lipids (unit 3)

Question 1

what are lipids?

Answer 1

also known as macromolecules (large and complex) - contains , carbon, hydrogen and oxygen
are fats and oils - liquid at room temp
fats - solid at room temp

Question 2

are lipids soluble on non-soluble in water?

Answer 2

they are non-polar meaning they are insoluble

Question 3

what does non-polar mean?

Answer 3

no regions of partial positive or partial negative charge, so they aren’t electrostatically attracted to water molecules - in lipids the outer shell electrons are more evenly distributed hence this case

Question 4

what are triglycerides

Answer 4

a lipid composed of one glycerol molecule and three fatty acids

Question 5

what is glycerol?

Answer 5

alcohol found in triglycerides

Question 6

what are fatty acids

Answer 6

long-chain carboxylic acids used in the formation of triglycerides

Question 7

how are triglyceride’s formed?

Answer 7

hydroxyl groups interact forming three water molecules and bonds between the fatty acid and the glycerol molecule

Question 8

what are the bonds called when triglycerides are formed?

Answer 8

ester bonds

Question 9

how do you reverse the reaction and what is it called?!

Answer 9

hydrolysis reaction - and use three water molecules to break it down

Question 10

what are saturated lipids?

Answer 10

fatty acid chains that contain no double bonds

Question 11

what are unsaturated lipids

Answer 11

fatty acids with double bonds

Question 12

why are unsaturated lipid’s usually oil?

Answer 12

because the double bonds cause the molecule to kink/bend meaning they can’t pack closely together therefore they’re liquid at room temperature

Question 13

monounsaturated meaning

Answer 13

one double bond

Question 14

polyunsaturated meaning

Answer 14

two or more double bonds

Question 15

what are phospholipids

Answer 15

modified triglyceride’s - phosphorus, carbon, h2 and o2

Question 16

how are phospholipids modified?

Answer 16

phosphate group replaces one fatty acid in the triglyceride

Question 17

are phospholipids soluble or insoluble in water?

Answer 17

soluble in water as inorganic phosphate ions have extra electrons meaning it’s negatively charged - and have a non-polar tail - hydrophobic (the fatty acid) and charged end - hydrophobic (head - phosphate group)

Question 18

hydrophobic

Answer 18

the physical property of a molecule that is repelled by water

Question 19

hydrophilic

Answer 19

the physical property of a molecule that is attracted to water

Question 20

how do phospholipids interact with water?

Answer 20

they form a layer on the surface of water (head/phosphate in the water and tail/fatty acids sticking out) - this creates a bilayer where the tail point towards the sheet centre and the heads surround them - helps form cell membranes as this separates cells’ aqueous environment from the aqueous cytosol
- also allows stability in plasma membranes

Question 21

what are sterols

Answer 21

steroid alcohols - lipid but not fats or oils
- complex alcohol molecules with 4 carbon rings and a hydroxyl group at one end
- dual hydrophobic/hydrophilic characteristics

Question 22

what is cholesterol

Answer 22

a type of sterol - comes from liver and intestine (also helps form cell membranes)
- it’s positioned between the phospholipids with the hydroxyl group at the outer membrane meaning it adds stability to cell membranes and regulates their fluidity by keeping them fluid at low temps and preventing excess fluidity at high temps

Question 23

what is cholesterol useful for other than cell membranes?

Answer 23

vitamin D, bile, and steroid hormones are also made using cholesterol

Question 24

some roles of lipids?

Answer 24

• membrane formation and hydrophobic barriers
• hormone production
• triglycerides have energy storage under skin eg thermal insulation for penguins and cushions vital organs
• waterproofing leaves and feathers
• electrical insulation for impulse transmission