B3 Organisation and the digestive system

Question 1

What is a cell?

Answer 1

The smallest unit of an organism, e.g. palisade cell, secretory cell

Question 2

What is a (living) tissue?

Answer 2

A group of cells with a similar structure and function, which all work together to do a particular job, e.g. leaf epithelium, muscle, lining of intestine.

Question 3

What is an organ?

Answer 3

A group of different tissues which all work together to do a particular job, e.g. heart, stomach, leaf.

Question 4

What is an organ system?

Answer 4

A group of different organs which all work together to do a particular job, e.g. digestive system, respiratory system, photosynthetic system.

Question 5

What is an organism?

Answer 5

An individual plant, animal or single-celled organism, e.g. human, daffodil, pine marten.

Question 6

What tissues does your stomach contain? What is their function?

Answer 6

Muscular Tissue - to churn the food and digestive juices of the stomach together
Glandular Tissue - to produce the digestive juices that break down food
Epithelial Tissue - covers the inside and outside of the organ.

Question 7

What are the functions of the pancreas?

Answer 7

It makes hormones to control blood sugar, as well as pancreatic juice that it releases into the small intestine containing enzymes (lipase, amylase and trypsin), breaks lipids down.
Contains 2 very different types of tissue to produce these secretions.

Question 8

What is the function of the stomach?

Answer 8

Absorbtion of molecules such as alcohol, muscular walls break down food physically.
* Enzymes break down proteins.
* Pepsin and gastric lipase present
* Hydrochloric acid and enzyme filled digestive juices involved

Question 9

What is the function of the salivary glands?

Answer 9

Produce saliva in mouth, contains amylase which breaks down starch to maltose (sugar)

Question 10

What happens in the mouth?

Answer 10

Mastication (chewing) of food begins breakdown into a bolus. Surface area increase makes enzymes able to work more effectively. Saliva is added to food which contains amylase (breaks down carbohydrates).

Question 11

What is the function of the liver?

Answer 11

Bile is produced here and stored in the gall bladder

Question 12

What is the function of the small intestine? What enzymes are present?

Answer 12

Bile dissolves fats, final breakdown of carbohydrates into glucose + proteins into amino acids. Walls are covered in villi to aid absorbtion of nutrients into the bloodstream by creating a very high surface area.
* Maltase, amylase, protease and lipase enzymes all at work.

Question 13

Why are carbohydrates, lipids and proteins so important?

Answer 13

They are the main compounds that make up the structure of a cell.
* Vital components in a balanced diet of any organism that can’t make its own food
* all large molecules often made of smaller molecules joined together as part of cell metabolism

Question 14

Why do you need carbohydrates? What elements do they contain?

Answer 14

Carbohydrates provide us with the fuel that makes all other reactions of life possible.
* They contain carbon, hydrogen and oxygen

Question 15

What are carbohydrates made up of?

Answer 15

All carbohydrates are made up of units of sugars
* Simple Sugars are made of 1 or 2 sugar units. Some contain only 1 sugar unit - e.g. glucose (C6H12O6) whereas others are made of 2 sugar units joined together - e.g. sucrose, compound we call sugar in everyday life.
* Complex Carbohydrates are made up of long chains of simple sugar units bonded together. e.g. starch and cellulose.

Question 16

What are some carbohydrate rich foods?

Answer 16

Bread, pasta, rice, potatoes

Question 17

Why do you need lipids? What elements do they contain?

Answer 17

Lipids are fats (solids) and oils (liquids)
* Contain carbon, hydrogen and oxygen

Uses
* They are the most efficient energy store in your body and an important source of energy in your diet.
* Very important in your cell membranes, as hormones and in your nervous system when combined with other molecules.

Question 18

What are lipids made up of?

Answer 18

Made up of 3 molecules of fatty acid joined to a molecule of glycerol.
* Glycerol is always the same, but fatty acids can vary

Question 19

What are some lipid rich foods?

Answer 19

Lipid rich foods include all oils - e.g. olive oil - as well as butter, margarine, cheese and cream
* Different combinations of fatty acids affects whether the lipid will be a liquid oil or solid fat

Question 20

What are proteins used for? What elements are they made up of?

Answer 20

Proteins are used for building up the cells and tissues of your body (structural components), as well as the basis of all your enzymes and in hormones such as insulin and antibodies (Destroy pathogens, part of immune system)
* 15-16% of your body mass is protein
* Contain carbon, hydrogen, oxygen and nitrogen

Question 21

What are some protein rich foods?

Answer 21

Meat, fish, pulses, cheese

Question 22

What are proteins made up of?

Answer 22

A protein molecule is made up of long chains of small units called amino acids
* Around 20 different amino acids - joined together in long chains by special bonds. Different arrangements of amino acids make different proteins.

Long chains of amino acids are folded, coiled and twisted to make specific shapes, these shapes allow other molecules to fit into the protein
* Bonds that hold the amino acids are very sensitive to temperature and pH and are easily broken.

Question 23

What does denatured mean?

Answer 23

If the bonds holding a protein’s shape are broken, the shape of the protein is lost and it can no longer function. The protein is denatured.
It is an irreversible process.

Question 24

What are enzymes? What is their function?

Answer 24

Enzymes are large protein molecules.

Enzymes control the rate of chemical reactions in your body
* They are special biological catalysts that speed up reactions
* Each enzyme reacts with a particular substrate (reactant)

Question 25

Why is the shape of an enzyme so vital?

Answer 25

The long chains of amino acids that make up the enzyme are folded to produce a molecule with an active site that has a unique shape so it can bind to a specific substrate molecule. If an enzyme becomes denatured, it loses its shape so can no longer bind to the substrate and cannot function.

Question 26

What is the lock and key theory?

Answer 26

A simple model of how enzymes work: * The substrate(s) of the reaction to be catalysed fits into the active site of the enzyme (like a lock and key) * Once in place the enzyme and substrate(s) bind together * Reaction takes place rapidly and the products are released from the surface of the enzyme * Enzyme is then ready to use again Enzymes can join small molecules together or break up large ones.

Question 27

What is metabolism?

Answer 27

The sum of all the reactions in a cell or in the body. Enzymes control metabolism

Question 28

What chemicals are used for the different food tests? How can you tell a positive/negative result

Answer 28

**Molecule - Chemical - Positive - Negative** Starch - Iodine - dark blue/black - orange/ brown Sugar - Benedict's Solution - green/yellow/orange/brick red - light blue Protein - Biuret's Solution - light purple - light blue Fat - ethanol - cloudy - clear

Question 29

How do you test for carbohydrates?

Answer 29

**Sugar** * Put a few drops of Benedict's solution into a test tube containing a food sample * Place in a water bath * If the solution changes colour, the food contains sugar **Starch** * Put a few drops of iodine into a test tube containing a food sample * If the solution turns dark blue or black, the food contains starch

Question 30

How do you test for lipids and protein?

Answer 30

**Lipids** * Add a few drops of distilled water and ethanol into a test tube containing a food sample. * Shake the solution gently * If the solution turns cloudy, the food contains lipids **Protein** * Add a few drops of Biuret's solution A and B (containing copper sulphate and sodium hydroxide) to a test tube containing a food sample * Shake the tube gently to mix * If the solution turns light purple, the food contains protein.

Question 31

What is the effect of temperature on enzymes?

Answer 31

Enzymes work at different rates depending on the temperature of their surroundings. If it gets too hot or cold the enzymes will denature and stop working. The optimum temperature for enzymes in our body is about 37°C (human body temperature).

Question 32

What is the effect of pH on enzymes?

Answer 32

Different enzymes have different optimum pH levels * Stomach enzymes such as pepsin require a low pH (conditions of pH 1.5-3.5) * Intestinal enzymes require a higher pH (lipase and intestinal amylase - conditions pf pH 6.7-8) * Amylase in the mouth has conditions of pH 6.8-7

Question 33

What enzymes are involved in digestion?

Answer 33

**Carbohydrase** (e.g. amylase) - break down carbohydrates into simple sugars **Protease** (e.g. pepsin) - break down proteins into amino acids **Lipase** - break down lipids into glycerol and fatty acids.

Question 34

What is bile? What is the function of bile?

Answer 34

Bile is produced in the liver and stored in the gall bladder before it is released into the small intestine. It is a dark green liquid. * It is an alkali so neutralises the substances from the stomach * It emulsifies (breaks down into small droplets) fats.

Question 35

How does jaundice occur? What is it an indicator of?

Answer 35

Jaundice occurs when bilirubin is deposited in the skin causing a yellow colour. * It is commonly an indicator of a liver issue or caused by gallstones which stop the bilirubin being excreted in the faeces.

Question 36

How do gallstones effect the effectiveness of bile in digestion?

Answer 36

Gall stones in the gall bladder can entirely prevent or reduce the amount of bile being released into the small intestine

Question 37

What is the method for testing how pH affects amylase activity on a starch solution?

Answer 37

1. Heat a water bath to 35°C - heat all solutions to this temp. 2. Put 2cm^3 of each pH solution into deparate test tubes and label 3. Put a drop of iodine into each well of a spotting tile 4. Add 4cm^3 of starch solution and 2cm^3 of amylase solution to the first pH solution - start stopclock 5. Every 10 seconds use a glass rod to transfer 1 drop of mixture into a well in the spotting tile. Rinse glass rod. 6. Repeat step 5 until iodine does not change colour. 7. Record time in results table and repeat steps 3-6 with all pH solutions