nutrition in humans Flashcards
what is nutrition
the process of obtaining food to release energy for growth, repair,and maintenance of the body
define ingestion
when food is taken into the body
define absorption
when digested food molecules are absorbed into the cells
define assimilation
when absorbed food molecules are converted into new protoplasm or used to provide energy
define egestion
the process of removing undigested food materials from the body
define peristalsis
the rhythmic, wave like muscular contractions in the wall of the alimentary canal
define deamination
the process by which amino groups are removed from amino acids and converted to urea
define detoxification
the process of converting harmful substances into harmless ones
describe the functions of the liver (4 functions)
- regulation of blood glucose concentration
- production of bile
- deamination of amino acids
- breakdown of alcohol
describe the structure of the mouth
salivary glands in the mouth secretes saliva, which contains salivary amylase to digest starch into maltose
saliva also softens the food
the chewing action of the teeth breaks up the large food pieces into smaller food pieces to increase Sa:V to speed up enzyme reaction.
the tongue helps to mix the food with the saliva. it also rolls the food into boli for swallowing
what is the pH of the mouth, stomach, and small intestine (duodenum)
7
1-2
8-9
describe digestion of starch
starch is digested by salivary amylase to maltose
maltose is digested by maltase to get glucose
describe the digestion of protein
protein is digested by pepsin into polypeptide
polypeptide is then digested by peptidase into amino acids
describe the digestion of fat
fat is emulsified by bile into smaller fat droplets. the smaller fat droplets are then digested by intestinal lipase into 3 fatty acids and 1 glycerol
what is the structure of the oesophagus
it is a narrow, muscular tube that extends to the stomach.
the muscles push food along the gut by peristalsis,
the rhythmic, wave-like muscular contractions in the wall of the alimentary canal. peristalsis is caused by the alternate contractions of the circular and longitudinal muscles in the walls
how does digestion take place in the stomach
gastric juice contains hydrochloric acid and pepsin.
peristalsis in the stomach walls break up food and mix the food with gastric juice.
pepsin found in gastric juice digests protein. its optimum ph is in the stomach as it is acidic
what is the structure of the stomach
a distensible muscular bag with a pyloric sphincter located at the place where the stomach joins the small intestine. the ring contracts and relaxes to allow food to pass from the stomach into the small intestine
the muscular walls contain gastric glands that secrete gastric juice.
gastric juice contains hydrochloric acid and pepsin.
the stomach is lined with a protective layer of mucus to protect frm hydrochloric acid
(peristalsis in the stomach walls break up food and mix the food with gastric juice.
pepsin found in gastric juice digests protein. its optimum ph is in the stomach as it is acidic)
what is the purpose for gastric juice in the stomach
gastric juice contains dilute hydrochloric acid (pH2), which stops action of salivary amylase by denaturing it, activates pepsinogen into pepsin, provides an acidic medium for pepsin action, and kills potentially harmful microorganisms in food.
what is the structure of the small intestine
it is a 6m long coiled up tube with 3 segments (duo,jeje,ile)
with folded inner walls with finger-like projections called villi
how does digestion take place in the small intestine?
chyme entering the duodenum stimulates:
the pancreas to secrete pancreatic juice
the gall bladder to release bile
the epithelial cells in the small intestine to produce intestinal juice.
what enzymes does pancreatic juice contain
pancreatic amylase, trypsin, and pancreatic lipase
what enzymes does the small intestine produce
maltase, peptidase, intestinal lipase
why is the optimal pH for small intestine 8-9
it stimulates the pancreas to secrete pancreatic juice, and the gall bladder to release bile.
the alkaline fluids neutralise the acidic chyme
and provide a suitable environment for the action of the pancreatic and intestinal enzymes
what does bile do
emulsifies fat into smaller fat droplets, increasing sa:v for lipase to act on, speeding up the rate of fat digestion
what does bile do
emulsifies fat into smaller fat droplets, increasing sa:v for lipase to act on, speeding up the rate of fat digestion
how is the small intestine adapted for absorption?
- thin walls to speed up absorption of digested food substances
- large surface area for absorption
the small intestine is long to ensure sufficient time for absorption
its inner surface is folded
the folds have villi
the epithelial cells of villi have microvilli - digested food substances continually transported away
by capillaries and lacteals in villi, it maintains a concentration gradient for absorption
describe the structure of a villi
small finger-like projections on the numerous folds on the inner wall. in each villus is a lymphatic capillary surrounded by blood capillaries. lymphatic capillary transports fats while blood capillaries transport sugars and amino acids away from the intestine
how is the concentration gradient of the absorption of digested food substances maintained
in each villus is a lymphatic capillary surrounded by blood capillaries. lymphatic capillary transports fats while blood capillaries transport sugars(glucose) and amino acids away from the intestine. the continual transport of digested food substances help to maintain the concentration gradient
what food substances are digested in the small intestine
sugars, amino acids, fatty acids, and glycerol
what does the large intestine do
absorbs water and mineral salts
what does the hepatic portal vein do
transports nutrient-rich blood from the small intestine to the liver
(mostly sugars and amino acids)
what does the hepatic vein do
distributes the remaining glucose and amino acids around the body
what is glucose used for in the body
glucose is used by cells for respiration to release energy
what are amino acids used for in the body
used by cells to form new protoplasm for growth and repair, and to form enzymes and hormones
explain how the liver regulates blood glucose concentration
the liver keeps the amount of glucose in the blood constant, esp after a heavy meal or after fasting.
when there is too much glucose in blood, insulin is secreted, which stimulates the liver cells to convert glucose into glycogen for storage, thus decreasing the blood glucose concentration
when there is too little glucose in the blood, glucagon is secreted and the liver converts glycogen to glucose to be released into the bloodstream, thus increasing glucose concentration in the blood
what happens to excess sugars and amino acids
most absorbed sugars are converted to glycogen and stored in liver
excess amino acids are deaminated
explain how the liver deaminates amino acids
the process where amino groups are removed from amino acids and converted to urea. urea is removed from the body in the unrine. the remains of the amino acids are converted into glucose in the liver. excess glucose is converted into glycogen
what is fat used for in cells
- synthesis of protoplasm (cell membranes)
- respiration for energy when glucose is insufficient
- excess fats are stored in adipose tissues
explain breakdown of alcohol in the liver.
the liver cells contain an enzyme called alcohol dehydrogenase, which breaks down alcohol into acetaldehyde, which can be broken down further to compounds that can be used in respiration to provide energy for cell activities
what are the effects of excessive consumption of alcohol on the digestive and nervous systems
excessive consumption could lead to liver cirrhosis.
a condition where liver cells are destroyed and unable to function, which can lead to liver failure and death
