ch6 nutrition in humans Flashcards
holozoic nutrition
-take in complex food and digest inside the body
-ingestion, digestion, absorption, assimilation, egestion
saprophytic nutrition
-fungi and bacteria (saprophytes)
-break down food outside the body
-absorb soluble nutrients into the body
-digestion, absorption, assimilation
parasitic nutrition
-parasites
-live on or inside body or other organisms and obtain food from them
-absorption, assimilation
5 main processes of human nutrition
-ingestion: take in food through mouth
-digestion : food is broken down into small soluble food molecules
-absorption: food molecules enter circulatory system
-assimilation: absorbed food molecules are taken up by cells for metabolism
-egestion: undigested and unabsorbed materials are removed as faeces
state of food throughout the alimentary canal
mouth cavity: solid
stomach: semi-solid
duodenum: thick liquid
ileum: thinner liquid
colon: semi-solid
rectum: harder pellet
4 types of teeth
-incisor: for biting and cutting food, chisel-shaped with flat sharp edges, one root
-canine: tearing flesh, pointed and curved, one root
-premolar: crushing and grinding food, broad top with cusps, one or two roots
-molar: crushing and grinding food, broad top with cusps, two or three roots
milk teeth
-dental formula: 2102/2102
-total number of teeth: 20
permanent teeth
-dental formula: 2123/2123
-total number of teeth: 32
structure of teeth and uses
enamel:
-outermost layer, non-living, made mainly of calcium salts
-hardest tissue in our body -> protects the tooth fro wearing down as a result of chewing
cementum:
-attaches the tooth to the jawbone through the periodontal membrane
dentine:
-bone-like substance, large amt of calcium salts
-living tissue containing living cytoplasm
pulp cavity:
-contain living cells, blood vessels, nerve fibres
-blood vessels supply oxygen and nutrients, and remove wastes
-nerve fibres detect temperature and pressure
physical and chemical digestion in the mouth cavity
physical: chewing (mastication)
chemical: catalysed by enzyme in saliva
physical and chemical digestion in stomach
physical: churning
chemical: catalysed by enzyme in gastric juice
physical and chemical digestion in small intestine
physical: emulsification by bile
chemical: catalysed by enzymes in pancreatic juice and enzymes on intestinal wall
mouth cavity
substances in saliva and uses
substances in saliva:
-salivary amylase: carbohydrase, catalyses breakdown of starch into maltose
-mucus: sticky, bind food particles together, moistens and lubricates the food -> easier to chew and swallow
-water: dissolves soluble substances -> taste food
swallowing
-tongue rises to push the bolus towards the pharynx
-soft plate moves up to prevent the bolus from entering the nasal cavity
-larynx rises so that the epiglottis covers the opening to the trachea
-bolus enters oesophagus
peristalsis
-moving food from the oesophagus to rectum
-muscles layers in walls of oesophagus contract alternatively -> wave-like movement to push the food down
stomach
substances in gastric juice and uses
pepsin:
-protease which catalyses the breakdown of proteins into peptides
-acidic medium
hydrochloric acid:
-provides an acidic medium for action of pepsin
-kills most bacteria in food
-denaturing of protein ingested
mucus:
-protects the stomach wall from being damaged by pepsin or hydrochloric acid
small intestine
substances in bile and uses
bile:
-green alkaline fluid produced by liver
-temporarily stored in gall bladder
-released through bile duct
-no digestive enzyme
bile contains:
bile salts:
-emulsify lipids into small droplets (physical digestion)
-facilitates chemical digestion by increasing surface area of lipids for lipase to act on
bile pigments:
-not part of digestion
-waste product formed from breakdown of haemoglobin
-excreted as faeces
sodium hydrogencarbonate:
-neutralises the acidic chyme -> protect the small intestine from being damaged
-provides alkaline medium
small intestines
substances in pancreatic juice and uses
pancreatic juice:
-produced by pancreas
-released through pancreatic duct
pancreatic juice contains:
pancreatic amylase:
-carbohydrase which catalyses the breakdown of remaining starch into maltose
- starch+water -pancreatic amylase-> maltose
pancreatic lipase:
-catalyses breakdown of lipids into fatty acids and glycerol
- lipids+water -pancreatic lipase-> fatty acids+glycerol
proteases:
-catalyses the breakdown of proteins into peptides, and peptides into amino acids
- proteins+water-proteases->peptides
- peptides+water-proteases-> amino acids
sodium hydrogencarbonate:
-neutralises acidic chyme
-provides alkaline medium
small intestine
intestinal juice
intestinal juice:
-produced by glands in wall of small intestine
-slightly alkaline
-mainly consists of water, mucus, sodium hydrogencarbonate
small intestine
epithelium
epithelium of small intestines have specialized cells that have enzymes embedded in their cell membranes
enzymes:
carbohydrases:
-catalyses breakdown of disaccharides into monosaccharides
-maltose -maltase-> glucose
- sucrose-sucrase-> glucose+fructose
- lactose-lactase-> glucose+galactose
proteases:
-catalyses breakdown of peptides into amino acids
structure of small intestine
wall:
-circular muscles and longitudinal muscles are present in the wall
-inner wall is highly folded
villi:
-finger-like projections
-each villus has lacteal
-lacteal is surrounded by network of capillaries
epithelium:
-one-cell thick
-large number of microvilli
uses of liver
carbohydrate metabolism:
-main site for storage of glycogen
-regulating blood glucose level
-after a meal: blood glucose level rises -> liver converts glucose to glycogen -> glycogen is stored in liver
-glucose level falls between meals: glucose in blood is used by cells in respiration -> liver converts stored glycogen back to glucose and releases into blood
uses of liver
lipid metabolism
-converts excess carbohydrates and amino acids into lipids -> transported and stored in adipose tissue
uses of liver
amino acid metabolism
-excess amino acids are broken down through deamination
-amino group is removed and converted into urea -> excreted in urine
-remaining part is converted into carbohydrates and lipids
-synthesises non-essential amino acids
