Biology: enzymes and digestion

Question 1

The hierachy of organisms

Answer 1

Cell: basic building block of life e.g nerve cell      Remember CT triple O
Tissue: e.g nerve cell tissue 
Organ e.g skin
Organ system e.g nervous system 
Organism e.g human body

Question 2

Describe the journey food would take ( from 👄 to 🍑)

Answer 2

Mouth: mechanical digestion in teeth and chemical by enzymes in saliva e,g amylase
Oesophagus: food is brought to the stomach via wave- like muscular contractions called peristalsis
Stomach: muscular sac limed with mucous. Food is mixed with hydrochloric acid and stomach enzymes and churned
Food then gets the hydrochloric acid neutralised by bile which is made in the liver, stored in the gall bladder and exited through the bile duct
The food then gets broken down by enzymes produced by the pancreas. The food then passes through the small intestine which produces more enzymes to break the food down. This is where the food is absorbed into the bloodstream. The water is removed from the food by the large intestine and put back into the bloodstream. The undigested food ( faeces ) is then stored in the rectum and exits through the anus

Question 3

What are the 6 major food nutrients

Answer 3

Proteins
Fats ( lipids ) 
Carbohydrates ( sugar, starch fibre ) 
Vitamins 
Minerals 
Water

Question 4

What is fat made up of and what enzyme breaks it down

Answer 4

Fats are made up of 3 fatty acids and 1 glycerol

It gets broken down by lipase

Question 5

What is protein made up of and what enzyme breaks it down

Answer 5

Made up of amino acids

Protease breaks it down

Question 6

What are carbohydrates made up of and what enzyme breaks them down

Answer 6

Made up of simple sugars ( e.g glucose )

Amylase breaks it down

Question 7

Describe the process of enzymes breaking down substrates

Answer 7

The enzyme’s active site and the substrate fit into one another, the bonds in the substrate are broken and the products are released. Enzyme is unchanged and can be reused.

Question 8

How do enzymes get denatured and what happens after that

Answer 8

The active site of the enzyme can change shape due to high temperatures ( i.e above 40 degrees C ) or change from normal pH range.
Damage is irreversible and enzyme will no longer break down the substrate molecules

Question 9

Give information on bile e.g what it is, does and where it comes from

Answer 9

Bile is not an enzyme
It is a green liquid made in the liver and stored in the gall bladder
It is an alkaline liquid so it neutralises hydrochloric acid leaving the stomach
It also emulsifies lipids to smaller droplets, this increases the surface area for lipase enzymes to work on

Question 10

What is an independent variable

Answer 10

E.g temperature
It goes on the X axis
It is the one that changes in the experiment

Question 11

What is the dependent variable

Answer 11

E.g the rate of enzyme action
It goes on the Y axis
The one you measure in the experiment

Question 12

What formula do you use to calculate the rate ( give all types and why )

Answer 12

Rate = 1/time 
Rate = 1000/time ( you may need a bigger number that is easier to plot on a graph 
Rate = change/ time ( how much something has changed over time )

Question 13

At pH2, kt takes 40 seconds for the enzyme pepsin to break down a protein. Calculate the rate of reaction

Answer 13

R=1/t

1/40 = 0.025 s-1 ( -1 is an indice ) ( s-1 means per second )

Question 14

The enzyme catalase catalyses the reaction where hydrogen peroxide is broken down into water and oxygen. 40cm cubed was released in 1 minute. Calculate the rate of the reaction ( choose what formula to use )

Answer 14

R = change/time
40/60 seconds = 0.67s-1 ( s-1 is an indice and means per second )

🤪

Question 15

What elements make up carbohydrates

Answer 15

Carbon, hydrogen, oxygen

Question 16

What elements make up protein

Answer 16

Carbon, hydrogen, oxygen, nitrogen, sulphur

Question 17

What elements make up lipids ( fats )

Answer 17

Carbon, hydrogen and oxygen

Question 18

Where is the production site of protease

Answer 18

Pancreas, stomach, small intestine ( ileum, duodenum)

Question 19

Where is the production site of lipase

Answer 19

Pancreas, small intestine

Question 20

Where is the production site of carbohydrase

Answer 20

Pancreas, small intestines, salivary glands

Question 21

Describe the rate of enzyme action when the temperature is increasing

Answer 21

The rate of reaction starts to rapidly increase as the temperature increases because their is more kinetic energy and therefore more collisions between the enzyme and substrate molecule. Now the enzymes are gradually becoming more efficient

Question 22

Describe the rate of reaction of enzymes at optimum temperature

Answer 22

Optimum temperature ( 35 - 41 degrees ) this is where there is the most kinetic energy and collisions between the enzyme and the substrate and rate of reaction is fastest. The enzymes are the most efficient at this temperature.

Question 23

Describe the rate of enzyme action when the temperature is increasing past optimum

Answer 23

As temperature goes past optimum, rate of reaction is slowing as the active site of the enzymes starts to denature. This is because the enzymes have less kinetic energy and there is less frequent collisions

Question 24

Describe the rate of enzyme action when the temperature is at around 54 degrees ( when enzymes have completely denatured )

Answer 24

The active site of the enzymes have completely denatured and cannot catalyse with the substrate there is no more reactions so rate of reaction is at 0

Question 25

How do you find the rate of reaction when reading a graph on a steadily increasing line ( straight line )

Answer 25

You find where the number lines up to the y axis on the graph or find the gradient of the line

Question 26

How do you find the rate of reaction on a graph that the line is curving

Answer 26

You draw a tangent

Question 27

Describe the method to the enzymes practical procedure

Answer 27

1. 3 test tubes: pHx, amylase, starch
2. One drop of iodine solution into each depression of spotting tile
3. 2cm cubed of each solution into a test tube and then a water bath and wait until all have reached 30C
4. Use syringe to place 2cm cubed of of starch into the buffered pH solution
5. Then use another syringe to put 2cm cubed amylase into the starch + pH test tube
6. Immediately start the clock and leave it on throughout the test
7. After every 20 seconds add one drop of the solution to one of the depressions in the spotting tile, the iodine should turn a blue black colour
8. Do this every 20 seconds until the iodine has no change in colour ( this is when the amylase has broken down all the starch )
9. repeat the test for other pHs
10. Record your results on a table

Question 28

What is the purpose of the enzymes required practical

Answer 28

To see how long an enzyme takes to break down a substrate with different levels of pH

Question 29

How do you test for starch

Answer 29

Add a few drops of iodine solution

Positive result: brick red - blue black colour

Question 30

How do you test for sugars ( e.g glucose )

Answer 30

Add a few drops of Benedicts’s solution
Heat gently for approx for 10 mins
Positive result: blue colour - brick red

Question 31

How do you test for protein

Answer 31

Add a few drops of biuret A and biuret B
Shake the test tube gently
Positive result: blue colour - violet colour

Question 32

How do you test for fats/ lipids

Answer 32

Add a few drops of water and ethanol
Positive result: white precipitate layer forms
OR
Solid lipids ( e.g not lemonade )
Brown paper, if it turns translucent then there is fats