biologists estimate up to how distinct species
100 million
cells vary in what three things
size, shape, chemical requirements
what do size, shape, chemical requirements of cells reflect
differences in cell function
specialization is typical of what kinds of organisms
multicellular organisms`
cells are all composed of the same sort of what?
molecules
in all organisms genetic information is in the form of what
genes
what is genetic information carried in
DNA molecules
the information is written in
the same chemical code
interpreted by what
the same chemical machinery
and replicated how
in the same way when an organism reproduces
the info in DNA is transcrived into
RNA
RNA is transcribed into what
protein
the appearance and behavior of a cell are dictated by
its protein molecules
what are some jobs of protein
structural supports, chemical catalysts, molecular motors
proteins are built from what
amino acids
all organisms use the same set of how many aa's
20 aa's
aa's are linked in different sequences giving each type a different
conformation
are viruses living?
no
why aren't viruses living
they have no ability to reproduce themselves by their own efforts
viruses are intert and inactive outside their host cells but they can
exert a control over a cell once they gain entry
is replication always perfect
no
what happens if genetic instructions are corrupted
mutations
mutations can create what
offspring with advantages, disadvantages, and neutral changes
what is the basis of evolution
genetic change and selection over time
how long ago must have the common ancestor of all cells lived
3.5-3.8 billion years ago
why are all cells so similar chemically
they had a common ancestor cell
what did evolution do to the common ancestor cell
it's descendants are every living thing on earth
what is a cells genome
the entire sequence of nucleotides in a n organisms DNA
what does a genome do
provides a genetic program that instructs the chell how to behave
all differentiated cell types from animals and plants are generated from what
a single fertilized egg cell
different cells express what
different genes
what is the implication that different cells express different genes
they use their genes to produce some proteins and not others
what do cells depend on to express genes
internal state and cues they and their ancestor cells have received from their surroundings
the study of cell biology started by
observation and dissection of tissues and cells
when and why were cells made visible
the 17th century and due to the invention of the light microscope
electron microscopes where invented when and allowed scientists to do what
1930s
allows scientists to view fine details of cells
the light microscope depended what
advances in glass lenses
which two men observed living cells
Robert Hooke and Antoni van Leeuwenhoek
what signals the official birth of cell biology
Papers by schleiden and Schwann in 1838-1839
what did schleiden and schwann's papers do
systematic investigation of plant and animal tissues with the light microscope SHOWED THAT CELLS WERE THE UNIVERSAL BUILDING BLOCKS OF LIVING TISSUES
what resulted do to schleiden and schwanns papers
cell theory
what is cell theory
the realization that all living cells are formed by the growth and division of existing cells
what did Louis Pasteur prove in 1860
living organisms can be generated only from existing organisms
what does charles darwins theory of evolution explain
how random variation and natural selection gave rise to diversity among organisms that share a common ancestry
what is an extracellular matrix
a dense material often made of protein fibers embedded in a polysaccharide gel
each cell is typically
5-20 microns in diameter
cells are mostly transparent and colorless. how can we view them
by staining cells with dyes that color particular components differently
cell components differ slightly in refractive index. how can we use this
small differences in refractive index can be made visible by specialized optic techniques
what is prominent in the middle of the cell
the nucleus
what indicates the presence of an enclosing membrane
a sharply defined boundary
what is around the nucleus and fills the cells interior
the cytoplasm
what cannot normally be resolved
structures smaller than 0.2 microns
what do fluorescence microscopes do
use sophisticated methods of illumination and electronic image processing to see fluorescently labeled cell components in much finer detail
super-resolution fluorecence microscopes push resolution limits to
20 nanometers
in electron microscopy cells have to be thinly
cut
what are organelles
seperate recognizable substructures with specialized functions
what is the membrane that seperates the interior of the cell from its external environment
the plasma membrane
how thick are plasma membranes and internal membranes
two molecules thick
what kind of microscope is used to look at thin sections of tissue
transmission electron microscope
what does the scanning electron microscope do
scatters electrons off the surface of the sample and so is used to look at the surface detail of cells
what have biologists developed to determine the precise 3d structure of proteins
x-ray crystallography
a bacterium contains essentially
no organelles
organisms whose cells have a nucleus are called
eukaryotes
organisms whose cells do not have a nucleus are called
prokaryotes
prokaryotes have what three kinds of shapes
spherical, rodlike, or corkscrew shaped
prokaryotes have what surrounding the plasma membrane
cell wall
what does the plasma membrane enclose in prokaryotes
the cytoplasm and DNA
thanks to their large numbers, rapid growth rates, and ability to exchange bits of information populations of prokaryotic cells can do what
evolve fast gaining adaptations, resistances, disadvantages
the chemical variety of prokaryotes is demonstrated by some bacteria being aerobic and others being
anaerobic
mitochondria are thought to evolve from
aerobic bacteria that began to live inside anaerobic ancestors of today's eukaryotic cells
any organic, carbon-containing material can be used as what by bacteria
food
how do prokaryotes play a unique and fundemental part in the life of earth
other living things depend on the organic compounds that these cells generate from inorganic materials
how do plants depend on bacteria
bacteria captures nitrogen from the atmosphere and plants take it from the soil that they live in
choloroplasts have evolved from
photosynthetic bacteria
archaea are also found in what that is hostile to other cells
environments
why might archaea be used to living in harsh environments
the environments resemble harsh conditions that resemble early earth
eukaryotic cells not only have a nucleus but they also have
membrane bound organelles
what is the nucleus
the most prominent organelle in a eukaryotic cell
what is it enclosed in
two concentric membranes that form the nuclear envelope
what does the nucleus contain
molecules of DNA
do prokaryotes have DNA
yes but they don't have a nucleus
what do mitochondria do
they are generators of chemical energy for the cell
how do the mitochondria generate chemical energy
they harness the energy from the oxidation of food to produce ATP
what is cellular respiration
when the mitochondrion consumes oxygen and releases CO2
why are mitochondria thought to habe evolved from engulfed bacteria
they contain their own DNA and reproduce by dividing in two.
in what kind of organisms are found chloroplasts
plants and algae
in addition to their two surrounding membranes what else to chloroplasts contain
internal stacks of membranes containing the green pigment chlorophyll
what do chloroplasts carry out
photosynthesis
what is photosynthesis
the trapping of sunlight in chlorophyll and using of the energy to manufacture of energy-rich sugar molecules
what is released as a by-product of photosynthesis
oxygen
how do plant cells extract this stored chemical energy
by oxidizing sugars in the mitochondria
how do chloroplasts resemble mitochondria
by containing their own DNA and reproducing by dividing in two