BIOL 111 Study Guide - Midterm Guide: Electrochemical Gradient, Semipermeable Membrane, Photochemistry
14 Nov 2018
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BIOLOGY 111 Midterm Summary Notes:
Useful Definitions:
Chemosis: the movement of ions across a semipermeable membrane down their
electrochemical gradient “Hydrogen ions, or protons, will diffuse from an area of high proton
concentration to an area of lower proton concentration, and an electrochemical concentration
gradient of protons across a membrane can be harnessed to make ATP. This process is related
to osmosis, the diffusion of water across a membrane, which is why it is called "chemiosmosis"”.
Germinate: to develop
Photosystems:are functional and structural units of protein complexes involved in photosynthesis
that together carry out the primary photochemistry of photosynthesis: the absorption of light and the
transfer of energy and electrons.
Blind Gut : A digestive cavity open only at one end
Cephalization: the concentration of sense organs and nervous control at the anterior end of
a body (the formation of a head & brain at the front of an organism)
Coelum: Internal fluid filled body cavity lined with a mesoderm
Protostome: the mouth appears before the anus in development
Deuterostome: The first opening (blastopore) becomes the anus and the mesoderm and the
coelom forms from outgrows of the primitive gut
Striated: Marked by transverse dark and light bands
Lecture 1-3: EVOLUTION AND CREATION OF LIFE
To be considered living you must undergo..
1. Energy Transformation: Transform energy to synthesize new molecules
2. Reproduction: Make nearly faithful copies of themselves
3. Homeostasis: regulate internal environment in response to external changes
Sources of Energy Include…
1. Light
2. Inorganic compounds
a. , H2, SH2
3. Organic compounds
a. Starch, fat etc.
Metabolic Systems:
●Autotrophs: Self- Feeding
○Photoautotrophs:
use light energy to make carbon dioxide and glucose
○Chemoautotrophs:
use chemical energy to make carbon dioxide and glucose
●Heterotrophs: Different- Feeding
○Chemoheterotroph:
consume organic molecules as BOTH energy source &
carbon source
■ Eg. Animals, Fungi, Bacteria
○Photoheterotroph
: use light as energy but obtain carbon from food
■ Eg. certain bacteria
Formation of Earth:
● The moon banged into earth which gave it its tilt
● Particles of kinetic energy heated up the earth
● You can see this through the formation of craters eg. Arizona Meteor Crater
● All the materials under the crater evaporated on impact
Panspermia: the idea that the universe is infiltrated with the seeds of life, and that life came
from outside
● Undirected Panspermia: Objects travel from planet to planet
This is taken seriously because there is a short interval between the appearance of the ocean
and the first sign of life. Could either be transported through : radiation (would probably kill
them), or ballistic ejection inside rocks. They are hypothesized to be able to survive atmospheric
impact because early bacteria are found in many places, such as egyptian tombs, arctic tundra,
○ Objections to undirected panspermia:
■ The radiation would kill the spores so it’s unlikely
■ Low star density so there are not a lot of sources of spores, not a large
enough gravitational pull to bring them in
● Directed Panspermia: aliens plant seeds on earth
The only advantage to this is that it seems like an effective dispersal method
○ Objections to directed panspermia: it has taken so long for intelligent life to form
on earth so it is unlikely they exist anywhere else
○ There is not strong enough evidence which shows for aliens existing
● Mis-directed panspermia: galactic pollution brought life to earth
NASA pollutes in space regardless how the amount of safety precautions and precision they
have, perhaps another civilization did the same thing and polluted earth with life
Planetary Protection:
● NASA wants to keep the numbers of microorganisms on bored in expeditions low
enough so the pollution on mars is acceptable
● The aim is NOT to keep it 0, but 1 in every 10,000
● There is an average of 300,00 microorganisms on board
Spontaneous Generation:
● It was once hypothesized that fleas, mice and other forms of life could spontaneously
generate without any former signs of life- the theory states that complex organisms can
spontaneously arise by natural processes and self-organize
● This was proven wrong by PASTEUR'S experiment
● It was said that with the right atmospheric conditions, life could evolve, this was
tested through Miller-Urays experiment
● Miller -Uray Experiment:
○ He replicated the early atmospheric conditions by placing basic inorganic
compounds (carbon dioxide, methane, ammonia, h2 etc.) and water in a closed
system and placing an electric signal through it to mimic lightening,
○RESULT: amino acids and nucleotides were created but they were unable to
synthesize themselves to create larger organic molecules necessary for the
development of life
Two possible roots for the Origin of Life:
Genetics First:
● There is no pathway seen which leads small molecules to form into DNA-protein
cells, which had created a deadlock in thinking of spontaneous generation and therefore
genetics first as an origin of life. Until 1987
●“There are RNA molecules catalyse chemical reactions, a role usually carried out
only by protein enzymes, these are called ribozymes. Ribozymes can facilitate the
creation of both peptide bonds in proteins, and the bonds between phosphate and
ribose in RNA.This means that under the right conditions some RNA sequences
could both store information and implement the information. RNA is considered
an attractive candidate as a primordial catalysis in the origin of
life.”https://www.quora.com/Can-or-Could-RNA-self-replicate
● Summary: there are RNA molecules existing which act as the enzyme ribozyme,
meaning it is possible for RNA molecules to both store and implement this information
and therefore be able to self replicate under the right situation
○ Because of this, it is hypothesized that there is an Archean ocean
population of self-replicating RNA which all other life has descended from
Problems with this theory:
■ The problem is the RNA molecules do not fit in a solution, because they
dissolve away from each other
■ If these replicating RNA did exist, they would most likely replicate more
non-replicating bacteria as there are more of them, and there could be no
evolution
○ HOWEVER, Jack W Szostak found a medium which can form cells
spontaneously: you can trap RNA molecules in vesicles which allow the rate of
photocell division to increase and therefore speed up evolution
Metabolism First: Reactions first occurred creating organic compounds and giving the
energy necessary for later self-replicating systems to produce
● Exergonic reactions can produce organic compounds which may be the basis for the first
metabolic system (can only happen when the thermodynamic system is far off of
equilibrium which is unlikely)
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