lipids part 2

what characteristics does the C-1 fatty acid have

it usually has 16 or 18 carbons and it is saturated

what characteristics does the C-2 fatty acid have

it usually has 18 or 20 carbons and it is unsaturated

what is the general structure of lipids

the head group is joined to glycerol via phosphodiester (covalent) bonds

the head group determines the surface properties of membranes

with neutral phospholipids are proteins usually active or inactive

the proteins are usually inactive and can’t function

if a protein is active on the surface what is happening to do so?

The negatively charged phospholipid got to surface, anchored receptor so its active where it needs to be. It can bind anything to receptor. Acts as a pocket to give a bigger space for the interaction to occur

what are sphingolipids

similar structure to phospholipids but do not have a glycerol backbone, they have a SPHINGOSINE unit made of a long chain of amino acids

what are the components of sphingolipids

Backbone is L is spinholipid

Linear backbone is glycerol

Ring structure (5/6 C) on a lipid = sphingolipid

what are ceramides

waxy lipid molecules composed of sphingosine and a fatty acid

they are found in high concentration within the cell membrane

what is sphingomyelin

it contains phosphocholine or phosphoethanolamine as a polar head group (technically also a phospholipid)

they are present in cell membranes, especially of nerve cells (found in myelin sheath)

are ceramides flexible and inert

yes!

where is sphingomyelin typically found?

in the brain/nerve cells

what are sterols

structural lipids present in the membranes of most eukaryotic cells

what do sterols contain

a steroid nucleus and four fused rings

three rings w/ 6 carbons and one ring with 5 carbons

what is the most common sterol

cholesterol

what is cholesterol

it is found in the cell membranes and it is involved in hormone and vitamin D synthesis

it is part of the lipoprotein structure that is responsible for hydrophobic lipid/fat transport

what is low-density lipoprotein (LDL)

bad cholesterol that has a higher lipid to protein ratio

what can LDL result in

a higher instance of oxidation that can lead to atherosclerosis (build up of fats)

plaques are hydrophobic lipids that can quickly stack and fill the bloodstream with cholesterol that won’t move

what does oxidized LDL molecules trigger

an immune response through inflammation where immune cells try to engulf the LDLs which forms foam cells that continue to induce more immune cells to travel to the site and the cycle continues

what is high-density lipoprotein (HDL)

good cholesterol that has a higher protein to lipid ratio

they can transport lipids from artery walls and reduce foam cell accumulation

what does HDL do

transports cholesterols from the rest of the body back to the live to recycle or break down

what does LDL do

transports cholesterols from the liver to the rest of the body

what is the lipid bilayer

it contains various lipids, carbs, and proteins embedded or associated with the bilayer

how permeable is the lipid bilayer

it is impermeable to charged or polar solutes BUT

semi-permeable to nonpolar or uncharged solutes

cell membrane review

Cell membrane is permeable to small np uncharged molecules. (can pass through cell mem)

Impermeable to charged polar or LARGE molecules (need to go via channels or receptors specific for molecule or protein)

what does amphipathic molecules form in water

micelles that leave the polar groups facing out towards the water and nonpolar groups facing in away from the water (due to hydrophobic interactions)

where are lipids found on the leaflet(bilayer)

•Usually, more neutral lipids are on the outer leaflet

•More charged lipids are found on the inner leaflet.

what do sterols do in the cell membrane

•Sterols heavily determine how fluid the cell membrane bilayers are.

•Sterols are nonpolar and therefore have strong interactions with the unsaturated fatty acid chains in the lipids within the bilayer.

•More fluid structure.

•Liquid-disordered state.

•These interactions limit and constrain the lipid motion within the bilayer. 

why are lipid compositions so different

FOR HOMEOSTASIS

how do lipids help with protein activation

•Protein activation is dependent on the proximity of certain lipids.

•Liquid ordered state may lock proteins into being active all the time.

•Can be good or bad.

•Liquid disordered state is more flexible.

•Proteins can be “shut off” until it is needed.

how do lipids move within the membrane

•Lateral Diffusion

•Moving within a single leaflet occurs very fast and does not require enzymes.

•Transbilayer Movement

•Movement between the inner and outer leaflets is very slow and often requires enzymes.

what is flippase

moves lipids from the outer to the inner leaflet

what does floppase do

moves lipids from inner to outer leaflet

how does passive transport move

•from areas of high concentration to low concentration.

•Spontaneous and does not require cell to expend energy.

how does active transport move

•from areas of low concentration to high concentration.

•Requires energy.

simple diffusion

•Movement of small nonpolar molecules directly through the cell membrane down a concentration gradient.

•Non-specific.

•Cannot be inhibited.

facilitated diffusion

•Movement of larger nonpolar or polar molecules down a concentration gradient.

•Facilitated through carrier proteins or protein channels.

•Highly specific

•Can be inhibited.

osmosis

•Passive movement of water molecules across the cell membrane.

what is the cell when its hypotonic

•When the cell has a higher solute concentration than in the extracellular solution.

•Water moves into the cell, causing the cell to well.

what is the cell when its hypertonic

•When the cell has a lower solute concentration than in the extracellular solution.

•Water moves out of the cell, causing it to shrink.

what is the cell when its isotonic

•When the cell and extracellular solution have equal concentration of solutes.

•There is no net movement of water.

primary active transport

•Uses energy (ATP) to transports ions or molecules against the concentration gradient.

secondary active transport

•Uses an electrochemical gradient to transport ions or molecules against the concentration gradient.

sodium potassium pump

•Requires ATP (Energy).

•The pump has a higher affinity for Na⁺ than K⁺.

•ATP generally needs to bind first.

•Then three Na⁺ ions bind.

•ATP is hydrolyzed, phosphorylating aspartate.

•ADP is released

•The pump undergoes a conformational change that releases Na⁺ into the extracellular region.

describe the Na/K+ pump

•With the pump in its conformational change, this form has a high affinity for K⁺.

•Two K⁺ ions bind, which induces the dephosphorylation of the pump.

•The pump undergoes another conformational change back to the normal orientation.

•K⁺  is released inside the cell.

what is secondary active transport also known as

•Also known as “co-transport”.

•Ion gradients formed by primary active transport of Na⁺ (for example) can provide the driving force for the transport of other molecules.

•Na⁺ - glucose symporter

•Where Na⁺ and glucose are transported across the membrane in the same direction.

Na+/glucose symporter

•Energy required comes from two sources:

•The chemical potential resulting from the greater concentration of Na⁺ outside versus inside the cell.

•The electrical membrane potential.

•Which is negative, so it draws the Na⁺ ions more inward.

•The strong thermodynamic tendency for Na⁺ to move inside the cell provides the energy needed for the co-transport of glucose alongside Na⁺.