Arrangement of DNA in Prokaryotes
DNA Supercoiling
To package the
DNA into the
cell requires
that the DNA
be supercoiled.
There are over 50
supercoiled
domains in the
E,coli
chromosome,
they are
stabilized by
association
with the
structural
proteins.
The Nucleus
The nucleus is both
a storehouse and a
processing factory
for genetic
information.
The process of
protein synthesis
occurs in the
cytoplasm
Chromosomes and DNA
Histones are spaced
along the DNA double
helix at regular intervals,
the DNA itself being
wound around each
histone molecule,The
packing forms a discrete
structure called a
nucleosome,Nucleosomes
aggregate and form a
fibrous material called
chromatin,Chromatin
itself can be compacted by
folding and looping to
eventually form an intact
chromosome
Mitosis (有丝分裂 )
? During cell division,the nucleus
divides following a doubling of
the chromosome number,a
process called mitosis,yielding
two cells,each with a full
complement of chromosome.
? Metaphase,chromosomes are
paired in the center of the cell.
? Anaphase,chromosomes are
separating.
Organelles,Mitochondria and Chloroplasts
? Eukaryotic cells have a number of important functions
localized in discrete bodies called organelles:
? Mitochondria,in which energy metabolism is carried
out,
? Chloroplasts:in which the process of photosynthesis is carried out in plants and algae.
Structure of the mitochondrion
A bilayer of phospho-
lipid with embedded
proteins.
Cristae(脊 ),sites of
enzymes involved in
respiration and ATP
production and of
specific transport
proteins that regulate
the passage of
metabolites into and
out of the matrix of the
mitochondrion.
Matrix(基质 ),contains a
number of enzymes involved
in the oxidation of organic
compounds (TCA cycle).
Structure of the chloroplasts
? Thylakoids(类囊体 ):the thylakoid
membrane is highly impermeable to
ions and other metabolites because its
function is to establish the proton
motive force necessary for ATP
synthesis.
Detailed structure of the chloroplasts
Stroma contains large amounts of the enzyme ribulose bisphosphate
carboxylase (RubisCO) that convert CO2 to organic form.
Relationships of organelles to bacteria
? It was suggested that
mitochondria and
chloroplasts are
descendents of ancient
prokaryotic organisms.
? Endosymbiosis theory:
Eukaryotes arose from
the engulfment of a
prokaryotic cell by a
large cell.
? Evidences:
? Mitochondria and
chloroplasts contain
DNA,
? Mitochondria and
chloroplasts contain
their own ribosomes
? Antibiotic specificity
? Phylogeny
What we have learned so far?
? Why is the bacterial cell wall rigid layer called peptidoglycan?
? What are the chemical reasons for the rigidity that is conferred on the
cell wall by the peptidoglycan structure?
? List several functions for the outer wall layer in Gram-negative
bacteria?
? What is the bacterial periplasm?
? What types of Bacteria have a periplasm and of what significant is the
periplasmic space?
? Why sucrose is able to stabilize bacterial cells from lysis by lysozyme?
? Describe the structure and function of a bacterial flagellum.
? What is the energy source for the flagellum?
? What types of cytoplasmic inclusions are formed by prokaryotes?
中秋快乐
DNA Supercoiling
To package the
DNA into the
cell requires
that the DNA
be supercoiled.
There are over 50
supercoiled
domains in the
E,coli
chromosome,
they are
stabilized by
association
with the
structural
proteins.
The Nucleus
The nucleus is both
a storehouse and a
processing factory
for genetic
information.
The process of
protein synthesis
occurs in the
cytoplasm
Chromosomes and DNA
Histones are spaced
along the DNA double
helix at regular intervals,
the DNA itself being
wound around each
histone molecule,The
packing forms a discrete
structure called a
nucleosome,Nucleosomes
aggregate and form a
fibrous material called
chromatin,Chromatin
itself can be compacted by
folding and looping to
eventually form an intact
chromosome
Mitosis (有丝分裂 )
? During cell division,the nucleus
divides following a doubling of
the chromosome number,a
process called mitosis,yielding
two cells,each with a full
complement of chromosome.
? Metaphase,chromosomes are
paired in the center of the cell.
? Anaphase,chromosomes are
separating.
Organelles,Mitochondria and Chloroplasts
? Eukaryotic cells have a number of important functions
localized in discrete bodies called organelles:
? Mitochondria,in which energy metabolism is carried
out,
? Chloroplasts:in which the process of photosynthesis is carried out in plants and algae.
Structure of the mitochondrion
A bilayer of phospho-
lipid with embedded
proteins.
Cristae(脊 ),sites of
enzymes involved in
respiration and ATP
production and of
specific transport
proteins that regulate
the passage of
metabolites into and
out of the matrix of the
mitochondrion.
Matrix(基质 ),contains a
number of enzymes involved
in the oxidation of organic
compounds (TCA cycle).
Structure of the chloroplasts
? Thylakoids(类囊体 ):the thylakoid
membrane is highly impermeable to
ions and other metabolites because its
function is to establish the proton
motive force necessary for ATP
synthesis.
Detailed structure of the chloroplasts
Stroma contains large amounts of the enzyme ribulose bisphosphate
carboxylase (RubisCO) that convert CO2 to organic form.
Relationships of organelles to bacteria
? It was suggested that
mitochondria and
chloroplasts are
descendents of ancient
prokaryotic organisms.
? Endosymbiosis theory:
Eukaryotes arose from
the engulfment of a
prokaryotic cell by a
large cell.
? Evidences:
? Mitochondria and
chloroplasts contain
DNA,
? Mitochondria and
chloroplasts contain
their own ribosomes
? Antibiotic specificity
? Phylogeny
What we have learned so far?
? Why is the bacterial cell wall rigid layer called peptidoglycan?
? What are the chemical reasons for the rigidity that is conferred on the
cell wall by the peptidoglycan structure?
? List several functions for the outer wall layer in Gram-negative
bacteria?
? What is the bacterial periplasm?
? What types of Bacteria have a periplasm and of what significant is the
periplasmic space?
? Why sucrose is able to stabilize bacterial cells from lysis by lysozyme?
? Describe the structure and function of a bacterial flagellum.
? What is the energy source for the flagellum?
? What types of cytoplasmic inclusions are formed by prokaryotes?
中秋快乐
