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IP Secondary 3 Biology > Chapter 3 - Biomolecules > Flashcards

Chapter 3 - Biomolecules Flashcards

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1
Q

Water (4 functions)

A
  • a solvent for chemical reactions
  • key component in cells, tissue fluid, digestive juices and blood
  • controls body temperature (water has high specific heat capacity)
  • transports dissolved substances
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2
Q

Carbohydrates

A

Organic molecules made up of the elements carbon, hydrogen and oxygen
- hydrogen : oxygen = 2 : 1

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3
Q

Monosaccharides

A
  • single sugars

- glucose, fructose, galactose

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4
Q

Disaccharides

A
  • double sugars

- maltose, sucrose, lactose

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5
Q

Polysaccharides

A
  • complex carbohydrates

- starch, cellulose, glycogen

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6
Q

Categorise glucose, fructose, galactose, maltose, sucrose, lactose, starch, cellulose and glycogen into

  1. reducing sugar
  2. non-reducing sugar
A
  1. reducing sugars: glucose, fructose, galactose, maltose, lactose, starch, cellulose, glycogen
  2. non-reducing sugar: sucrose
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7
Q

Condensation reaction

A

Two simple molecules are joined together to form a larger molecule with the removal of one water molecule.

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8
Q

Hydrolysis (hydrologic reaction)

A

A water molecule is needed to break up a complex molecule into smaller molecules

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9
Q

Functions of carbohydrates [5]

A
  1. Forms supporting structures (e.g. cell wall)
  2. Can be converted into other organic compounds (amino acids and fats)
  3. Formation of nucleic acids (e.g. DNA)
  4. Synthesise lubricants (e.g. mucus)
  5. Synthesise nectar in some flowers
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10
Q

Chemical formula of glucose

A

C6H12O6

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11
Q

Glucose: function

A

A substrate for respiration, provides energy for cell activities

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12
Q

Starch: structure

A

Several thousand glucose molecules joined together

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13
Q

Starch: function

A
  • Storage form of carbohydrates in plants

- Can be digested to glucose when needed (to provide energy for cell activities)

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14
Q

Glycogen: structure

A

Many glucose molecules joined together, branched molecule

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15
Q

Glycogen: function

A
  • Storage form of carbohydrates in mammals

- Can be digested to glucose when needed (to provide energy for cell activities)

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16
Q

Cellulose: structure

A

Many glucose molecules joined together

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17
Q

Cellulose: function

A
  • Cellulose cell wall protects plants from bursting or damage
  • Cannot be digested in humans, serves as dietary fibres that prevent constipation
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18
Q

Why are glycogen and starch suitable as storage materials in cells? [4]

A
  • Insoluble in water: do not change the water potential in the cells
  • Large molecules: cannot diffuse through cell membranes, so they will not be lost from the cell
  • Can be easily hydrolysed to glucose: when energy is needed
  • Compact shapes: occupy less space than all the individual glucose molecules that make up a glycogen or starch molecule
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19
Q

Fats

A

Organic molecules made up of the elements carbon, hydrogen and oxygen.
(Fats contain much less oxygen in proportion to hydrogen)

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20
Q

Functions of fats (5)

A
  1. A source and store of energy
  2. An insulating material that prevents excessive heat loss
  3. A solvent for fat-soluble vitamins and many other vital substances
  4. An essential part of protoplasm, especially in cell membranes
  5. A way to reduce water loss from the skin surface
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21
Q

Proteins

A

Organic molecules made up of the elements carbon, hydrogen, oxygen and nitrogen (sulfur may also be present)

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22
Q

Amino acid: structure

A
  1. amino group (NH2)
  2. acidic group (COOH)
  3. side chain
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23
Q

Polypeptide

A

A chain of amino acids formed in the condensation reaction

bonded by peptide bonds

24
Q

Functions of proteins (3)

A
  1. Synthesis of new protoplasm
  2. Synthesis of enzymes and some hormones
  3. Formation of antibodies
25
Q

Nucleic acid: function

A

Stores and transfers genetic information

26
Q

Enzymes

A

Biological catalysts that alter or speed up a chemical reaction, without itself being chemically changed at the end
(MOST enzymes are proteins)

27
Q

Examples of enzymes

A
  • Lipase (fats → glycerol + fatty acids)
  • Amylase (starch → maltose
  • Maltase (maltose → glucose)
  • Protease (protein → amino acids)
28
Q

Catalyst

A

A substance which can alter or speed up a chemical reaction, without itself being chemically changed at the end of the reaction
(an enzyme is a biological catalyst)

28
Q

What are hydrolases?

A

Enzymes that catalyse hydrolytic reactions

29
Q

Examples of hydrolases

A
  • Carbohydrases (digest carbohydrates)
  • Proteases (digest proteins)
  • Lipases (digest fats)
31
Q

Activation energy

A

The energy needed to start a reaction

need to raise activation energy to a certain point before 2 reactants can react

32
Q

Anabolic reactions

A

Build up complex substances

e.g. ammonia acids → proteins, condensation reaction

33
Q

Catabolic reactions

A

Break down complex substances

e.g. LAMP reactions, hydrolysis

34
Q

Lock-and-key hypothesis

A
  1. Substrate enters the active site of the enzyme
  2. Substrate binds to the active site of the enzyme, forming an enzyme-substrate complex
  3. Chemical reaction occurs
  4. Products leave the active site of the enzyme
35
Q

Only a substrate with shape ________ to that of the active site of the enzyme can fit to form the enzyme-substrate complex

A

complementary

36
Q

Induced-fit hypothesis

A
  1. The shapes of the active site and the substrate are not exactly complementary
  2. Active site changes shape slightly in the presence of a specific substrate to become complementary, forming an enzyme-substrate complex
  3. Chemical reaction occurs
  4. Products leave the active site of the enzyme
37
Q

Characteristics of enzymes (Mode of action)

A
  1. Speed up chemical reactions (by lowering the activation energy)
  2. Required in minute amounts
  3. Highly specific in action (each enzyme generally catalyses only one particular reaction)
  4. Their presence does not alter the nature or properties of the end-products of a reaction
37
Q

Rate of reaction/enzyme activity is affected by:

A
  1. Temperature
  2. pH
  3. Substrate and enzyme concentrations
39
Q

At high temperatures, the enzyme is ________

A

DENATURED

  • Change in the 3D structure of the enzyme → loss/alteration of enzyme’s active site
  • Substrate molecules can no longer fit into the active site
40
Q

How do enzymes lower the activation energy of an reaction?

A

Provide an alternative reaction pathway of lower activation energy

41
Q

At low temperatures, the enzyme is ________

A

INACTIVE

- Kinetic energy is low → chances of substrate colliding with the enzyme is very low

42
Q

At ________ temperature, the rate of enzyme activity is highest

A

optimum

43
Q

Graph for enzyme activity against temperature

A

(image)

44
Q

________ are most active in acidic solutions, ________ are most active in alkaline solutions

A

some

some

45
Q

When there are extreme changes in acidity/alkalinity, the enzyme is ________

A

DENATURED

  • Change in the 3D structure of the enzyme → loss/alteration of enzyme’s active site
  • Substrate molecules can no longer fit into the active site
46
Q

At ________ pH, the rate of enzyme activity is highest

A

optimum

47
Q

Graph of enzyme activity against pH

A

(image)

48
Q

Test for reducing sugars

A

BENEDICT’S TEST

  1. Add Benedict’s solution to food sample
  2. Shake the mixture
  3. Heat in boiling water bath for 2-3min
49
Q

Observations for reducing sugar test

A
  • Mixture, with ppt, turned from blue to green → trace amounts
  • Mixture, with ppt, turned from blue to yellow → moderate amounts
  • Mixture, with ppt, turned from blue to orange-red → large amounts
  • Mixture remained blue → absent
50
Q

Test for starch

A

IODINE TEST

1. Add a few drops of iodine solution to food sample

51
Q

Observations for starch test

A
  • Iodine solution turned from brown to blue-black → present

- Iodine solution remained brown → absent

52
Q

Test for fats (liquid sample)

A

ETHANOL EMULSION TEST

  1. Add ethanol to food sample
  2. Shake contents thoroughly
  3. Add water and shake
53
Q

Test for fats (solid sample)

A

ETHANOL EMULSION TEST

  1. Add ethanol to cut food sample
  2. Shake contents thoroughly
  3. Decant ethanol into another test tube with water. Shake.
54
Q

Observations for fats test

A
  • White emulsion → present

- Mixture remains clear → absent

55
Q

Test for proteins

A

BIURET TEST

  1. Add sodium hydroxide solution to food sample
  2. Shake mixture thoroughly
  3. Add 1% copper(II) sulfate solution dropwise, shaking after each drop
56
Q

Observations for protein test

A
  • Mixture turned from blue to violet → present

- Mixture remained blue → absent

IP Secondary 3 Biology (8 decks)

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