3.5 Lipids Flashcards
What are the two most common types of lipid/
Fats and oils
Which elements do lipids contain?
Carbon, hydrogen, oxygen
What state are fats and oils typically at at room temp?
Fats = solid
Oils = liquid
Why are they non-polar
Their electrons are more evenly distributed
Why are they insoluble in water?
Because they have no charged areas (non-polar) so do not interact with the polar molecule water
What is the name for the type of molecule that lipids are?
Macromolecules
contain no repeating units (not monomers or polymers)
What are the 3 kinds of lipid?
Triglycerides
Phospholipids
Sterols
What are triglycerides made of?
Macromolecules made of 1 glycerol molecule and 3 fatty acids
What bonds are involved in triglycerides and what kind of reaction is it?
Forms strong ester bonds between each fatty acid and glycerol
Process known as esterification
CONDENSATION REACTION as water is removed during formation of each ester bond
What happens when triglycerides are broken down and what type of reaction is it?
3 water molecules need to be supplied to reverse the reaction
HYDROLYSIS REACTION
Example of a saturated fat
Butter
Example of an unsaturated fat
Oil
Where do saturated/unsaturated fats typically come from?
Saturated = animal fat
Unsaturated = plants and seeds etc
Functions of trigylcerides
Long term energy storage
Thermal insulation to prevent heat loss e.g. penguins
Protection of vital organs
Buoyancy for aquatic animals e.g. whales
Features of saturated fats
no double bonds
some evidence to suggest they can lead to coronary heart disease (solid at room temp)
Features of unsaturated fats
contain double bonds
cannot pack close together due to double bonds (liquid at room temperature)
1 double bond…
monounsaturated
2 or more double bonds…
polyunsaturated
What happens if you have too much of any fat…
Can lead to obesity
What are phospholipids made from originally?
modified triglycerides
What elements are phospholipids made from?
Carbon, hydrogen, oxygen and phosphorus
Why are phosphate ions soluble in water?
They are negatively charged and so interact with the charges within the polar water molecule
Structure of a phospholipid:
One of the fatty acid chains in a triglyceride is replaced with a phosphate group
Has a charged head and non-polar tails
Difference between head and tails of a phospholipid
Head = negatively charged and so is hydrophilic (attracts water)
Tail = non-polar and so is hydrophobic (repels water)
How does the dual structure affect how phospholipids interact with water?
Form a layer on top of water with phosphate heads IN the water with the tails STICKING OUT
Known as surface active agents (surfactants for shorts)
Function of phospholipids:
Forming cell membranes
How are phospholipids used in forming cell membranes?
Heads inside aqueous cytosol inside cell with tails pointing outwards,
Another layer of heads outside cell in aqueous outer environment with tails pointing inwards
Tails trapped between 2 layers of heads
What type of molecule is glycerol
An alcohol (-OH)
What type of molecule are fatty acids
Carboxylic acids (-COOH)
Features of sterols
Also known of steroid alcohols
Not fats/oils
Complex alcohol molecules with 4 carbon ring structure with (OH) group at one end
Hydroxyl group is polar so is HYDROPHYLIC but rest of molecule is HYDROPHOBIC
What kind of molecule is cholesterol?
Sterol
Where in the body is cholesterol primarily manufactured?
Liver and intestines
Function of cholesterol:
Cell membrane formation
positioned between phospholipids with hydroxyl group on the outskirts of membrane
What happens to cholesterol and its function at low temps?
Adds stability to membrane and regulates fluidity by keeping membranes fluid at low temps
What happens to cholesterol and its function at high temps?
Adds stability and regulates fluidity of membranes by stopping them from becoming too fluid at high temperatures
(move faster at room temps so require more stabilising)
What else is cholesterol used to manufacture?
Bile
Vitamin D
Steroid hormones
Roles of lipids:
Membrane formation and creation of hydrophobic barriers
Hormone production
Electrical insulation necessary for impulse transmission
Waterproofing e.g. birds’ feathers + plant leaves
What else are lipids used for?
Long term energy storage
Thermal insulation to reduce heat loss e.g. penguins
Cushioning to protect vital organs like heart and kidneys
Buoyancy for aquatic animals e.g. whales
Identification of lipids test:
EMULSION TEST:
Sample is mixed with ethanol
Mixed with water and shaken
IF a white emulsion forms, then lipids are present
IF solution remains clear, test is negative
What factors make it difficult to find out the health impacts of one specific food type?
Difficult to isolate the impact of one nutrient
Believed that nutrients don’t work in isolation - combined effect
People may underestimate what they eat/forget
Difficult to know ingredients (eating out)
Do saturated or unsaturated fats have high energy?
Both have high energy
What can excess energy intake lead to?
Obesity
How do ester bonds form?
Between hydroxyl group of glycerol and hydroxyl group of fatty acids during a condensation reaction producing water
How are ester bonds broken?
Broken using water in a hydrolysis reaction which is the reverse reaction of their formation
How does a lipid emulsion test work?
Dissolved in ethanol
Water added and shaken
Lipids are displaced by water which is more soluble in ethanol
Lipids left in suspension which forms a milky white emulsion if they are present
