organisation and digestive system-b3

Question 1

What are cells?

Answer 1

Cells are the basic building blocks of life that make up all living organisms.

Question 2

What are tissues?

Answer 2

A tissue is a group of similar cells that work together to carry out a particular function.

Question 3

What are examples of tissues?

Answer 3

Muscular tissue, which contracts to move whatever it’s attached to
Glandular tissue, which makes and secretes chemicals like enzymes and hormones
Epithelial tissue, which covers some parts of the body e.g inside the gut.

Question 4

What are organs?

Answer 4

An organ is a group of different tissue that work together to perform a certain function.

Question 5

What is an organ system?

Answer 5

An organ system is a group of organs working together to perform a particular function. Organ systems work together to make entire organisms.

Question 6

What are enzymes?

Answer 6

Enzymes are catalysts produced by living things. Enzymes are all large proteins, and all proteins are made up of chains of amino acids.

Question 7

What is a catalyst?

Answer 7

A catalyst is a substance which increases the speed of a reaction without it being changed or used up in the reaction.

Question 8

Lock and key enzymes

Answer 8

Chemical reactions usually involve things either being split apart or joined together.
Every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction.
Enzymes are really picky- they usually only catalyses one specific reaction. This is because for enzymes to work, the substrate has to fit into its active site. If the substrate doesn’t match the enzymes active site, then the reaction won’t be catalyzed.

Question 9

How does temperature affect enzymes?

Answer 9

Changing the temperature changes the rate of an enzyme catalyzed reaction. A higher temperature increases the rate at first. But if it gets too hot, some of the bonds holding the enzymes break. This changes the shape of the enzymes active site, so the substrate won’t fit any more. The enzyme is said to be denatured. All enzymes have an optimum temperature that they work best at.

Question 10

How does pH affect enzymes?

Answer 10

The pH also affects enzymes. If it’s too high or too low, the pH interfers with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme. \
All enzymes have optimum pH that they work best at. It’s often neutral pH 7, but no always e.g pespin is an enzyme used to break down proteins in the stomach. It works best at pH 2 which means it is well suited to the acidic conditions there.

Question 11

Why do starch, proteins and fats have to be broken down?

Answer 11

They are big molecules. They are too big to pass through the walls of the digestive system, so digestive enzymes break these big molecules into smaller ones like sugar(e.g glucose and maltose), amino acids. glycerol and fatty acids. These smaller, soluble molecules can pass easily through the walls of the digestive system, allowing them to be absorbed into the bloodstream.

Question 12

What is the role of salivary glands in digestion?

Answer 12

These produce amylase enzyme in the saliva

Question 13

What is the role of the stomach in digestion?

Answer 13

It squeezes the food with it’s muscular walls.
It produces the protease enzyme, pepsin
It produces hydrochlorid acid to:
kill bacteria and give the right pH for the protease enzyme to work.

Question 14

What is the role of the liver in digestion?

Answer 14

Where bile is produced. Bile neutralises stomach acid and emulsifies fat

Question 15

What is the role of gall bladder in digestion?

Answer 15

Where bile is stored, before it’s released into the small intestine.

Question 16

What is the role of the pancreas in digestion?

Answer 16

Produces protease, amylase and lipase enzmes. It releases these into the small intestine

Question 17

What is the role of the small intestine in digestion?

Answer 17

Produces protease, amylase and lipase enzymes to complete digestion. This is also where the digested food is absorbed out of the digestive system into the blood.

Question 18

What is the role of the large intestine in digestion?

Answer 18

Where excess water is absorbed from the food

Question 19

What is the role of the rectum in digestion?

Answer 19

Where the faeces(made of mainly indigestible food) are stored before they bid you a fond farewell through the anus. The faeces are excreted from the anus.

Question 20

What is the required practical?

Answer 20

The enzyme amylase catalyses the breakdown of starch to maltose. It’s easy to detect starch using iodine solution- if starch is present, the iodine solution will change from browny-orange to blacl-blue.

Question 21

What is the method of the required practical?

Answer 21

1) Put a drop of iodine solution into every well of a spotting tile.
2) Place a bunsen burner on a heat proof mat, and a tripod and gauze over the Bunsen Burner. Put a beaker of water on top of the tripod and heat the water until it is 35*C(use a thermometer to measure the temperature). Try to keep the temperature of the water constant throughout the experiment.
3) Use a syringe to add 1cm cubed of amylase solution and 1cm cubed of buffer solution with a pH of 5 to a boiling tube. Using test tube holders, put the tube into the beaker of water and wait for 5 minutes.
4) Next, use a different syringe to add 5cm cubed of a starch solution to the boiling tube.
5) Immediately mix the contents of the boiling tube and start a stop clock.
6) Use continuous sampling to record how long it takes for the amylase to break down all the starch. To do this, use a dropping pipette to take a fresh sample from the boiling tube every 30 seconds and put a drop into the well. When the iodine solution remains browny-orange, starch is no longer present.
7) Repeat the whole experiment with buffer solutions of different pH values to see how pH affects the time taken for the starch to be broken down.
8) Remember to control any variables each time(e.g concentration and volume of amylase solution) to make it a fair test.

Question 22

What is the enzyme that converts carbohydrates to simple sugars?

Answer 22

Carbohdrase. Amylase is an example

Question 23

Where is amylase made?

Answer 23

The salivary glands, the pancreas and the small intestine

Question 24

What is the enzyme that converts proteins into amino acids?

Answer 24

Protease

Question 25

Where is protease made?

Answer 25

The stomach(it's called pepsin there)
The pancreas
The small intestine

Question 26

What is the enzyme that coverts lipids into glycerol and fatty acids?

Answer 26

Lipase

Question 27

Where is lipase made?

Answer 27

The pancreas and the small intestine

Question 28

What is bile?

Answer 28

Bile is produced in the liver and stored in the gall bladder before being released into the small intestine.
Bile neutralises the stomach acid and emulsifies fat. In other words it breaks fat into tiny droplets. This gives a much bigger surface area of fat for the enzyme lipase to work on- which makes the digestion faster.

Question 29

Why do we need bile?

Answer 29

The hydrochloric acid in the stomach makes the pH too acidic for enzymes in the small intestine to work properly. Bile is alkaline- it neutralises the acid and makes conditions alkaline. The enzymes in the small intestine work best in these alkaline conditions.

Question 30

How do you prepare a food sample?

Answer 30

1) Get a piece of food and break it up using a pestle and mortar.
2) Transfer the ground up food to a beaker and add some distilled water
3) Give the mixture a good stir with a glass rod to dissolve some of the food.
4) Filter the solution using a funnel lined with filter paper to get rid of the solid bits of food.

Question 31

How do you test for sugars?

Answer 31

Sugars are found in all sorts of food such as biscuits, cereal and bread. There are two types of sugars- non reducing and reducing. You can test for reducing sugars in foods using the Benedicts test:

1) Prepare a food sample and transfer 5cm cubed to a test tube
2) Prepare a water bath so that it is set to 75*C
3) Add some benedicts solution to the test tube(about 10 drops) using a pipette.
4) Place the test tube in the water bath using a test tube holder and leave it in there for 5 minutes. Make sure the tube is pointing away from you.
5) If the food sample contains a reducing sugar, the solution in the test tube will change from the normal blue colour to green, yellow or brick red- it depends on how much sugar is in the food.

Question 32

How do you test for starch?

Answer 32

Foods like pasta, rice and potatoes contain a lot of starch

1) Make a food sample and transfer 5cm cubed of your sample to a test tube
2) Then add a few drops of iodine solution and gently shake the tube to mix the contents. If the sample contains starch, the colour of the solution will change from browny-orange to black or blue-black

Question 33

How do you test for proteins?

Answer 33

You can use a biuret test to see if a type of food contains protein. Meat and cheese and protein rich.

1) Prepare a sample of your food and transfer 2cm cubed of your sample to a test tube
2) Add 2cm cubed of biuret solution to the sample and mix the contents of the tube by gently shaking it
3) If the food sample contains protein, the solution will change from blue to purple. If no protein is present, the solution will stay blue.

Question 34

How do you test for lipids?

Answer 34

Ethanol test-ethanol added to a solution gives a cloudy white layer if a lipid is present. Ethanol is highly flammable and harmful.