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Biology IGCSE > 2.7 - 2.14 > Flashcards

2.7 - 2.14 Flashcards

1
Q

what chemical elements are present in carbohydrates

A

CHO carbon, oxygen, hydrogen

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2
Q

what chemical elements are present in protein

A

CHON carbon, oxygen, hydrogen, nitrogen

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3
Q

what chemical elements are present in lipids

A

CHO carbon, hydrogen, oxygen

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4
Q

what are the monosaccharides of carbohydrates

A

simple sugars (glucose or fructose)

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5
Q

what is the disaccharide of carbohydrates

A

maltose (two glucose) and sucrose (one glucose one fructose)

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6
Q

what is a polysaccharide of carbohydrates

A

starch, glycogen, cellulose (formed when lots of molecules join together)

(they are insoluble therefore used as storage molecules)

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7
Q

what are most lipids in the body made up of

A

triglycerides

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8
Q

what are triglycerides

A

one glycerol molecule and three fatty acid chains

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9
Q

what are proteins formed from

A

amino acids (20 different types)

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10
Q

what are examples of proteins

A

enzymes, hemoglobin, ligaments, keratin

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11
Q

food test practical:
how to prepare a food sample to be nutrient tested

A
  • break up the food
  • transfer to test tube and add distilled water
  • mix the food in the water
  • filter the mixture using a funnel and filter paper and collect the solution
  • use the solution for the food tests
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12
Q

food test practical:
what is the test for glucose and how do you carry it out

A

the test is benedict’s solution

  • you add the benedict’s solution to the sample in a test tube
  • you heat it for 5 minutes

A positive test will be a color change from blue to to orange/brick red

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13
Q

food test practical:
what is the test for starch and how do you carry it out?

A

the test is iodine solution

  • add drops of iodine solution to the sample in a test tube

A positive test will show a color change from orange to brown to blue black

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14
Q

food test practical:
what is the test for protein and how do you carry it out?

A

the test is biuret solution

  • add drops of biuret solution to the sample in a test tube

A positive test will show a color change from blue to violet/purple

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15
Q

food test practical:
what is the test for lipids and how do you carry it out?

A

the test is ethanol

  • add 4 cm^3 of ethanol to the sample in a test tube and shake
  • once the sample dissolved in the ethanol, strain the ethanol solution in another test tube
  • add the ethanol solution to 4cm^3 of cold distilled water

A positive test will show a cloudy emulsion

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16
Q

what is the role of enzymes in a chemical reaction

A

they work as biological catalysts to speed up the rate of reaction without being used up in the process

17
Q

why are enzymes necessary

A

they maintain reaction speeds of all metabolic reactions (ex. digesting 1 meal would take 2-3 weeks to digest but with enzymes it only takes 4 hours)

18
Q

what is it called when the enzyme and the substrate are grouped together

A

the enzyme substrate complex

19
Q

what are factor that can affect enzyme action

A

temperature and pH

20
Q

what is the optimum temperature in the human body for enzyme action

A

37°c

21
Q

what happens to enzymes when it is above the optimum temperature

A

the bonds break and the enzyme is denatured

22
Q

what happens when the enzymes are in a temperature under their optimum temperature

A

they work slower as there is less kinetic energy so the molecules move slower and therefore there is less collision between the enzyme and the substrates

23
Q

enzyme activity practical:
what are we investigating

A

the effect on temperature on the activity of amylase which digests starch into maltose

24
Q

enzyme activity practical:
what does the time mean depending on the temperatures

A

the faster it is, the faster the enzyme is working

25
Q

what improvements could be made to this method of testing enzyme activity

A
  1. use water baths for more precise temperatures
  2. a colorimeter can be used to measure the progress of the reaction more accurately
26
Q

what is the optimum pH for most enzymes

A

pH of 7

27
Q

what is the optimum pH for acidic conditions

A

pH of 2 for the stomach for example

28
Q

what is the optimum pH for alkaline conditions

A

pH of 8 or 9 in the duodenum for example

29
Q

what happens if the pH is too far from the optimum pH

A

the enzymes can denature

30
Q

enzyme pH practical:
what is the enzyme that digests starch

A

amylase

31
Q

enzyme activity practical:
what improvements can we make to this investigation

A
  1. the starch and amylase solution should be placed in a water bath at optimum temp. before being used
  2. a colorimeter can be used to measure the progress of the reaction more accurately.

Biology IGCSE (9 decks)

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