Lipids and Proteins Flashcards

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1
Q

Draw/describe the basic structure of a triglyceride?

A

One glycerol molecule attached to three fatty acids in a E shape

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2
Q

Describe how the structure of a protein depends on the amino acids it contains (6 marking points)

A
  • the structure of a protein is determined by the position of amino acids/ ionic bonds/ hydrogen bonds/R groups
  • the primary structure is the sequence of a/a
  • the secondary structure is formed by H bonds: Alpha helix and Beta pleated sheets
  • tertiary structure is caused by interactions between a/a
  • this determines the specific shape of the protein, e.g// enzyme’s active site, complementary shape of antibodies to receptors
  • the Quaternary structure involves multiple polypeptide chains joined together
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3
Q

Give 5 functions of lipids (phospholipids and triglycerides)?

A
  • Energy source; when oxidised they release up to 2x the amount of energy than CHOs
  • Insulation; for example myelin, which helps nerve signals travel
  • Protection; surround and protect vital organs
  • Cell membranes; phospholipids make up cell membranes
  • Waterproofing; waxy cuticle and glands in skin
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4
Q

How is a triglyceride formed?

A
  • One glycerol molecule reacts with 3 fatty acids
  • condensation reaction (releases water)
  • ester bonds are formed
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5
Q

What properties of triglycerides make them suited for their function?

A
  • Insoluble in water (non-polar); so does not impact the water potential of cells
  • High ratio of O to H atoms; release water when oxidised
  • High ratio of energy storing C-H bonds; good source of energy
  • low mass:energy ratio; lots can be stored in a smaller mass, reduces the mass animals have to carry
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6
Q

What 2 functional groups are involved in the formation of peptide bonds?

A

COOH on one a/a and NH2 on the other

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7
Q

What two elements is a peptide bond between?

A

C-N

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8
Q

What 3 types of bond can be formed in the tertiary structure of a protein?

A
  • Hydrogen bonds
  • disulfide bridges
  • ionic bonds
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9
Q

Describe a test that could be carried out to confirm the presence of lipids. Include a positive result

A
  • add ethanol to sample
  • add water and shake
  • white emulsion will form if lipids are present
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10
Q

Describe a test that could be carried out to confirm the presence of proteins. Include a positive result

A
  • add sample to test tube and add Biuret’s solution
  • if proteins are present, turns from blue to violet
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11
Q

How are phospholipids arranged in a cell membrane?

A
  • form a bilayer
  • hydrophobic tails facing inwards, away from water
  • hydrophilic heads face outwards, towards water
  • this way the hydrophobic tails have minimal contact with water
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12
Q

How are phospholipds suited for their function?

A
  • hydrophobic tails; prevent water soluble substances from moving in/out of the cell
  • hydrophilic heads and hydrophobic tails mean a bilayer is formed
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13
Q

Give 4 functions of proteins

A
  • transport proteins
  • enzymes
  • antibodies
  • structural proteins
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