Lecture Nineteen - Nutrients and digestion I Flashcards
What does the average adult human use in their bodies?
What are the three baic functions of diet/food?
Chemical energy = Fuel for ATP production.
Organic building blocks = Source of organic N and C.
Essential nutrients = Essential aa, fatty acids, vitamins (non-caloric) and minerals (non-caloric).
What are proteins?
Structural (e.g. keratin) & regulatory function.
No storage in adult mammals (cf bird egg white).
Degraded to amino acids.
Easily digested, animals have necessary enzymes.
20-22 amino acids for protein synthesis.
50% of organic material in mammals is protein.
What are lipids?
Glycerol and fatty acids.
Storage & membrane function.
Fats, oils, waxes, phospholipids, sterols.
Animals synthesis most.
Insoluble, not easily digested.
Emulsification to aid in digestion.
More energy per mass than carbohydrates.
What are carbohydrates?
Functions:
Storage (starch, glycogen).
Structural (cellulose, chitin).
Some easily digested, some not.
Disaccharides (e.g., sucrose) & polysaccharides (starch, glycogen) hydrolysed.
Structural polysaccharides (cellulose, chitin) = most organisms cannot digest, require symbiotic microorganisms.
What is undernourishment and malnourishment?
- Undernourishment
Less energy than required.
Use up stored fat and carbohydrates.
Break down own proteins.
Lose muscle mass.
Suffer protein deficiency of the brain.
Die or suffer irreversible damage.
- Malnourishment
Long-term absence of essential nutrients.
Deformities, disease and death.
What are the stages of food processing?
Ingestion, digestion, absorption and elimination.
What are suspension, substrate, fluid and bulk feeders?
Suspension feeder = an aquatic animal which feeds on particles of organic matter suspended inthe water, especially a bottom-dwelling filter feeder.
Substrate feeder = live in or on their food source and eat their way through it. Examples of substrate feeders include caterpillars and earthworms. Caterpillars eat their way through the green tissues of leaves. Earthworms eat their way through the soil, ingesting soil particles containing partially decayed organic material as they go.
Fluid feeders = obtain food by sucking or licking nutrient-rich fluids from live plants or animals. Fluid feeders have mouth parts that are adapted to pierce or rip skin or leaf tissue. The same or other mouth parts are used to suck or lick the blood or sap that is their food. Examples of fluid feeders include mosquitoes, ticks, aphids, spiders, bees, butterflies, vampire bats, and hummingbirds.
Bulk feeders = include many animals and most vertebrates (including humans). Bulk feeders ingest fairly large pieces of food and some, like the great blue heron, swallow their food whole. Other bulk feeders use tentacles, pincers, claws, fangs, or jaws and teeth to kill prey, to tear off pieces of meat or vegetation, or to take in mouthfuls of animal or plant food.
What is intracellular digestion?
In its broadest sense, intracellular digestion is the breakdown of substances within the cytoplasm of a cell. For example, following phagocytosis, the ingested particle (or phagosome) fuses with a lysosome containing hydrolytic enzymes to form a phagolysosome; the pathogens or food particles within the phagosome are then digested by the lysosome’s enzymes.
Intracellular digestion can also refer to the process in which animals that lack a digestive tract bring food items into the cell for the purposes of digestion for nutritional needs. This kind of intracellular digestion occurs in many unicellular protozoans, in Pycnogonida, in some molluscs, Cnidariaand Porifera. There is another type of digestion, called extracellular digestion. In amphioxus, digestion is both extracellular and intracellular.
What is extracellular digestion?
Extracellular digestion is a process in which saprobionts feed by secreting enzymes through the cell membrane onto the food.
The enzymes catalyse the digestion of the food into molecules small enough to be taken up by passive diffusion, transport or phagocytosis.
These nutrients are transferred into the blood or other body fluids. Since digestion occurs outside the cell, it is said to be extracellular.
It takes place either in the lumen of the digestive system, in a gastric cavity or other digestive organ, or completely outside the body.
Extracellular digestion is a form of digestion found in all saprobionticannelids, crustaceans, arthropods, lichens and chordates, including vertebrates.
How does human digestion work?
Food enters through the mouth.
Anylase, mucin and buffer act on it in the mouth.
Moves to stomach through the esophagus and stay there fore 2-6 hours.
Moves to small intestine. Cholecystokinin (CKK) releases enzymes and bile and this secretion releases sodium bicarbonate (from the pancreas).
Small intestine absorbs nutrients.
Moves into large intestine where most of the water is absorbed and some vitamins.
NOTE: Look at digestion process in text book, lecture notes are pretty useless for this and you’ll probably need to know this in more detail than the lecturer gave :(
