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Biology- Porteous > 3.1.3 Lipids > Flashcards

3.1.3 Lipids Flashcards

1
Q

Name two groups of lipid?

A

Triglycerides

Phospholipids

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2
Q

How are triglycerides formed?

A

The condensation of one molecule of glycerol and three molecules of fatty acid

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3
Q

What bond is formed during the condensation of one molecule of glycerol and three molecules of fatty acid?

A

Ester bond

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4
Q

Where is the R group in a triglyceride?

A

The fatty acid molecule

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5
Q

Is the R group of a fatty acid saturated or unsaturated?

A

It can be both

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6
Q

How does a phospholipid differ from a triglyceride?

A

One group of fatty acids is removed

A phosphate containing group joins the molecule

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7
Q

How do lipids insulate?

A

A layer of fat under the skin

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8
Q

How do leaves reduce transpiration?

A

With a waxy cuticle on the upper surface of the leaf

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9
Q

Why do seeds need a fat store?

A

As an energy store to aid growth

When oxidised, lipids provide more than twice the energy as carbs and release valuable water

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10
Q

Where else are fats found in animals?

A

Around organs for protection (eg kidney)

Under the skin for insulation as fats are slow conductors of heat

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11
Q

Where are fats found in cells?

A

Cell membrane
Separate substances inside and outside cell
Contribute to flexibility

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12
Q

How do insects prevent dehydration?

A

They have a lipid based waxy cuticle

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13
Q

Why is triglyceride not a polymer?

A

There are no repeated subunits

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14
Q

What elements are involved in a triglyceride?

A

Carbon
Hydrogen
Oxygen (least)

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15
Q

What are the properties of a triglyceride?

A

Insoluble in water

Soluble in organic solvents (alcohol)

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16
Q

What’s the general formula of a triglyceride?

A

RCOOH

17
Q

Describe saturated fats?

A

Single carbon-carbon bonds
Straight chains
More dense at room temperature
Straight chains are compact

18
Q

Describe unsaturated fats?

A

One or more carbon-carbon double bonds
Kinky chains as double bonds make it bend
Less dense so liquid at room temperature
Kinky chains can’t be tightly packed

19
Q

What’s the difference between a monounsaturated fats and polyunsaturated fats?

A

Monounsaturated fats have just one carbon carbon double bond whereas polyunsaturated fats have more than one carbon carbon double bond

20
Q

What’s the structure of a triglyceride?

A 
H      O
H-C-O-C-R
    H      O
H-C-O-C-R
    H      O
H-C-O-C-R
    H
21
Q

Describe the test for a lipid?

A

Take a dry, grease-free test tube
Add ethanol to solution
Shake to dissolve any lipid
Add water and shake
A cloudy white emulsion indicates a lipid is present
Repeat with water instead of solution X (should remain clear)

22
Q

Why does a sample containing a lipid produce a cloudy-white colour in the lipids test?

A

The alcohol with the lipid in doesn’t dissolve in water so forms an emulsion

23
Q

Why are phospholipids useful as cell membranes?

A

The two layers of phospholipids have hydrophobic ends facing toward each other to make a micelle which controls what substances come in and out

24
Q

List the 4 main roles of lipids.

A

Source of energy
Waterproofing
Insulation
Protection

25
Q

What is the formula for glycerol?

A

CH2OH

26
Q

What is the formula for a fatty acid?

A

HOOC

27
Q

Why are hydrocarbon chains with no carbon to carbon double bonds described as saturated?

A

All carbon atoms are linked to the maximum possible number of hydrogen agoms

28
Q

What makes triglycerides good storage molecules?

A

Low mass to energy ratio
Lots of energy stored in a small volume
Good for animals as it reduces the mass they have to carry as they move

29
Q

Why don’t triglycerides affect the water potential of a cell?

A

They’re large and non polar
This makes them insoluble in water
So their storage doesn’t affect osmosis in cells

30
Q

How do triglycerides provide a good source of water?

A

High ratio of hydrogen to oxygen atoms

This means they release water when oxidised

31
Q

What makes phospholipids polar?

A 
Each end (pole) behaves differently in water
Hydrophilic heads (phosphate molecules) attract water
Hydrophobic tails (2 fatty acids) repel water
32
Q

How does the phospholipid structure have any association with cell recognition?

A

By combining with carbohydrates within the cell-surface membrane they can form glycolipids
Glycolipids are important in cell recognition

Biology- Porteous (14 decks)

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