Lipids, Membranes, and the First Cells

plasma membrane or cell membrane

life's defining barrier that is built of lipids and proteins; cluster of molecules that forms part of the boundary between life (inside the cell) and non-life (outside the cell); A SELECTIVE BARRIER: it keeps damaging compounds out of the cell and allows useful into the cell; because it does this the reactants collide more frequently and so the chemical reactions that are needed for life occur more frequently

lipid bilayers

what do lipids spontaneously form due to increase in entropy

RNA-theory of biological evolution

this theory claims that life began with a catalytic RNA molecule that could replicate itself and that as the offspring of this molecule multiplied, natural selection could have favored the most efficient versions. The second great theory that biologists are excited about states that the history of life occurred when the descendants of these replicators became enclosed within a membrane

cell

the most efficient and dynamic reaction vessel that forms after life secured a membrane

lipid

a catchall term for carbon-containing compounds that are found in organisms and are largely non-polar and hydrophobic-- meaning that they do not dissolve readily in water; (this compound can dissolve but only in non-polar organic compounds); the orientation of C-C bonds is a key factor in this structure; characterized by physical properties rather than chemical structure

isoprenes

these can be linked up into chains called isoprenoids; we look at this to understand why lipids are insoluble in water; these contain carbon atoms bound to hydrogen atoms; key building block of important lipids found in organisms; FULL OF POTENTIAL ENERGY BECAUSE OF HYDROCARBON BONDS

hydrocarbons

molecules that contain only carbon and hydrogen; these are non-polar due to the equal sharing of electrons between carbon and hydrogen due to their approximately equal EN; since these bonds form no partial charges these are hydrophobic; this explains why lipids cannot dissolve in water

fatty acid

a simple lipid consisting of a hydrocarbon chain bonded to a carboxyl (-COOH) functional group; this is one of the key building blocks of important lipids found in organisms; ISOPRENOID+CARBONYL GROUP= this; NOT MONOMERS!

Carbon double bonded to Carbon

when this happens, the attached atoms are found in a plane instead of a 3-D tetrahedron; these atoms are locked in place; they cannot rotate freely like the single bonds of these atoms; a kink is produced in an otherwise straight hydrocarbon chain

saturated hydrocarbon chains

chains that consist of only single bonds between the carbons; it has the max amount of hydrogens that can bond to the carbon skeleton

unsaturated hydrocarbon chains

chains that consist of double bonds between the carbons; the C-H bond is removed resulting in the double carbon bond which has a lesser amount of hydrogen atoms attached to it

hydrocarbon tail length and saturation/desaturation

these two things determine lipid fluidity

beeswax

extremely long saturated hydrocarbon chains so most dense of the three things we mentioned in class; a saturated lipid that is extremely solid in room temperature

veggie oil

dominated by "polyunsaturated" lipids with hydrocarbon chains that contain multiple double carbon bonds; a highly UNsaturated lipid which is liquid at room temperature

butter

consists of primary saturated lipids; a highly saturated lipid which is solid at room temperature

physical property

what are lipids categorized by (i.e their insolubility in water)?

C-C and C-H bonds

What is a lipid's insolubility in water due which is relative to polar functional groups? This leads to its variability in structure in cells: fats, steroids, phospholipids are examples

fats

non-polar molecules composed of three fatty acids that are linked to a three-carbon molecule; NOT POLYMERS!; STORAGE OF CHEMICAL ENERGY

glycerol

the three-carbon molecule that fats are linked to; and why fats are also called triacylglycerols/triglycerides; goes from hydrophilic to hydrophobic

oils

when the fatty acids are polyunsaturated they form these liquid triacylglycerols

energy storage

the primary role of fats in organisms, and especially in humans who cannot produce their own energy like plants can

dehydration reaction

when this specific thing occurs, fats are formed; the hydroxyl group (OH) of the glycerol binds with the carboxyl group (CdoublebondO and HO) of the fatty acid

ester linkages

the way the glycerol and fatty acids are joined when the H comes off of the hydroxyl group and goes into the water leaving just the O and then that HO from the fatty acid also goes into the water leaving just the C which then binds with the left over O

steroids

a family of lipids distinguished by a bulky, four-ring structure; they differ from one another by the functional groups or side groups attached to different carbons in those hydrophobic rings; the four-ring structure gives it polarity and rigidity which separates it from other lipids; VERY POTENT MESSENGER COMPOUND; AFFECTS FLUIDITY; starting point for the synthesis of other important molecules, USED TO MODERATE FLUIDITY AND PERMEABILITY IN THE MEMBRANE; cholesterol are an example of this macromolecules

cholesterol

an important component of plasma membranes in many organisms

phospholipids

Consist of a glycerol that is linked to a phosphate group and two hydrocarbon chains of either isoprenoids or fatty acids. The phosphate group is also bonded to a small organic molecule that is charged or polar; like triglycerides they both contain fatty acids and glycerol; contain two fatty acids and one hydrophilic heads; VERY IMPORTANT IN THE FORMATION OF LIPID MEMBRANE; these are crucial components of the plasma membrane

function and structure of lipids

1. storing chemical energy; 2. capture and respond to sunlight; 3. serve as signals between cells; 4. form waterproof coatings on leaves and skin; 5. act as vitamins used in many cellular processes

membrane-forming lipids

these kinds of lipids have a polar, hydrophilic region in addition to the non polar, hydrophobic region found in all lipids

amphipathic

compounds that contain both hydrophilic and hydrophobic elements ("dual sympathy"); this kind of nature is found in phospholipids and serves as the responsibility for life's defining barrier; DO NOT DISSOLVE IN WATER BECAUSE OF HYDROPHILIC HEADS AND HYDROPHOBIC TAILS

micelles

tiny droplets that form when the hydrophilic heads of a set of lipids interact with the water molecules by hydrogen bonding and the hydrophobic tails interact with each other; they form a sort spherical shape; tend to form from fatty acids or other simple amphipathic hydrocarbon chains; FORM SPONTANEOUSLY; they are much more stable than independent phospholipi ds in a solution

lipid bilayer

form when two sheets of lipid molecules align; tend to form from phospholipids that contain two hydrocarbon tails; FORMS SPONTANEOUSLY; much more stable than phospholipids in solution; HIGHLY SELECTIVE

ions

what cannot cross selectively permeable membranes unless they get "help" from other membrane proteins?

degree of saturation and hydrocarbon chain length

what are the two key aspects that affect membrane fluidity and permeability?

unsaturated hydrocarbon tails

this when packed together into a lipid bilayer, creates kinks created by double bonds that produce spaces among the tails which reduce the strenght of the van der Waals interactions, which hold the hydrophobic tails together, thereby WEAKENING THE BARRIER TO SOLUTES

fluidity

What is permeability related to, which thereby shows the affect temperature has on the permeability of membranes?

diffusion

this process is responsible for the movement of liquids across a lipid bilayer; the movement of molecules and ions that results from their kinetic energy; they are in constant motion; so can move spontaneously/ without any input energy

concentration gradient

a difference in solute concentration

High to low concentration

what happens when the concentration gradient exists and there is an increase in entropy?

osmosis

this is the spontaneous process of the movement of only unbound water molecules across selectively permeable membranes; WATER MOVES FROM THE SIDE WITH THE LOWER CONCENTRATION OF SOLUTE TO HIGHER CONCENTRATION OF SOLUTE; THIS OCCURS ONLY WHEN A SOLUTE CANNOT PASS THROUGH THE SELECTIVELY PERMEABLE MEMBRANE

hypotonic

if the solution inside the membrane does not have a lot of solute relative to the exterior, then the solution (water) is going to want to move toward the outside-->the inside of the membrane is said to be ______ because it has a lot of water and not as much solute as the outside; the outgoing water causes the water to shrink/shrivel.

hypertonic

if the solution inside the membrane has alot of solute relative to the exterior, then the solution (water) is going to want to move toward the inside--> the inside of the membrane is said to be ______ because it has alot of solute in the inside relative to the outside; this incoming liquid causing the vesicle to swell.

isotonic

if the solution has the same amount of concentration in and outside of the membrane, then the shape stays the same and the membrane is said to be _____.

Yes

Can negatively charged ribonucleotides get across lipid bilayers and inside lipid-bounded vesicles? Yes/No?