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Evo Bio ch 6,7,8
| Question | Answer |
|---|---|
| Life began long ago most of the geological record | is lost |
| Cells today are complex, and most thrive in environments that are different form the early earth. This effects how well we can | use living species to predict what the first species wee like |
| The oldest definite fossils are | bacteria, over 3 BYO. There are controversial indications of life older than 3.5 BYO. |
| Deep homologies of life: | all living things are made of cells, with homologous structures, molecules and biochemistry |
| Deep homologies of cell structure: | -Cell membranes -Cytoplasm -Centralized genome -Protein complexes (ribosomes, membrane pumps) |
| Deep homologies of molecules: | -Polysaccherides -Lipids -Proteins -Nucleic acid |
| Polysaccherides: | are made with sugars. A commonly used sugar today is glucose. They are a common source of stored chemical energy and structure. Sugars are precursors for many other molecules |
| Lipids: | most contain fatty acid chains and glycerol |
| Proteins: | are made from amino acids. there are -20 different amino acids used by cells. Chains of amino acids are peptides or polypeptides |
| Proteins are used as | enzymes (catalysts), and also for structures, communication, transport and movement |
| Nucleic acids: | include DNA and RNA both are made with nucleotides. Nucleotides contain a 5- carbon sugar, a phosphate group and a nitrogenous base |
| In cells, DNA is double stranded where | bases on one strand form hydrogen bonds with complementary bases on the other strand. (A=T G=C) |
| Transcription | DNA stores info in the form of GENES. A gene is a region of DNA used as a template to make complementary RNA |
| The genotype> the phenotype because | translation RNA is then used to make a polypeptide (and so protein) |
| Translation takes place in | the cytoplasm, in ribosomes |
| 3 main kinds of RNA | mRNA, tRNA, and ribosomal RNA rRNA |
| Replication | Making a copy of its' information before dividing |
| Life is an EMERGENT PROPERTY when | DNA, RNA, protein,lipids, and polysaccs interact and become inter dependent on each other |
| panspermia | The theory that life on the earth originated from microorganisms or chemical precursors of life present in outer space. Most biologists shy away from the panspermia hypothesis but space may have contributed molecules |
| Pre-biotic or organic evolution | a period of evolution of lifes' atoms and molecules before life |
| Prerequisites for the origin of the first molecules | 1. critical atoms must be in good supply 2. there must be precursor molecules that can make the first building blocks 3. abundant water 4.source of energy 5. a reducing environment(H rich compounds not so much O2) |
| The Miller-Urey experiment | an experiment where biotic amino acids, nucleo bases, sugars, HC chains and even coenzymes can be made prebiotically. (in test tubes with elements and an energy source) |
| Abiotic synthesis of building blocks makes | racemix mixtures. But well shaped polymers must use only one handed molecules. |
| All cellular amino acids are | left handed and all sugars are right handed |
| Polymerization: the simple recipe for making polymers | a.energy source such as heat or UV light b. various mineral and clay surfaces c. deep sea hydrothermal vents |
| Various mineral and clay surfaces provide a kind of catalyst for polymerizing | amino acids> peptide chains, ans nucleotides> short nucleic acids |
| Deep sea hydrothermal vents | are a natural M-U like system for making building blocks+ complex mineral surfaces.Polymers may also form there |
| What may have existed? | competition for polymer formation + selection for handedness and stability |
| Membranes | the first structures |
| Phospholipids spontaneously form | lipid bi-layers in water |
| membranes are | selectively permeable |
| simple droplets of membranes are | protocells |
| Made in a lab, protocells can | -trap enzymes, nucleic acids or polysacch. - diffused into smaller molecules -carry out simple polymerization rxns inside - grow and divide |
| Life amounts to the inter-dependent synthesis of biomolecules and their macromolecules. A major route known today is known as the | CENTRAL DOGMA of molecular biology (Dna>Rna>Protein) |
| How could DNA, RNA, Protein be made first w/o the other? | It might have involved a molecule that can play >1 role. |
| Rna molecules can store | genetic info. and act as Rna enzymes= ribosomes |
| Some of the RNA ribosomes: | -Telomere elongation factor ribosome - Ribosome for trimming tRNA - Ribosome for splicing mRNA - Ribosome in ribosomes that catalyze peptide bond formation during translation |
| RNA nucleotides are also essential for protein based enzyme activity: | NAD+, FAD+, ATP, GTP |
| The first life forms were based on | RNA enzymes that were able to replicate themselves. - these life forms perhaps did not have DNA, nor need they be based on 'cells' w/ lipid membranes |
| Labs have modeled the hypothetical RNA world by | making randomized RNA molecules, and testing their ability to self replicate. -in these experiments there is variation n competition so selection for speed and accuracy |
| Rna is | unstable. RNA can only be a few dozen base pairs long. Longer RNA is less stable |
| RNA>RNA replication has | a hi mutation rate |
| Further research on RNA replication has found | competing populations of RNA enzymes self replicate each other. Cooperation arises naturally |
| Some ribosomes can cooperate to make | proteins |
| Why DNA? | -RNA>RNA synthesis has a hi mutation rate -DNA is more stable, meaning it isnt catalytic. No DNA can make DNA or RNA on its own |
| How to make DNA from RNA? | Reverse transcriptase. - it can make RNA form RNA, DNA from RNA or DNA from DNA |
| The genetic code contains | 64 triplet codons from mRNA specify ~20 amino acids. - for most codons, the 3rd base is non specific - nearly universal |
| Today, pyruvate is at | the heart of cell metabolism, and synthesis of many cell compounds including a large num of amino acids |
| spontaneous formation of pyruvate include | 'pre biotic' deep sea volcanic vents |
| Pyruvate would have been a main source for synthesis of | amino acids, adding to the primitive genetic code from a resource at volcanic vents--a good place for life to begin |
| Amino acids have tended to 'commandeer' codons in proportion to how often | they are used in proteins |
| missence mutation | is a point mutation in which a single nucleotide is changed, resulting in a codon that codes for a different amino acid |
| Most codons that code for the same amino acid share | the first 2 bases. The third base (most error prone) codon-anticodon base pair has the least effect |
| The first codon/anticodon base pairs are | the next most error prone. Many errors here substitute an amino acid for a chemically similar amino acid |
| The genetic code has continued to | evolve ( a little) in different lineages |
| Alkaline vents | possibly a better and more cellular cradle for life (contains H2, CH3,NH3,CO2, etc.) |
| Metal ions are | inefficient catalysts but are the key prosthetic group in many enzymes |
| phosphorolated acetyl is used instead of | ATP in many deep sea bacteria ( could be energy before ATP) |
| Abiotic and Biotic formation of acetyl and pyruvate involve complexes of | Ni, Fe and S.The enzymes making acetyl contain the same elements |
| LUCA | Last universal common ancestor. Also known as Progenote |
Created by:
awahay
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