lipids

Question 1

What are lipids?

Answer 1

lipids are a class of non-polar organic molecules, that include triglycerides (adipose tissue), phospholipids (bilayer), cholesterol (animal cell membranes), and steroids (hormones).

Question 2

lipids function acronym: SHIPS

Answer 2

S- storage of energy- triglyceride
H- hormonal roles- steroids
I- insulation- thermal
P- protection of organs
S-structural roles - cholesterol

Question 3

what are triglycerides?

Answer 3

triglycerides are lipids that are used for long term energy storage. they are composed of a glycerol molecule covalently linked to three fatty acid chains- via condensation reactions.

Question 4

what are saturated fatty acids?

Answer 4

saturated fatty acids, possess no double bonds between the carbon in the hydrocarbon chain.

Question 5

what are unsaturated fatty acids?

Answer 5

unsaturated fatty acids, have double bonds between the carbon molecules, in the hydrocarbon chain.

Question 6

characteristics of a Cis isomer

Answer 6

-hydrogen atoms are on the same side
-double bond creates a kink in the fatty acid chain
-are loosely packed, and are usually liquid
-occur commonly in nature
-generally good for health

Question 7

characteristics of trans isomers

Answer 7

• hydrogen atoms are on different sides
  -double bond does no create a kink- linear
• are tightly packed, and usually solid.
• occurs in processed food
• generally bad for health

Question 8

What are LDLs?

Answer 8

they are low density lipoproteins, that are used to transport cholesterol from the liver, to the rest of the body, which is bad for your health.

Question 9

What are HDLs?

Answer 9

they are high density lipoproteins, that scavenge excess cholesterol and return it to the liver for disposal, which is good for your health.

Question 10

what do cis fats to to levels of cholesterol?

Answer 10

cis fats raise the levels of HDL, which lowers blood cholesterol.

Question 11

what do saturated fats do to levels of cholesterol?

Answer 11

saturated fats raise the levels of LDL, which raises blood cholesterol.

Question 12

what do trans fats do to levels of cholesterol?

Answer 12

tans fats raise the levels of LDL, and lower HDL.

Question 13

What can high levels of cholesterol lead to?

Answer 13

it can lead to atherosclerosis, and lead to health issues, such as CHD

Question 14

what is the evidence for the health risks associated with diets rich in lipids?

Answer 14

-there is a positive correlation between the intake of saturated fats, and CHD
-intervention studies have shown that lowering intake of saturated fats, reduces onset CHD
-in patients who have died from CHD, there were high levels of trans fats deposited in the arteries.

Question 15

what is the evidence against the health risks associated with diets rich in lipids?

Answer 15

-certain populations have diets rich in fat, but low rates of CHD (maasai tribe in africa)
-genetic factors play a significant role
- intervention studies are influenced by cohort size and composition, and study duration.

Question 16

why are carbohydrates and lipids a prefered energy source, compared to proteins?

Answer 16

this is because, protein digestion produces nitrogenous waste, due to the presence of an amine group. this waste is toxic to cells, and has to be removed via excretion by the kidneys

Question 17

what is beta glucose?

Answer 17

beta glucose contains 6 carbons, 12 hydrogens, and 6 oxygens.
it is a sugar that fuels respiration.
it is a base for polymers.
it is a hexagon shape- hexose sugar.

Question 18

what is galactose?

Answer 18

it is a hexose sugar also, with 6C, 12H, and 6O.
it is less sweet that glucose.
it is found in milk.

Question 19

what is fructose?

Answer 19

it is a pentose sugar.
found in fruit and honey.
it is the sweetest carbohydrate.

Question 20

what is ribose?

Answer 20

-pentose sugar
-backbone of DNA and RNA

Question 21

what is a disaccharide?

Answer 21

-two glucose joined together
-carbon 12
-hydrogen 22
-oxygen 11

Question 22

what is lactose?

Answer 22

-glucose + galactose
-carbon 12
-hydrogen 22
-oxygen 11

Question 23

what is sucrose?

Answer 23

-glucose + fructose
-carbon 12
-hydrogen 22
-oxygen 11

Question 24

what bond is between the triglyceride head, and its tails?

Answer 24

ester bonds

Question 25

what is the test for lipids?

Answer 25

dissolve the food in ethanol, and add water, and mix. if lipids are present, a white emulsion will form.

Question 26

why do lipids make good membranes?

Answer 26

lipids make good membranes, due to the structure of phospholipids. they have a hydrophilic head on the outside, meaning they are attracted to water. and their two fatty acid tails, are on the inside, and are hydrophobic, so they are protected by the phosphate head. this makes the membranes very stable.

Question 27

what is the role of cholesterol?

Answer 27

it strengthens membranes, and makes hormones.

Question 28

What happens if all the glycogen stores are used up?

Answer 28

-excess energy from cellulose is converted to lipids in the liver.
-its packaged into LDL, and transported to the adipose tissue.
-if energy is needed, fat from the adipose tissue is mobilized as HDL, and transported to the liver, and used to release energy in respiration.
-LDLs have more saturated fat and cholesterol- cholesterol is absorbed by WBCs in atheroma formation.