Transcript Cells Powerpoint

Prokaryotic Cells
•domains Bacteria & Archaea
•1-10 μm
•DNA located in nucleoid
region
•cell wall
•capsule
•pili
•flagella
Eukaryotic Cells
•plasma membrane
•cytosol/cytoplasm
•ribosomes
•chromosomes
•domain Eukarya (protists,
fungi, plants, & animals)
•10-100 μm
•DNA located in nucleus
•organelles
Limits on Cell Size
• as a cell increases in size, its volume grows
proportionally more than its surface area
• cells need a surface area large enough to
accommodate its volume
• if the surface area : volume ratio is too great,
the rate of chemical exchange with the
environment may be too slow to meet the
cell’s needs
Generalized Animal Cell
Generalized Plant Cell
Nucleus
• contains most of the cell’s
genes
• directs protein synthesis
by synthesizing mRNA
• surrounded by a porous
double membrane called
the nuclear envelope
• DNA is organized into
chromosomes (made up
of chromatin)
• nucleolus – sythesizes
rRNA (ribosomal
subunits)
Ribosomes
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made of rRNA and protein
carry out protein synthesis
free ribosomes make proteins that function within cytosol
bound ribosomes make proteins destined for insertion
into membranes, for packaging within organelles, or for
secretion
Endomembrane System
• consists of membranes related through direct
physical continuity or by vesicles
• includes:
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nuclear envelope
endoplasmic reticulum
Golgi apparatus
lysosomes
vacuoles & vesicles
plasma membrane
Endoplasmic Reticulum
• continuous with nuclear envelope
• rough ER
• has ribosomes attached to surface
• makes secretory proteins
• makes membrane
• smooth ER
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lacks ribosomes
synthesizes lipids
metabolizes carbohydrates
detoxifies drugs/poisons
stores calcium ions
Golgi apparatus
• consists of flattened membranous sacs
• two poles:
• modifies products of ER, stores
• cis = receiving end
• trans = shipping end
them, “tags” them, & sends
them to other destinations
• manufactures macromolecules
(ex: polysaccharides)
Lysosome
• contains hydrolytic
enzymes
• fuse with vesicles or
vacuoles to…
• digest macromolecules
• recycle organic material
(ex: old organelles)
• break down food
• destroy invaders
Vacuoles
• similar to lysosomes
because they carry out
hydrolysis in plant &
fungal cells
• food vacuoles store &
break down food
• contractile vacuoles pump
excess water out of cell
• central vacuole of plant
cells stores organic
compounds & ions, acts as
a disposal site for waste,
contains pigments, and
may contain poisons for
defense against predators
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
– helps 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
– helps 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