b3 Flashcards
what is a cell
the basic building blocks of living organisms
what is a tissue
group of cells with a similar structure and function
what is an organ
aggregations of tissues performing specific functions
organ system
group of organs that have been organised into a system which work together to form organisms
function of mouth in the digestive system
mechanical digestion happens.
teeth chew the food. also place where salivary amalyse is secreted which is an enzyme.
oesophagus in digestive system
connects mouth to the stomach, where food goes down after being swallowed
stomach in digestive system
has hydrochloric acid which kills bacteria in food and also provides the optimum pH for some enzymes to work in
has muscles that also mechanically digest food
small intestine
where absorbtion of digested food molecules into the blood happen. the illeum is long and lined with villi which increases the surface area
large intestine
absorbs water from remaining material to produce faeces
pancreas
produces the digestive enzymes
liver
produces bile to help with the digestion of lipids
gall bladder
stores bile and releases into small intestine when lipids need to be digested
what are enzymes?
biological catalysts that are made from proteins
- they speed up chemical reactions that happen in the body and are not used up
explain the lock and key theory
the substrate binds to the active site of the enzyme because the shape of the active site is complimentary to the shape of the enzyme.
this causes a chemical reaction to produce smaller molecules.
what does amalyse do
breaks down starch into glucose. secreted by small intestine, pancreas and salivary glands
site of digestion is small intestine and salivary glands
what do proteases do?
break down proteins into amino acids
secreted by pancreas, stomach and small intestine
site of digestion is small intestine and stomach
what do lipases do?
break down lipids into fatty acids and glycerol
secreted by pancreas and small intestine
site of digestion is small intetine
what are the products of digestion used for
to build new carbohydrates, lipids and proteins.
some glucose is used in respiration
amino acids are used t build proteins like antibodies and enzymes
products of lipid digestion are used to build cell membranes and hormones.
function of bile
made in liver, stored in gall bladder
- it is alkaline so neutralises the stomach acid in small intestine, providing optimum pH for the digestion of lipids
- it also emulsifies the fat to form small droplets which increases the surface area so more area for the enzyme to act on
both of these increase the rate of fat breakdown by lipase
test for reducing sugars
benedicts solution - heat the sample and add the reagant.
if it turns from blue to brick red, it is a positive test
test for starch
add iodine to the food sample, if it changes from brown to blue-black, it is positive test
test for lipids
add ethanol and a few drops of distilled water. if it turns cloudy, then it is positive test
test for proteins
biuret test - if it changes colour from blue to lilac then protein is present
how does temperature affect the rate of enzyme activity
work fastest at optimum temperature -> 37 degrees celcius in human body
too high temeratures leads to the bonds holding the enzyme together to be broken. this means that it loses it’s shape, therefore the shape of the active site is no longer complimentary to the shape of the substrate, so it cannot bind together.
too low temperatures means that the enzyme does not have enough kinetic energy so there are fewer frequent collisions so both enzymes and their substrates collide at a lower rate
what happens when an enzyme is denatured
the shape of the active site is lost completely. substrates cannot fit into denatured enzymes as the specific shape of their active site has been lost
effect of pH on enzyme activity
optimum pH is normally 7, but some have acidic optimum pH and some have alkaline optimum pH.
if the pH is too high or too low, the bonds that hold the amino acid chain together to make up the protein can be destroyed.
this will change the shape of the active site, so the substrate can no longer fit into it, reducing the rate of activity.
describe an experiment to investigate effect of pH on rate of amalyse activity
