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Flashcards in Topic 2 Deck (17):
1

What are cells?

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

2

How do cells become specialised?

The process by which cells become specialised for a particular job is called differentiation. Differentiation occurs during the development of a multicellular organism.

3

What are the types of tissue?

Muscular tissue - Contracts (shortens) to move whatever it's attached to.
Glandular tissue - Makes and secretes chemicals like enzymes and hormones.
Epithelial tissue - Covers some parts of the body, e.g. the inside of the gut.

4

What are the different type of cell groups?

Tissue - A group of similar cells that work together to carry out a particular function.
Organ - A group of different tissues that work together to perform a certain purpose.
Organ system - A group of organs working together to perform a particular function.

5

What are enzymes and catalysts?

Enzymes are biological catalysts, which reduce the need for high temperatures and we only have enzymes to speed up the useful chemical reactions in the body. Enzymes are all large proteins and all proteins are made up of chains of amino acids.

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

6

How doe enzymes work?

Every enzyme has an active site with a unique shape that fits onto the substance involved in a reaction.
Enzymes usually only catalyse one specific reaction. This is because, for the enzyme to work, the substrate has to fit into its active site. If the substrate doesn't match the enzyme's active site, then the reaction won't be catalysed.

7

How does temperature and pH effect enzymes?

Like with any reaction, a higher temperature increases the rate at first. But if it gets too hot, some of the bonds holding the enzyme together break. This changes the shape of the enzyme's active site, so the substrate won't fit any more. The enzyme is said to be denatured.

The pH also affects enzymes. If it's too high or low, the pH interferes with the bonds holding the enzyme together. This changes the shape of the active site and denatures the enzyme.

8

How do you calculate rate of reaction?

Rate = 1000 / Time

9

How are starchs broken down?

Starch -Amylase-> Maltose (and other sugars)
Amylase is made in three places:
The salivary glands.
The pancreas.
The small intestine.

10

How are proteins broken down?

Proteins -Protease-> Amino acids
Protease are made in three places:
The stomach (it's called pepsin there).
The pancreas.
The small intestine.

11

How are lipids broken down?

Lipid -Lipase-> Glycerol and fatty acids
Lipases are made in two places:
The pancreas.
The small intestine.

12

What does bile do?

Bile is produce in the liver. It's stored in the gall bladder before it's released into the small intestine.
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.
It emulsifies fat (it breaks the fat into tiny droplets).

13

What is the digestive system made up of?

Salivary glands:
These produce amylase enzyme in the saliva.
Liver:
Where bile is produced. Bile neutralises stomach acid and emulsifies fats.
Stomach:
It pummels the food with its muscular walls.
It produces the enzyme protease enzyme, pepsin.
It produces hydrochloric acid for two reasons, to kill bacteria and to give the right pH for protease to work (2 pH).
Gall bladder:
Where bile is stored, before it's released into the small intestine.
Pancreas:
Produces protease, amylase and lipase enzymes. It releases these into the small intestine.
Large intestine:
Where excess water is absorbed from the food.
Small intestine:
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.
Rectum:
Where the faeces are stored before they bid you a fond farewell through the anus.

14

How do you test for sugars?

The Benedict Test:
1. Prepare a food sample and transfer 5 cm3 to a test tube.
2. Prepare a water bath so that it's set to 75oC.
3. Add some Benedict's 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 us in the food.

15

How do you test for starch?

The Iodine Solution Test:
1. Make a food sample and transfer 5 cm3 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.

16

How do you test for proteins?

The Biuret Test:
1. Prepare a sample of your food and transfer 2 cm3 of your sample to a test tube.
2. Add 2 cm3 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 pink or purple. If not protein is present, the solution will stay blue.

17

How do you test for lipids?

The Sudan III Test:
1. Prepare a sample of the food you're testing. Transfer about 5 cm3 into the test tube.
2. Use a pipette to add 3 drops of Sudan III stain solution ti the test tube and gently shake the tube.
3. Sudan III stain solution stains lipids. If the sample contains lipids, the mixture will separate out into two layers. The top layer will be bright red. If no lipids are present, no separate red layer will form at the top of the liquid.