Chapter 1: Principles of Life
• Are composed of a common set of chemical components such as
nucleic acids and amino acids, and similar structures such as cells
enclosed within plasma membranes
• Contain genetic information that uses a nearly universal code to
specify the assembly of proteins
• Convert molecules obtained from their environment into new
• Extract energy from the environment and use it to do biological work
• Regulate their internal environment
• Replicate their genetic information in the same manner when
• Share sequence similarities among a fundamental set of genes
• Evolve through gradual changes in their genetic information
The critical step for the evolution of life was the appearance of nucleic
acidsmolecules that could reproduce themselves and also serve as templates
for the synthesis of large molecules with complex but stable shapes. The
variation in the shapes of these large, stable moleculesproteins enabled
them to participate in increasing numbers and kinds of chemical reactions
with other molecules. The next step in the origin of life was the enclosure of
complex proteins and other biological molecules by membranes that
contained them in a compact internal environment separate from the
surrounding external environment. Molecules called fatty acids played a
critical role because these molecules do not dissolve in water; rater, they
form membranous films. When agitated, these films can form spherical
vesicles, which could have enveloped assemblages of biological molecules.
The first unicellular organisms were prokaryotes. Prokaryotic cells consist of
genetic material and other biochemicals enclosed in a membrane. Over time,
photosynthetic prokaryotes became so abundant that vast quantities of O2,
which is a byproduct of photosynthesis, slowly began to accumulate in the
atmosphere. Aerobic metabolism (energy production using O2) is more
efficient than anaerobic (nonO2using) metabolism, and it allowed
organisms to grow larger.
Another important step in the history of life was the evolution of cells with
membraneenclosed compartments called organelles; within which
specialized cellular functions could be performed away from the rest of the cell. One of these organelles, the nucleus, came to contain the cell’s genetic
information. The nucleus gives these cells their name: eukaryotes. The
eukaryotic cell is completely distinct from the cells of prokaryotes, which
lack nuclei and other internal compartments. Some organelles are
hypothesized to have originated by endosymbiosis when larger cells ingested
smaller ones. The mitochondria that generate a cell’s energy probably evolve
from engulfed prokaryotic organisms. And chloroplaststhe organelles
specialized to conduct photosynthesiscould have originated when
photosynthetic prokaryotes were ingested by larger eukaryotes.
Cellular specialization enabled multicellular eukaryotes to increase in size
and become more efficient at gathering resources and adapting to specific
Organisms reproduce by replicating their genomes. This replication process
is not perfect, however, and changes, called mutations, are introduced almost
every time a genome is replicated.
Molecular data in particular have been used to separate the tree into three
major domains: Archaea, Bacteria, and Eukarya. Organisms in the Archaea
and Bacteria are singlecelled prokaryotes. However, members of these two
groups differ so fundamentally in their metabolic process that they are
believed to have separated into distinct evolutionary lineages very early.
Species belonging in the their domain, Eukarya, have eukaryotic cells whose
mitochondria and chloroplasts originated from endosymbiosis of bacteria.
The organisms genome is the sum total of all the information encoded by its
genes. Nucleic acid molecules contain long sequences of four subunits called
nucleotides. The sequence of these nucleotides in DNA allows the organism
to make proteins. Each gene is a specific segment of DNA whose sequence
carries the information for building or controlling the expression of one or
more proteins. Protein molecules govern the chemical reactions within cells
and form much of an organism’s structure.
The most basic cellular work is the building, or synthesis, or new complex
molecules and structures from smaller chemical units.
A group of individuals of the same species that interact with one another is a
population, and populations of all the species that live and interact in the
same area are called a community. Communities together with their abiotic
(nonliving) environment constitute an ecosystem.
Evolutionchange in the genetic makeup of biological populations through
timeis a major unifying principle of biology.
The hypothesisprediction method has five steps
1. Make observations
2. Asking questions 3. Forming hypothesis, or tentative answers to the questions
4. Making predictions based on the hypotheses
5. Testing the predictions by making additional observations or
The variable that is manipulated is called the independent variable, and the
response that is measured is the dependent variable.
Biology Lecture 1:
Genome is the full genetic information of an organism. Bacteria are the
• Prokaryote (no cell nucleus)
• 30 min
Chapter 2 (Part 1): Atoms and Molecules
Most atoms are electrically neutral because the number of electrons in an
atom equals the number of protons. The mass of a proton serves as a
standard unit of measure called the Dalton. An element is a pure substance
that contains only one kind of atom. For electrical neutrality, each atom has
the same number of electrons as protons. The mass number of an atom is the
total number of protons and neutrons in its nucleus. The further away an
electron shell is from the nucleus, the more energy the electron must have. A
chemical bond is an attractive force that links two atoms together in a
molecule. Ionic bonds form when atoms gain or lose one or more electrons
to achieve stability. Covalent bonds are the strong bonds that form when
atoms share electrons. An ion is an electrically charged particle that forms
when an atom gains or loses one or more electrons. Positively charged ions
are called cations (Na+). Negatively charged ions are called anions (Cl).
Ionic bonds result in stable molecules that are often referred to as salts.
Because ionic attractions are weak, salts dissolve in water. The water
molecules are oriented with their negative poles nearest to the cations and
their positive poles nearest to the anions. A covalent bond forms when two
atoms attain stable electron numbers in their outermost shells by sharing one
or more pairs of electrons. The attractive force that an atomic nucleus exerts
on electrons in a covalent bond is called its electronegativity. Heat of
vaporization means that a lot of heat is required to change water from its
liquid to its gaseous state. Cohesion is defined as the capacity of water
molecules to resist coming apart form one another when placed under tension. Polar moleculeshydrophillic and nonpolar molecules are known as
Biology Lecture 2:
Daltonmass of one proton or neutron (1.7*10^24 grams)
Living things are mostly composed of 6 elements: Carbon, Hydrogen,
Nitrogen, Oxygen, Phosphorus, and Sulfur
Behavior of electrons determines whether a chemical bond will form and
what shape the bond will have.
Octet rule atoms with at least two electron shells form stable molecules so
they have eight electrons in their outermost shells
Ionic bondattraction of opposite charges
Covalent bond sharing of electron pairs (strongest)
Hydrogen bond sharing of H atoms
Hydrophobic interactioninteraction of nonpolar substances in the presence
of polar substances (especially water)
Ionic attractions are weak, so salts dissolve easily in water.
Properties of molecules are influenced by characteristics of the covalent
bonds: These characteristics include: orientation, strength & stability,
multiple bonds, and degree of sharing electrons.
Orientationlength, angle, and direction of bonds between any two elements
are always the same
Strength and stability covalent bonds are vey strong; it takes a lot of energy
to break them
Degree of sharing electrons is not always equal. Electronegativity increases
across the period and decreases down a group.
Macromolecules are large molecules formed by covalent linkages of smaller
molecules. Four kinds of macromolecules are typically found in living
organisms: proteins, nucleic acids, carbohydrates, and lipids. Except for the
lipids, the other 3 kinds of biological macromolecules are polymers.
Polymers are formed and broken apart in reactions involving water.
Condensation removal of water links monomers together. Hydrolysis
addition of water breaks a polymer into monomers. Carbohydrates are a large group of molecules that have similar composition,
but differ in several important properties
Composition: carbon + water
Some carbohydrates are small and are cal