b3

Question 1

what is a cell

Answer 1

the basic building blocks of living organisms

Question 2

what is a tissue

Answer 2

group of cells with a similar structure and function

Question 3

what is an organ

Answer 3

aggregations of tissues performing specific functions

Question 4

organ system

Answer 4

group of organs that have been organised into a system which work together to form organisms

Question 5

function of mouth in the digestive system

Answer 5

mechanical digestion happens.
teeth chew the food. also place where salivary amalyse is secreted which is an enzyme.

Question 6

oesophagus in digestive system

Answer 6

connects mouth to the stomach, where food goes down after being swallowed

Question 7

stomach in digestive system

Answer 7

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

Question 8

small intestine

Answer 8

where absorbtion of digested food molecules into the blood happen. the illeum is long and lined with villi which increases the surface area

Question 9

large intestine

Answer 9

absorbs water from remaining material to produce faeces

Question 10

pancreas

Answer 10

produces the digestive enzymes

Question 11

liver

Answer 11

produces bile to help with the digestion of lipids

Question 12

gall bladder

Answer 12

stores bile and releases into small intestine when lipids need to be digested

Question 13

what are enzymes?

Answer 13

biological catalysts that are made from proteins
- they speed up chemical reactions that happen in the body and are not used up

Question 14

explain the lock and key theory

Answer 14

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.

Question 15

what does amalyse do

Answer 15

breaks down starch into glucose. secreted by small intestine, pancreas and salivary glands
site of digestion is small intestine and salivary glands

Question 16

what do proteases do?

Answer 16

break down proteins into amino acids
secreted by pancreas, stomach and small intestine
site of digestion is small intestine and stomach

Question 17

what do lipases do?

Answer 17

break down lipids into fatty acids and glycerol
secreted by pancreas and small intestine
site of digestion is small intetine

Question 18

what are the products of digestion used for

Answer 18

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.

Question 19

function of bile

Answer 19

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

Question 20

test for reducing sugars

Answer 20

benedicts solution - heat the sample and add the reagant.
if it turns from blue to brick red, it is a positive test

Question 21

test for starch

Answer 21

add iodine to the food sample, if it changes from brown to blue-black, it is positive test

Question 22

test for lipids

Answer 22

add ethanol and a few drops of distilled water. if it turns cloudy, then it is positive test

Question 23

test for proteins

Answer 23

biuret test - if it changes colour from blue to lilac then protein is present

Question 24

how does temperature affect the rate of enzyme activity

Answer 24

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

Question 25

what happens when an enzyme is denatured

Answer 25

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

Question 26

effect of pH on enzyme activity

Answer 26

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.

Question 27

describe an experiment to investigate effect of pH on rate of amalyse activity