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IGCSE Edexcel Biology > B5 Biological Molecules and Enzymes T7-8 > Flashcards

B5 Biological Molecules and Enzymes T7-8 Flashcards

Biological molecules 2.7 identify the chemical elements present in carbohydrates, proteins and lipids (fats and oils) 2.8 describe the structure of carbohydrates, proteins and lipids as large molecules made up from smaller basic units: starch and glycogen from simple sugars, protein from amino acids, and lipid from fatty acids and glycerol

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1
Q

What are carbohydrates made of chemically?

A

hydrogen, oxygen, carbon

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2
Q

What are the large molecules of carbohydrates in animals and plants?

A

animals+fungi -> glycogen
plants -> starch

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3
Q

What do the polymers of carbohydrates break down into?

A

glucose (sugars)

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4
Q

What does the body use glucose for?

A

release energy for respiration

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5
Q

What are proteins made of chemically?

A

hydrogen, oxygen, carbon, sulfur, nitorgen, phosphorus

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6
Q

What are the large molecules of proteins?

A

proteins

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7
Q

What do the polymers of proteins break down into?

A

amino acids

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8
Q

What does the body use amino proteins for?

A

growth + repair of cells

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9
Q

What are lipids made of chemically?

A

hydrogen, oxygen, carbon

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10
Q

What are the large molecules of lipids (fats)?

A

fat molecule = triglycerides

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11
Q

What do the polymers of lipidss break down into?

A

3 fatty acids + 1 glycerol

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12
Q

(3 points)

What are lipids/fats used for in the body?

A
  1. insulation - heat
  2. long term energy store
  3. make cell membranes
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13
Q

Practical: investigate food samples for the presence of starch

What is the food test for starch?

What solution is added?

A

1) Pipette the sample solution into wells or on a tile
2) Add drops of iodine solution and leave for 1 minute
3) Record any colour change
● If starch is present the solution will turn blue-black
● If starch is not present the solution will remain brown

orange -> blue black

IODINE

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14
Q

Practical: investigate food samples for the presence of glucose

What is the food test for glucose?

What solution is added?

A

1)Add the sample solution into a test tube
2) Add drops of Benedict’s solution into the test tube
3) Heat in a water bath at 60-70°C for 5 minutes
4) Take test tube out and record the colour
● If glucose is present the solution will turn brick red
● If glucose is not present that the solution will remain blue

blue -> brick red

BENEDICT

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15
Q

Practical: investigate food samples for the presence of proteins

What is the food test for proteins?

What solution is added?

A

Add the sample solution into a test tube
2) Add drops of Biuret solution into the test tube
3) Leave for 1 minute and then record the colour
● If protein is present the solution will turn purple
● If protein is not present that the solution will remain blue

blue -> purple

BIURET

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16
Q

Practical: investigate food samples for the presence of proteins

What is the food test for lipids?

A

1)Add 2cm3 of ethanol to the test solution
2) Add 2cm3 of distilled water
3) Leave for 3 minutes and then record the colour
● If fat is present a milky white emulsion will form
● If fat is not present that the solution will remain colourless

colourless -> milky white emulsion

ETHANOL

17
Q

Define enzyme

A

biological catalyst
- speeds up a chemical reaction

18
Q

Define catalyst

A

substance whih changes the rate of a chemical reaction without being changed itself

19
Q

Explain the enzyme substrate complex

A

Each enzyme has a uniquely shaped active site where the substrate binds together

The substrate shape is complementary to the shape of the active site

20
Q

Define activation energy

A

energy needed for a chemical reaction to take place

21
Q

Explain how enzymes work

A

1) the active site is complementary to the substrate
2) the substrate and active site collide forming the enzyme substrate complex
3) enzyme breaks the substrate into products and they leave the active site, so the enzyme is reused

22
Q

Optimum temperature for enzymes

(where enzymes work the fastest)

A

37°C (body temperature)

23
Q

How temperature affects enzymes

A

The rate of reaction increases with an increase in temperature, molecules gain kinetic energy causing more successful collisions and a faster reaction rate.
Up tothe optimum, where it works the fastest
After optimum temperature,active site no longer complementary to substrate, enzymes DENATURES and eventually reaction stops.

24
Q

What happens to enzymes when the temperature becomes too hot?

A

active site changes shape, substrate is not complementary so can’t fit in.
enzyme is denatured and can no longer work

25
Q

[5 marks]

Practical: investigate how enzyme activity can be affected by changes in temperature

A

1) Starch solution is heated to set temperature
2) Amylase is added
3) Iodine is added to each well after a minute
4) Measure the time it takes until the iodine stops turning blue-black (this means that starch is not
present as amylase has broken the starch down into glucose)
5) Repeat the test with different temperature

26
Q

SAFETY MEASURES

Practical: investigate how enzyme activity can be affected by changes in temperature

A

eye protection - safety

27
Q

Optimum pH for enzymes

A

generally -> 7
stomach (acidic) -> 2

28
Q

How pH affects enzymes

A

If the pH is too high or too low, the forces that hold the amino acid chains that make up the
protein will be affected
This will change the shape of the active site, so the substrate can no longer fit in
The enzyme is denatured and doesn’t work

29
Q

CATALASE

Practical: investigate how enzyme activity can be affected by changes in pH

TRIPLE AWARD

A

1) catalase speeds up the breakdown of hydrogen peroxide -> oxygen + water
2) when reaction happens oxygen bubbles are given off -> hgiher the foam, faster the enzyme is working

30
Q

Practical: investigate how enzyme activity can be affected by changes in pH

TRIPLE AWARD

A

Method:
1) Place 5cm3 buffer solution pH 2, 4, 6, 8 into boiling tubes
2) Add a potato chip - same size each rime
3) Add 1cm3 washing up liquid to each tube
4) Add 5cm3 H2O2
5) After 10 mins measure heignht of foam

31
Q

Practical: investigate how enzyme activity is affected by changes in pH

dependent variable

TRIPLE AWARD

A

volume of oxygen produced

32
Q

Practical: investigate how enzyme activity is affected by changes in pH

independent variable

TRIPLE AWARD

A

different pH levels

33
Q

Practical: investigate how enzyme activity is affected by changes in pH

control variable

TRIPLE AWARD

A

boiled potato (denatured enzyme)
to show no oxygen produced

34
Q

What does a buffer solution do

A

changes the pH

IGCSE Edexcel Biology (28 decks)

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