Bio-nutrition in humans(h) Flashcards
what are the different processes?
ingestion,digestion,absorption,assimilation
State the definitions of these processes.
ingestion:process in which food is taken into the body
digestion:chemical digestion and physical digestion
absorption:the process where digested food molecules are absorbed into body cells.
assimilation:absorbed food molecules are converted into new protoplasm or used to provide energy(crosses over to the circulatory system)
What are the 2 types of digestion? State the definitions.
chemical digestion: (breaking down of food) hydrolosis of large insoluble food molecules into smaller soluble molecules by enzymes.(enzymes)Optimum pH: mouth(pH 7), stomach(pH 2), small intestine(pH 8). Optimum temperature:37.5 degrees.
physical digestion: physically breaking up food into smaller pieces which increases the surface area to volume ratio of food, so that enzymes can digest the food more efficiently. e.g chewing, emulsification, churning.
what processes happen in the mouth?
chemical digestion: salivary amylase catalyses the breakdown of starch into maltose.
physical digestion:chewing of food by teeth, physically breaking down food into smaller pieces. smaller pieces of food have a larger surface area to volume ratio, which allows the salivary amylase to digest starch more efficiently. The tongue functions to mix food with saliva and shapes it into balls called boli.
what do the salivary ducts secrete?
they secrete saliva into the buccal cavity and mouth, which contains salivary amylase.
What does the epiglottis do?
It functions to prevent food from entering the trachea by closing the opening of the trachea and prevents choking.
How does the oesophagus move food to the stomach?
peristalsis .It is the rhythmic wave-like contractions of the muscles to mix and propel the food along gut.
which muscles play a part in peristalsis?
longitudinal muscles(on the outer side of the gut wall)
circular muscles(on the inner side of the gut wall)
How do they work together to carry out peristalsis?
the longitudinal muscles are antagonistic, one set of muscles relax, the other set of muscles of muscles contract. When the circular muscles contract, the longitudinal muscles relax. As a result, the wall of the gut constricts and becomes narrower and longer. The food is pushed forward. When the longitudinal muscles contract, the circular muscles relax. The gut dilates, that is, it becomes wider and shorter. This widens the lumen for food to enter.
What kind of digestion occurs in the stomach?how long is food stored in the stomach?
protein digestion.3-4 hours.
What do the muscular walls secrete and what do they contain?
the walls contain gastric glands that secrete gastric juices. It contains inactive pepsinogen , hydrochloric acid and mucus.
Where is the pyloric sphincter located?What is its function?
it is located at the place where the stomach joins the small intestine. When rings contract, entrance to small intestine closes. When rings relax, entrance opens allowing food to pass from the stomach to the small intestine.
What is the kind of physical digestion happens in the stomach?
Churning. Churning of the stomach causes food to breakdown into even smaller pieces, churning also mixes the food with gastric juice.
what is chyme?
It is the mixture of ingested food and gastric juice.
Why is pepsinogen inactive?
it prevents the pepsin from digesting cells that secrete the enzyme.
What is the function of the hydrochloric acid in the stomach?
-kills bacteria ingested with food
-stops the action of salivary amylase by denaturing it.
-activates the inactive pepsinogen into pepsin
-creates an acidic environment which is the optimum pH for pepsin.
what is pepsin?
it is a type of protease enzyme that catalyses the digestion of protein into polypeptides.
where does the digestion and absorption take place in the small intestine?
duodenum:most of the digestion occurs
jejunum and ileum: mainly absorption of digested food
what are the chemical secretions in the duodenum and what do they contain?
pancreatic juice:pancreatic amylase, trypsin( a protease), pancreatic lipase
intestinal juice: maltase, sucrase, lactase, lipase, erepsin, end enterokinase
bile:produced in the liver and stored in the gall bladder.
what is bile? Does the temperature affects its function? What is its function
No.it is not an enzyme thus it is not involved in chemical digestion, only physical digestion. It emulsifies fat into fat droplets. This increases surface area to volume ratio of fats, increases the digestion of of fats by the enzyme lipase.
What adaptations does the small intestine have to increase rate of absorption?
- the inner walls of the small intestine is highly folded.
- the folds are lined with multiple finger-like projections called villi.
- small intestine is long enough to provide sufficient time for absorption.
- epethelial cell of the villi have numerous microvilli on their surface.
- epthelium of villi is 1 cell thick to allow for rapid absorption.
- Absorbed substances that enter the lacteal and blood capillaries are
constantly transported away, maintaining a steep concentration gradient
between the lumen and villi to maximise diffusion rate of digested
substances into villi.
what does the lacteal of the villi do?
Glucose and amino acids diffuse into blood capillaries of villi to be
transported to the liver.
Glycerol and fatty acids diffuse into the epithelial cells of villi, where they
reform into triglycerides, then enter the lacteal as fat globules.
what happens in the liver?
glucose is used as a source of energy.it is assimilated,then oxidised during tissue respiration to release energy for vital activities of the cells.the excess glucose is returned to the liver and stored as glycogen. A hormone called insulin is secreted by the islets of langerhaans in the pancreas, and stimulates live cells to convert excess glucose to glycogen.A hormone called glucagon is secreted by the islets of langerhaans in the pancreas, which converts the sored glycogen into glucose, which is then transported by the body to the cells.
what are amino acids used for?
The new protoplasm is used for the growth and repair of worn-out parts of the body and also used to form enzymes and hormones.
what is the hepatic vein, hepatic artery and hepatic portal vein?
hepatic vein:remaining glucose and amino acids leave liver to be distributed around the body, there is a high concentration of urea.(glucose+amino acids are of a normal concentration). Hepatic artery: oxygenated blood from the heart(glucose+amino acids are of low concentration). Hepatic portal vein:from the small intestine(nutrient rich, glucose +amino acids are of high concentration.) ps remember to refer to diagram on the notes.
what is the function of fats?
-used to build protoplasm
-when glucose is in short supply, fats are broken down to provide the energy for vital activities of the body.
-excess fat is stored in tissue called adipose tissues. They protect hearts and kidneys by acting as shock absorbers.
Functions of liver
Bile production
Iron storage
Glucose regulation
DeToxification
Amino acids –> Urea (Deamination)
Protein synthesis
BIGTAP
for diabetes,why is there weight loss?
-lack insulin thus cells can’t take glucose in
-cells don’t get enough energy and start to burn up fat and muscle reserves for energy instead.
elaboration for blood glucose concentration:
insulin is secreted when blood glucose concentration is high, glucagon is secreted when blood glucose concentration is low.
elaboration of deamination of amino acids:
excess amino acids that can’t be stored in the liver is transported to the liver and converted to urea in deamination. It is a process in which amino groups are removed from amino acids and converted to urea.(look at diagram in notes)
elaboration of production of bile:
stored in gall bladder temporarily.
elaboration of iron storage:
worn out cells are destroyed by the spleen(a gland found near the liver). haemoglobin is brought to the liver, the liver breaks down the haemoglobin and stores the iron released.bile pigments are formed in the break down of fat.
elaboration of protein synthesis:
it synthesises proteins found in blood plasma from amino acids in the diet.plasma proteins include prothrombin and fibrinogen, essential in the clotting of blood.
elaboration on detoxification:
the process of converting harmful substances into harmless ones through a process called detoxification. alcohol is converted into acetaldehyde(harmless, can be converted into glucose as a source of energy).
the effects of excessive consumption of alcohol
-reduced self control
-reduced reaction time, increased reaction speed
-slows down brain function:slurring of speech, breathing and heart rate slows down
-liver cirrhosis
-high blood pressure
-loss of muscle tissue
-greater chance of infection
-nausea
-brain injury
what if the gall bladder is removed?
-less bile secreted
-less emulsification, slow digestion of fats by lipase.
must reduce fat intake and eat smaller meals with more protein.
why do the fatty acids and glycerol diffuse instead of diffusing as fats?
Fatty acids and glycerol diffuse into the lacteal and recombine to form oil droplets(liquid fat transports hormones/vitamins that are oil based)
Explanation
-fats too big to pass through walls
-fats digested into fatty acids and glycerol,small enough to pass through
-recombine into fats
