ch.4 molecular evolution, cellular evolution and the osmosis crisis Flashcards
List the characteristics of an amphipathic molecule? Name one amphipathic molecule.
has polar and non-polar region
example: triglyceride (glycerol(polar) + 3 fatty acids(non-polar)) OR a phospholipid (phosphate group (polar) + 2 fatty acid chains (non-polar))
What is a liposome? How is a liposome made?
liposome: small bubble bounded by an amphipathic molecule; small (70-300 nM) piece of water, surrounded by “lipid bilayer,” 2 lines of amphipathic molecules, an inner line with its polar heads contracting the captured piece of water, and an outer line with its polar heads facing the other way i.e. toward surrounding water. 2 lines orient their nonpolar tails toward each other and away from water
it’s made in any sort of energetic disturbance in a pool of water with amphipathic molecules in it
Describe the circumstances (use the words, solute, inside, outside, hyperosmotic, hypoosmotic, flow of water) that would
a. lyse a red blood cell
there would need to be more solute inside of the cell to create a hypo-osmotic solution, so water would flow from outside of the cell into cell, eventually causing it to burst (lyse)
Describe the circumstances (use the words, solute, inside, outside, hyperosmotic, hypoosmotic, flow of water) that would
b. shrink a red blood cell
there would need to be more solute outside of the cell to create a hyper-osmotic solution, so water would flow from inside of the cell to outside of the cell, causing it to shrink
Describe the circumstances (use the words, solute, inside, outside, hyperosmotic, hypoosmotic, flow of water) that would
c. make a red blood cell happy (neither shrink nor swell/lyse)
there would need to be equal amounts of solute inside and outside a cell to create an iso-osmotic solution, so water would not diffuse leaving it at an equilibrium
Name and describe the problem that the evolution of a membrane solved.
evolution of membrane solved osmosis crisis because membranes are selectively permeable, so they can replicate outside the cell since the inside of the cell was too full with ever-increasing number of solute molecules (RNA polymers)
Describe what is meant by the “osmosis crisis?” What, exactly, caused it?
osmosis crisis: (low to high concentration) ever-increasing number of solute molecules (RNA polymers) inside the cell, which means that water will tend to flow in the cell by osmosis (hypo-osmotic solution). This eventually leads to the lysis of cells.
it was caused by large RNA’s not being able to diffuse to lower concentrations outside. This meant that RNA strands in cells were replicating themselves, increasing their concentration as each newly replicated polymer remained trapped in the cell’s fatty acid liposomes
What intracellular structure evolved to solve the osmosis crisis? How did it do that and what important energy molecule is also required for that solution?
protein pump evolved to solve osmosis crisis. It pumped protons (hydrogen ions) out of the cell, which equalized the total number of solutes and reduced the concentration of protons inside the cell. Nucleoside triphosphates were the energy source
Describe how natural selection works using the following words: replication, mutation, polymorphism, competition, extinction.
When RNA replicates, ribozyme replicase replicates RNA at a much faster pace than RNA spontaneously replicating with itself. Because of the rapid replication, there’s a possibility for slight errors in the RNA code, which are called mutations. Mutations create polymorphisms and variations in the population. Polymorphism allows variation and variation brings persistence. New mutations allow RNA molecules to compete against their environments and each other for survival (aka natural selection). Without mutations, RNA would grow extinct because creating complements and copies of itself makes it unadaptable to changes in the environment. SCARCITY OF NUCLEOTIDE TRIPHOSPHATES means that slower replicases go extinct. Mutations are also promises for genetic change in organisms.
Explain how a constraining micro-environment improves replication. Use the words, RNA nucleotides, RNA polymers, ribozyme replicase, diffusion.
RIbozyme replicase will be able to catalyze replication of RNA faster due to all the materials needed like RNA nucleotides, RNA replicase, and RNA polymers being nearby. This causes local concentration of RNA polymers to increase, causing catalysts and reactants to collide more often, which further increases replication rate. However, because of diffusion, concentration of replicase never gets that much higher than surrounding waters. (Diffusion always keeps local concentration from increasing a lot) With the environment not being constrained, all the materials needed would diffuse and spread apart, taking longer to gather the materials needed to replicate RNA.
Define osmosis using the following words in your answer: solute, solvent, diffusion, semi-permeable membrane.
osmosis: diffusion of solvent from low to high concentrations across a semi-permeable membrane depending on where the higher concentration of solute is(low solvent=high solute & high solvent=low solute)
Regarding diffusion across a lipid bilayer:
a) Define diffusion
spreading of molecules from high to low concentration
Regarding diffusion across a lipid bilayer:
b) Know what types of molecules can diffuse across a phospholipid bilayer. Name some examples of each.
- hydrophobic molecules (fat soluble): fatty acids
- uncharged molecules: O2, CH3, anything nonpolar
- small molecules: CO2, O2, and a little H2O
Regarding diffusion across a lipid bilayer:
c) Know what types of molecules can’t diffuse across a phospholipid bilayer. Name some examples.
- hydrophillic molecules: glucose, sucrose, etc
- ions: Na+, Cl-, Ca2+, etc
- large molecules: carbohydrates, proteins, etc
