bio 204 wk 4

What are the characteristics of an amphipathic molecule? Name one.

A amphipathic molecule has a polar region and a nonpolar region.

8) How does a constraining micro-environment improve replication? Use the words, RNA nucleotides, RNA polymers, ribozyme replicase, diffusion.

A catalyst, which is an RNA replicase, can catalyze the replication of more strands of RNA because the RNA strands are closer together -- higher density, which prevents diffusion. The higher concentration of RNA and catalyst improves replication and limits diffusion.

What is a liposome? How is a liposome made?

A liposome is a constraining agent. It is surrounded by a lipid bilayer with two lines of the amphipathic molecule. They are made in the laboratory by vigorously mixing a solution of amphipathic molecules in water. They can also be found in nature where any sort of energetic disturbance of a pool of water with amphipathic molecules can make liposomes.

13) In the ancient RNA world, RNA was critically involved in two processes: 1) being replicated 2) catalyzing chemical reactions. In the DNA world, what molecule is replicated, and what molecule catalyzes chemical reactions? How have these molecules improved upon the two processes as initially performed by RNA?

DNA is being replicated and a protein catalyzes the reaction. Amino acids (what a protein is made of) have a much greater versatility because there are 20 different amino acids to choose from. The range in structure is much greater than the range of structure available in the four ribonucleotides. DNA is more stable than RNA because the lack of an OH group on its base. The lack makes the hydrogen bonds between the bases more stable and keeps the DNA in its double stranded form, which is more stable

9) Draw a fatty-acid membrane surrounding a liposome with the following labels: water, polar heads, non-polar tails.

In notebook

11) What is osmosis? Use the following words in your answer: solute, solvent, diffusion, semi-permeable membrane.

Osmosis is the diffusion of water, which are solvent molecules, through a semi- permeable membrane to an area of high concentration to an area of low concentration in a direction that should equalize the solutes.

14) In the DNA world, what are the two distinct synthetic pathways initiated by DNA? How do these pathways differ from their equivalent in the RNA world?

In the RNA world, RNA can only replicate itself. DNA can either replicate itself or it can undergo transcription. This initiates the making of a protein catalyst. RNA does not need to make a catalyst because it is a catalyst itself, so it can undergo replication and self- catalyzing.

7) Describe how natural selection works using the following words: replication, mutation, polymorphism, competition, extinction.

Mutations are caused during replication in RNA creating polymorphisms amongst the RNA species. These mutations help diversify the population of RNA and create competition between the different species based on which one can replicate faster. Eventually, because of the competition, the species that are slower go extinct.

12) From what person did Watson and Crick steal (surreptitiously borrow?) a critical x-ray diffraction photo, thereby allowing them to deduce the structure of DNA, the chemical that genes are made of?

Rosalind Franklin!

Name and describe the problem that the evolution of a membrane solved.

The evolution of a membrane solved the osmosis crisis. Membranes are selectively permeable, so they can replicate outside the cell.

What, specifically, is the "osmosis crisis?" What, exactly, caused it?

The osmosis crisis refers to the crisis involving the large RNA molecules which were trapped inside the fatty acid liposomes, meaning that they could not diffuse toward lower concentrations outside at all. RNA strands in the cell replicate, causing their concentration to increase and newly replicated polymers remain trapped inside the cells.

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?

The proton pump evolved to solve the osmosis crisis. The pump actively pumps hydrogen ions out of the cell, which reduces the concentration of protons inside. This equalizes the total number of solutes. Nucleoside triphosphate is the energy source for this.

10) We've learned how more efficient replicase ribozymes will be selected for over more slowly replicating ribozymes. With the advent of protocells, how might ribozymes that have NO replicase function ever evolve?

When a ribozyme is in a protocol it is protected from stuff that wants to tear RNA strands apart, eventually without this protection it is able to catalyze itself and self replicate. Sometimes they are not the right shape and they occur as a proton pump are useful. If there is a proton pump, there can't be any lysis.

Describe the circumstances (use the words, solute, inside, outside, hyperosmotic, hypoosmotic, flow of water) that would lyse a red blood cell, shrink a red blood cell, make a red blood cell happy (neither shrink nor swell/lyse),

When the outside solution is hypo-osmotic, water flows into the cell, causing it to swell and lyse. When the outside solution is hyperosmotic, water flows out of the cell, causing the cell to shrink. A iso-osmotic cell has an equal amount of solute and solution inside and outside, so there is no net flow of water. The cell remains the same size, so the cell is happy.