3.5 Lipids

Question 1

What are the two most common types of lipid/

Answer 1

Fats and oils

Question 2

Which elements do lipids contain?

Answer 2

Carbon, hydrogen, oxygen

Question 3

What state are fats and oils typically at at room temp?

Answer 3

Fats = solid
Oils = liquid

Question 4

Why are they non-polar

Answer 4

Their electrons are more evenly distributed

Question 5

Why are they insoluble in water?

Answer 5

Because they have no charged areas (non-polar) so do not interact with the polar molecule water

Question 6

What is the name for the type of molecule that lipids are?

Answer 6

Macromolecules
contain no repeating units (not monomers or polymers)

Question 7

What are the 3 kinds of lipid?

Answer 7

Triglycerides
Phospholipids
Sterols

Question 8

What are triglycerides made of?

Answer 8

Macromolecules made of 1 glycerol molecule and 3 fatty acids

Question 9

What bonds are involved in triglycerides and what kind of reaction is it?

Answer 9

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

Question 10

What happens when triglycerides are broken down and what type of reaction is it?

Answer 10

3 water molecules need to be supplied to reverse the reaction
HYDROLYSIS REACTION

Question 11

Example of a saturated fat

Answer 11

Butter

Question 12

Example of an unsaturated fat

Answer 12

Oil

Question 13

Where do saturated/unsaturated fats typically come from?

Answer 13

Saturated = animal fat
Unsaturated = plants and seeds etc

Question 14

Functions of trigylcerides

Answer 14

Long term energy storage
Thermal insulation to prevent heat loss e.g. penguins
Protection of vital organs
Buoyancy for aquatic animals e.g. whales

Question 15

Features of saturated fats

Answer 15

no double bonds
some evidence to suggest they can lead to coronary heart disease (solid at room temp)

Question 16

Features of unsaturated fats

Answer 16

contain double bonds
cannot pack close together due to double bonds (liquid at room temperature)

Question 17

1 double bond…

Answer 17

monounsaturated

Question 18

2 or more double bonds…

Answer 18

polyunsaturated

Question 19

What happens if you have too much of any fat…

Answer 19

Can lead to obesity

Question 20

What are phospholipids made from originally?

Answer 20

modified triglycerides

Question 21

What elements are phospholipids made from?

Answer 21

Carbon, hydrogen, oxygen and phosphorus

Question 22

Why are phosphate ions soluble in water?

Answer 22

They are negatively charged and so interact with the charges within the polar water molecule

Question 23

Structure of a phospholipid:

Answer 23

One of the fatty acid chains in a triglyceride is replaced with a phosphate group
Has a charged head and non-polar tails

Question 24

Difference between head and tails of a phospholipid

Answer 24

Head = negatively charged and so is hydrophilic (attracts water)
Tail = non-polar and so is hydrophobic (repels water)

Question 25

How does the dual structure affect how phospholipids interact with water?

Answer 25

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)

Question 26

Function of phospholipids:

Answer 26

Forming cell membranes

Question 27

How are phospholipids used in forming cell membranes?

Answer 27

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

Question 28

What type of molecule is glycerol

Answer 28

An alcohol (-OH)

Question 29

What type of molecule are fatty acids

Answer 29

Carboxylic acids (-COOH)

Question 30

Features of sterols

Answer 30

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

Question 31

What kind of molecule is cholesterol?

Answer 31

Sterol

Question 32

Where in the body is cholesterol primarily manufactured?

Answer 32

Liver and intestines

Question 33

Function of cholesterol:

Answer 33

Cell membrane formation
positioned between phospholipids with hydroxyl group on the outskirts of membrane

Question 34

What happens to cholesterol and its function at low temps?

Answer 34

Adds stability to membrane and regulates fluidity by keeping membranes fluid at low temps

Question 35

What happens to cholesterol and its function at high temps?

Answer 35

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)

Question 36

What else is cholesterol used to manufacture?

Answer 36

Bile
Vitamin D
Steroid hormones

Question 37

Roles of lipids:

Answer 37

Membrane formation and creation of hydrophobic barriers
Hormone production
Electrical insulation necessary for impulse transmission
Waterproofing e.g. birds’ feathers + plant leaves

Question 38

What else are lipids used for?

Answer 38

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

Question 39

Identification of lipids test:

Answer 39

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

Question 40

What factors make it difficult to find out the health impacts of one specific food type?

Answer 40

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)

Question 41

Do saturated or unsaturated fats have high energy?

Answer 41

Both have high energy

Question 42

What can excess energy intake lead to?

Answer 42

Obesity