Lipids

Question 1

what is saponification?

Answer 1

saponification is base catalyzed hydrolysis of triglycerides into glycerol and 3 fatty acid salts.

Na+ and a fatty acid anion form a salt.

Question 2

what is glycerol?

Answer 2

a 3 carbon chain species each with an alcohol group attached (triol)

Question 3

what is amphoteric vs. amphipathic mean?

Answer 3

amphoteric / amphiprotic - act as acid or base

amphipathic - hydrophilic and hydrophobic

Question 4

Fats (triglycerides) are more efficient at energy storage (than carbs) for two reasons. What are they?

Answer 4

1. Fat hydrophobicity allows for tight packing compared to carbs
2. Bond for bond, fats contain more energy than sugars.

Question 5

what is the reason for triglycerides producing more energy per carbon than carbs?

Answer 5

The basic principle of extracting energy from “foodstuffs” is by oxidizing them. The further we can oxidize something the more energy we get.

Fats are more reduced (i.e. less oxidized) then sugars. Therefore, we are oxidize fats further than we can with sugars.

Question 6

What is Diacylglycerol phosphate (DG-P)?

Answer 6

this is the phospholipid used to make lipid-bilayers. Often the phosphate group binds an even more polar molecule such as choline.

Question 7

Diaglyceorl phosphate (DG-P) is the main phospholipid in the bilayer of cells. 3 things intrinsic to the bilayer effect its fluidity. What are they and how do they effect fluidity?

Answer 7

1. degree of saturation of the fatty acid tail. The less saturated (i.e. the more double bonds) the more fluid the membrane.
2. length of fatty acid tails. The shorter the tails, the more fluid the membrane (less interaction)
3. cholesterol which maintains optimal fluidity at both high and low temperatures.

Question 8

what is a terpene?

Answer 8

any molecule built from isoprene units (one isoprene unit is C5H8)

• |=- (isoprene were SB - and DB = and vertical bond is |)

Question 9

what is a terpenoid? what is one example of one?

Answer 9

a terpenoid is when terpene is functionalized with other elements (O, S, N, etc.)

an example of a terpene is vitamin A which is in the opsin / retinol complex for vision.

Question 10

what is a lipoprotein?

Answer 10

Lipoproteins are soluble proteins that bind and carry fat or any other lipids within the blood plasma.

Question 11

what is the basic structure of a steroid?

Answer 11

tetracyclic ring system which is the basic structure of cholesterol (all steroids looks like cholesterol)

Question 12

What are sphingolipids and waxes?

Answer 12

sphingolipids are similar to phospholipids except that they have a sphingosine backbone instead of a glycerol backbone. The most important sphingosine fatty acid in humans makes up myelin.

waxes are long chain fatty acids esterified to long chain alcohols.

Question 13

What are the 4 fat-soluble vitamins, briefly what are they used for in the body?

Answer 13

vitamins = DEAK

D - increases Ca+ reabsorption when converted to calcitrol
E - important anti-oxidants
A - in retinal for vision, immune aid, and epithelial maint
K - coagulation of blood (clot factor)

Question 14

upon digestion, chylomicrons and other lipoproteins are transported through the lymph and blood to various organs. When unbound they diffuse into the cells where triglyceride hydrolysis occurs. The triglycerides must be hydrolyzed into free fatty acids to allow for the process of Beta-oxidation (break down of fat for energy). Explain what occurs to these fatty acids before Beta oxidation occurs?

Answer 14

at the outer mitochondrial membrane, the triglycerides are hydrolyzed into free fatty acids.

With the help of Acyl-CoA synthetase the fatty acids are converted into acyl adenylate and then further converted to Acyl-coA (attached to coenzyme A!!)

Question 15

What enzyme converts the free fatty acid to Acyl-CoA? Does this require ATP?

Answer 15

Acyl-CoA synthetase converts it.

this conversion takes up 2 ATP

Question 16

What is beta oxidation? What does it produce?

Answer 16

Beta oxidation is the conversion of Acyl-CoA into Acetyl CoA which can go on to enter the Krebs cycle!

B-oxidation occurs in “rounds” depending on the size of the fatty acid undergoing it. Each round of beta oxidation cleaves off 1 acetyl group (2 carbons). Each time, the acetyl group undergoes a couple of reactions forming 1 NADH and 1 FADH2. Once the fatty acid reaches its last 4 carbons, rather than completing two more rounds this last 4 is directly converted to acetyl-coA and produces no NADH or FADH2

Question 17

for a 12 carbon fatty acid, how many Acetyl-CoA groups are made? How many NADH and FADH2 groups are made?

Answer 17

2 ATP’s are used to convert the fatty acid into Acyl-CoA molecules. This Acyl-CoA molecule undergoes 5 rounds of beta oxidation to produce 5 NADH and 5 FADH2. the final 4 carbons split to produce no NADH or FADH2.

therefore
6 Acetyl-CoA
5 NADH
5 FADH2
note: this is all prior to Krebs cycle and oxidative phosphorylation.

Question 18

what is ketogenesis? when is it used?

Answer 18

ketogenesis is the conversion of Acetyl-CoA into ketone bodies which are able to cross the blood-brain-barrier. As a result, in times of starvation, the Acetyl-CoA generated from the beta oxidation (not glycolysis / PDC since you are starving) is converted to ketone bodies which enter the CNS and is then converted back to acetyl-coA for respiration.

Question 19

what is acetoacetate?

Answer 19

during ketogenesis, Acetyl-CoA undergoes a few reactions forming Acetoacetate. This can either remain as the ketone body that enters the BBB or it can convert into acetone or B-hydroxybutyrate.

Question 20

Fatty Acid synthesis:
Beta oxidation first primed a fatty acid to form Acyl-CoA (primed by Acyl-CoA synthetase). Following this Acyl Co-A undergoes successive rounds whereby 2 carbon units (acetyl units) are cleaved off for Fatty acid respiration.

Explain what occurs in fatty acid synthesis?

Answer 20

In fatty acid synthesis, Acetyl-CoA is converted back into free fatty acids.

Question 21

Explain the process of fatty acid synthesis including Acetyl-CoA carboxylase, fatty acid synthase, and Acyl carrier protein.

Answer 21

Acetyl-CoA carboxylase adds a CO2 group to Acetyl-CoA to activate it. The product is called Malonyl-CoA (acetyl with extra CO2)

Then fatty acid synthase binds an acetyl-coA group at its Acyl carrier protein (ACP) site. This Acetyl-coA group shifts go another site and the primed malonyl-coA binds the ACP site. Now together, one de-carbxoylation reaction and 2 successive reduction reactions occur to add 2 carbons to the growing fatty acid.

Question 22

What is Malonyl-CoA?

Answer 22

the product formed after Acetyl-CoA carboxylase adds CO2 to an acetyl group.

Question 23

What purpose does NADPH have in fatty acid synthesis? where does it come from?

Answer 23

NADPH comes from the pentose phosphate pathway (along with ribose-5-phosphate) when G6P interacts with G6P dehydrogenase (instead of isomerizing into F6P or using a phosphatase to become glucose)

It is used to perform the reducing reactions that bind the two acetyl groups together after the decarboxylation.

Question 24

What is pyrophosphate?

Answer 24

when two phosphate molecules are bound together the P-O-P molecule is called pyrophoshate.

The linkage (P-O-P) is called an anhydride linkage.

Question 25

Nucleic acids are composed of a 5C sugar, a nitrogenous base, and a phosphate group. Which carbon’s contain the sugar and phosphate groups?

Answer 25

carbon number 1 contains the nitrogenous base
carbon number 5 contains the phosphate backbone

deoxyribose - contains only 3’OH
ribose - contains 3’OH and 2’OH

Question 26

why are phosphate bonds highly energetic?

Answer 26

the P groups repel each other a lot
orthophosphate (phosphate alone) has lots of resonance so its favourable to form.

pyro –> ortho

Question 27

What is a nucleic acid, nucleoside, nucleotide, and dNTP,

Answer 27

nucleic acid = polymer of sugar + base + phosphate
nucleoside = sugar + base
nucleotide = ester of nucleosides which know includes phosphate

when a nucleotide has 3 phosphate residues its called a dNTP which is the building block of DNA

Question 28

what is the difference between a phosphodiester bond and an anhydride linkage?

Answer 28

phosphodiester bond is the bonds between nucleotides within DNA
this exists between the 3’OH and the 5’phosphate

anhydride linkage is the bond between two phosphate groups

Question 29

how many h bonds are between A-T and G-C

Answer 29

A-T = 2
G-C = 3

AT rich DNA segments denature faster than CG rich segments. (therefore have a lower melting point)

GC segments stabilize DNA

Question 30

true or false, prokaryotic DNA is linear

Answer 30

false, prokaryotes have a single piece of circular DNA. Humans have 46 chromosomes (23 from each parent)

Question 31

True or false, eukaryotes have DNA gyrase which supercoils DNA to make it more compact.

Answer 31

false, this is only in prokaryotes. Eukaryotes DON’T have gyrase enzyme

Question 32

DNA + H2A, H2B, H3, and H4 resembles what?

Answer 32

the H’s are histone dimers which form an octamer of histones. The DNA coils around this. together it is called a nucleosome.

H1 is also there which joins linker DNA to the nucleosome

Question 33

Closely packed nucleosomes are called?

Answer 33

chromatin

Question 34

what two amino acids are found in histones? why are these two found?

Answer 34

arginine (R) and lysine (K)

these are positive (basic) AA’s which associate with the negative phosphate backbone of DNA

Question 35

what is heterochromatin and euchchromatin?

Answer 35

upon staining DNA (often with Giemsa dye)

dark bands are called heterochromatin which are less transcriptionally active

light bands are called euchchromatin which are more transcriptionally active

Question 36

what is a chromosomes centromere, p arm, q arm

Answer 36

centromere is the the area of the chromosome that spindle fibres attach during cell division. it holds the chromosome together.

the P arm is typically the shorter u and the q arm is typically the longer u.

Question 37

what is metacentric, submetacentric, acrocentric, and telocentric chromosomes?

(refer to chromosome centromere positioning)

Answer 37

metacentric is when q = p

submetacentric is when q > p

acrocentric is when q&raquo_space; p

telocentric is when p is virtually non existent. (one long af q arm connected to a centromere)

Question 38

during protein synthesis, what type of RNA is the product of transcription?

Answer 38

Heterogenous RNA (HnRNA) which is an mRNA precursor. Poly-A tail, 5’ cap, and splicing must occur before its considered mRNA

Question 39

true or false, heterogenous RNA is found in all organisms.

Answer 39

false, prokaryotes do not splice RNA nor add protective components. Therefore the transcribed RNA molecule is immediately mRNA.

Question 40

what is a ribozyme?

Answer 40

catalytic RNA. One kind of rRNA is a ribozyme.