Nutrition, Digestion, and Absorption Flashcards
what does the body do with food
must be ingested, digested (broken down into small molecules), absorbed and undigested material eliminated
why is it called a gastrovascular cavity?
because it is a place to digest food and a place to distribute it to the rest of the body; connects to outside world via single opening
How are acetyl groups relevant to nutrition?
The acetyl group (CH3CO––) is used to build more complex molecules
Acetyl groups must be obtained from food.
Carbs, fat, protein: How are they stored and when are they used?
In animals, energy is stored as
–glycogen (carbohydrate)
–triglycerides (a type of lipid, informally known as ‘fats’)
Proteins are used generally used only under starvation conditions (plasma proteins first, leading to edema)
Carbohydrates
Monosaccharides
4 kcal per gram
Used for: Energy; building other macromolecules and cell structures
Fats
Fatty acids, monoglycerides
9 kcal per gram
Used for: Energy storage; building other macromolecules and cell structures, especially cell membranes
Proteins
Amino acids, small peptides
4 kcal per gram
Used for: Building other proteins and other organic molecules, such as signaling substances
Sodium (source in diet)
Table salt, dairy foods, meat, eggs, processed foods
Sodium (major functions)
Nerve and muscle action; water balance; principal positive ion in extracellular fluid
What are “microminerals”?
Microminerals are elements required In relatively small amounts
Main function of B vitamins
Act with enzymes to speed metabolic reactions, or act as raw materials for chemicals that do so.
Work with enzymes to promote necessary biochemical reactions. (Coenzymes)
Two most important water-soluble vitamins
B and C
Main functions of Vitamin C (absorbic acid)
Assists in the maintenance of teeth, bones, and other tissues.
Main dietary sources of vitamin C
Vitamin C is abundant in many fruits (e.g., kiwi, strawberry, citrus) and in many vegetables (e.g., bell peppers, brocoli, spinach)
What is unique to humans in terms of vitamin C?
Humans are among a few species that cannot manufacture vitamin C
Vitamin definition
Vitamins: small organic molecules that facilitate various cellular and physiological processes
Herbivores
consume plants
Carnivores—
prey on animals
Omnivores
prey on both animals and plants
Detritivores
ingest particles of dead organic matter.
Predators
feed on living organisms.
Filter feeders
filter small organisms from an aquatic environment
Important fat-soluble vitamins
Vitamin A, D, E, K
Main functions of vitamin A
Produces the visual pigment needed for good eyesight; also used in making bone
Dietary sources of vitamin A
Carotene is responsible for the color of yellow and orange fruits and vegetables. It is converted into vitamin A within our bodies
Main functions of Vitamin D
- Absorbing calcium (from gut, DCT), strengthening bones
- Supporting muscle function
- Preventing some types of cancer
(colorectal, breast, prostate) - Decreasing risk of heart disease and stroke
What is the only vitamin that humans can synthesize?
Vitamin D, yet many people get inadequate amounts
Vitamin D possible deficiency/excess symptoms
Deficiency: poor formation of bones and teeth, irritability.
Excess: diarrhea and fatigue
Vitamin D dietary sources
Fish is the richest source of vitamin D; shellfish and egg yolks provide smaller quantities; fortified foods (such as milk, soy, and breakfast cereals) are imporant sources for most people.
Vitamin E main functions
Protects lipids in cell membranes and other cell components, antioxidant
Vitamin E dietary sources
Vitamin E is abundant in nuts, vegetable oils, whole grains, and egg yolk.
Vitamin K main functions
produces clotting agent in the blood
Vitamin K deficiency/excess
Deficiency: prolonged bleeding, slow wound healing.
Excess: liver damage
Dietary Sources vitamin K
Leafy green vegetables and some fruits (avocado, kiwi) are rich in vitamin K, which is also manufactured by intestinal bacteria.
Recommended daily intake of vitamin D for adults:
600-1000 IU
What do stomachs and crops have in common?
Stomachs and crops are storage chambers that allow for gradual digestion.
The stomach may function in storage, food processing (mixing, with or without grinding), with or without chemical digestion.
What are gizzards used for?
Birds grind food with small stones in their gizzards.
In birds, what is the role of the cecum
Microbes aid in digestion in the cecum, which is well-developed in herbivores
Digestive pathway in bird
esophagus -> crop -> two chambered stomach -> small intestine -> cecum -> common opening for digestive and urinary system
The two stomachs in birds
Proventiculus and the gizzard
- Proventiculus is not a true stomach, true stomachs secrete HCl and digestive enzymes
Digestive pathway in worm
Mouth -> pharynx -> esophagus -> crop -> gizzard -> intestine -> anus
Digestive pathway in cockroach
Mandibles (w/ salivary glands) -> esophagus -> crop -> gizzard -> intestine -> rectum -> anus
Digestive pathway in rabbit
Teeth -> esophagus -> stomach -> small intestine -> cecum -> large intestine -> rectum -> anus
What is the gizzard like as an organ?
It has a very muscular nature
Why can’t animals break down cellulose?
Animals cannot produce cellulases—enzymes that break down cellulose.
What are ruminants?
Ruminants are animals that have four-chambered stomachs
Rumen
The rumen contains microorganisms that ferment cellulose into absorbable nutrients (esp. fatty acids) for the host.
Reticulum
The reticulum stores
partially-digested material and regurgitates it.
Omasum
Food then travels to the omasum where it is concentrated by water absorption and some nutrients (ions, fatty acids) are absorbed.
Abomasum
The abomasum is the true stomach. Secretes HCl to help break down protein.
Microorganisms are also digested by the host, and provide protein.
What is unique to vertebrate’s digestive system?
In vertebrates, the intestinal wall has folds that increase the surface area for interaction with the food and for increasing nutrient absorption
Cecum in herbivores
a fermentation chamber in some herbivores; not prominent in large ruminants, omnivores, and carnivores (why not?).
Coprophagy
Reingestion of nutritive feces in herbivores that depend on microbial digestion in cecum.
Why is it good to mechanically digest food?
Mechanical digestion of food
increases efficiency of energy extraction by increasing surface area
What do snails use to mechanically digest food?
radula
What do arthropods use to mechanically digest food?
mandibles
How do earthworms increase surface area in their digestive system?
a typhlosole, a longitudinal infolding of the intestinal wall.
How do sharks increase surface area in their digestive system?
spiral valve
How are shark’s teeth different from mammals?
Sharks: multiple rows of deciduous teeth
are set in gum tissue
Mammals: teeth are set in a bony jaw
How do vertebrates increase surface area in their digestive system?
The gut wall is folded
The epithelium is folded into finger-like projections called villi.
Surface cells of villi have smaller projections called microvilli.
