Download The Structure of Cell: Part II

Slide 1
The
Structure of
Cell:
Part II
Slide 2
Plastids
Plastids
• Chromoplasts
–Chloroplasts
responsible for
photosynthesis.
• Leukoplasts responsible
for storage of starch.
2
Plastids are organelles that are found in certain plant cells. They arise from unspecialized
plastids called proplastids. There are 2 different types of plastids- chromoplasts that contain
pigments and leukoplasts that store starch. Chromoplasts contain pigments such as xanthophylls
and carotenes. Chloroplasts are a type of chromoplast that contain chlorophyll and other
pigments. They convert light energy into chemical energy and are found in leaves and stems.
Slide 3
Structure of Chloroplast
Chloroplasts have three
membranes. The outer
two are smooth and the
inner one makes stacks of
thylakoids or grana. The
chlorophyll and other
pigments are found in the
thylakoid membrane
where light energy is
converted into chemical
energy.
3
Slide 4
Thylakoid
A stack of
thylakoids is a
granum. The matrix
found around the
thylakoid is called
the stroma. It
contains enzymes
for carbohydrate
synthesis.
4
An electron transport chain is embedded in the thylakoid membrane. In addition, there are
collections of chlorophyll and other pigments which collectively are called photosystems. The
photosystems are able to donate light-energized electrons to the electron transport chain.
Slide 5
Ribosomes
Ribosomes are workbenches for
protein synthesis. They are made
from rRNA and proteins to form
two subunits. They do not
contain any membranes. Cells
can have thousands.
5
All cells contain ribosomes because all cells must synthesize proteins.
Slide 6
Evolution of
Organelles
The endomembrane
system includes all
the organelles that
are derived from one
another, or are
continuous with one
another.
They have evolved from the folding in of the plasma
membrane over time. The membrane system includes the
nucleus, the E.R., the Golgi apparatus and the lysosomes.
6
Graphic http://faculty.collegeprep.org/~bernie/sciproject/project/Kingdoms/Protista4/Protists/Relationship%20to%20Evoluti
on.htm
Slide 7
The Endomembrane System
7
Slide 8
8
The mitochondria, chloroplasts and the flagella evolved from prokaryotic cells that engulfed
other prokaryotic cells. Instead of being destroyed, the prokaryotic cell took up residence and
began replicating and dividing inside the host cell. Over time some of the genes of the engulfed
cell were transferred to the host cell making them dependent on the host and becoming
organelles. This is the endosymbiosis hypothesis.
Evidence for endosymbiosis
Chloroplasts and mitochondria
• Have circular DNA like prokaryotic cells
• Have ribosomes similar to prokaryotic cells
• Do protein synthesis similar to prokaryotic cells
Slide 9
The Cytoskeleton
Gives the cell shape
Movement of organelles
Cytoplasmic streaming in plant cells
The cytoskeleton found throughout the cytosol in eukaryotic cells.
Functions of the cytoskeleton
• Move the cell.
• Move organelles within the cell
• Provide support and structure
• Cytoplasmic streaming (not prokaryotic cells)
Types of structures• microtubules and
• microfilaments
• intermediate filaments
9
Slide 10
Organelles Moving on the Cytoskeleton
10
Slide 11
Microtubules
11
Microtubules• Hollow tubes made of protein spheres.
• Used for cell shape, cilia, flagella & centrioles.
• Are used to move organelles (like a monorail) and chromosomes.
Microtubules are made in two regions called the centrosomes which are found on the outside
of the nucleus. Centrosomes in animals contain centrioles but are not found in higher plant
cells.
Slide 12
Cilia and
Flagella
Flagella and cilia are composed of ( 9 double + 2
single ) microtubules .
12
Flagella and cillia differ in length and the number found on a cell. Usually cilia are
shorter coat the cell, whereas flagella are longer and usually bundle 1-8 on the end of a
cell. Flagella typically propel a cell through a medium, whereas cilia may either move a
cell or move materials past a stationary cell, as in the cilia found lining the respiratory
pathway.
Dynein is the motor protein that bends the flagellum and cilium by interacting with the
cross-link proteins. The dynein spokes alternately grab the microtubules and release the
other microtubules causing the cilium or flagellum to bend.
Slide 13
Flagellated Cells
Flagellated sperm cells
13
Slide 14
Ciliated Cells
Paramecium moving
with cilia.
Chlamydomonas moving
with cilia.
14
Slide 15
Movement of Flagella
and Cilia
Both flagella and
cilia are covered
with the plasma
membrane.
15
Slide 16
Difference Between Flagella and Cillia
16
Slide 17
Centrioles and
Microtubules
Centrioles are
microtubule
organizing centers for
animal cells.
They are constructed
of nine triplet
microtubules.
Basal bodies anchor
cilia and flagella.
17
Centrioles are made of nine triplets of microtubules. This structure is also identical to the
interior of a basal body which anchors flagella and cilia in the cell. Cilia and flagella are identical
in structure but differ in length, movement, and number found on a cell.
Slide 18
Microfilaments
Microfilaments are made
from two intertwined
strands of actin subunits.
They are thinner than
microtubules.
18
Microfilaments are two strands of protein made of actin subunits and are used for supporting
the cell shape and changing the shape of the cell. They are also involved in muscle contraction,
movement of pseudopods, cytoplasmic streaming and microvilli of the small intestines.
Microfilaments are used to bear tension, resisting pulling forces within the cell.
Slide 19
Muscle Contractions and Cytoplasmic Streaming
19
Slide 20
Cytoplasmic Streaming
20
The cytoskeleton is found throughout the cytosol in eukaryotic cells.
Functions of the cytoskeleton
• Move the cell
• Move organelles within the cell
• Provide support and structure
• Cytoplasmic streaming (not prokaryotic cells)
Two main types of structures are microtubules and microfilaments with a third minor type
called intermediate filaments.
Slide 21
Intermediate Filaments
21
Slide 22
Cell Walls
Most cells have materials external to the
plasma membrane.
Cell walls are found in prokaryotes, plants,
fungi and some protists.
Cell walls of plants are made of cellulose;
in fungi they are made of chitin; in
prokaryotes they are murein (or muramic
acid) and in protists they vary.
22
Cell walls give shape and prevent turgid cells from bursting. Plant cells may have a
primary cell wall (outer most walls) and a secondary cell wall (inside the primary). The
middle lamella is a substance holds the walls together.
Slide 23
Plasmodesmata
Plasmodesmata are
channels between
plant cells that allow
direct flow from one
cell’s cytoplasm to
the cytoplasm in
adjacent cells.
23
Slide 24
Glycocalyx or Extracellular Matrix
Animal cells lack cell walls but have an extra cellular matrix
(ECM) or glycocalyx. The ECM is made of glycoproteins such as
collagen, proteoglycan, and fibronectins. These glycoproteins
are connected to receptor proteins in the cell membrane called
integrins. Used for support, adhesion, movement and identity.
24
Slide 25
Animal Cell Junctions
• There are several types of
intercellular junctions in animal cells
• Tight junctions- membranes of
neighboring cells are pressed
together
• Desmosomes-(anchoring junctions)
fasten cells together into strong
sheets
• Gap junctions-(communicating
junctions) provide cytoplasmic
channels between adjacent cells like
plasmodesmata in plant cells
25
Slide 26
Animal Cell Review
26
Slide 27
Plant Cell Review
27