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MABS Biochemistry > lecture 4 > Flashcards

lecture 4 Flashcards

Fatty Acids and Lipids

1
Q

what is the structural role of membranes in cells?

A

they serve as the boundary for the cell separating the inside of the cell from the exterior environment; they sequester nutrients, fuels and exclude toxins

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2
Q

what are the components that make up cell membranes?

A

composed of lipids, proteins, and a variety of small molecules

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3
Q

eukaryotes have membrane enclosed organelles, T/F?

A

true, prokaryotes do not; prokaryotes have a cell wall outside the plasma membrane

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4
Q

what are the major classes of lipids?

A

fatty acids, steroids, lipid vitamins, terpenes

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5
Q

what are the most common lipid species we will deal with in this course?

A

glycerophospholipids and sphingolipids

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6
Q

describe the make-up of triacylglycerols

A

glycerol backbone with three fatty acids

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7
Q

what are examples of triacylglycerols?

A

adipose stores and blood lipoproteins

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8
Q

describe the structure of glycerophospholipids?

A

glycerol backbone, two fatty acids and a polar phosphate head group

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9
Q

describe the structure of ether glycerolipids?

A

glycerol ether backbone attached to 1 fatty acid and phosphate polar head group

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10
Q

describe the structure of sphingophospholipids?

A

sphingosine backbone with 1 fatty acid tail and attached phosphate head group

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11
Q

describe the structure of glycolipids?

A

sphingosine backbone with a fatty acid tail and carbohydrate

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12
Q

what are some examples of ether glycerolipids?

A

plasmalogens and platelet activating factor

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13
Q

what are the examples of glycerophospholipids?

A

phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol bisphosphate, phosphatidylglycerol, cardiolipin

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14
Q

what is an example of a sphingophospholipid?

A

sphingomyelin

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15
Q

what is an example of a glycolipid?

A

cerebroside, sulfatides, globosides, gangliosides

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16
Q

what are the structural features of fatty acids?

A

polar head contributed by the oxygens and the non polar tail comprised of hydrocarbons

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17
Q

what does the shape of the fatty acid tail depend on?

A

double bonds

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18
Q

if we say saturated in reference to the fatty acid tail, what do we mean?

A

no double bonds

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19
Q

if we say unsaturated in reference to the fatty acid tail, what do we mean?

A

double bonds

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20
Q

how do saturated fats pack?

A

tightly and they are solid at room temperature, less fluid like and have a high melting point

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21
Q

how do unsaturated fats pack?

A

they are fluid at room temperature and do not pack as well

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22
Q

why are cis bonds important?

A

types of bonds our body requires and therefore predominates in our bodies; these bonds disrupt packing of chains: the kinks prevent regular packing of long linear chains; these bonds decrease melting points of chains and allows them to be fluid like at body temperature

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23
Q

what are trans fats?

A

like saturated fats except this type of double locks the configuration, they use less fluid, and are more packed. Also bad for our health because they raise our LDL and lower our HDL

24
Q

Why is arachidonic acid important?

A

20 carbon s and 4 cis double bonds and this structure is one of the most powerful signaling molecules int the body that help us use the bathroom, deliver babies, dilate blood vessels, bronchoconstriction during an asthma attack

25
Q

why are saturated fats important for the lipid bilayers?

A

they stiffen lipid bilayers to just the right amount of fluidity

26
Q

what length carbon chains are common in humans?

A

16 and 18 carbon chains most common, 2-3 carbons important metabolically

27
Q

what are fats even numbered?

A

its important for beta oxidation

28
Q

what are the carbon numbers of the following common fatty acids: arachidonic acid, linoleic acid and linolenic acid?Why are these special

A

20,18, 18; arachidonic acid is a key fatty acid in cell signaling used for prostaglandins, thromboxanes, leukotrienes; linoleic and linolenic acids are considered essential fatty acids with linoleic acid important in making arachidonic acid in humans; alpha linolenic acid is used for making EPA which makes DHA

29
Q

Additionally, what are the number of carbons for palmitic acid, stearic acid, arachidonic acid (4 double bonds), palmitoleic acid; of these which are saturated and which unsaturated?

A

16, 18 both saturated; 20 (4 double bonds), 16 (1 double bond) both unsaturated

30
Q

what are triacylglyerols from a structural point and name some properties?

A

glycerol backbone with three fatty acids; storage mechanism is that they are tightly packed and have low water content; highly hydrophobic that excludes water; fatty acids cleaved at acyl group by lipase which can result in free fatty acids and either diacyl or monoacylglycerol or glycerol

31
Q

what are glycerophospholipids (phospholipids), name an example, from a structural point and name some properties?

A

these are similar to triacylglycerol except the carbon 3 of the glycerol backbone has a phosphate moiety in which we can have specific molecules attach to this to give the lipid specific structure and function; an example is phosphatidic acid which is the parent compound of all phospholipids

32
Q

what should we pay attention too when it comes to glycerophospholipid head groups?

A

we have polar charged head groups increasing the polar nature at that end of the molecule, each serving their own function; like ethanol amine is small and this allows for closer packing

33
Q

phosphatidyinositol importance?

A

-OH groups allow for attachments, phosphates, which make it PIP2 which sits in membrane like a raft; once signal comes it contracts, IP3 is free and it binds to receptor causing contraction, conduction, transmission

34
Q

what is hydrolyzed by phospholipase enzymes? where?

A

glycerophospholipids; phospholipase A1 releases FA at position 1 on glycerol; phospholipase A2 releases FA at position 2 on glycerol; phospholipase C releases phosphorylated base at position 3 and phospholipase D releases the free base

35
Q

Describe the 2 functions phosphotidylinositol (PI) plays in relation to signal transduction?

A

you start with PI and then you have a kinase and PI is transformed into PIP2 not doing anything, however a signal comes along saying it needs IP3 and then phosphlipse C comes along and clips (between phosphate and glycerol head group) of PIP2 from the membrane and you have IP3/DAG and diffuses into cytoplasm and bind to receptor; another enzyme can act on PIP2, PI 3-kinase, which adds another phosphate and is recognized as a binding site by a protein and they interact and it is activated - insulin acts this way, it turns PI 3-kinase and allows other kinases to bind

36
Q

talk about structure and function of sphingolipids

A

sphingolipids look like glycerol but they are not; 18 carbon amino alcohol (sphingosine) as base structure for sphingolipids in membrane and act like phospholipids but are different.

37
Q

what happens to the sphingosine when you add an amide linkage

A

it becomes ceramide and when you add a phosphate group and a head group you develop choline sphingomyelin, found in nerve cells (found along the myelin sheath)

38
Q

what happens if you add a single sugar to ceramide, no phosphate?

A

a cerebroside is formed, also a glycolipid

39
Q

what happens if you attach a polysaccharide to the ceramide?

A

gangliodie is formed

40
Q

describe the importance of ganglioside?

A

used primarily in cell surface recognition and binding of specific proteins and factors to cell surface, also known as glycolipids

41
Q

often times a patient’s lysosome is missing an enzyme or molecule to do its job, in this case dispose of lipids, what happens?

A

lysosome accumulates fats and swells and it gets big developing inclusion bodies. Enzyme deficiency causes a particular disease due to its inability to remove an accumulated lipid

42
Q

what is Ras protein?

A

a g-protein involved in cell growth and so when it receives a signal the receptor acknowledges and this activates Ras and its lipid anchor goes to membrane and it binds continuing signal transduction

43
Q

how is cholesterol formed?

A

start with isoprenes, put together and rearrange bonds and start making things looking like isomer and put together to shape cholesterol

44
Q

why are isoprene important?

A

they can serve as lipid anchors for proteins, precursors for cholesterol - hydrophobic with an oxygen

45
Q

what is the basic lipid bilayer structure, ID the orientation of lipids in the bilayer and polar non polar parts of the structure?

A

lipids are amphiphilic molecules that form lipid bilayers with a polar head and non polar tail, water is excluded to the non polar nature of the hydrophobic interior of the lipid bilayer only allowing the smallest of polar molecules to enter excluding larger molecules like amino acids, fats and glucose

46
Q

what is the fluid nature of the lipid bilayer?

A

very fluid, polar head groups solid at room temperature with liquid interior allowing for cellular/protein flexibility, molecules moving in/out and vesicles. Keep in mind saturated fats with cholesterol cause cause rest of chain to work around it causing curvature. Since this can be found in the membrane, it controls fluidity of the membrane

47
Q

What carries out the most specific functions of the lipid bilayer?

A

proteins, i.e. - inner mitocondrial membrane has ETC so proteins related to this. Different membranes have different functions containing different proteins, and again the we would see the cell membrane containing receptors

48
Q

what the two types of membrane proteins?

A

integral and peripheral proteins

49
Q

what are integral proteins?

A

proteins embedded in the bilayer that span the membrane, remember polar parts exposed to aqueous portion and non polar parts exposed to hydrophobic core

50
Q

what are peripheral proteins?

A

proteins that associate with the bilayer but do not penetrate it, i.e. - association is non covalent with either bilayer lipids or integral proteins

51
Q

when you see a glycolipid/glycoproteins, what part of the cell is this?

A

viewing from the outside the cell

52
Q

what are lipid anchored proteins?

A

lipid molecule that has a portion of their structure that is hydrophobic and will stay bound to the hydrophobic part of the bilayer anchoring protein to the bilayer , i.e.- acetylcholinesterase which splits acetylcholine to terminate synaptic transmission; also G-proteins are another example that have lipid anchors

53
Q

what is the lipid portion of a lipid anchored protein called?

A

lipid anchor, remember this keeps it close or at the surface of the membrane

54
Q

what parts of the lipid anchor associate with the cell membrane?

A

the lipid anchor associates with the bilayer and the polypeptide associates with the aqueous phase on the inside or outside surface of the membrane

55
Q

why are glycolipids/glycoproteins important to RBCs?

A

red blood cell plasma membranes contain glycolipids and glycoproteins that determine blood type. This determines which glycosyltransferase is present and so this oligosaccharide present becomes recognized by the immune system as foreign.

56
Q

why is type O blood special?

A

type O individuals encode a defective transferase, hence do not have additional carb on the H substance

MABS Biochemistry (54 decks)

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