Nucleus
Nucleus
Nucleus
Ø
Contains the DNA,
which stores
information for
making proteins via
transcription and
translation.
Ø
Contains the
nucleolus, which is
where ribosome
subunits are made.
Ø
Has a double
membrane with pores
through it which
allows eukaryotic cells
to separate the
activities of gene
transcription and
translation.
Nucleus
Nucleus
Ribosomes
Ø
Catalyses the synthesis of
polypeptides (proteins) during
translation.
Ø
Are composed of two subunits that
come together to form a
functioning structure.
Ribosomes
The ribosome is made from dozens of
proteins arranged on a scaffold composed of
ribosomal RNA (rRNA) that functions as a
ribozyme:
Ribosomes
Ø ‘Free’ synthesize
polypeptides
used within the
cell.
Ø ‘Bound’
synthesize
polypeptides that
are secreted
from the cell or
become integral
proteins in the
cell membrane.
Rough Endoplasmic Reticulum
Rough Endoplasmic Reticulum
Rough Endoplasmic Reticulum
The RER membrane is
continuous with the nuclear
envelope, which surrounds the
cell nucleus.
Ø
Rough Endoplasmic Reticulum
Ø
The RER is a series of
connected flattened
membranous sacs that play a
central role in the synthesis
and transport of
polypeptides.
Ø
Has bound ribosomes which
synthesize the polypeptide
and release it to the inside of
the RER.
Smooth Endoplasmic Reticulum
Ø The SER is a series of
connected flattened
membranous sacs that are
continuous with the RER.
Ø In contrast to the RER,
smooth endoplasmic
reticulum lacks ribosomes
and is not involved in protein
synthesis.
Ø The main functions of SER
are the synthesis of
phospholipids (B1.1.9) and
cholesterol (B2.1.12*) for
the formation and repair of
membranes.
Golgi Apparatus
Golgi Apparatus
Golgi Apparatus
Ø
Modifies polypeptides into
their functional state.
Ø
Sorts, concentrates and
packs proteins into vesicles.
Ø
Depending on the contents,
the vesicles are dispatched
to one of three destinations:
Ø
Within the cell, to organelles
called lysosomes (e.g.
digestive enzymes).
Ø
The plasma membrane of
the cell (e.g. integral
proteins).
Ø
Secretion to the outside of
the cell via exocytosis (e.g.
hormones)
Camillo Golgi (1843-1926)
Vesicles
Vesicles are membrane bound sacs that
contain and transport materials within cells
Ø
Transport vesicles
move molecules
between locations
inside the cell by
budding off one
organelle
compartment and
fusing with another.
Ø
Secretory vesicles
secrete molecules
from the cell via
exocytosis. They are
also how new
phospholipids are
added to the cell
membrane.
Lysosome
Lysosome
Lysosome
Lysosome
◎ Lysosomes are small
spherical organelles,
enclosed by a single
membrane.
◎ Contain digestive enzymes
that work in oxygen-poor
areas and lower pH.
◎ The enzymes digest large
molecules to degrade and
recycle the components of
the cell's own organelles
when they are old or
damaged (autophagy), or if
the cell is 'starving' in the
absence of nutrients.
◎ Also has an immune
defence function, by
digesting pathogens that
have been engulfed by
phagocytes.
Mitochondria
Mitochondria
Mitochondria
Ø
Mitochondria are
adapted for production
of ATP by aerobic
cellular respiration.
Ø
The mitochondrion
is surrounded by a
double membrane.
Ø
The inner
membrane is
folded to form
cristae.
Ø
The matrix is the
space within the
inner membrane.
Chloroplasts
Chloroplasts
Chloroplasts
Ø Chloroplasts are adapted for
photosynthesis, which captures light
energy and uses it with water and
carbon dioxide to produce glucose.
Ø Within the chloroplasts are light-absorbing
pigments such as chlorophyll embedded
within thylakoid membranes.
Ø Thylakoid membrane forms thylakoid
discs which are stacked into grana.
Vacuoles
Vacuoles
Large
Vacuoles
Ø
Mature plant cells have a
large central vacuole that
occupies 30% - 90% of the
volume of the cell.
Ø
The vacuole is surrounded
by a membrane called the
tonoplast.
Ø
In addition to water
storage, the main role of
the vacuole is to maintain
turgor pressure against
the cell wall. The turgor
pressure is mechanism
the plants use to remain
upright (turgid).
The vacuoles of onion cells were stained with a
red pigments. Then, concentrated salt water
was added. The vacuoles started to lose water
by osmosis. A picture was taken every 2
seconds to make a time lapse.
Centrioles
Centrioles
Centrioles
Ø Centrioles are paired
cylindrical-shaped
organelles composed of
nine groups of three
microtubules organized
with radial symmetry.
Ø Functions of centrioles
include:
Ø
Arrangement of the mitotic
spindle during cell division.
Ø
Serve as anchor points for
microtubules in the
cytoplasm and for cilia and
flagella (when modified to
become a basal body).
Cilia and Flagella
Cilia and flagella are extensions from the cell surface which aid in cell
movement. They are formed from modified centrio les called a basal body.
If the protrusions are
short and numerous
they are termed cilia.
Cilia beat in
coordination with each
other.
If the protrusions are
longer and less
numerous (usually only
one or two) they are
termed flagella. Flagella
move independently of
each other.
Cell Wall