteria digest fiber, make vitamins
Involuntary Muscles and Glands
Gastrointestinal motility (peristalsis, segmentation)
Liquefying process: chyme
(chewing, saliva)
Stomach muscles with the help of the pyloric sphincter
What is absorption?
- The small intestine:
where most of the absorption takes place
villi and microvilli
specialization in the intestinal tract
where do the nutrients go?
- Lymphatic system - most lipid-soluble nutrients
- bloodstream - through the liver by way of the hepatic portal vein
- circulatory route of blood (in relation to nutrient absorption) is Heart to artiest to capillaries (in intestines) to hepatic portal vein to liver to hepatic vein to heart
Carbohydrates
- include sugars, starch, fiber
- energy nutrients compose of monosaccharides
- carbo = carbon
- hydrate = water
Carbohydrates are the bodies PREFERRED energy source (CHO)
Types of Carbohydrates
- Simple
- Complex
Simple Carbs
monosaccharides
disaccharides
Complex Carbs
polysaccharides
Examples of monosaccharides
- glucose
- fructose
- galactose
Examples of disaccharides
- maltose (glucose + glucose)
- sucrose (glucose + fructose)
- lactose (glucose + galactose)
Examples of polysaccharides
- Fibre (soluble
- Starches
- Glycogen (storage form in animals/humans. Not dietary)
Saccharide =
sugar molecule
Lactose Intolerance
Lactose -> broken down by lactase to galactose + glucose
- babies born with lactase
- decreases with age (some people faster than others)
- If lactose continues through GI undigested (draws in water, creates gas in colon, explosive diarrhea)
Complex Carb: Oligosaccharides
3-10 monosaccharides
Complex Carbs: Polysaccharides
large molecules composed on chains of hundreds or even thousands of monosaccharides
- starch
- fibre
- glycogen
Glycogen - CHO storage in animals/mammals
- The body breaks off a chain when it needs energy
- Made and stored in the liver
- Found in our muscle & liver (not in foods - meat to a limited extent)
- Role in blood glucose regulation (ie. low blood sugar stimulates the release of glucagon which breaks down the glycogen to form glucose - the body and brain want glucose
Starch - CHO storage in plants
A plant polysaccharide composed of glucose and digestible by human beings
- Food sources: (grain products, legumes, starchy vegetables)
Fiber - CHO not well digested
- complex, not completely broken down to be used as energy
- polysaccharide but with bonds that human enzymes can’t break
- can be 2kcal/g when fermentation present
- found in plant-based foods - Examples: cellulose, pectins, gums, mucilages, non-polysaccharide lignins
Insoluble Fiber
Doesnt dissolve in water. Passes unchanged through colon
-Normalize bowel movements/increase regularity
(Roughage, bulk fiber)
Soluble Fiber
Dissolves in water. Gels like pectin/gelatin
1. holds water in stool
2. Binds cholesterol and simple sugars
3. Delays transit time
(sponge)
AI for fiber
38g/day for men
25 g/day for women
Concern that Canadians are not meeting their fibre requirements
Harmful effects of excessive fiber
- mineral balance
- nutrient displacement
- energy requirements
- Increased fluid needs
-Increased fluid needs whenever a laxative is given or fiber intake is increased
-Energy requirements – fiber doesn’t supply energy
-Nutrient displacement
Insulin
pancreatic hormone that regulates blood glucose levels
Glucagon
pancreatic hormone that releases glycogen from liver
Somatostatin
hormone produced by pancreas & hypothalamus that inhibits insulin and glucagon
Glycemic Index
a method of classifying foods according to their potential for raising blood glucose
Glycemic response
the extent to which a food raises the blood glucose concentration and elicits an insulin response
Glycogenolysis
process converting glycogen back to glucose
Gluconeogenesis
process producing glucose from fat & protein (not very efficient for fat)
Sugar alcohols are carbohydrates and have the same energy as sugar
False
Sugar alcohols occur naturally in fruit and veggies
True
Sugar alcohols have very little, if no, known side effects
False
Examples of sugar alcohol are erythritol, mannitol, and xylitol
True
A common non-nutritive sweetener is aspartame?
True
Studies indicate that aspartame may cause bladder tumours in lab animals
False
Sugar alcohols and non-nutritive sweeteners DO contribute to dental caries
False
Non-nutritive sweeteners contain no calories
True
Examples of non-nutritive sweeteners are: stevia, saccharin, aspartame, and sucralose
True
Using sugar alternatives can help people loose excess weight
False
