Nutrients in humans Flashcards
Define digestion and absorption [6]
Digestion - Digestion is the process where large, insoluble molecules are broken down to small, soluble molecules [1] that can be absorbed into the body cells. Digestion can be a physical process which involves mechanical breakup of food into smaller pieces to increase surface area to volume ratio for faster chemical digestion. [1] Digestion can be a chemical process which involves the breaking of bonds in molecules which involves enzymes. [1]
Absorption - Products of digestion such as glucose and amino acids [1] will be taken into the bloodstream [1] through the villi by processes active transport and diffusion. [1] digested fats is absorbed via lacteal through diffusion.
Describe the digestion and absorption processes of protein in mammals [6]
physical digestion in the mouth and stomach to break up into smaller pieces to increase surface area to volume ratio for faster chemical digestion by enzymes
stomach; pepsin; digest protein into short polypeptides
trypsin from pancreas digest remaining protein into short polypeptides
erepsin / peptidase from small intestine digest short polypeptides into amino acids Absorption of a.a in the small intestine into blood stream
via active transport and diffusion
Describe the digestion and absorption processes of starch in mammals [6]
physical digestion in the mouth to break up into smaller pieces to increase surface area to volume ratio for faster chemical digestion by enzymes
mouth; salivary amylase; digest some starch into maltose
pancreatic amylase from pancreas digest remaining starch into maltose in the
small intestine
maltase from small intestine digest maltose into glucose
Absorption of glucose in the small intestine into blood stream
via active transport and diffusion
Describe the digestion and absorption processes of fats in mammals [6]
physical digestion in the mouth to break up into smaller pieces to increase surface area to volume ratio for faster chemical digestion by enzymes
bile synthesized by liver and secreted by gall bladder for emulsification of fats from big oil droplet to smaller oil droplets [1] to increase SA to vol ratio for faster rate of chemical digestion by lipases [1]
pancreatic lipase from pancreas and intestinal lipase digest fats into glycerol and fatty acids in the small intestine
Absorption of fatty acids and glycerol into epithelial cells in the small intestine[1], combine to fat globule and absorbed into lacteal via diffusion [1]
A sample of the juice taken from the stomach after meal is tested with benedict, biuret, iodine and ethanol emulsion test. Describe and explain the possible results of the four food tests on the sample. [4]
Benedict – remain blue / green precipitate; very little maltose is present as stomach does not have carbohydrase to digest starch to simple sugars
biuret – violet; some protein still present has it is not completely digested in the stomach by pepsin.
iodine - blue-black; most of starch still present as stomach does not have carbohydrase to digest starch to simple sugars
ethanol emulsion test – white emulsion; fat is not digested in stomach as it does not have lipase.
In the gastric bypass surgery, a portion of the stomach is removed to help patient in controlling obesity. Describe and explain the possible implication of the surgical procedure and changes to the patient’s lifestyle as a result. [4]
Protein digestion will be less efficient/less protein digested as there’s less pepsin in the stomach to digest proteins to polypeptides[1] patient has to decrease intake of proteins/increase intake of amino acids that is readily absorbed [1]
Smaller stomach not able to store as much food / stomach stores less food[1] patient has to take frequent small meals [1]
less gastric juice thus less HCL to activate pepsinogen to pepsin for protein digestion [1] patient has to decrease intake of proteins/increase intake of readily absorbed amino acids [1]
Describe the role of bile in digestion process [3]
Physical digestion in emulsification of fats to breakup big fat globules into smaller fat globules
To increase surface area to volume ratio for faster chemical digestion by lipase [1] into glycerol and fatty acids [1]
Gall stones is a medical condition in which it can block the bile duct and the pancreatic duct, preventing the release of the bile juice and pancreatic juice into the duodenum. Describe and explain the possible impact on nutrient digestion if this was to happen. [5]
Pancreatic duct:
Absence of lipase/No lipase to digest fat into fatty acids and glycerol [1]
Absence of trypsin/No trypsin to digest proteins into short polypeptide [1]
Absence of pancreatic amylase/no pancreatic amylase to digest starch into maltose [1]
Less overal digestion of foods , less absorption of digested nutrients thus lead to malnutrition.
Bile duct:
No/less emulsification of fat globules to smaller fat globules, thus reduce surface area to volume ratio[1] decreasing the rate of fat digestion by lipase into fatty acids and glycerol[1]
OR
Hydrochloric acid from gastric juice might burn the internal lining of the duodenum as it is not neutralised by the alkaline pancreatic juice and bile [1] intestinal and pancreatic digestive enzymes will denature in acidic pH, thus unable to digest nutrients, resulting in indigestion. [1]
Explain how the small intestine is adapted in absorption of digested nutrients in mammals [6]
long; to increase time for more efficient absorption of digested nutrients
inner wall is folded; to increase surface area for faster absorption of digested
nutrients
presence of numerous finger-like projections called villi on the folds; increase surface area for faster absorption of digested nutrients
wall of each villus made of one layer of epithelial cells to shorten distance for faster diffusion and active transport.
presence of lacteal / lymphatic capillaries in villus for faster absorption of fats via diffusion
rich in blood capillaries for faster absorption of glucose and amino acids via diffusion and active transport
continuous blood flow to maintain steep concentration gradient between blood and lumen of intestines for faster diffusion of digested nutrients into blood capillaries
Explain how the villus is adapted in absorption of digested nutrients in mammals [4]
wall of villus made of one layer of epithelial cells to shorten distance for faster diffusion
presence of microvilli on epithelial cells to further increase surface area to volume ratio for faster absorption of digested nutrients
presence of lacteal/ lymphatic capillaries in villus for faster absorption of fats via diffusion
rich in blood capillaries for faster absorption of glucose and amino acids via diffusion and active transport
continuous blood flow to maintain steep concentration gradient between blood and lumen of intestines for faster diffusion of digested nutrients into blood capillaries
Describe the functions of the liver in carbohydrate metabolism. [6]
Maintain constant blood glucose level in the blood plasma
increase blood glucose level above normal receptor Islet of Langerhans in the pancreas get stimulated corrective mechanism to release more insulin stimulate the liver and skeletal muscles excess glucose convert into glycogen to be stored blood glucose level back to normal [3]
decrease blood glucose level below normal receptor Islet of Langerhans in pancreas get stimulated corrective mechanism for more glucagon production stimulate liver stored glycogen convert back into glucose to be released into blood stream blood glucose level back to normal [3]
Describe the fate of amino acids in the liver. [4]
Amino acids used to synthesize plasma proteins in the liver
Excess amino acids goes through deamination.
The amino group will be converted to urea to be excreted out of the body
The carbon residue will be converted into glucose and then into glycogen to be stored in the liver
Describe the long term and short term effect of excessive alcohol consumption on the human body. [6]
Short term
Memory loss; Longer reaction time; Reduced self – control, hang-over
Long term
Liver cirrhosis; gastric ulcers; Addiction leading to withdrawal symptoms ; obesity ;
Describe the functions of the liver [5]
Produces bile which emulsifies fats in physical digestion [1]
breaks down the haemoglobin to form bile pigments and stores the iron
released. [1]
Excess amino acids are deaminated where their amino groups are removed and
converted to urea for excretion. [1]
Detoxification of harmful substances such as alcohol by alcohol dehydrogenase
and breaking them down into less harmful substances [1]
Regulates blood glucose level with the aid of insulin and glucagon [1]
Describe the parts played in the digestion and assimilation of food by the pancreas and liver. [6]
1) The pancreas
Digestive juice to small intestine: lipase (fats to glycerol & f.a) trypsin (protein to short polypeptides), amylase (starch to maltose)
Islet of Langerhans secrete insulin to regulate blood glucose level by stimulating liver / skeletal muscles to take up excess glucose and convert to glycogen
Islet of Langerhans secrete glucagon stimulating liver to convert stored glycogen to glucose when starving.
2) The liver
Bile to emulsify fats to increase SA / vol ratio for faster chemical digestion by lipase.
Regulate blood glucose level by stimulated by insulin to take up excess glucose and convert to glycogen, or stimulated by glucagon to convert stored glycogen back to glucose.
Deamination of excess a.a to form urea to be excreted.
