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biological molecules Flashcards

- role of water - food tests - carbohydrates, fats and proteins - enzymes

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1
Q

what are the three types of carbohydrates?

A

monosaccharides, disaccharides and polysaccharides

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2
Q

examples of simple sugars/monosaccharides

A

glucose, fructose and galactose

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3
Q

examples of complex sugars/disaccharides

A

sucrose, lactose and maltose

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4
Q

examples of polysaccharides

A

starch, glycogen and cellulose

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5
Q

functions of carbohydrates

A
  1. energy source
  2. used in the formation of nucleic acids (DNA, RNA)
  3. can be converted to other organic compounds like fats and amino acids
  4. used to synthesise lubricants
  5. form supporting structures (cellulose cell wall in plants)
  6. used in the production of nectar in some flowers
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6
Q

what are carbohydrates made up of?

A

carbon, hydrogen and oxygen

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7
Q

chemical formula of glucose

A

C6H12O6

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8
Q

what are fats made up of?

A

carbon, hydrogen and oxygen

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9
Q

what does a fat molecule consist of?

A

1 glycerol molecule attached to fatty acid molecules

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10
Q

are saturated fats healthy or unhealthy?

A

saturated fats are unhealthy

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11
Q

functions of fats

A
  1. efficient source and storage form of energy
  2. solvent for fat-soluble vitamins, sex hormones and related hormones
  3. an essential part in cells, especially in cell membranes
  4. restrict water loss from skin surface
  5. acts an insulating material that prevents excessive heat loss
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12
Q

fats can be broken down into?

A

fatty acids and glycerol

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13
Q

what are proteins?

A
  • made up of 20 amino acids
  • each amino acid has an amino group (-NH2), a carboxylic acid group (-COOH) and a carbon side chain (denoted by R) which can contain sulfur and nitrogen
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14
Q

functions of proteins

A
  • synthesis of protoplasm, for growth and repair of worn-out body cells
  • synthesis of enzymes
  • synthesis of hormones
  • synthesis of antibodies
  • source of energy
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15
Q

glycogen is synthesised from?

A

glucose

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16
Q

polypeptides and proteins are synthesised from?

A

amino acids

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17
Q

what are lipids synthesised from?

A

fatty acids and glycerol

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18
Q

examples of reducing sugars

A

glucose, fructose and maltose

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19
Q

what is used to test for presence of reducing sugars?

A

Benedict’s test using Benedict’s solution

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20
Q

describe procedure of Benedict’s test

A
  1. Place 2cm^3 of each food sample into a test tube
  2. Add 2cm^3 of Benedict’s solution to the food sample
  3. Shake the mixture and place the test tube in a boiling water-bath for 2-3 mins
  4. Record the colour of the solution
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21
Q

observation when no reducing sugar is present

A

Benedict’s solution remained blue

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22
Q

observation when traces of reducing sugar is present

A

Benedict’s solution turned from blue to green

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23
Q

observation when moderate amounts of reducing sugar is present

A

Benedict’s solution turned from blue to yellow/orange

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24
Q

observation when large amounts of reducing sugar is present

A

Benedict’s solution turned from blue to red/ red precipitate formed

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25
Q

describe procedure for test for starch

A
  1. Add a few drops of iodine in potassium iodide solution to a food sample
  2. Record your observations
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26
Q

observation when there is starch present

A

iodine solution turns from yellowish-brown to blue-black

27
Q

observation when there is no starch present

A

iodine solution remains yellowish brown

28
Q

what test is done to test for fats?

A

ethanol emulsion test

29
Q

describe procedure for ethanol emulsion test on samples in liquid state

A
  1. Add 2cm^3 of ethanol to a drop of liquid sample in a test tube and shake the mixture thoroughly
  2. Add 2cm^3 of water to the mixture and shake the mixture
  3. Record your observation
30
Q

describe procedure for ethanol emulsion test on samples in solid state

A
  1. Crush the solid sample into small pieces using a mortar and pestle and place the pieces in a test tube
  2. Add 2cm^3 of ethanol into the test tube and shake thoroughly
  3. Allow the solid particles to settle. Carefully decant (pour off the top layer of ethanol) the ethanol into another test tube containing 2cm^3 of water and shake the mixture
  4. Record your observation
31
Q

observation when there is presence of fats

A

cloudy white emulsion is formed

32
Q

what test is done to test for proteins?

A

biuret test

33
Q

describe procedure of biuret test

A
  1. To 2cm^3 of liquid food sample, add an equal volume of biuret solution
  2. Shake well and allow the mixture to stand for 5 minutes
  3. Record your observation
34
Q

observation when there is presence of proteins

A

the biuret solution changes from blue to violet

35
Q

observation when there is no presence of proteins

A

the biuret solution remains blue

36
Q

roles of water

A
  1. essential component of protoplasm
  2. medium for chemical reactions
  3. transport agent for digested substances and excretory products from tissue cells to excretory organs
    - transport agent for hormones from glands to target organs/tissues
  4. essential component of lubricant found in joints, digestive juices and blood
  5. required for hydrolytic reactions
  6. regulates body temperature by production of sweat
37
Q

what are the main chemical elements found in all biological molecules?

A

oxygen, carbon and hydrogen

38
Q

define enzymes

A

enzymes are biological catalysts made up of proteins which speed up the chemical reactions within an organism and remain chemically unchanged at the end of the process

39
Q

define catalyst

A

a catalyst is a substance that can speed up a chemical reaction, and remain chemically unchanged at the end of the reaction

40
Q

what enzymes digest carbohydrates?

A

carbohydrases such as amylase

amylase is found in the mouth (saliva) and the small intestine

41
Q

amylase digests starch to?

A

maltose

42
Q

what enzymes digest protein?

A

proteases (pepsin and trypsin)

pepsin (found in stomach)
trypsin (found in the small intestine)

43
Q

pepsin digests proteins to?

A

polypeptides

44
Q

trypsin digests proteins to?

A

polypeptides

45
Q

what enzymes digest fats?

A

lipases

46
Q

lipase digests fats to?

A

fatty acid and glycerol

47
Q

maltase digests maltose to?

A

glucosew

48
Q

why are enzymes required in minute amounts?

A

enzymes remain chemically unchanged after a reaction and can be re-used

49
Q

why are enzymes highly specific?

A

each enzyme has an active site with a specific shape which will fit only a certain substrate

50
Q

do enzymes catalyse reversible or irreversible reactions?

A

reversible reactions!

51
Q

2 factors that enzymes are affected by

A

pH and temperature

52
Q

are substrates the “lock” or the “key”?

A

substrates are the KEY

53
Q

are the enzymes the “lock” or the “key”?

A

enzyme is the lock

54
Q

what is formed when the substrate binds to the active site of the enzyme?

A

enzyme-substrate complex

55
Q

what is an active site?

A

an enzyme has a specific 3D shape. It has a depression called the active site.

56
Q

what is the lock and key hypothesis?

A
  • only the substrate with a 3D shape COMPLEMENTARY to that of the active site can fit into the enzyme which results in the formation of an enzyme-substrate complex
  • the enzyme is like a lock while the substrate is a key
  • the substrate fits into the enzyme just like a key fits into a lock
57
Q

what occurs after the substrate binds to the active site of the enzyme and forms a enzyme-substrate complex?

A

a chemical reaction occurs and the substrate is converted to the products. later, the products leave the active site. the enzyme remains unchanged and can catalyse another reaction.

58
Q

is an enzyme more or less active at low temperatures?

A

less active! at low temps, the kinetic energy of molecules is low. enzyme and substrate molecules move slowly. the rate of the substrate colliding with the enzyme is very low

59
Q

what is the optimum temperature of most human enzymes?

A

40-45°C

60
Q

define optimum temperature

A

temperature at which the enzyme is most active

61
Q

what does increasing the temperature above the optimum temperature do to the enzyme and the rate of enzyme reaction?

A

the enzymes become denatured. the active site of the enzyme molecule begins to lose its original shape and is no longer complementary to the shape of the substrate molecules

62
Q

optimum pH if amylase in saliva

A

pH 7

63
Q

optimum pH of protease in stomach

A

pH 2

64
Q

optimum pH of protease in small intestine

A

pH 8

biology (9 decks)

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