Transcript Biological Molecules: Lipids

Why does the camel have a hump?
Biological Molecules:
Lipids
Links to G.C.S.E
Bonding
Balanced diet and food tests
Hormones
Respiration
 State that lipids (fats & oils) are a range
of biological molecules including
triglycerides
Key definition: lipids
 Lipids are a diverse group of chemicals
that dissolve in organic solvents, such as
alcohol, but not in water.
 They include fatty acids, triglycerides and
cholesterol.
Functions of lipids
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An energy source for respiration
Energy storage
Constituent of biological membranes
Insulation- e.g. whale blubber
Protection e.g. waxy cuticle in plants
Make up steroid hormones e.g.
testosterone, oestrogen, progesterone
Molecular structure of glycerol
Fatty acid molecule showing acid group
Fatty acids
 All fatty acids have an acid group at one end
(the same as on an amino acid)
 The rest is a hydrocarbon chain, anything
from 2-20 carbons long
 The most common fatty acids Have 18
carbons in the hydrocarbon chain
 The terms unsaturated and polyunsaturated is
often used when discussing healthy foods.
 Saturated fats are a feature of a poor diet.
 A saturated fatty acid is one where all bonds
possible are made with hydrogen.
Saturated and unsaturated fatty acids
Formation of triglyceride molecule
• Compare the structure of triglycerides
and phospholipids.
• Explain how the structure of triglyceride
and phospholipid and cholesterol
molecules relates to their functions in
living organisms.
Formation of a phospholipid molecule
How does the structure of these
molecules aid their function?
PHOSPHOLIPIDS
 Phospholipids are almost identical to triglycerides
with one important difference, the addition of a
phosphate molecule.
 The phosphate head is HYDROPHILIC while the rest
is hydrophobic.
 This gives the phospholipid molecule the capacity to
form cell membranes
 The molecules may vary in how saturated the fatty
acids are which alters the fluidity of the membrane
and is useful at varying temperatures.
TRIGLYCERIDES
 Respiration of these molecules requires the hydrolysis of the
ester bonds that hold the fatty acids and glycerol together
 Then both can be respired to carbon dioxide and water which
releases energy for the generation of ATP.
 Lipids contain about twice the energy as the same amount of
carbohydrate.
 Their insolubility means they can be stored in a compact way
without affecting the water potential of the cell contents
 The respiration of these molecules gives out more water than
carbohydrate.
 This is metabolic water vital to many organisms.
Cholesterol structure
 CHOLESTEROL
 A small molecule made from 4 carbon based
rings which is found in al biological
membranes.
 Its small, narrow structure and hydrophobic
nature allow it to sit between the
phospholipid hydrocarbon tails.
 Here it regulates the fluidity of the
membrane.
 Testosterone, oestrogen and vit D are made
from cholesterol
 The lipid nature of these hormones
means they can pass through the lipid
bilayer
 Cholesterol is vital to living organisms
and can be made in the liver
 High cholesterol is a problem in humans
because it can cause gall stones and/ or
atherosclerosis
 There is also a genetic condition called
hypercholesterolaemia which is caused
because the cells don’t respond to the
signal to stop production
Lipids & respiration
 Respiring lipids requires the hydrolysis of the
ester bonds holding the fatty acids & glycerol
together.
 Both the glycerol & fatty acids can be broken
down to give carbon dioxide & water.
 This releases energy to generate ATP molecules.
 The insolubility of lipids means they make good
compact storage molecules that do not affevt the
water potential of the cell.
 It also gives out more water than carbohydrate.
 This ‘metabolic water’ is vital to some organisms
 State that lipids (fats & oils) are a range of
biological molecules including triglycerides
 Compare the structure of triglycerides and
phospholipids.
 Explain how the structure of triglyceride
and phospholipid and cholesterol
molecules relates to their functions in living
organisms.