Flashcards
Module: Adaptations for nutrition
Q: Define autotrophic nutrition:
Organisms that make their own food from the simple, inorganic raw materials,
carbon dioxide and water.
This can be either photoautotrophic or chemoautotrophic.
Q: Define heterotrophic nutrition:
Organisms cannot make their own food and consume complex organic molecules
produced by autotrophs.
Q: Describe and explain the types of heterotrophic nutrition:
1. Saprotrophic: organisms that have no specialised digestive system and they secrete
enzymes onto food material outside the body for extracellular digestion. They
absorb the soluble products of digestion across their cell membranes by diffusion
and active transport.
2. Parasitic: an organism that obtains its nutrition from living in or on a host, which is
harmed.
3. Holozoic: nutrition involves the processes of ingestion, digestion, absorption,
assimilation and egestion. The food is processed in a specialised digestive system.
Herbivores, omnivores and carnivores are examples. Detritivores feed on dead and
decaying material.
Q: Describe the nutrition of unicellular organisms such as Amoeba.
Use holozoic nutrition.
Single celled and have a large SA:Vol ratio.
Obtain nutrition via diffusion, facilitated diffusion or active transport across the
membrane.
Take in larger molecules and microbes by endocytosis, into food vacuoles, which
fuse with lysosomes, and their contents are digested by lysosomal enzymes.
Describe the nutrition of multicellular organisms such as Hydra:
Diploblastic, comprising of two layers of cells, the ectoderm and endoderm,
separated by a jelly layer containing a network of nerve fibres.
It Is cylindrical and has tentacles at the top surrounding its mouth, the only body
opening.
When hungry, it extends its tentacles and when small organisms brush against them,
their stinging cells discharge and paralyse the prey. The tentacles move the prey into
the hollow body cavity.
Endodermal cells secrete protease and lipase, though not amylase, and the prey is
digested extracellularly. The products of digestion are absorbed into the cells and
indigestible remains are egested through the mouth.
Q: Why does food need to be digested?
Food is insoluble and too big to cross membranes and be absorbed into the blood.
, Polymers, and must be converted to their monomers, so they can be rebuilt into
molecules needed by body cells.
Q: What are the functions of the gut?
1. Ingestion
2. Digestion: either by mechanical or chemical\
3. Absorption
4. Egestion
Q: Describe the structure of the gut wall:
1. The outermost layer, the serosa, is tough connective tissue, protecting the gut wall.
The gut moves while processing food and the serosa reduces friction with abdominal
organs.
2. The muscle comprises two layers in different directions, the inner circular muscles
and the outer longitudinal muscles. They make coordinated waves of contractions,
peristalsis. Behind the ball of food (bolus), circular muscles contract and longitudinal
muscles relax, pushing the food along.
3. The submucosa is connective tissue containing blood and lymph vessels, which
remove absorbed products of digestion, and nerves that coordinate peristalsis.
4. The mucosa is the innermost layer and lines the gut wall. Its epithelium secretes
mucus, lubricating and protecting the mucosa.
Q: Roles of the Buccal cavity?
Mechanical digestion begins in the mouth, where food is mixed with saliva by the
tongue and chewed with the teeth. The foods surface area increases, giving enzymes
more access.
Saliva is a water secretion containing: Amylase (starch into maltose), mucus
(lubrication down the oesophagus), as well as, HCO3- and CO32- ions (so pH is slightly
alkaline, the optimum for amylase.)
Q: Roles of the oesophagus:
No role in digestion, but carries food to the stomach by peristalsis.
Q: Roles of the stomach:
Food enters the stomach and is kept there by the contraction of two sphincters, the
pyloric and cardiac.
The stomach wall muscles contract rhythmically and mix the food with gastric juice,
secreted by glands in the stomach.
Gastric juice is secreted from glands in depressions of the mucosa, called gastric pits.
It contains:
1. Peptidases, secreted by zymogen, or chief cells, at the base of the gastric pit.
Pepsinogen, an inactive enzyme, is secreted and activated by H+ ions to pepsin, an
endopeptidase which hydrolyses proteins to polypeptides.
