biochem post quiz

spingolipids

sphingosine provides the backbone, rather than glycerol

parent compound is ceramide

at least 60 different ones exist (phospholipids and glycolipids)

typically, a fatty acid is joined to C2 on sphingosine via an amide linkages

3 major subclasses of sphingolipid (all derivatives of ceramide)

phosphosphingolipids

1. sphingomyelins- phosphate (myeline sheath common in nerve, brain and spinal cord)

Glycosphingolipids

2. cerebrosides- one sugar

3. gangliosides- multiple sugars

- sphingomyelins insulate the axons of some neurons, therefore sphingolipids are important in the membranes of nervous tissue in higher animals

- glycosphingolipids are also important components of never and muscle membranes

different variations of sphingolipids (different things you can add on to C3)

more complex glycosphingolipids

ceramide backbone with two or more esterified sugars

one must be a silica acid (produces net negative charge on lipid)

determine certain elements of tissue and organ specificity

• cell-cell regongtiion and tissue immunity, never impulse transmission, ect.

see buildup of GM2 in Tay-sachs disease victims

sialic acid

adds negative charge at neutral ph which can determine tissue and organ specificity

phospholipid and sphingolipid degradation

cells continually degrade and replace membrane lipids

phospholipids and sphingolipids are degraded in lysosomes by enzymes called lipases

each hydrolyzable bond has its own enzyme

defects I the turnover of membrane lipids lead to a number diseases

gangliosides are degraded by a set of lysosomal enzymes that catalyze the stepwise removal sugar units, finally yielding the parent coumdpond, ceramide

a genetic defect in any of these hydrolytic enzymes leads to dangerous accumulation of lipids in the cell

known as lysosomal storage disease

blood groups

sterols and cholesterol

sterols-

present in most eukaryotic cell membranes, bacteria cannot synthesize sterols

steroid nucelus: four fused rings (almost planar)

hydroxyl group (polar head) in the A-ring

various non polar side chains

precursors to steroid hormones (lack non polar side chain)- potent biological signals that regulate gene expression

sterols such as colestterol are present where

in most eukaryotic cel membranes. affect membrane fluidity. increase fluidity in saturated fat portions and (destabilize) decrease membrane fluidity in non saturated fats and increases stability

isoprenoids

steriods

• steroid hormones testosterone, estradiol, cortisol

terpenes

• diverse group of molecules often recognized by their characteristic flavors, ordors and color

lipid vitamins

• A, D, E, K

Eicosanoids

prostaglandins

thromboxanes

leukotrienes

steroid hormoones

oxidized derivatives of sterols

• have the sterol nucleus but lack the non polar alkyl chain attached to the D ring of cholesterol

amazing array of. cellular functions including salt balance, metabolic function and sexual funciton

steroid hormones are potentent signalers that move through the bloodstream on protein carriers to target issues where they enter cells, bind to receptor proteins in the nucleus, and trigger changes in gene expression and metabolism

terpenes

based on the isoprene structure comprised of five-carbon units with conjugated double bonds (abs visible light)

many are recognized by their characteristic flavors odors, and colors

vitamin A (retinol)

20- carbon terpene hormone and visual pigment of vertebrate eye obtained in the diet either directly or indirectly from beta-carotene it is a precursor to retinal and retinoid acid

retinal initiates the response of rod and cone cells of the retina to light, producing. neuronal signal to the brain

retinoid acid regulates gene expression in the development of skin cells

fat soluble vitamins

cannot be synthesized in body, need to get in diet for proper health

fat soluble (A, D E K)

vitamin A

• found in fish oils liver, eggs, whole milk, ubtter

• deficientcy- dry skin and eyes, retarded eye development, night blindness

vitamin D

• found in milk, butter

• vitamin D deficiency defective bone formation- rickets (need sunlight)

Vitamin D3

• formed in skin from exposure to UV light

• regulates metabolism of calcium uptake in kidney, intestine, and bone

fat soluble vitamins

vitamin E

• destroys oxygen radicals

• found din eggs, oils, wheat germ

• deficinec- scaly skin, muscle weakness

vitamin K

• deficiency shows blood clotting

• K1 found in green plant leaves

ubinquinonne (VItamin Q- not actually a vitamin)

• electron carriers in the redox reactions that drive ATP synthesis in mitochondria and chloroplasts

• 
  

eicosanoids

paracrine hormones derived form the 20-carbon polyunsaturated fatty acid, arachidonic acid (20:4 delta 5,8,11,14)

1. prostaglandins

2. thromboxanes

3. leukotrienes

they all serve as potent biological signals

prostaglandins

contain a 5-carbon ring- first identified in prostate- some stimulate smooth muscle contraction, others elevate body temperature, inflammation, and pain

thromboxane

have a 6 membered ring contain either

they are produced by platelets for blood clotting

NSAIDS inhibit…

COX (cyclooxyrgenase) enzymes that form prostaglandins and thromboxane from arachidonic acid

leukotrienes

contain 3 conjugated double bonds. they trigger smooth muscle contrition in the airway leading to asthma and anaphylaxis

prednisone targets the enzyme that converts arachidonic acid to specific leukotrienes

chapter 10: important notes

• lipids are a structurally and functionally diverse class of molecules that are poorly soluble in water

• TAGs are the main storage lipids

• phospholipids are the main constituents of membranes

• sphingolipids play roles in cell regognition

• cholesterol is both a membrane lipid and the precursor for steroid hormones

• some lipids carry signals form cell to cell and from tissue to tissue (biologically active)

nucleic acids

do not break it down it for energy (dont metabolize it), only use it for its primary purpose

information transfer in cells (central dogma)

information encoded in a DNA molecule is transcribed via synthesis of an RNA molecule

the sequence of the RNA molecule is read and is translated into the sequence of amino acids in a protein

• DNA replication→ transcription → translation

nucleic acids structure

contain nucleobases (nitrogenous bases)

nucleic acids are the polymers and nucleotides are the monomers

include a 4 carbon sugar, phosphate, and nucelobases

nitrogenousb uses are pyrimidines or purines

pyrimidine

have a benzene with two nitrogens include

cytosine

thyamine

uracil

purines

benzene with two nitrogens and an attached face carbon sugar

include:

adenine and guanine know the numbers the nitrogen nitrogen 1 vs 9

cytosine

has an amine group

thiamine

has a methyl group

and double bonded oxygen

(keynote)

biggest pyrimidines

uracil

two amides (=o)

found on RNA

adenine

nitrogen at the top

guanine

contains amine and is buffer than adenine

structure and chemistry of baes

nitrogen containing heterocyclic aromatic amines

planar or almost planar structures

resonance in cyclic rings allows nucleotide bases to absorb UV light around 250-270 nm (260)

good H-bond donors and acceptors

nucleases contain

nitrogenous base

nucleoside contain

nitrogenous base

pentose sugar

what bond if we are attached to a sugar

N-linked

typically in beta form

reacting with anomeric carbon

nucleotides contain

nitrogenous base

pentose sugar

phosphate (1+)

nomenclature

just recognize

functions of nucleic acids

storage of genetic information (DNA)

transmission of genetic information (MRNA)

protein synthesis (t-RNA and rRNA)

processing of pre-mRNA (small nuclear RNA)

functions of nucleotides

energy for metabolism (ATP)

coenzymes (NAD+)

single transduction (cAMP)

pentose sugar in nucleic acids and nucleotides

beta-D-ribofruranose

4 different puckers

c2 endo

c2 exo

c3 endo

c3 exo

ribose vs deoxyribose

small difference affects secondary structure function and stability

syn and anti conformatoins

rotation around the glycosidic bond is sterically hindered. two conformations are possible- anti and syn

anti confirmation is favored in normal DNA (B DNA)

how to form DNA bond

the phosphate residue slows nucleotides to be joined to form oligo and poly nucleotides

adjacent nucleotides are held together by 3’,5’ phosphodiester bonds

the 3’ OH group in one NT and the 5’ OH in teh second are bonded through ester links to the same phosphate

rna/dna backbone

backbone is negatively charged

sequence is always read 5’ to 3’ !!!!! phosphate to OH

in terms of genetic information, this corresponds to N to C in proteins

secondary structure of RNA

single stranded

pretty hydrophobic, so they dont want to be touching all the liquid near them

folds in to specific 3D structures

determining structure is very complicated

hydrolysis of RNA

RNA is unstable, if slightly acidic conditions transesterification reaction can occur :(