biochem unit 4 Flashcards
Lipids
how many molecules does it include
are they defined by structure and if not how are they defined
arre they largely hydrophilic or hydrophobic
or what can they be, amphipathic or hydrophilic?
what are the 3 functions of lipids and examples of them
Lipids include many types of molecules
They are not defined by their structure; they are defined by having low solubility in water and high solubility in non-polar solvents
They are largely hydrophobic
OR they can be amphipathic (remember?)
Functions:
1. Energy Storage - Fats and oils- TAGs
- structural
- glycerophospholipids - membrane lipids
- spingolipids
- sterols (membranes) - Other/Specific Biological Activities
- enzyme co-factors
- electron carriers
- light-absorbing pigments like chlorophyll
- hormones, etc. like sterols
Storage Lipids: Fatty Acids
what are the simplest lipids
their basic structures exemplifies what lipid model and what are the parts of the model
what kind of acids are fatty acids, with what kind of chains
are most natural fatty acids branched or unbranched
what kind of bonds do some of them have
do most fatty acids have an odd or even number of carbons
The simplest lipids are fatty acids which are also constituents of many more complex lipids
Their basic structure exemplifies the amphipathic lipid model:
- A long hydrocarbon chain (“tail” – hydrophobic)
- A terminal carboxyl group (“head” – hydrophilic)
Fatty acids are carboxylic acids with highly reducedhydrocarbon chains
(4-36 carbons; C4 – C36)
Most natural fatty acids are unbranched
Some have double bonds (stay tuned)
Almost all natural fatty acids have an even numberof carbons (12-24)
Saturated and Unsaturated Fatty Acids
how many bonds in:
saturated
unsaturated
polyunsaturated
on what carbon is the carb. acid on
how many carbons and hydrogens do alkanes have and how do you know, is there a double bond
how many carbons and hydrogens do alkenes have and how do you know, is there a double bond
each time that we introduce a double bond, how many hydrogens do we lose
saturated means ____ amount of H’s possible
Saturated:
NO DOUBLE BONDS
Monounsaturated:
ONE DOUBLE BOND
Polyunsaturated:
MORE THAN ONEDOUBLE BOND
C1 = carboxylic acid
Most double bonds are at C9, C12, C15
alkane (no double bond)
CnH(2n+2)
so 2 carbons
H = 2(2 + 2) = 2 x 2 + 2 = 6!
alkene (one double bond)
CnH2n
so 2 carbons
H = 2 x 2 = 4
we lost 2 hydrogens when we introduced a double bond!
saturated = max. amount of H’s possible
Saturated and Unsaturated Fatty Acids
what conformation do saturated chains adopt
which is more abundant is nature, unsaturated or saturated
what configuration are the double bonds in for unsaturated fatty acids
what does unsaturated prevent and what does it increase
are there many or few van der waals in double bonds
what does this result in
The saturated chain adopts extendedconformations
- packed neatly
- max amount of van der waals
Unsaturated fatty acids areslightly more abundant innature
The double bonds in naturalunsaturated fatty acids arecommonly in the cis configuration
double bonds kink the chain
double bonds prevent close-packingand increases flexibility
with double bonds, there is fewer van der Waals interactions, changes in melting point
What is the impact of this? - more fluid membrane
Saturated and Unsaturated Fatty Acids: Naming
what is the first number
what is the number after the colon
what is teh number after the delta
what is omega
what does 18:1 delta 9 mean
what does 20:5 delta 5,8,11,14,17 omega 3 mean
The first number is how many carbons are present
The number after the colon is the number of double bonds present
The number(s) after the delta denotes which carbons have the double bonds
The ω (omega) numbers refer to how many carbons away from the methyl end of the fatty acid chain that the first carbon=carbon double bond appears
18:1 delta 9 =
- 18 carbons
- one double bond
- double bond is at the 9th carbon
20:5 delta 5,8,11,14,17 omega 3 =
- 20 carbons
- 5 double bonds
- double bond is at the 5,8,11,14,17 carbons
- omega 3 = starting from the last carbon, the first double bond we meet is at the 3rd carbon
which of the following fatty acids would have the lowest m.p
16:0
18:0
20:0
18:1
18:2
18:2
remember that double bonds have more impact than amount of carbons
Saturated and Unsaturated Fatty Acids
the longer the carbon chain, the higher the…
what do double bonds increase in the chain, how does this effect th evan der waals interactions and thus the melting point
what do double bonds decrease
more double bonds means what about the meltinng point
Let’s look at some trends of lipid propertiesas a function of lipid structure…
The longer the carbon chainthe higher the melting point
Double bonds increase kinks in the chain disruption in van der Waals associations and decreases the melting point
So, double bonds decrease themelting point
More double bonds, lower melting point
Energy Storage Lipids: TriAcylGlycerols (TAGs)
fatty acids are often incorporated in what
what kind of functional group connects the fatty acid to the ____
how many fatty acuds in each ester linnkage to how many glycerols
Fatty acids are often incorporated in Triacylglycerols (also called triglycerides, fats, TAGs)
These are fatty acid esters of glycerol
Three fatty acids each in ester linkage to 1 glycerol
Energy Storage Lipids: TriAcylGlycerols (TAGs)
advantages of storing energy lipids vs polysaccharides
are the carbon atoms highly reduced or oxidized, what does this mean for the energy density compared to polysaccahrides
arre they hydrophobic or hydrophilic, are they hydrated, what does this mean about the water weight
what do TAGs serve against the cold
carbon atoms are highly reduced (lots of hydrogens); this means that the energy density is 2x what it is in polysaccharides
these hydrophobic molecules are not hydrated, so the cells do not carry extra water weight
they serve as insulation against cold
Structural (Membrane) Lipids
what head group and tail do they have
what are the 3 things that Diversification can come from
properties of the head group can determine what
different organisms have different or the same lipid head group compositions
different tissues have different or the same lipid head group compositions
Contain a polar head group (variable) and nonpolar tails (usually fatty acids)
Diversification can come from:
Modifying a different backbone
Changing the fatty acids
Modifying the head groups
The properties of head groups determine the surface properties of membranes
Different organisms have different membrane lipid head group compositions
Different tissues have different membrane lipid head group compositions
Structural (Membrane) Lipids: Phospholipids
what is it called
what is the backbone
how many fatty acids, on which carbons, how many staurated or unsaturated
what functional group is the linkage
which carbon has a highly polar or charged group attached through what bond
(A) Glycerophospholipids
Backbone: Glycerol + Phosphate
Fatty Acids:2 Fatty Acids, 1 at C1, 1 at C2Usually one sat. and one unsat.
Ester linkage (whether TAGs or glycerophospholipids)
Head Group Attachment:C3 carbon has a highly polar or charged group attached through a phosphodiester bond
Glycerophospholipids contain _____ fatty acids and a _____.
1, sphingosine group
2, sphingosine group
1, polar head group
2, polar head group
3, polar head group
2, polar head group
Lipids as Signals
what is the name of the molecule that is a signal, and what is it
what are its derivatives involved in
activation of this pathway results in a variety of what
what is this required for
Phosphatidylinositol is a membrane lipid and is a signal!
It’s derivatives are involved in intracellular signal-transduction pathways such as the PIP2 IP3 DAG PKC pathway
Activation of this pathway results in a variety of cellular functions such as structure and metabolism regulation
Required for LTP
Structural/Signaling Lipids: (C) Sterols
what molecules can most bacteria not synthesize
what does the stroid nucleus contain
which ring is the polar head group in
how manyy non-polar sisde chains does it contain
what does it effect
what do Sterol + unsaturated FA’s do to motion
what do Sterol + saturated FA’s do to fluidity
Isoprenoids
Most bacteria cannot synthesizesterols
The steroid nucleus is four fusedrings (almost planar)
The polar head group (hydroxyl)is in the “A” ring
Often contain various non-polarside chains
Affects cell membrane fluidity
Sterol + unsaturated FA’s constrained motion
Sterol + sat FA increased fluidity
Steroids (Oxidized Sterols)
what are they used for
oxidized sterols =
what are they transported by from what site to target tissues
do receptors have a high or low affinity for them
what are the major types
what is the structure
Molecules used in intercellular signaling (makes sense because they are hydrophobic and can go through the membrane of cells)
Oxidized sterols = steroids
Transported by protein carriers from the site of synthesis to target tissues (long distance definition of “hormone”)
Receptors have a high affinity for them, so…
Major Types:
Sex Hormones (testosterone, estradiol
Adrenal Cortex Hormones (cortisol)
Anti-inflammatory drugs (Prednisone)
4 fused rings + oxygens = steroid
Eicosanoids (20-C Fatty Acid Derivatives)
what is it derived from, what kind of molecule is this
what is arachidonic acid derived from
what do they act on, what kind of signaling is this
what do they all serve as
what are the 3 classes their function
Derived from arachidonic acid (20-C PUFA)
Arachidonic acid is derived from membrane lipids cutwith a phospholipase
Act on cells near the site of synthesis Paracrine signaling
All serve as potent biological signaling molecules
Three Classes:
Prostaglandins (regulatory; fever, pain, inflammation)
Thromboxanes (made by platelets, aid in clotting)
Leukotrienes (3 conjugated double bonds; asthma)
Eicosanoids (20-C Fatty Acid Derivatives)
3 classes and their function
Prostaglandins:
Stimulate smooth muscle contraction
Elevate body temp, inflammation, pain
Thromboxanes:
Produced by platelets for clotting
Leukotrienes:
Stimulate smooth muscle contraction
In the airway asthma, anaphylaxis
The eicosanoids are _____ and derived from _____.
A. Intracellular messengers,Phosphatidylinositol
B. Paracrine hormones,Arachidonic acid
C. Steroids,Cholesterol
B. Paracrine hormones,Arachidonic acid
Testosterone, estradiol, cortisol, and prednisone are…
A. Prostaglandins
B. Thromboxanes
C. Leukotrienes
D. Steroids
E. Sphingolipids
D. Steroids
what are the 5 functions of the membrane
- Compartmentalization
Separate energy-producing reactions from energy-consuming ones - Keep proteolytic enzymes away from important cellular proteins
Import & Export
- Import (Selective import of nutrients) and Export (Selective export of waste/toxins)
Maintain electrical and chemical potent
- (retain metabolite and ion balance)
Sense external signals and transmit information into the cell
- Transporters
- Receptors (Pharmacology!)
- Adhesion Molecules (Glycoconjugates, lectins, and the like)
Fluid-mosaic model:
what is it mostly comprised of – what kind of lipids
what 2 other molecules are there too
what does the pohospholpid bilayer provide for the membrane
it contains proteins and modified protein to do what
is it semi or fully permeable and what does that mean
what can molecules move through
Comprised of a lipid bilayer of primarilyamphipathic phospholipids
Some sterols and carbohydrates too…
The phospholipid bilayer gives fluidity andelasticity to the membrane.
Contains proteins and modified proteinsto diversify functions
Semipermeable – what can and cannot move throughthe membrane is controlled
Through the lipid bilayer and through proteins
What’s in a Membrane: proteins
what do the proteins do and of what molecules
what are the 2 ways that membrane proteins interact with the lipids of the membrane
what are the targets of many drugs what do pharmacologists call these targets
Membranes have proteins that mediate and regulate the transport of metabolites, macromolecules, and ions
Membrane proteins interact with the lipidsof membranes in a variety of ways:
Electrostatic interactions w/polar groups
Hydrophobic regions embedded in thehydrophobic core
Membrane proteins are the targets of manydrugs, so pharmacologists call these“drug receptors”
membrane proteins interact with the phospholipids of the membrane through hydrophilic interactions (electrostatic interactions on the cytosolic sides) and hydrophobic interactions of the hydrophobic core
What’s in a Membrane: Proteins
what does integral membrane and through what interactions
how are integral proteins removed
what does monotropic mean
what does bitopic mean
what does polytopic mean
what are bitopic and polytopic also referred to as
what does amphitropic mean, do they associated reversibly or permeanantly, how are they attached, what regulated
Integral: embedded within the lipid bilayer through strong hydrophobic interactions. proteins are stuck in the membrane and cannot move from membrane
Removable only with agents that interfere with hydrophobic interactions (soaps)
Monotopic – interacts with one side of the membrane
Bitopic – Traverses the membrane once
Polytopic – Traverses the membrane more than once
Bitopic and Polytopic are also referred to as: Transmembrane Proteins (TM)
Peripheral: loosely associated with membrane via noncovalent interactions. Still proteins but connected through a loose connection and can still move
Amphitropic: associates reversibly with membranes; attached by weak interactions or through attached lipids; binding often regulated. Can be found in both membrane and cytosol
What’s in a Membrane: Integral Membrane Protein
are intregral proteins throughout the whole membrane or just in own spot, how many times can they weave in and out of the membrane
how are amino acids arranged in TM proteins
are TM segments mostly hydrophilic or hydrophobc
where are charged amino acds found
Integral/Transmembrane proteins span the entire membrane and may weavein and out several times.
Amino acids in TM proteins clusterin distinct regions
TM segments are predominantlyhydrophobic
Charged amino acids are only found in aqueous domains
What’s in a Membrane: Amphitropic
Tethered to a membrane through a covalent bond to a lipid anchor
Anchors are attached by specific enzymesand can later be removed
Reversible: sometimes associated,sometimes not
Transport Across Membranes
are biological membranes permeable
is the lipid bilayer hydrophilic or hydrophobic, what is it impermeable or permeable to
what do you need for ionic and polar substances
how are large things transported
Biological Membranes are selectively permeable
Also: semipermeable
The lipid bilayer is hydrophobic and is impermeable to most molecules exceptsmall non-polar molecules (like CO2, O2, N2, small steroids)
Need membrane proteins for ionic and polar substances
Endo/Exocytosis for big things!
