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Notes Ch. 6 part 2
Mitochondrion
• site of cellular respiration
• enclosed by 2
membranes: outer is
smooth & inner is
convoluted (cristae)
• between membranes is
intermembrane space
• interior is called the
matrix
• contains its own DNA &
ribosomes
• number in cell is related to
cell’s level of metabolic
activity
Chloroplast
• site of photosynthesis
• contains chlorophyll
• found in leaf cells & cells
of other green organs
• enclosed by 2 membranes
with a narrow
intermembrane space
• interior fluid is called the
stroma
• stroma contains stacks of
membranous sacs called
thylakoids (a stack of
thylakoids is called a
granum)
• contains its own DNA &
ribosomes
Peroxisome
• bound by a single layer
of phospholipids
• contains enzymes that
catalyze oxidation
reactions producing
hydrogen peroxide
(H2O2) as a by-product
• additional enzymes
break down the H2O2
which is toxic to the cell
Cytoskeleton
• network of fibers
extending throughout
cytoplasm
• provides mechanical
support to the cell
• maintains the shape of the
cell
• anchors organelles
• involved in cell movement
(cilia & flagella)
• may also be involved in
the regulation of
biochemical activities
Components of the
Cytoskeleton
• microtubules
– shape & support the cell
– serve as tracks for the movement of organelles
– separate chromosomes during cell division
– “9+2” arrangement and dynein arms cause cilia &
flagella to beat
– grow out from centrosome (which includes a pair
of centrioles in animal cells)
continued
• microfilaments (actin filaments)
– built from molecules of actin
– help cell bear tension (pulling forces)
– play a role in cell motility
– works with myosin to cause muscle cell contraction in
animals & cytoplasmic streaming in plant cells
• intermediate filaments
– help cell bear tension
– reinforces shape of cell
– helps anchor organelles
– make up nuclear lamina (lining on nuclear side of
nuclear envelope)
Cell Wall
• protects & maintains
shape of plant cell
• prevents excessive
uptake of water
• composed primarily of
cellulose in plants &
chitin in fungi
• perforated by channels
called plasmodesmata
that connect adjacent
cells
Extracellular Matrix
• consists primarily of glycoproteins (carbohydrate
attachments to membrane proteins)
• most abundant glycoprotein is collagen
Intercellular Junctions
• Plant Cells
– plasmodesmata = cytoplasmic channels between
adjacent plant cells
• Animal Cells
– tight junctions = bind cells tightly together to
prevent fluid from leaking into surrounding tissues
– desmosomes = anchoring junctions (fasten cells
together)
– gap junctions = cytoplasmic channels between
adjacent animal cells