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A Level Biology: 2.1.2 Biological Molecules > 2.1.2e Lipids > Flashcards

2.1.2e Lipids Flashcards

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1
Q

What are lipids

A

Lipids are macromolecules, composed of carbon, hydrogen & oxygen.

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2
Q

What are the 2 main types of lipids

A
  • Triglycerides (the main component of fats & oils)
  • Phospholipids
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3
Q

What are lipids soluble in

A

Organic solvents such as alcohols & acetone

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4
Q

Function of lipids

A
  • STORAGE OF ENERGY for long-term use (eg. triglycerides)
  • HORMONAL roles (eg. steroids sa. oestrogen & testosterone)
  • INSULATION - both thermal (triglycerides) & electrical (sphingolipids)
  • PROTECTION of internal organs (eg. triglycerides & waxes)
  • STRUCTURAL components of cells (eg. phospholipids & cholesterol)
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5
Q

Lipid properties: compared to carbohydrates

A

The proportion of carbon to oxygen & hydrogen is smaller than in carbohydrates.

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6
Q

Property of lipids (involving reaction w water)

A

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

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7
Q

What is the mnemonic for the function of lipids

A

SHIPS

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8
Q

What are triglycerides & phospholipids an example of

A

Macromolecules - large molecules composed of several smaller ones, but not necessarily a polymer

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9
Q

see showbie slide 5 for diagrams of types of lipids

A
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10
Q

How are triglycerides formed

A

Triglycerides are formed when condensation reactions occur between 1 glycerol & 3 fatty acid chains

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11
Q

What is the linkage within triglycerides

A

The hydroxyl (-OH) groups of glycerol combine with the carboxyl (-COOH) groups of the fatty acids to form an ester linkage (known as esterification)

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12
Q

How are triglycerides broken down

A

During breakdown (eg for metabolism), these ester bonds are broken down by hydrolysis

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13
Q

What does the condensation reaction to form triglycerides cause

A

The condensation reaction results in the formation of 3 molecules of water

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14
Q

see showbie slide 6 for diagrams of triglyceride

A
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15
Q

Formation of the ester bond and release of water in triglycerides

A
  • A H from glycerol combines w an OH from fatty acid to make water.
  • The formation of an ester bond is a condensation reaction
  • For each ester bond formed, a water molecule is released
  • 3 fatty acids join to 1 glycerol molecule to from a triglyceride
  • Therefore, for 1 triglyceride to form, 3 water molecules are released
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16
Q

see slide 9-13 for formation of triglycerides

A
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17
Q

2 types of triglycerides

A

Triglycerides can either be saturates or unsaturated, depending on the composition of the fatty acid chains

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18
Q

How do animals tend to store triglycerides

A

As fats (solid)

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19
Q

How do plants tend to store triglycerides

A

As oils (liquid)

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20
Q

How many different types of fatty acids are there

A

Over 70 different types, which vary in chain lengths, presence and number of double bonds

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21
Q

What are fatty acids

A

Long hydrocarbon chain that are found in certain types of lipids (triglycerides & phospholipids).
Fatty acids may differ in the length of the hydrocarbon chain & in the no. of double bonds

22
Q

What are saturated fatty acids

A

Fatty acids that possess no double bonds between their carbon atoms are SATURATED (they have the maximum no. of H atoms). This generates fats that are usually solid at room temp

23
Q

Structure of saturated fatty acids

A

Linear in structure, originate from animal sources (eg fats) & are typicall7 solid at room temp

24
Q

see slide 14-19 for saturated & unsaturated fatty acids

A
25
Q

What are unsaturated fatty acids

A

Fatty acids with at least 1 double bond between carbon atoms are UNSATURATED - either monounsaturated (1 double bond) or polyunsaturated (more than 1 double bond)

26
Q

Structure of unsaturated fatty acids

A

Bent in structure, originate from plant sources (eg. oils). They are usually liquid at room temp.
Unsaturated fatty acids have at least 1 double bond between carbon atoms, which cause the chain to kink (see slide 15)

27
Q

Eg of unsaturated fats; polyunsaturated

A

found in fish & some veg.

tuna, seeds

28
Q

Eg of unsaturated fats: monounsaturated

A

found in plant-based foods & oils

avocados, olive oil

29
Q

Eg of saturated fats from vegetables

A

coconut, palm oil

30
Q

Eg of saturated fats

A

found in animal fats & dairy products

fatty meats, butter, milk

31
Q

Eg of trans fats

A

found in fast foods & processed snacks

deep fried food, sweets

32
Q

see slide 20 for types of fatty acids and their bonds table

A
33
Q

What is a phospholipid

A

Structure is similar to triglyceride, but one fatty acid chain replaced with a phosphate group

34
Q

Structure of phospholipids

A
  • Glycerol plus 2 fatty acids & a phosphate group
  • The ‘polar head’ refers to the glycerol & phosphate. It is hydrophilic, meaning it attracts water
  • The fatty acids ‘tails’ are hydrophobic, meaning they repel water

(see slide 21-25 for structure)

35
Q

Why do phospholipids form bilayer in water

A

Phospholipids are amphipathic (they have both hydrophobic & hydrophilic parts). As a result, phospholipid molecules form monolayers or bilayers in water

36
Q

Function of phospholipids

A
  • Play crucial role in forming plasma membrane of cells
  • In an aqueous environment, being polar means a bilayer can be formed
  • They form a bilayer w the fatty acid ‘tails’ facing into eachother, & the ‘polar heads’ facing outwards & dissolving in the aqueous intra- and extracellular fluids
  • The hydrophilic heads can be used to hold at the surface of the cell surface membrane
  • Their structure allows them to form glycolipids w carbohydrates which are important on the cell surface membrane for cell recognition
  • Ideal for forming cell surface membranes as they enable integration of other molecules into the ‘mosaic’ & help regulate movement of molecules in & out of cells
37
Q

What is cholesterol

A

Sterols (steroid alcohols) are another type of lipid found in cells

38
Q

Where is cholesterol manufactured

A

Manufactured primarily in the liver & intestines

39
Q

Structure of cholesterol

A

Has a 4 carbon ring structure w a hydroxyl (OH) group at one end

(see slide 29)

40
Q

Function of cholesterol

A
  • Important in the formation & fluidity of cell surface membranes & in the production of certain hormones eg. testosterone
  • Forms a small, thin molecule that fits into the lipid bilayer giving strength & stability
  • Needed to make Vitamin D
41
Q

Is cholesterol soluble in water

A

NO. Like all lipids, cholesterol is insoluble in water. In order to be transported in the bloodstream, insoluble cholesterol is combined w proteins to form soluble lipoproteins
There are 2 major lipoproteins

42
Q

What are the 2 major lipoproteins

A
  • Low-density lipoproteins
  • High-density lipoproteins
43
Q

What are Low-density lipoproteins (LDLs)

A

LDLs - BAD
Triglycerides (from fats in our diet) combine w cholesterol & proteins to form LDLs which transport the cholesterol to our body cells

44
Q

Function of Low-density lipoproteins

A
  • Carry cholesterol from the liver to the rest of the body
  • Bind to receptors on cell surface membranes before being taken up by the cells where the cholesterol is involved in the synthesis & maintenance of cell membranes
  • Excess LDL overload on these membrane receptors, results in high blood cholesterol levels, which may be deposited in the artery walls forming atheromas
45
Q

What are High-density lipoproteins (HDLs)

A

HDLs - GOOD
‘H’ for ‘Hoover’. HDLs are made when triglycerides (from fats in diet) combine w cholesterol & proteins. They have a higher % of protein & less cholesterol compared to LDLs, hence their higher density

46
Q

Function of High-density lipoproteins

A
  • HDLs scavenge & ‘hoover’ up excess cholesterol in the arteries & carries it to the liver where it is broken down & passed out of the body
  • This lowers the blood cholesterol levels, & helps remove the fatty plaques of atherosclerosis
47
Q

What is ‘bad’ about LDLs and ‘good’ about HDLs

A
  • LDLs raise blood cholesterol levels & are associated w the formation of atherosclerotic plaques, whilst HDLs lower blood cholesterol levels.

Therefore, it is desirable to maintain a higher HDL:LDL ratio in the blood

48
Q

Dietary factors that increase cholesterol levels

A

High intake of certain types of fats will differently affect cholesterol levels in blood
- SATURATED fats increase LDL levels (& HDL as shown in studies, but much more LDL), raising blood cholesterol levels
- TRANS fats increase LDL levels & decrease HDL levels, significantly raising blood cholesterol
- UNSATURATED fats increasing HDL levels, lowering blood cholesterol
- MONOSATURATED fats helps removal of LDLs from blood
- POLYSATURATED fats increase activity of the LDL receptor sites so the LDLs are actively removed from blood

49
Q

Exam q: Compare LDLs & HDLs

A

LDL carry cholesterol from liver to body cells
- Bind to receptors on cells which takes in cholesterol
- Raises blood cholesterol
- Increase deposition of fats in artery wall
- Form plaques/atheromas

HDL carry cholesterol from body to liver
- Bind to receptors on liver cells
- Liver takes in excess cholesterol
- Reduces blood cholesterol
- Therefore reduces deposition of fats
- Decreases risk of plaques/atheromas

50
Q

Why is health advice constantly changing

A

As technology develops and so our understanding of biological processed increases

51
Q

What is food synergy according to health advice

A

It is now generally believed that nutrients do not work in isolation but as part of the combined effect of a whole range of nutrients - food synergy

52
Q

Why is the data used in health advice reports often flawed

A
  • Bc the subjects involved in the studies often do not provide accurate info when diet is concerned. Ppl tend to underestimate what they eat, forget what they have eaten & dont know the exact ingredients of meals (particularly if eating out)
  • Ppl are also different due to genetics & so respond diffrerently to different nutrients

A Level Biology: 2.1.2 Biological Molecules (9 decks)

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