Adaptations For Nutrition Flashcards
What are autotrophic organisms?
Organisms that synthesise their own food their own food (complex molecules) from simple inorganic raw materials (light or chemical energy)
Define photoautotrophic
- Organisms that use light as the source and perform photosynthesis
- They are green plants, some protoctista and some bacteria
- This type of nutrition is described as holophytic
Define chemoautotrophic organisms
- Use the energy from chemical reactions
- These organisms are all prokaryotes and they perform chemosynthesis
- This is less efficient than photosynthesis and the organisms that do this are no longer dominant life forms
Define heterotrophic
What do heterotrophic organisms eat?
- organisms that cannot make their own food and consume complex organic molecules produced by autotrophs, so are consumers
- they eat autotrophs or organisms that have, themselves, eaten autotrophs
- dependent on producers for food
Define saphrotrophic (saprobiont)
- how do they absorb soluble products?
- An organism that derives energy and raw materials for growth from the extracellular digestion of dead or decaying material
- they absorb the soluble products of digestion across their cell membranes by diffusion and active transport
Define parasitic
- obtaining nutrition from another living organism, the host
- endoparasites= live in the body of the host
- ectoparasites= live on its surface
E.g. Tapeworm
Define holozoic
- nutrition used by most animals
- They ingest food, digest it and egrets the indigestible remains
- digested material is absorbed into the body tissues in a specialised digestive system
- animals that eat plants are herbivores
- animals that eat other animals are carnivores
Explain nutrition in unicellular organisms
- animal-like protoctista, such as Amoeba use holozoic nutrition
- single celled organisms with large surface area to volume ratio
- They obtain all the nutrients they need by diffusion, facilitated diffusion or active transport across the cell membrane
- they take in larger molecules and microbes by endocytosis, into food vacuoles, which fuse with lysosomes, and their contents are digested by lysosomal enzymes
- the products of digestion are absorbed into the cytoplasm and indigestible remains are whetted by exocytosis
Nutrition in multicellular organisms
- hydra live in fresh water, attached to leaves or twigs by a basal disc
- 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 through the mouth into the hollow body cavity
- Endodermal cells secrete protease and lipase, through not amylase, and they prey is digested extracellularly
- The products of digestion are absorbed into the cells and indigestible remains are egested through the mouth
What is a tube gut?
- Many animals have a distinct anterior and posterior end and a digestive system that is a tube with two openings
- Food is ingested at the mouth and indigestible wastes are egested at the anus
- More complex animals have a more complex gut, including different sections with different roles
Why must food be digested?
Because the molecules are:
- 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
Where does digestion and absorption occur?
Why?
- In a long, hollow, muscular tube
- It allows the movement of its contents in one direction only
- Each section is specialised and performs particular steps in the processes of mechanical and chemical digestion and absorption
How is the food propelled along the gut?
By peristalsis
What are the 4 main functions of the human gut?
- INGESTSION: taking food into the body through the mouth
- DIGESTION: the breakdown of large insoluble molecules into soluble molecules that are small enough to be absorbed into the blood
- ABSORPTION: The passage of molecules and ions through the gut wall into the blood
- EGESTION: the elimination of waste nor made by the body, including food that cannot be digested e.g. Cellulose
Functions of parts of the digestive system: Mouth
- ingestion
- digestion of starch
Functions of parts of the digestive system: oesophagus
- carriage of food to stomach
Functions of parts of the digestive system: stomach
- digestion of protein
Functions of parts of the digestive system: duodenum
- digestion of carbohydrates, facts and proteins
Functions of parts of the digestive system: ileum
- digestion of carbohydrates, fats, proteins
- absorption of digested food
Functions of parts of the digestive system: colon
- absorption of water
Functions of parts of the digestive system: rectum
- storage of faeces
Functions of parts of the digestive system: anus
- egestion
Define mechanical digestion
Define chemical digestion
- mechanical digestion: cutting and crushing by teeth and muscle contractions of the gut wall, increases the surface area over which enzymes can act
- Chemical digestion by the secretion of digestive enzymes. Bile and stomach acid contribute to chemical digestion
Structure of the gut wall:
- throughout its length, the gut wall consists of four tissue layers surrounding a cavity, the lumen of the gut
- The proportions of the different layers of the gut wall vary, depending on the function of the part of the gut
The structure of the gut wall: serosa
- 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 other abdominal organs
The structure of the gut wall: muscle
- the muscle comprises two layers in different directions, the inner circular muscles and outer longitudinal muscles
- They make coordinated waves of contractions, peristalsis
- behind the ball of food, circular muscles contract and longitudinal muscles relax, pushing the food along
The structure of the gut wall: submucosa
- the submucosa is connective tissue containing blood and lymph vessels, which remove absorbed products of digestion, and nerves that co-ordinate peristalsis
The structure of the gut wall: mucosa
- The mucosa is the innermost layer and lines the gut wall
- It’s epithelium secretes mucus, lubricating and protecting the mucosa
- In some regions of the gut, it secretes digestive juices and in others, absorbs digested food
Absorption of nutrients by gut epithelium cells is only possible if …
- macromolecules i.e. Carbohydrates, fats and proteins, are first digested into smaller molecules
Different enzymes digest the different food molecules and usually
More than one type is needed for the complete digestion of a particular food
Digestion of carbohydrates
- polysaccharides are digested into disaccharides and then monosaccharides
- Amylase hydrolysed starch to the disaccharide maltose and maltase digests maltose to the monosaccharide, glucose
- Similarly, sucrase digests sucrose and lactase digests lactose
- The general name for carbohydrate-digesting enzyme is carbohydrase
How are proteins digested
- Proteins are extremely large molecules
- They are digested into polypeptides, then dipeptides and then amino acids
- the general name for protein digestion enzymes are proteases and peptidase
- endopeptidases hydrolyse peptide bonds within the protein molecule, then exopeptidases hydrolyse peptide bonds at the ends of these shorter polypeptides
What enzyme breaks down fats and what does it produce?
Fats are digested to fatty acids and monoglycerides by lipase
Regional specialisation of the mammalian gut: buccal cavity
What is the effect of chewing the food?
What does saliva contain?
What is the function of Mucus?
mechanical digestion begins in the mouth or buccal cavity, where food is mixed with saliva by the tongue and chewed with the teeth.
- chewing increases the surface area of the food, giving enzymes more access
- amylase, beginning the digestion of starch into maltose
- HCO3- and CO3- 2- Ions, so the pH in the mouth is slightly alkaline, the optimum for amylase
- Mucus, lubricating the foods passage down the oesophagus
Regional specialisation of the mammalian gut: oesophagus
- has no role in digestion, but carries food to the stomach
- its wall shows the tissue layers in their simplest forms
Regional specialisation of the mammalian gut: the stomach
What keeps food in the stomach?
What is the volume of the stomach?
- Food enters the stomach and is kept there by the contraction of two spincters, or rings of muscles
- the stomach has a volume of 2dm³ and food may stay there for several hours
- the stomach walls contract rhythmically and mix the food with gastric juice secreted by glands in the stomach wall
Where is gastric juice secreted?
- from glands in depressions in the mucosa, called gastric pits