Class Notes (806,507)
Canada (492,261)
Biology (Sci) (2,417)
BIOL 215 (71)
Neil Price (36)
Lecture 3

BIOL215 Lecture 3 Notes.pdf

3 Pages
Unlock Document

McGill University
Biology (Sci)
BIOL 215
Neil Price

BIOL215 Lecture 3 Notes The final step in the evolution of cells must have been the formation of an outer membrane that encased the nucleic acids and proteins Believe that precursor molecules which could form abiotically could have included fatty acids Fatty acids (palmitic acid, oleic acid) are hydrocarbons Understand the hydrophilic and hydrophobic components in a molecule (bimolecular layer) See example of micelles fuse to form vesicles How might the association between nucleic acids and membranes lead to the formation of a stable entity that displays cellular behavior? 1. Osmotic stress 2. Creation of an electrochemical gradient (energy) A theory of life's beginnings: 1. Prebiotic chemicals react to form small organic molecules in a watery environment ("soup") 2. Polymerization and dehydration ("crepes") form nucleic acids and proteins 3. RT copies RNA into complementary DNA, which replicates 4. DNA replicates; RNA from DNA builds proteins. lipids form spheres 5. Self-replicating system enclosed in a permeable protective lipid sphere The hypothesis for the origin of metabolism (see diagram): • Precursor cells (progenotes) use A as energy source • As A is depleted those cells that evolve an enzyme to convert B into A thrive • Natural selection would favour progenotes that used diverse substrates A popular view is that life may have first evolved in the deep sea near hydrothermal vents (boundaries between plates and the Earth's crust) • UV radiation would have destroyed most macromolecules in the sea surface - ozone was not created until 2 was produced • Clays (serve as template upon which the nucleic acid precursor aligned) and metal catalysts All organisms have similar requirements for life: Liquid water • Water accounts for 50-90% of an organism's mass • Is a universal solvent; stabilize other molecules via H-bonding, polar molecule allows for bonding • All chemical reactions necessary for life occur in water • Elements which make up essential biomolecules An energy source • Energy is used to assemble elemental elements/building blocks (i.e. C, N, Fe) into complex molecules for the construction of organisms; motility; acquire other resources... • Organisms use one of 3 main sources of energy: • Light (photosynthesis) • Organic molecules (breaking bonds to extract bond energies) Inorganic molecules (chemosynthesis) • • Organisms can be classified by how they obtain energy and carbon - C is one of the most important elements used for growth • Autotrophs (self-feeder): in organic C - 2O • Photosynthetic (light - electromagnetic energy) PAR 400-700 nm (photoautotroph) Chemosynthetic (inorganic molecules - chemical bond energy) H , H S, NH , Fe(II), etc. • 2 2 (chemoautotroph); occurs quite often in deep-sea bacteria • Heterotrophs (other-feeders): organic molecules for energy and C - (chemical bond energy) carbohydrates, proteins, fats • Herbivores (plant only) • Carnivores (meat only) • Omnivores (plant and meat) • Detritivores (remains of dead organic matter produced from animals and plants) The rate at which organisms can take in energy is limited. The limitations may be caused by • external constraints: • Shortage (or reduced availability) of food in the environment • Food quality: elemental composition/chemical defense •The limitation may be caused by internal constraints: • Digestion • Enzyme catalysis •In photoautotrophs, the energy intake increases as the energy availability arises. We can see how the internal and external limitations affect photoautotrophs •Energy intake by organisms is limited •Organisms "adapt" in such a way as to maximize their rate of energy intake •Because energy intake is limited organisms cannot simultaneously maximize all of life's functions: (i.e. allocation of energy to reproduction reduces the amount of energy available for defense; TRADE OFF) •See sun and shade plants
More Less

Related notes for BIOL 215

Log In


Don't have an account?

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.