Digestion Flashcards
what is digestion
a proccess in which large insoluble biological molecules are hydrolysed into smaller soluble molecules that can be absorbed across the cell membrane into the bloodstream
function of food biological molecules
provide cells with energy via respiration and to build other molecules for cell growth and repair
function of the mouth
contains teeth which break down food into smaller peices to increase SA:V
carb digestion begins here (amylase)
food is shaped into a bolus that can then travel own the oesophagus
function of the oesophagus
hollow tube with muscular walls for peristalsis to pass food down,
function of the stomach
protein digestion begins
glandular tissue produces enzymes
muscular tissue churns food -
acid helps to enable enzyme activity. (low ph is detrimental for many microorganisms that may be in food)
function of the small intestine
divided into 3 sections (duodenum, jejunum, ileum)
food passes through lumen
peristalsis occurs due to muscles on wall
carb, lipid and protein digestion all occur in the duodenum (enzymes produced in pancreas and here)
soluble food molecules absorbed into bloodstream by villi
ileum has villi - water absorbtion also occurs here
large intestine function
any water remaining in food that was not able to be digested is absorbed here
undigested food material (faeces) is stored in rectum and removed via anus
what type of enzymes are digestive enzymes and why
extracellular enzymes because work outside of cells eg. in blood
3 main types of digestive enzymes
carbohydrase protease
lipase
path of hydrolysis from starch
starch
amylase(mouth, pancreas and small intestine)
maltose
maltase (epethilial cell walls in small intestine)
glucose
why is maltase found in the cell wall of the small intestine epithelial cells
along with other disaccharidases ,
allows the absorbtion of monosaccharides back into the blood stream at epithelial cells
how is the lining of the small intestine adapoted
folded and microvilli present increasing the surface area
more dissacharides can be absorbed
lifecycle of protein digestion
protein (lumen of gut)
endopeptidase (lumen of gut)
polypeptides (lumen of gut)
exopeptidase
dipeptides (cells surface memb of epithelial cell )
dipeptidase (cells surface memb of epithelial cell )
amino acids (cells surface memb of epithelial cell )
what does endopeptidase do in the STOMACH
hydrolyses peptide bonds partially to create smaller protein chunks
enzyme is secreted with HCL to make stomach acid acidic
how is the acidic mixture of stomach acid neutralised
fluid secreted by the pancreas contains endopeptidase and exopeptidease
what does endopeptidase do
hydrolyse peptide bonds within polypeptide chains producing dipeptides
what does exopeptidase do
hydrolyse peptide bonds at the ends of polypeptide chains producing dipeptides
what happens when fatty liquid arrives in the small intestine
(bile)
bile which is made in the liver and secreted in the gall bladder
bile salts bind to the fatty liquid and breaks the fatty droplets into smaller ones via emulsification
increses surface area of fatty droplets so digestive enzymes can work
cycle of lipids
lipids
bile salts (occuring in small intestine)
emulsified lipids
lipase
fatty acids + glycerol
what is the practical for investigating how PH affects enzyme reaction rates
use of amylase to breakdown starch and iodine to indicate if the reaction has occured
use a continuous smpling method to monitor the progress on a spotting tile
investigating how PH affects enzyme reaction rates method
place iodine solution on each tile (orange brown solution)
label a test tube with the ph that will be tested for
put amylase into the test tube
add buffer solution to the test tube
in another test tube add starch to the amylase and buffer solution
start stopwatch and mix
after 10 seconds put a drop of solution onto the tile
if the tile goes blue black the starch is still present
wait 10 seconds and place another drop onto the tile
repeat every 10 seconds until all the starch has been hydrolysed so there is no colour change
limitations of the Ph affect on rate of reaction experiment
and solution
colour is subjective so use a colorimeter to distinguish if the solution is getting lighter
temperature may not be maintained - use a water bath at a controlled temperature
practicle for the affect of bile salts on enzyme reaction rates
bile salts aid the proccess of emulsification
binding to fat dropletes and breaking them into smaller fat droplets
can only act on the surface of the fat droplets so emulsification increases the surface area for lipase to act on
method of investigating the affect of bile salts on a reaction
lipase solution is mixed with lipids and bile salts and the rate of reaction is measured
do a control with just lipase and lipids
rate of reaction measeured by measuring PH level with a universal indicator
when the PH levels off , digestion of the substrate is complete
can be carried out with different concentrations of bile salts
where are the products of digestion absorbed
through the epithelial lining
where are specific amino acid cotransport proteins found
within the cell surface membrane of the epithelial cells in the ileum
how does the amino acid cotransport work
amino acids transported only when sodium ions are present
for every sodium ion, an amino acid is transported in
occurs by facilitated diffusion down the conc gradient
how is the concentration gradient maintained from the lumen into the ileum for amino acids
the concentration gradient is maintained as active transport of sodium ions into the blood
at what site are monosaccharides reabsorbed
sodium/ pottasium pump in the cell membrane of epithelial cells
how are monosaccharides absorbed
sodium ions and glucose ions are cotransported from the lumen into the epethilial cells by facilitated diffusion
glucose moleccules the facilitatedly diffuse into the capillary
how is conc grad maintained glucose
sodium ions actively being transported out of the epithelial cells into blood
what do the monoglycerides and fatty acids associate with phospholipids and bile salts to make
micelles
why are micelles needed
lipids are not very soluble so micelles aid the transport of these molecules to the epethilial cells
the micelles break down and add to a pool of lipids that are dissolved in the small intestine to free the molecules up so the lipids can enter the epethilial cells by diffusion
what type of diffusion for lipids
non soluble so simple
what happens to triglycerides
packaged into lipoproteins called chlomicrons
where they can enter lacteal ( al lymph vessel)
eventually enter blood stream
visking tubing practical method
Fill a section of Visking tubing with a mixture of starch and amylase solutions
Suspend the tubing in a beaker of water for a set period of time
Take samples from the liquid outside of the visking tubing at regular intervals and test for the presence of starch and glucose
Starch is tested for using iodine. A blue-black colour is produced in the presence of starch
Glucose is tested for using Benedict’s reagent. An orange-red precipitate is formed in the presence of glucose
The amylase present inside the visking tube digests and breaks down starch into glucose
Glucose is small enough to diffuse across the partially permeable membrane
Over time the concentration of glucose in the liquid outside the visking tube should increase as more starch (substrate) has been digested
As a result, the amount of precipitate produced from the Benedict’s reagent test will increase over time
The rate of absorption/diffusion can be investigated more quantitatively by:
Estimating the concentration of glucose that has diffused into the liquid surrounding the Visking tubing at each time interval (separate beakers are set up for each time interval) using the semi-quantitative Benedict’s test
Comparisons between the time intervals can be made with a set of colour standards (known glucose concentrations) or a colorimeter to give a more quantitative set of results
A graph could be drawn showing how the rate of absorption changes with the concentration gradient between the inside and outside of the tubing
