Biochem: Lipids

Question 1

Lipids can be broken down structurally into 2 main classes:

Answer 1

1. those based on fatty acid structure
2. those based on isoprenoid structure

Question 2

is unsaturated fatty acid, the ones with double bonds or no double bonds

Answer 2

has the double bonds

Question 3

Does cis or trans form create a “bend” in the structure which increases the membrane fluidity?

Answer 3

cis

Question 4

does cis bonds allow for looser and tighter packing of phospholipids?

Answer 4

looser, more fluidity

Question 5

where does fatty acid synthesis occur?

Answer 5

cytoplasm

Question 6

what are the substrates of fatty acid synthesis?

Answer 6

acetyl CoA and Malonyl CoA

Question 7

what is malonyl CoA?

Answer 7

Acetyl CoA with an extra CO2 group added

Question 8

what enzyme do you need for fatty acid synthesis?

Answer 8

fatty acid synthase

Question 9

how many fatty acid chains can be made at once with one fatty acid synthase?

Answer 9

2 fatty acid chains can be made

Question 10

the fatty acid synthase contains 2 S groups which are from?

Answer 10

one from cysteine and one from B5

Question 11

Cysteine binds with what?

Answer 11

acetyl groups

Question 12

B5 binds with what?

Answer 12

malonyl groups

Question 13

what are some Coenzymes for fatty acid synthesis?

Answer 13

B7, B5, and B3

Question 14

what does B7 (biotin) do?

Answer 14

helps add CO2 to acetyl CoA to make malonyl CoA

Question 15

what is the enzyme that converts acetyl CoA to Malonyl CoA?

Answer 15

Acetyl CoA Carboxylase

Question 16

Explain the steps of the fatty acid synthesis

Answer 16

1. acetyl group joins
2. malonyl group joins
3. acetyl and malonyl groups combines with loss of CO2
4. oxygen removed as water, NADPH donates H’s
5. fatty acid chain shifts over

Question 17

how do you get to a 16 carbon chain?

Answer 17

you keep adding malonyl CoA until you get to 16 carbon

Question 18

when you get the desired number of carbons, how do you get the chain off the enzyme?

Answer 18

use water to break the bond by hydrolysis

Question 19

how do you make odd-numbered fatty acid chains?

Answer 19

starting with propionyl CoA (3C) rather than acetyl CoA (2C) in step one can make odd numbered chains

Question 20

what is the enzyme to create double bonds hence creating unsaturated fatty acids?

Answer 20

desaturase enzymes

Question 21

what are the 3 hormones that regulate fatty acid synthesis?

Answer 21

glucagon, insulin, epinephrine

Question 22

how does glucagon and epinephrine regulate fatty acid synthesis?

Answer 22

both inhibit acetyl CoA carboxylase

Question 23

how does insulin regulate fatty acid synthesis?

Answer 23

activates acetyl CoA carboxylase

Question 24

what are triglycerides

Answer 24

3 fatty acids attached to a glycerol backbone via an ester link

Question 25

which packs tighter and therefore stores energy more efficiently? triglycerides or glycogen?

Answer 25

triglycerides

Question 26

what is the process called for triglyceride synthesis?

Answer 26

lipogenesis

Question 27

where does lipogenesis happen?

Answer 27

liver and adipocytes: in the cytosol

Question 28

what are the steps of lipogenesis?

Answer 28

- make the substrates - transfer 2 fatty acid chains to the backbone sequentially - replace the phosphate on the backbone with the 3rd fatty acid chain

Question 29

what enzyme adds a phosphate to glycerol to create glycerol-3-phosphate? (glycerol backbone)

Answer 29

glycerol kinase

Question 30

what is a way adipose tissue and the liver make the glycerol backbone?

Answer 30

Convert DHAP to glycerol-3-phosphate using glycerol-3-phosphate dehydrogenase

Question 31

after making the back bone, what do you make?

Answer 31

make the fatty acyl CoA

Question 32

fatty acids are added to a CoA carrier using what?

Answer 32

ATP

Question 33

what does the CoA do to the fatty acid?

Answer 33

carry the fatty acid chains to the backbone and transfer them over

Question 34

how many fatty acid chains do you add to the glycerol-3-phosphate

Answer 34

2 fatty acid chains

Question 35

what is the last step to triglyceride synthesis?

Answer 35

removing the P and adding the last fatty acid chain

Question 36

what do both phospholipids and glycosphingolipids both contain:

Answer 36

1. a backbone 2. lipid 3. head group

Question 37

how are phosphoglyceride formed?

Answer 37

you start with a phospholipid and then an ethanol amine is added to it

Question 38

how to add a head group to a phosphoglyceride?

Answer 38

first, a CMP is added to create a good leaving group. Next, the CMP is removed and head group is attached via nucleophilic substitution

Question 39

what is sphingomyelin?

Answer 39

phospholipid that is a sphingolipid

Question 40

what is different between sphingolipids and phospholipids?

Answer 40

the backbone, for sphingolipids, the backbone is sphingosine

Question 41

what type of lipids are cerebrosides and gangliosides?

Answer 41

sphingolipids

Question 42

what are the headgroups of gangliosides?

Answer 42

1 or more sialic acid plus 1 or more additional monosaccharides

Question 43

what are the headgroups of cerebrosides?

Answer 43

monosaccharide head group

Question 44

accumulation of sphingolipids leads to what?

Answer 44

sphingolipid storage diseases

Question 45

what's Tay-Sachs Disease?

Answer 45

GM2 accumulates in lysosomes due to an enzyme deficiency - most severe excesses occur in the brain, build up leads to neuronal cell damage

Question 46

what are eicosanoids?

Answer 46

derived from arachidonic acid or similar 20 carbon fatty acids

Question 47

prostaglandins is a ?

Answer 47

eicosanoid

Question 48

what are some physiological functions of eicosanoids?

Answer 48

- vasodilation - vasoconstriction - platelet aggregation

Question 49

what are waxes?

Answer 49

mixtures of non-polar molecules, including fatty acids linked to long-chain hydrocarbon alcohols via ester bonds

Question 50

what are the categories of isoprenoids?

Answer 50

1. terpenes 2. mixed terpenes 3. steroids

Question 51

what are terpenes?

Answer 51

isoprene units linked together

Question 52

what is the smallest terpene?

Answer 52

2 isoprene units linked together = monoterpene

Question 53

diterpene

Answer 53

4 isoprene

Question 54

squalene

Answer 54

a triterpene

Question 55

beta carotene

Answer 55

tetraterpene

Question 56

what is a mixed terpene

Answer 56

terpenes with a non-terpene component attached

Question 57

what is steroids

Answer 57

complex molecules made from 6 isoprene units and contain 4 fused rings with various substituents - made from cholesterol

Question 58

what are the steps to cholesterol synthesis??

Answer 58

3 acetyl CoA -> HMG-CoA -> HMG-CoA reductase creates mevalonate -> sqalene -> cholesterol

Question 59

what is the rate limiting enzyme for cholesterol synthesis?

Answer 59

HMG-CoA reductase

Question 60

what does high cholesterol do to HMC-CoA reductase?

Answer 60

it inhibits it from creating more cholesterol

Question 61

what is a cholesterol-lowering drug?

Answer 61

atorvastatin (lipitor)

Question 62

what does the liver use cholesterol for?

Answer 62

- make bile - make lipoproteins (LDL) to carry cholesterol to the tissues

Question 63

how does LDL turn to cholesterol at the tissue cells

Answer 63

LDL binds to receptor on the cell and is internalized LDL is broken down inside the cell and cholesterol is released

Question 64

what is familial hypercholesteremia?

Answer 64

an inherited defect in LDL-receptors which leads to an increase in circulating LDL, and therefore cholesterol in the blood which increases the risk of myocardial infarction

Question 65

cholesterol is a precursor to what?

Answer 65

steroid hormones

Question 66

how does cholesterol convert to steroid hormones?

Answer 66

cholesterol is first converted to pregnenolone, which is then converted to other steroid hormones

Question 67

plant sterols can compete with intestinal cholesterol absorption which in turn do what?

Answer 67

helps lower LDL cholesterol levels

Question 68

cardiac glycosides are derivatives of what?

Answer 68

plant sterols