Lipids Flashcards

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1
Q

What are lipids?

A

Lipids contain less oxygen molecules than carbohydrates

They are non-polar & hydrophobic (insoluble in water)

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2
Q

There are two groups

A

Triglycerides - the main component of fats & oils
Phospholipids

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3
Q

Non-polar molecule

A

When electrons are shared equally, so the molecule is not charged

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4
Q

Triglycerides have two monomers:

A

Glycerol is an alcohol (C - OH)

Fatty acids contain a methyl group (-CH3) at one end of the chain, and a carboxyl group at the other end (-RCOOH)

Fatty acids can vary in length and saturation

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5
Q

Saturated triglyceride

A

Hydrocarbon chain is saturated (single bonds of carbon)

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6
Q

Monounsaturated triglyceride

A

1 double bond of carbon in hydrocarbon chain

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7
Q

Polyunsaturated triglyceride

A

More then 1 carbon double bond in the hydrocarbon chain

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8
Q
A
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9
Q

How are triglycerides formed?

A

By esterification - an ester bond forms when a hydroxyl (-OH) group on glycerol bonds with the carboxyl (-COOH) group of the fatty acid

Three fatty acids join to one glycerol molecule to form a triglyceride

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10
Q

Triglyceride function

A

Protection - triglycerides within adipose tissue protects organs from the risk of damage

Insulation - triglycerides are used to insulate nerve fibres & within adipose tissue below the skin

Buoyancy - the low density of fat tissue helps animals to float more easily

Energy storage - the many C-H bonds can be oxidised in cellular respiration to release lots of energy → used to produce ATP
Plants store triglycerides in the form of oils (within seeds & fruit)
Mammals store triglycerides as oil droplets in adipose tissue (a reserve energy source)

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11
Q

The structure of phospholipids

A

Phospholipids have only two fatty acids

The third has been replaced by a phosphate ion (PO4 3-)

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12
Q
A
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13
Q

The structure of phospholipids

A

As the phosphate is polar, it is soluble in water (hydrophilic)

The fatty acid ‘tails’ are non-polar and insoluble in water (hydrophobic)

Phospholipids are therefore amphipathic - contains both hydrophobic & hydrophilic parts

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14
Q

What does the structure of phospholipids form?

A

In the presence of water due to the hydrophobic and hydrophilic parts phospholipids will form monolayers or bilayers.

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15
Q

Phospholipid function

A

Phospholipids are the building block of cell membranes
They act as a barrier to water-soluble molecules & can control what substances enter and leave the cell

Different compositions of phospholipids helps to change the fluidity of the cell membrane
Mainly saturated fatty acids - membrane will be less fluid
Mainly unsaturated fatty acids - membrane will be more fluid

Phospholipids also control the orientation of proteins present in the cell membrane
Weak hydrophobic interactions hold proteins in place, but still allow them to move

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16
Q

Emulsion test for lipids

A

Add ethanol and distilled water
If lipids are present, a milky emulsion will form (the solution appears ‘cloudy’); the more lipid present, the more obvious the milky colour of the solution