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IGCSE - Biology > Biological molecules > Flashcards

Biological molecules Flashcards

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1
Q

What are the three main biological molecules?

A
  • Carbohydrates
  • Proteins
  • Lipids
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2
Q

What are carbohydrates?

A

Molecules made up of simple sugars

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3
Q

What elements do carbohydrates contain?

A

Carbon, hydrogen and oxygen.

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4
Q

What are starch and glycogen?

A

Large complex carbohydrates made up of smaller units (glucose and maltose molecules) joined together in a long chain.

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5
Q

What are proteins?

A

A long chain of amino acids

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6
Q

What elements do proteins contain?

A

Carbon, hydrogen, oxygen and nitrogen.

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7
Q

What are lipids?

A

Molecules made up of fatty acids and glycerol

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8
Q

What elements do lipids contain?

A

Carbon, hydrogen and oxygen.

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9
Q

How do you test for glucose?

A

Benedict’s reagent

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10
Q

What colour is benedicts reagent?

A

Blue

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11
Q

What happens if glucose is present?

A

A coloured precipitate is formed. The colour of the precipitate changes from: blue-green-yellow-orange-brick red

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12
Q

The higher the concentration of glucose…

A

… The further the colour change goes!

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13
Q

How do you test for starch?

A

Iodine test

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14
Q

If starch is present?

A

Sample changes colour to a dark blue-black one

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15
Q

If theres no starch?

A

Sample stays browny-orange

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16
Q

What are enzymes?

A

Biological catalysts in metabolic reactions

17
Q

What is a catalyst?

A

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

18
Q

What are enzymes made of?

A

Proteins - long chain of amino acids folded into unique shapes to help the enzymes do their job

19
Q

What is a substrate?

A

A molecule that is changed in a reaction

20
Q

What is the active site?

A

The part where the substrate joins onto the enzyme.

21
Q

What has to be correct to fit the active site?

A

The shape of the substrate otherwise the enzyme wont work

22
Q

What is the model called when the substrate fits the active site perfectly?

A

The “lock and key” model

24
Q

The higher the temperature…

A

The quicker the rate of the reaction (up to a certain point) as the enzymes and substrate particles have more energy, so more about more - higher collision rate

25
Q

The lower the temperature…

A

The slower the reaction, so lower collision rate

26
Q

What happens if the enzyme gets too hot?

A

The bonds holding the enzymes together break.

27
Q

If the enzyme loses its shape…

A

The active site doesn’t fit the substrate anymore. This means it cant catalyse the reaction and its stops - the enzyme is said to be denatured

28
Q

What is the optimum temperature?

A

Where the enzyme works the quickest, which in this case is 37 degrees - same as humans

29
Q

How else can enzymes be affected?

A

By the pH

30
Q

If the pH is too high or low…

A

It interferes with the bonds holding the enzymes together changing the shape of the active site and denaturing the enzyme

31
Q

What is the optimum pH of an enzyme?

A

pH 7 (neutral)

32
Q

What enzyme is an exception for the optimum pH?

A

Pepsin - This enzyme is used to break down proteins in the stomach and works best at pH 2 (acidic conditions)

33
Q

What two enzymes can you use to show how temperature effects its activity?

A

Catalase and amylase

34
Q

What equipment is needed in the catalase experiment?

A
  • Water bath
  • Beaker
  • Boiling tube (containing source of catalase)
  • Measuring cylinder
  • Delivery tube
36
Q

How can you use catalase in an experiment?

A
  • Breaks down hydrogen peroxide into water and hydrogen
  • Can collect oxygen produced and measure how much is given off in a certain amount of time (measuring cylinder)
  • Can change the temperature in water bath and see how they affect the activity of the catalase
37
Q

What variables in the catalase experiment need to be controlled in order to make it a fair test?

A
  • Enzyme concentration
  • pH
  • Volume of solution
38
Q

What equipment is needed in the amylase experiment?

A
  • Spotting tile
  • Pipette
  • Beaker
  • Boiling tube
  • Iodine solution
39
Q

How can you use amylase in an experiment?

A
  • Catalyses the breakdown of starch into maltose
  • Use iodine to detect starch (the substrate)
  • Time how long it takes for starch to disappear by regularly sampling starch solution
  • Adjust water bath temperature to see the affect of amylase activity
42
Q

How can the functioning of enzymes be affected?

A

By changing the temperature (changes the active site) as it changes the rate of the enzyme catalysed reaction

IGCSE - Biology (20 decks)

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