B3 - Organisation + Digestive system

Question 1

Give the basic hierarchy of structures in an organism:

Answer 1

-cells, building blocks of all living organisms

-tissue, group of cells with similar structure + function

-organs, groups of tissues that perform specific functions

-organs are organised into organ systems that work together to form organisms

Question 2

What is the digestive system?

Answer 2

an organ system which digests and absorbs food into the bloodstream

Question 3

Name all of the 10 organs in the digestive system:

Answer 3

-mouth
-oesophagus
-stomach
-liver/pancreas/gallbladder
-small + large intestine
-rectum
-anus

Question 4

Describe how the small intestine is adapted for efficient absorption:

Answer 4

-villi provide larger SA
-capillaries are one cell thick for shorter diffusion distance
-efficient blood supply from capillaries to maintain CG
-lots of mitochondria in cells for respiration to release energy which is required for active transport
-SI is very long which increases time for diffusion

Question 5

What is an enzyme? Describe its structure:

Answer 5

-a biological catalyst (proteins) used to speed up specific metabolic reactions based on the shape of their active site

-has an active site, which is the place where a complementary substrate binds to and undergoes a chemical reaction

Question 6

Explain the lock and key theory of enzyme action:

Answer 6

-substrate binds to enzyme’s complementary active site
-substrate is broken down into products rapidly
-the products are released, enzyme is left unchanged

Question 7

What factors affect the rate of enzyme action? Why might being outside optimum conditions affect it?

Answer 7

-temperature
-pH

-being outside optimum conditions can denature the enzyme by changing the shape of its active site, so it can no longer bind to its substrate

Question 8

What are proteins used for in the body?

Answer 8

-structural components of tissues (muscles/tendons)
-hormones
-antibodies
-enzymes

Question 9

What enzymes do certain digestive organs secrete?

Answer 9

salivary - amylase

stomach - protease

SI + pancreas - lipase, amylase, and protease

Question 10

What do the 3 enzymes do in the body?

Answer 10

carbohydrase - carbs to simple sugars

protease - protein to amino acids

lipase - lipids to glycerol/fatty acids (which lowers pH)

Amylase is a type of carbohydrase, and breaks down starch into glucose

Question 11

What are the products of digestion used for?

Answer 11

-used to build new carbs/proteins/lipids

-some glucose used for respiration

Question 12

What is a villus? Describe its structure:

Answer 12

-a finger-like projection from of the epithelial tissue in the SI used to increase the speed at which biomolecules are absorbed into the bloodstream

-lots of microvilli on its surface (^SA)
-capillaries close to all of them (to ventilate CG)

Mention capillary adaptations in a question about villi’s adaptations

Question 13

Where is bile made, and what does it do? Explain how:

Answer 13

-made in liver, stored in gall bladder, used to ^rate of fat breakdown by lipase

-alkaline, neutralises HCl from stomach
-emulsifies fat to form smaller droplets which increases SA

Question 14

Why does excess sugar make you overweight?

Answer 14

-provides more energy than needed
-stored as fat, adds to body mass

Question 15

RP4 - How do you prepare a sample of food to be tested for the 4 different components?

Answer 15

-grind up with pestle/mortar
-put in beaker with distilled water, stir until most dissolves
-filter into boiling tube using funnel + filter paper to remove solids left over

Question 16

RP4 - Describe the test for simple sugars:

Answer 16

-take 5cm^3 food sample
-add 10 drops of B’s sol, place in 70°C water bath for 5 mins

-stays blue if not present, green (mid) and brick red if lots present

Question 17

RP4 - Describe the test for starch:

Answer 17

-take 5cm^3 food sample
-add few drops iodine solution, stir

-if present, brown to blue black

Question 18

RP4 - Describe the test for proteins:

Answer 18

-take 2cm^3 food sample
-add 2cm^3 biuret solution, stir

-if present, blue to purple

Question 19

RP4 - Describe both tests for lipids:

Answer 19

-take 5cm^3 food sample
-add 3 drops Sudan III, stir

-if present, red layer forms on top of solution

(OR add ethanol, shake, add distilled water, present if white cloudy emulsion layer forms)

Question 20

How could you test milk to show that it contains proteins and different types of carbohydrates:

Answer 20

-test for proteins by adding Biuret solution to milk, if blue to purple then proteins are present
-test for starch (a carbohydrate) by adding iodine solution, if brown to blue-black then starch is present
-test for sugars by adding Benedict’s solution and then heat in a water bath to 75°C, if blue to brick-red then sugars are present

Question 21

RP5 - Describe how you can prepare the necessary equipment for investigating how pH affects enzyme action:

Don’t explain how to use the equipment yet

Answer 21

-label a spotting tile with times of 30s intervals and put a few drops of iodine in each

-take at least 5 labelled test tubes and put 2cm^3 pH buffers in each one (pH 3-7)

-put starch, amylase and buffer solutions in water bath at 25°C and leave for a few minutes to allow them to equilibrate temperature

Question 22

RP5 - Describe how you can use the equipment set up previously to investigate how pH affects the rate of amylase action:

Answer 22

-in a pH buffer boiling tube, add 2cm^3 amylase, then 2cm^3 starch and start timing
-add a drop of the mixture to each well using a glass rod at each time interval, washing the rod every time
-repeat until the well stays brown and doesn’t go blue-black, record that time

-calculate rate by 1/time
-repeat with all other pH buffers
-plot rate vs pH

Question 23

If the villi were damaged, why might they cause poor growth?

Answer 23

-damaged villi means less SA for absorption of biomolecules
-fewer glucose and amino acids absorbed (NOT proteins)
-less glucose so less energy released from aero resp.
-less AAs and less energy, so less proteins can be synthesised

Question 24

How are enzymes made?

Answer 24

-ribosomes make proteins for enzymes from amino acids
-mitochondria provide energy from aero. resp. for the protein synthesis

Question 25

Why can enzymes only act on one type of substrate?

Answer 25

each active site has a specific shape, so it only fits one type of substrate and can’t fit any other

Question 26

Name 5 functions of the liver:

Answer 26

-breaks down excess proteins/amino acids (deamination)
-breaks down lactic acid
-stores glycogen
-produces bile
-breaks down other toxins (eg alcohol)

(E, LGBT)

Question 27

Why might enzyme action be very slow at low temperatures?

Answer 27

-enzyme and substrate have low kinetic energy at low temperature
-fewer enzyme-substrate collisions, so fewer enzyme-substrate complexes are formed