BIO 130 Notes
template polymerization- way in which info is copied.
two strands of DNA are pulled apart, and each serves as a template for synthesis of
a new complementary strand.
Transcription: DNA RNA
Translation: mRNA proteins
Code read out by tRNA’s
Anticodon on tRNA helps recognize codon on mRNA
In all cells, the expression of individual genes is regulated independently of one
another. Therefore, the cell adjusts the rate of transcription and translation of
different genes independently.
Life requires free energy: energy in a physical system that can be converted to do
Universal feature of all cells: All cells require ATP for the synthesis of DNA and
RNA. ATP is also the carrier of free energy and helps to drive other chemical
Another universal feature: cells are enclosed by a plasma membrane. It is a
selective barrier that enables the cell to concentrate all the nutrients it gathers
from its environment. Helps to retain them and synthesize them.
The molecules that form the plasma membrane are amphiphilic- one part is
hydrophobic ( water-insoluble) and the other is hydrophilic (water-soluble). form
Hydrophobic tails are made of hydrocarbon polymers.
General principle: cells produce molecules whose chemical properties
cause them to self-assemble into structures a cell needs.
Minimum number of genes for a viable cell in today’s environment is 200-300.
The cell replicates its information by separating the paired DNA strands, and using
each as a template for polymerization to make a new DNA strand with a
complementary strand of nucleotides.
The same strategy of templated polymerization is used to transcribe portions of
information from the DNA into RNA.
This in turn guides the production of proteins, which are principal catalysts in
reactions in the cell, serve as selective transporters in he selective membrane. The
function of a specific protein depends on the amino acid sequence, which is specified
by the nucleotide sequence of a corresponding DNA
Organisms that derive energy directly from the nonliving world fall into two
categories: those that harvest the energy of sunlight (phototropic-feeding on
sunlight), and those that capture their energy from energy-rich systems of
inorganic chemicals in the environment (lithotropic-feeding on rock)
Phototropic and lithotropic organisms are PRIMARY energy converters, and are
the most plentiful form of life.
Organotropic organism (feeding on organic chemicals in living things) depend on
primary energy converters.
Lithotropic organisms are microscopic, and humans do not usually see them
because of where they are found, usually in Earth’s crust or deep in the ocean. Some
use aerobic reactions and some anaerobic.
Six elements required to make a cell: H, C, N, S, O, P
Procrayotes are classified based on biochemistry and nutritional requirements. They
have two groups: bacteria and archaea.
Archaea are found in inhabiting environments such as ocean depths, and bogs. In
appearance, they are NOT easily distinguished from bacteria. But at a molecular
level, archaea resemble eucaryotes in the machinery used for handling gene info
(replication..etc) but resemble bacteria more closely in the way of metabolism and
New Genes Are Generated From Pre-Existing Genes
Intragenic mutation- an existing gene is modified by changes
Gene Duplication- an existing gene is duplicated
Segment Shuffling- two or more existing genes are broken and rejoined to forma
Horizontal (intercellular) transfer- DNA is transferred from the genome of one
cell to another, even to other species. This is opposite to vertical transfer, which is
from parent to progeny (usually happens!).
Orthologs- genes related by descent (common ancestor)
Paralogs- related genes that have diverged
Homolgs- genes related by descent (both above are homologs)
Viruses (bacteriophages) – vectors for gene transfer
Horizontal gene transfer occurs more in prokaryotes (result: evolution of
mitochondria) become resistant by this!
Sex results in horizontal exchange of genetic info
Prokaryotes are most diverse obtain energy from inorganic (dead) chemical
sources. All originated from a common ancestor.
Eukaryote cells= bigger size, more elaborate, genomes are bigger too
Differences from prokaryotes: have a nucleus, a nuclear envelope that separates
DNA from cytoplasm, have larger cells, have a cytoskeleton to control shape and
allow for movement.
Free-living eukaryotic cells are called protozoa, which can change shape rapidly
and engulf things by the process of phagocytosis.
Eukaryotic cells MAY have originated as predators (flexible + large)