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BIOL 115 Study Guide - Midterm Guide: Tight Junction, Cell Junction, Chemical Polarity

Biology (Sci)
Course Code
BIOL 115
Robert Levine
Study Guide

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BIO LECTURE NOTES: Midterm 1 Stuff!
This course allows us to think critically about Biology in what we read about Science/Biology in
Being skeptical always, asking questions always, always being ready to change your point of view.
What is Science?
1. A way of knowing things
2. A body of Knowledge accumulated through scientific investigation
The Scientific Way of Finding Things Out”
Observation, then Question, then Hypothesis (informed guess), then Experiments (try to reject some
hypotheses), then Conclusion
Theory: if hypothesis comes to be recognized as broad and general (like the cell theory). So “a broad
intellectual construct, supported by evidence, that has explanatory power”.
Scientific method at work” Pasteur tests “spontaneous generation”.
Observation: When you start with a sterile flask of sterile meat broth, a growth of living material generally
appears in the broth.
Question: What is the source of the living material?
He had 2 Hypotheses: 1. The living material came from nothing “spontaneous generation”. 2. The living
material is derived from living material outside the flask.
Pasteur’s experiment: He made an s-curve in the neck of a flask with sterile broth in it, so that any particles
from the outside would not contact broth. It remained sterile until he removed trap, or tipped flask to mix
trapped dust into broth.
The situation where he doesn’t break/tip the flask is called the control. Compares results to this.
Conclusion: No growth appears in the broth unless dust is admitted from outside. No spontaneous generation.
Example of necessity of control: Hemodynamic idea that if you tie off internal mammilaries in chest it will
relieve anginas. Was successful, people had relief, but some guy decided to do a control experiment. Made
incisions but didn’t tie off vessels in some patients, tied off vessels in others. Discovered that there was no
Attributes of Living things
Hierarchy is... (bottom up)
Atoms: smallest unit of a molecule
Molecule: smallest unit of a compound that still fits the properties of the compound

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Cell: Smallest unit of a living thing
Tissue: a group of cells with a common structure/function
Organ: compound of a number of tissues... a bunch of tissues
Organism: The entire creature
Population: Several organisms of same kind in a particular area
Community: interacting populations in a particular area
Ecosystem: community plus environment
Biosphere: Regions of the Earth’s crust, waters, and atmosphere inhabited by living things.
Living things take in energy. Major energy capturers are plants (they capture energy from sun)
Plants capture from sun, animals capture from plants, animals/plants die and bacteria/fungi capture that
energy (decomposition) (also other animals eat dead animals)
Homeostasis living organisms maintain their internal environment. Maintain constant body temperature
(dogs pant, humans sweat, rabbits ears)
Living systems respond to the environment: nervous system: smell, vision, hearing, touch, etc.
Living organisms change over time. They evolve. Pigeons for example (diff kinds produced with breeding.
Darwin). Bacteria (resistant strains)
Cavalvade of Organisms (various types of living things)
There are three major domains of living things
Bacteria (prokaryotes/single celled, earliest organisms), Archaea (prokaryotes/single celled, earliest
organisms), and Eukayra (eukaryotes(have a nucleus)). Eukaryotes include plants, fungi, animals, and protista
(single celled)
Animalia: Multicellular, Eukaryotic (cells have nucleus), Heterotrophic (ingestion, they eat stuff), have complex
organ systems like brain, stomach, heart, digestive tract, etc.
Plants: Multicellular, Eukaryotic, cellulose cell walls, Autotrophic (they make their own energy by using
sunlight. Photosynthesis), complex organ systems (transport systems, support systems, reproductive organs)
Fungi: Tremendous source of pharmaceutical agents, also some poisonous, hallucinations. Most are
multicellular, eukaryotic, chitin cell walls (chitin also makes up insect exoskeleton), heterotrophs (not
injestion, but absorption. Secrete enzymes and absorb digested material, tissues (but not organ systems), can
be pathogenic (can cause disease. E.g. ringworm, athlete’s foot)

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Protistans: Eukaryotes that are single-celled for the most part. Multicellular ones would be like kelp and
seaweed. Can be pathogenic (sleeping sickness, etc.), some are autotrophs (algae, with cell walls), some
heterotrophs (ingestion)
Bacteria:Spherical, rod-shaped, helical. Only some are pathogenic (we are full of non-pathogenic bacteria),
unicellular, do not have nucleus (prokaryotes), cell walls, most are heterotrophic, some are autotrophs.
Archaea (Extremophiles): Live in extreme conditions (in methane, high temperatures, highly acidic
environments, etc). Unicellular, prokaryotes, cell walls, some autotrophic, some chemotrophic (use methane
or sulphur compounds to generate energy)
Bits of nucleic acid (DNA or RNA) surrounded by a shell of protein. Sometimes they’ll have a bit of cell
membrane around them from the last cell they were inside. Can’t do anything on their own. But when they
get into a living system, they take it over and use its elements to reproduce, and then burst the cell and enter
the environment. One thing they can do is make more of themselves, effectively. Tricky question whether or
not they’re living. Most of the ones we know are pathogenic.
Prions: proteins that get out of hand and can behave like living organisms (though they’re not)
Viroids: bits of naked RNA that can cause disease in plants.
(Lecture 2)
ATOMS AND MOLECULES: Building Blocks of Living Organisms
Elements: materials on Earth that cannot be broken down further.
Living organisms are really separate from their environment. Part of being alive means being separate from
their environment. Humans and the Earth’s Crust have diff. Concentrations of various elements.
Atoms: nucleus contains protons and neutrons, and clouds of electrons around it. In ordinary atoms, the
number of protons and electrons are equal (balanced charge). In ions there will be differences. Most of the
weight comes from protons/neutrons. Electrons weigh almost nothing. Atomic weight of an atom is the sum
of the number of protons and neutrons. Number of protons is atomic number (determines the element).
Electrons very broadly dispersed from nucleus which is really tiny.
Electrons distributed in electron clouds that have diff energy levels, outside of the nucleus. First shell holds 2e,
after than all other shells hold 8e.
Isotopes: When the neutrons of an element vary. Diff atomic weight. Isotopes are not stable, don’t like having
these extra neutrons. Some of these neutrons break down as radioactivity, so isotopes are often radioactive.
When radioactive decay occurs in isotopes, they can become a different element.
Isotopes in Biology and Medicine: e.g. PET scans. Radioactive tracer.
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