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IGCSE Biology > Biological molecules > Flashcards

Biological molecules Flashcards

1
Q

What does DNA stand for?

A

Deoxyribonucleic acid

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2
Q

What are the 4 types of nitrogen bases in DNA?

A
  • Adenine
  • Thymine
  • Guanine
  • Cytosine
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3
Q

Why does the 4 bases of DNA matter?

A

Determines what biological instructions are contained in a strand of DNA

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4
Q

What pairs do the bases go in?

A

Adenine —> Thymine (A,T)
Guanine —> Cytosine (G,C)

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5
Q

What is the test for glucose?

A

Benedict’s solution

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6
Q

What’s the method for carrying out the test for glucose?

A
  1. Add Benedict’s solution to the sample solution in a test tube
  2. Heat in a boiling water bath for 5 minutes
  3. Take the test tube out of the water bath and observe the colour
  4. A positive test will show a colour change from blue to orange / brick red
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7
Q

What is the test for starch?

A

Iodine solution

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8
Q

What’s the method for carrying out the test for starch?

A
  1. Add drops of iodine solution to the food sample
  2. A positive test will show a colour change from orange-brown to blue-black
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9
Q

What is the test for protein?

A

Biuret solution

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10
Q

What’s the method for carrying out the test for protein?

A
  1. Add drops of Biuret solution to the food sample
  2. A positive test will show a colour change from blue to violet / purple
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11
Q

What is the test for lipids?

A

Ethanol

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12
Q

What’s the method for carrying out the test for lipids?

A
  1. Mix the food sample with 4cm3 of ethanol and shake
  2. Allow time for the sample to dissolve in the ethanol
  3. Strain the ethanol solution into another test tube
  4. Add the ethanol solution to an equal volume of cold distilled water (4cm3)
  5. A positive test will show a cloudy emulsion forming
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13
Q

How to prepare a sample for food tests?

A
  1. Break up the food using a pestle and mortar
  2. Transfer to a test tube and add distilled water
  3. Mix the food with the water by stirring with a glass rod
  4. Filter the mixture using a funnel and filter paper, collecting the solution
  5. Proceed with the food tests
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14
Q

What does CORMS stand for?

A
  • Change
  • Organism
  • Repeat
  • Measurement 1
  • Measurement 2
  • Same
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15
Q

What’s the chemical element for carbohydrates?

A

Carbon, Hydrogen and Oxygen

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16
Q

What’s the chemical element for lipids?

A

Carbon, Hydrogen, Oxygen

17
Q

What’s the chemical element for protein?

A

All contain carbon, hydrogen, oxygen and nitrogen

18
Q

What is a monosaccharide?

A

A monosaccharide is a simple sugar e.g. glucose (C6 H12 O6) or fructose

19
Q

What is a disaccharide?

A

Made when two monosaccharides join together

20
Q

What happens to glucose molecules when they contain lots of energy?

A

They can be released in respiration by breaking the bonds between the carbon atoms

21
Q

Name 2 examples of disaccharides

A
  • Maltose is formed from two glucose molecules
  • Sucrose is formed from one glucose and one fructose molecule
22
Q

What is a polysaccharide?

A

Formed when lots of monosaccharides join together

23
Q

Name 3 examples of polysaccharides

A

Starch, glycogen or cellulose are all formed when lots of glucose molecules join together

24
Q

Why are polysaccharides useful?

A

They are insoluble so they can be used as storage molecules

25
Q

How many different amino acids in a protein?

A

20

26
Q

How are proteins formed?

A

By long chains of amino acids

27
Q

Explain the lock and key method

A
  1. Enzymes have a specifically shaped active site - this is where a specific substrate molecule fits in order for a reaction to take place
  2. If the shape of the active site does not match the shape of the molecule that fits into it, the reaction will not take place
  3. Antibodies are proteins produced by certain types of white blood cells that attach to antigens on the surface of pathogens
  4. The shape of the antibody must match the shape of the antigen so that it can attach to it and signal it for destruction
28
Q

What do enzymes act as?

A

Biological catalysts to speed up the rate of a chemical reaction without being changed or used up

IGCSE Biology (20 decks)

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