Digestion

Question 1

what is digestion

Answer 1

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

Question 2

function of food biological molecules

Answer 2

provide cells with energy via respiration and to build other molecules for cell growth and repair

Question 3

function of the mouth

Answer 3

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

Question 4

function of the oesophagus

Answer 4

hollow tube with muscular walls for peristalsis to pass food down,

Question 5

function of the stomach

Answer 5

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)

Question 6

function of the small intestine

Answer 6

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

Question 7

large intestine function

Answer 7

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

Question 8

what type of enzymes are digestive enzymes and why

Answer 8

extracellular enzymes because work outside of cells eg. in blood

Question 10

3 main types of digestive enzymes

Answer 10

carbohydrase protease
lipase

Question 11

path of hydrolysis from starch

Answer 11

starch

amylase(mouth, pancreas and small intestine)

maltose

maltase (epethilial cell walls in small intestine)

glucose

Question 12

why is maltase found in the cell wall of the small intestine epithelial cells

Answer 12

along with other disaccharidases ,

allows the absorbtion of monosaccharides back into the blood stream at epithelial cells

Question 13

how is the lining of the small intestine adapoted

Answer 13

folded and microvilli present increasing the surface area

more dissacharides can be absorbed

Question 14

lifecycle of protein digestion

Answer 14

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 )

Question 15

what does endopeptidase do in the STOMACH

Answer 15

hydrolyses peptide bonds partially to create smaller protein chunks

enzyme is secreted with HCL to make stomach acid acidic

Question 16

how is the acidic mixture of stomach acid neutralised

Answer 16

fluid secreted by the pancreas contains endopeptidase and exopeptidease

Question 17

what does endopeptidase do

Answer 17

hydrolyse peptide bonds within polypeptide chains producing dipeptides

Question 18

what does exopeptidase do

Answer 18

hydrolyse peptide bonds at the ends of polypeptide chains producing dipeptides

Question 19

what happens when fatty liquid arrives in the small intestine

(bile)

Answer 19

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

Question 20

cycle of lipids

Answer 20

lipids

bile salts (occuring in small intestine)

emulsified lipids

lipase

fatty acids + glycerol

Question 21

what is the practical for investigating how PH affects enzyme reaction rates

Answer 21

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

Question 22

investigating how PH affects enzyme reaction rates method

Answer 22

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

Question 23

limitations of the Ph affect on rate of reaction experiment

and solution

Answer 23

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

Question 24

practicle for the affect of bile salts on enzyme reaction rates

Answer 24

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

Question 25

method of investigating the affect of bile salts on a reaction

Answer 25

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

Question 26

where are the products of digestion absorbed

Answer 26

through the epithelial lining

Question 27

where are specific amino acid cotransport proteins found

Answer 27

within the cell surface membrane of the epithelial cells in the ileum

Question 28

how does the amino acid cotransport work

Answer 28

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

Question 29

how is the concentration gradient maintained from the lumen into the ileum for amino acids

Answer 29

the concentration gradient is maintained as active transport of sodium ions into the blood

Question 30

at what site are monosaccharides reabsorbed

Answer 30

sodium/ pottasium pump in the cell membrane of epithelial cells

Question 31

how are monosaccharides absorbed

Answer 31

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

Question 32

how is conc grad maintained glucose

Answer 32

sodium ions actively being transported out of the epithelial cells into blood

Question 33

what do the monoglycerides and fatty acids associate with phospholipids and bile salts to make

Answer 33

micelles

Question 34

why are micelles needed

Answer 34

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

Question 35

what type of diffusion for lipids

Answer 35

non soluble so simple

Question 36

what happens to triglycerides

Answer 36

packaged into lipoproteins called chlomicrons where they can enter lacteal ( al lymph vessel) eventually enter blood stream

Question 37

visking tubing practical method

Answer 37

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