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Secondary 3 > Biology - Biological Molecules > Flashcards

Biology - Biological Molecules Flashcards

1
Q

What are the three major types of biological molecules found in living organisms?

A

Carbohydrates, lipids, proteins.

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2
Q

What are carbohydrates and what are they made of?

A

They are organic molecules made up of elements carbon, hydrogen and oxygen. Hydrogen : Oxygen = 2:1

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3
Q

Classes of carbohydrates

A
  • Single sugars/Monosaccharides (glucose - plants and animals, fructose - plants, rarely animals, galactose, ribose)
  • Double sugars/Disaccharides (maltose, sucrose, lactose)
    Sugars are sweet and soluble in water and provides energy to do work.
  • Complex carbohydrates/Polysaccharides (starch, glycogen, cellulose)
    Not sweet and insoluble in water.
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4
Q

What are organic compounds?

A

Organic compounds refer to carbon-containing compounds that are found in living organisms. These compounds contain both hydrogen and oxygen.

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5
Q

What are macromolecules?

A
  • All organic compounds are macromolecules
  • Large molecules composed of thousands of covalently bonded atoms
  • Some are polymers built from repeating units called monomers
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6
Q

How are the saccharides related?

A

Monosaccharides are linked together by condensation reaction to form disaccharides and polysaccharides.

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7
Q

What is condensation reaction?

A

Links stuff. A condensation reaction (a chemical reaction) where two molecules are joined together to form a large molecule usually with the removal of one water molecule.
E.g. glucose + glucose –> maltose + water (the link between the two maltose thingies is the glycosidic bond)

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8
Q

What is hydrolysis?

A

Opposite of condensation reaction, breaks stuff down. A reaction in which a water molecule is needed to break a complex molecule into simpler substances. E.g. disaccharide into its monosaccharide units

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9
Q

What are polysaccharides?

A
  • Complex carbohydrates aka polysaccharides
  • Made of many monosaccharides linked together through condensation reaction
  • May occur as long, straight or branched cells
  • Some are polymers of monosaccharides
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10
Q

What is maltose and sucrose, and how can they be broken down?

A

Maltose occurs in germinating grains, and one molecule consists of two glucose molecules bonded together. glucose + glucose –> maltose
A sucrose molecule is made up of one glucose and fructose molecule joined together. glucose + fructose –> sucrose
A double sugar can be split into two single sugars by enzymes. e.g. maltose (with enzyme maltase) –> glucose + glucose

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11
Q

What are reducing sugars and how to test for them?

A

Glucose, fructose and maltose are reducing sugars. Reducing sugars produce a red precipitate when tested with the same amount of Benedict’s solution, which is mixed in a test tube and placed in a boiling water-bath.

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12
Q

What are complex carbohydrates?

A
  • Made up of many similar molecules of single sugars joined together to form a large molecule
  • Starch, glycogen and cellulose are made of of numerous glucose molecules. The glucose molecules are linked in different ways (different structures, chemical, biological properties)
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13
Q

What are the characteristics of starch?

A
  • Made up of thousands of glucose molecules joined together
  • Storage form of carbohydrates in plants
  • When needed, can be digested to glucose to provide energy for cell activities
  • Found in storage organs in plants
  • Broken down into maltose (disac) by enzyme amylase, and maltose into glucose by enzyme maltase (monomer)
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14
Q

What are the characteristics of cellulose?

A
  • Many glucose molecules joined together
  • Bonds between glucose units different from starch
  • Cellulose cell wall protects plant cells from bursting/damage.
  • Cannot be digested.
  • Serve as dietary fibre –> prevents constipation
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15
Q

What are the characteristics of glycogen?

A
  • Branched molecule, many glucose molecules joined together
  • Storage form of carbs in mammals. When needed, it is digested to glucose to provide energy for cell activities.
  • In animals, stored mainly in the liver and muscles
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16
Q

What are the functions of carbohydrates?

A
  • substrate for respiration to provide energy for cell activities
  • form supporting structures e.g. cell walls
  • formation of nucleic acids, e.g. DNA
  • synthesise lubricants (mucus)
  • synthesise nectar in flowers
17
Q

What are fats?

A
  • Type of lipid
  • Organic molecules made up of carbon, hydrogen, oxygen (much less oxygen)
  • Fats occur as solid in room temp, oils occur as liquid in room temp
18
Q

What are triglycerides?

A
  • Major group of lipids
  • Also known as fats
  • Made of two compounds; 3 fatty acid molecules + 1 glycerol molecule –? linkage between the glycerol and the fatty acids is the Ester linkage
  • All triglycerides are macromolecules, but they are NOT polymers.
    e.g. tristearin needs to be broken down into glycerol + 3 stearic acid molecules by the enzyme lipase
19
Q

Structure of fatty acids and what happens when saturated vs unsaturated?

A

Organic molecule, has a carboxyl group (- COOH).
When saturated, the fatty acid chain is straight.
When unsaturated, the chain has kinks where double bond occurs.

20
Q

Function and structure of glycerol

A

Glycerol is the alcohol that usually makes up triglyceride.
Has 3 carbons (in the middle)
Each carbon bears a hydroxyl group (- OH)

21
Q

What are the functions of fats?

A
  • Source and long-term source of energy (higher energy value than carbs)
  • Insulating material; prevents excessive heat loss
  • Reduce water loss from skin surface; glands secrete oily substance
22
Q

How can we test for fats?

A

Ethanol emulsion test –> test for presence of fats
White emulsion formed when ethanol and water are added to fats
emulsion = suspension of small drops of liquid into another liquid
add ethanol –> shake –> add water –> shake

23
Q

What are proteins?

A

Organic materials made up of carbon, hydrogen, oxygen, nitrogen. Sulfur may be present. Proteins are always present in all cells.

24
Q

What is the structure of proteins?

A
  • Built up from amino acids
  • An amino acid is made up of an amino group (–NH2), acidic/carboxyl group (-COOH) and a side chain (R)
25
Q

What are polypeptides?

A

Many amino acids joined together linearly by condensation.
Polypeptides can also join to form even longer chains. A protein molecule is made up of these long chains folded together. Peptide bonds (linkages) are formed between the amino acids in the polypeptide chain.

26
Q

What are the sources and functions of protein?

A
  • Found in both animals and plants
  • synthesises new cytoplasm
  • growth and repair of worn-out cell parts
  • synthesis of enzymes
  • formation of antibodies to combat diseases
27
Q

How can we test for proteins?

A

Biuret test. Turns violet when proteins are present. Add an equal volume of biuret solution and shake well.

Secondary 3 (22 decks)

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