ORGANISATION PART A

Question 1

What is the definition of a cell?

Answer 1

The basic building blocks of life and what everything is made up of

Question 2

Where does physical digestion occur during digestion?

Answer 2

Teeth - grinding your food into smaller pieces and then mixed with saliva before travelling down the oesophagus

Question 3

Where does chemical digestion occur?

Answer 3

When enzymes break down food into soluble food molecules so they can be absorbed by the blood

Question 4

State the hierarchy

Answer 4

Cell Tissue Organ Organ System Organism

Question 5

What happens in the mouth during digestion?

Answer 5

First food is chewed in the mouth. The food is mixed with saliva. Enzymes in the saliva begin to digest the starch into smaller sugar molecules.

Question 6

What happens in the oesophagus / gullet in digestion?

Answer 6

The food then passes down the oesophagus into the stomach

Question 7

What happens in the stomach in digestion?

Answer 7

In the stomach, enzymes begin the digestion of proteins. The stomach contains hydrochloric acid which helps the enzymes to digest proteins. The food spends several hours in the stomach. The churning action of the stomach muscles turns the food into a fluid increasing the surface area for the enzymes to digest.

Question 8

What happens in the small intestine in digestion?

Answer 8

The fluid then passes into the small intestine. At this point, chemicals are released into the small intestine from the liver and the pancreas. The pancreas releases enzymes which continue the digestion of starch and protein. They also start the digestion of lipids. The walls of the small intestine release enzymes to continue the digestion of protein and lipids. In the small intestine, the small food molecules produced from digestion are absorbed into the bloodstream ( by diffusion or active transport )

Question 9

State information about bile

Answer 9

The liver releases bile which helps to speed up the digestion of lipids. Bile also neutralises the acid released from the stomach.

Question 10

What about the large intestine?

Answer 10

Now the fluid makes its way through the large intestine, where water is absorbed into the bloodstream. Finally, the faeces is released from the body.

Question 11

What is an enzyme?

Answer 11

Enzymes are proteins, therefore they are made up of amino acids. Amino acids are joined together in a long chain, which is folded to produce a unique 3D structure

Question 12

What is the enzymes shape determined by?

Answer 12

• the sequence of amino acids in its structure
• the bond which forms between the atoms of those molecules

Question 13

What do different types of enzymes have?

Answer 13

They have different shapes and functions as their structure is different

Question 14

In order for a reaction to take place, what kind of energy is needed?

Answer 14

Activation energy

Question 15

Where can the energy come from?

Answer 15

The energy involved in the reactants colliding. If there is insufficient energy in the collisions, a catalyst can be used to increase the rate of reaction

Question 16

What type of catalysts are enzymes? And describe

Answer 16

Biological catalysts - they are substances which increase the rate of reaction without being used up

Question 17

What is the definition of activation energy?

Answer 17

The minimum amount of energy, particles must have to react

Question 18

Where are carbohydrates digested and what do these enzymes break down ? Into ?

Answer 18

Carbohydrates are digested in the mouth, stomach and small intestine
Carbohydrase / amylase enzymes break down starch into sugars

Question 19

Where are proteins digested and what do these enzymes break down ? Into ?

Answer 19

Proteins are digested in the stomach and small intestine.
Protease enzymes break down proteins into amino acids

Question 20

Where are fats digested and what do these enzymes break down ? Into ?

Answer 20

Fats are digested in the small intestine
Lipase enzymes break down fat into fatty acids and glycerol

Question 21

Explain the lock and key theory

Answer 21

A substrate fits into an enzymes active site, like a lock and key. The enzyme is the lock and the substrate is the key.

Question 22

Explain denaturation of enzymes

Answer 22

Applying heat to enzymes makes them move but also vibrate. This puts a strain n the bonds that holds the molecules together and causes denaturation of the enzymes active site

Question 23

What two things can alter an enzymes shape

Answer 23

Temperature and pH

Question 24

Explain this practical: effect of pH on amylase

Answer 24

2. Grab 3 testubes - first with 10cm cubed of starch solution, second with 2cm cubed of amylase solution and the last with 1cm cubed buffer solution. All are used to help control the pH
3. Put one drop of iodine in each row of the pH you are doing in a spotting tile
4. Add the amylase and pH buffer to the starch solution and the start the stopwatch.
5. Put a drop of mixture on the first drop of iodine and record the colour in the table.
6. Repeat every 20 seconds until no colour change or 5 minutes has passed
7. Repeat with a different pH

Question 25

What is the role of bile

Answer 25

To emulsify lipids, breaking them up into tiny droplets and to neutralise stomach acid and produce the optimum pH for enzymes in the small intestine

Question 26

How do we test for starch?

Answer 26

Using a spotting tile, add a few drops of iodine solution to the food you are testing. Result - turns blue / black if starch is present

Question 27

How do we test for protein / s ?

Answer 27

Using a spotting tile, add a few drops of Biuret solution to the food you are testing. Result - turns purple if protein is present

Question 28

How do we test for reducing sugar?

Answer 28

In a boiling tube, cover the food with Benedict’s solution . Put tube in a water bath at 80 degrees for 5 minutes. Result - turns brick red if reducing sugar is present ( may be green or orange if reducing sugar is less present )

Question 29

How do we test for lipids?

Answer 29

In a test tube, add 1cm cubed of ethanol to the food. Put in a bung and shake thoroughly. After, add 1cm cubed of water to the same tube. Result - turns milky white or cloudy if lipid is present