enzymes and digestion Flashcards
What are enzymes
all enzymes are proteins that function as a biological catalyst, speeding up rate of reactions such as photosynthesis, respiration, digestion and many others in living organisms, join small molecules into larger ones
catalyst
a substance that speeds up chemical reactions without being changed or consumed during the reaction
how do enzymes work
the molecules on which an enzyme acts is the substrate, while the molecule formed is called the product
enzymes work because the shape of the substrate fits into the shape of a special region called the active site, so they collide the substrate fits snugly into the active site of the enzyme
enables the enzyme to catalyze the reaction and split the substrate into its products. The enzymes molecule is not changed or used up by this reaction and is available to repeat reaction every time it collides with a substrate molecule
Lock and key model
a particular enzyme will only act on a particular substrate just only particular key will open a particular door.
tight fit between an enzymes active site and the substrate
explains enzyme specificity each enzyme is specific and will only work on its particular substrate.
Inhibitors
some molecules slow down enzyme activity
these molecules look like the substrate and so fit loosely or partially into the active site of enzymes. Such molecules are called inhibitors because, while they occupy the active site of the enzyme, substrate molecules cannot enter and be broken down, leads to a reduced(inhibited reaction)
effects of temperature on enzyme activity
the line is rising- shows rate of reaction increasing, enzyme molecules and substrate molecules are gaining more energy, colliding more and reacting more
optimum temperature
temperature at which the rate of reaction is at its highest (40*)
the line is dropping
rate of reaction is decreasing at this part of the graph. Enzyme molecule has been denatured , meaning shape of enzyme has been irreversibly changed because of the high temperatures.
If active site has changed, not substrate molecule can fit in and no reaction can occur
procedure for effect of temperature
set up 5 water baths at 10* 20* 30* 40* and 50*
label 5 test tubes with starch and temp of water bath
label 5 test tubes with amylase and temperature of a water bath
use a syringe to measure 5cm of 1 percent of starch solution into each of the test tubes labelled starch
use another syringe to measure 5cm of 1 percent amylase solution into each of the test tubes labelled amylase
place one starch and one amylase labelled test tube in each water bath for at least 5 minutes
prepare a spotting tile for each temperatures by placing on drop of iodine into each of the dimples
starting with 10 * water bath, pour amylase solution into starch solution. Use clean dropping pipette to sample mixed solution and start a timer.
Add one drop of sample to the iodine solution in the first dimple of the spotting tile and note any color change. Return remainder of sample into test tube
repeat sampling steps 8 and 9 every minute until iodine shows no color change. Record time taken for starch to be digested in minutes
repeat steps 8,9 and 10 with each of the water bath i n turn
effect of PH on enzyme activity
enzymes work best at particular PH in the body. Enzymes in the mouth have an optimum PH of about 7 but enzymes in stomach have an optimum PH of 2
changing PH away from optimum PH causes a decrease in the activity of the enzyme
due to an irreversible change in the enzymes active site or denaturation. further away from the optimum change the lower the enzyme activity
Denaturation
and irreversible change to the shape of the enzymes active site and the substrate cannot fit into it anymore
Effect on oh ph. on the action of pepsin
exposed photographic film contains black grains of silver. stuck on by a layer of gelatin. Gelatin is a form of protein. Protease enzymes break down proteins into amino acids. Pepsin is a type of protease.
After 30 minutes each strip of film was removed from test tube and washed.
If gelatin had been digested, film turned colorless
Effect of enzyme concentration
them ore enzymes there are the faster the rate of reaction because there are more active sites for the substrates to attach to
the rate eventually levels off because the are not enough substrate molecules to react with the extra enzymes
Commercial enzymes
these enzymes are thermostable- they can work at a wide range of temperatures and they break the complex, large insoluble down into small soluble molecules that dissolve in water
4 examples of thermostable enzymes
pre digesting food for babies
extracting juice from fruit
making lactose free products and softening centers if chocolate.
Digestion
digestion is the breakdown of large complex insoluble molecules into simple soluble molecules
The ileum
enzymes get broken down here but the main function is the absorption of digested food products
how is the ileum adapted for absorption of food
long and folded
good blood supply
large surface area(villi and microvilli)
thin
Villi
the presence of millions of microscopic outgrowths called villi on the inner surface of the ileum increases surface area
lacteal
absorbs breakdown product of lipids ( glycerol and fatty acids) and return them to blood later
villus
finger liked shape to increase surface area
capillary network
absorbs breakdown products of protein ( amino acids) and starch( glucose)
surface epithelium cells
single layer of cells reducing distance molecules diffuse
Villi adaptations
excellent blood supply so absorbed food substances can be transported away and replaced with blood low in digested food molecules, maintaining a high concentration gradient
The thin a permeable surface lining each villus consisting of a single layer of surface epithelium cells- this reduces number of cells between the lumen of the gut and the capillaries and lacteal
