Chapter 3 Flashcards
Digestion
process of breaking food into components small enough to be absorbed by the body
Absorption
process of taking substances into the interior of the body
Gastrointestinal (GI) tract
hollow tube consisting of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus
Watery diarrhea means
you’re not absorbing nutrients
Transit time
amount of time it takes food to pass the length of the GI tract
i. Varies upon what you eat
Feces
body waste, including unabsorbed food residue, bacteria, and dead cells
a. Enzymes
proteins that speed up chemical rxns;
remain unchanged
i. Hormones
ii. Made some place specific & they travel by blood
specific synthesis site; travel by blood to their target organ; action at receptors (proteins) on cell membrane
What is direction (in terms of organs) of digestion?
Brain –> mouth –> stomach –> gallbladder, liver, and pancreas –> small intestine –> large intestine –> anus
digestion and the brain
Digestion starts in brain w/ sense of smell and sight
Mouth
> entry point for food into the digestive tract
saliva
chewing
Importance of saliva
Saliva contains:
Salivary amylase: starts to break down carbs
Lysozymes: inhibit bacterial growth in mouth
Importance of chewing
Chewing: Mechanically breaks food down
The smaller, the easier to digest
Increases surface area for contact w/ digestive enzymes
Stomach
holding and mixing tank (2 to 4 hours)
- Hydrochloric acid (HCL) to digest food , make certain minerals easier to absorb
- Hormones (inactive → active)
- “Chyme” (the partially digested food)
Small intestine
95% of digestion and absorption
Gallbladder
stores bile (produced by liver)
a. Bile
emulsifies fat (makes absorption easier)
liver
produces bile
- Pancreas
secretes
a. Digestive enzymes
b. Bicarbonate ions – raises pH from stomach HCL
In what form do we absorb carbs?
single sugar units
In what form do we absorb proteins?
amino acids
In what form do we absorb lipids?
Triglycerides: made up of fatty acids
[No cals in cholesterol, only in triglycerides]
What is the system of transport of WATER-soluble nutrients?
portal system: goes from intestinal tract to liver
What is the system of transport of FAT-soluble nutrients?
lymph: bypasses liver, can be deposited directly into blood
3 types of absorption
Passive, facilitative, active
Passive Abspt
no carrier, no energy (ATP) needed
i. Need: concentration gradient
ii. Water, some fats, some minerals
Facilitative Abspt
carrier, no energy needed
i. Need: concentration gradient
ii. Fructose
Active Abspt
carrier, energy needed
i. Carbohydrate, amino acids
Large Intestine
> Comprises the colon & the rectum
Can absorb: water, some vitamins & minerals
Intestinal microflora are produced here
Water, nutrients, and fecal material may spend up to 24hrs in large intestine
III. Probiotics – live bacteria; health benefits?
> Unclear whether adding in probiotics has any health benefits
NATURAL food sources like plain yogurt and other fermented products have live bacteria – is beneficial
IV. Prebiotics
> Not digested by small intestines
In colon: can stimulate growth/activity of certain types of bacteria
Food sources: onions, garlic, bananas, artichokes, raw oats, unrefined flour & barley
GI Tract’s Role in Immune Fxn
> GI tract plays big role in protecting body from infection
>Limits abpt of toxins & disease-causing organisms
What are food allergies and common food allergens?
Food allergies: absorbing protein whole
>Wheat, shellfish and fish, nuts, milk, eggs
- Enteral nutrition
tube feeding
- TPN: total parenteral nutrition
fed directly to a vein, but high risk of infection, gut starts to atrophy overtime
d. Catabolic pathways
release energy (trapped in chemical bonds); breaking down energy trapped at ATP
e. Anabolic
use energy to synthesize products
VIII. Adenosine Triphosphate (ATP)
a. Food energy
b. Break of phosphate group high-energy bonds
IX. Carbohydrate metabolism
a. Glycolysis – Glucose (6 carbon) catabolized to pyruvate (3 carbon)
1. Pyruvate → acetic acid (2 carbon)
b. Sources of glucose for glycolysis
i.Glycogen – stored carbs on liver and in mscls
>Mscl glycogen are ONLY used to fuel working mscl
ii.Gluconeogenesis – use amino acids to create glucose
X. Lipid metabolism
> Metabolism of triglycerides (TG)
Lipolysis (occurs in adipose/fat tissue itself)
>TG → free fatty acid (FFA) (and glycerol)
Beta oxidation – catabolism of FFA
>End with acetic acid (2 carbon)
XII. Fate of acetic acids
> Enters Citric acid cycle (AKA Krebs cycle, TCA cycle)
>2 carbon acetic acid enters → end w/ CO2, electrons
Electron transport chain – where most of ATP is generated
>Final pathways for ATP prodxn
>[See figure in book]
