Download Structures of the Cell

Structures of the Cell
Cell Theory
1. All living things are composed of cells.
2. Cells are the basic unit of structure and function
in living things.
3. All cells come from preexisting cells.
Cell Size
• Microscopic to the size of an ostrich egg yolk
Microscopes
• Light Microscope - visible light passes through a
specimen and then through glass lenses, which
magnify the image
SEM
• Scanning electron microscopes (SEMs) focus a
beam of electrons onto the surface of a specimen,
providing images that look 3-D
TEM
• Transmission electron microscopes (TEMs) focus
a beam of electrons through a specimen
• TEMs are used mainly to study the internal structure
of cells
Cell fractionation
• Cell fractionation takes cells apart and separates
the major organelles from one another
Fig. 6-5b
TECHNIQUE (cont.)
1,000 g
(1,000 times the
force of gravity)
10 min
Supernatant poured
into next tube
20,000 g
20 min
80,000 g
60 min
Pellet rich in
nuclei and
cellular debris
150,000 g
3 hr
Pellet rich in
mitochondria
(and chloroplasts if cells
are from a plant)
Pellet rich in
“microsomes”
(pieces of plasma
membranes and
cells’ internal
membranes)
Pellet rich in
ribosomes
Cell Types- Eukaryotes
• Eukaryotes (animals, plants, protists, fungi)
-have a nucleus bound by an envelope
-have membrane bound organelles
-large cells
Cell Types- Prokaryotes
• Prokaryotes- (bacteria)
- No nucleus, they have a nucleoid - an unbound
region where their DNA is found
- No membrane bound organelles.
- Small cells
Cell Parts
(a)
• Organelles –cell structures with specialized functions
• Cell Membrane- organelle that regulates what comes in and
out of the cell, provides protection, and support.
• phospholipid Bilayer- structure of the cell membrane
• Hydrophilic
Carbohydrate side chain
head
• Hydrophobic
Hydrophilic
Tail
region
Hydrophobic
region
Hydrophilic
region
Phospholipid
Proteins
(b) Structure of the plasma membrane
Cell Wall
• Cell wall- surrounds cell membrane only in plants
• Made out of cellulose (starch)
• Adds extra support
Nucleus
(center
of
the
cell)
Nucleus- center of the cell, contains nucleic acid (DNA)
•
• Enclosed by a nuclear envelope –lipid bilayer. It has pores.
• Nucleolus – inside the nucleus. Makes ribosomal RNA that
form ribosomes.
Nucleus
Nucleolus
Chromatin
Nuclear envelope:
Inner membrane
Outer membrane
Nuclear pore
Pore
complex
Rough ER
Cytoplasm
• Cytoplasm- in between cell membrane and nucleus. Made
of a fiber matrix and a liquid called cytosol.
• Holds organelles in place
• Kind of like “Jello
With fruit in it”
•
Mitochondria
Mitochondria- release energy stored in glucose in the form
of ATP through cell respiration.
• Double membrane (inner and outer) , the inner has folds
called cristae and that form the mitochondrial matrix and the
inner membrane space.
Intermembrane space
Outer
membrane
Inner
membrane
Cristae
Matrix
0.1 µm
Plastids
• Store materials in plants – (chloro- plasts-
Chloroplasts
• Chloroplasts- make glucose from sunlight (only in plants)
through photosynthesis.
• Contains the pigment chlorophyll that makes plants green
• Thylakoid – discs containing chlorophyll stacked in granum
• Stroma – fluid in the space outside the granum.
Stroma
Inner and outer
membranes
Granum
Thylakoid
Ribosomes
• Make proteins
Endoplasmic Reticulum (ER)
• ER – makes and transports materials through the cell in
vesicles
-Smooth ER – makes and transports lipids and
carbohydrates
-Rough ER – contains, ribosomes to make and transport
proteins (gives it its rough look)
Golgi Apparatus
• Labels, packages, sorts and sends molecules from
the ER out of cells in vesicles.
Lysosome
• Lysosomes – membrane sacs filled with enzymes that break
down materials (food or old organelles)
• Lysosomes will merge with food vacuoles break down food
or engulf (phagocytosis) an old organelle to digest and
recycle it.
• Peroxisomes - are like mini lysosmes that contain an
enzyme called catalase that converts peroxide in to water
and oxygen.
Vacuoles
• Store materials (food, water, etc)
• Plants have a large central vacuole, animals
have may small scattered vacuoles
•
•
•
•
•
•
•
Endomembrane
system
All connected by membrane or vesicles
Nuclear envelope
Rough ER
Smooth ER
Golgi
Lysosomes
Vacuoles
Cytoskeleton – frame work
• Made of 3 types of fibers
Microtubules
• Three main types of fibers make up the cytoskeleton:
– Microtubules are the thickest of the three components of
the cytoskeleton, help separate cells during cell division,
make up flagellum, and guide moving vesicles like a
train track
– Ex. 9 microtubules make up a centriole.
Intermediate Filaments
– Intermediate filaments are fibers with diameters in a
middle range. They, anchor organelles and maintain cell
shape
Microfilaments
– Microfilaments, also called actin filaments, are the
thinnest components and are found in muslces for
contracting.
• In muscle cells, thousands of actin filaments are arranged
parallel to one another
• Thicker filaments composed of myosin interact with the
thinner actin fibers
Cell
Junctions
Plasmodesmata – pores in the
•
cell walls between plant cells
• Gap Junctions – pores in the
membranes between animal cells**
• Desmosomes – anchores that
hold cells together**
• Tight Junctions – tightly pressed
cells to seal fluid out**
Animal vs. Plant
Animal Cells
Plant Cells
No cell wall
Cell Wall
No chloroplasts
Chloroplasts
Lysosomes
Lysosomes (rarely)
Scattered Vacuoles
Large Central Vacuole