Download Ch7-2CellStructure - Saint Joseph High School

Cell Structure
Nucleus, Organelles, and
Cytoplasm
• The nucleus is an internal compartment
that houses the cell’s DNA
• Organelles are other internal structures
that carry out specific functions in the
cell
• Cytoplasm is everything inside the
cell membrane but outside the
nucleus
Flagella and Cilia
•Cilia are short, hair-like
structures that protrude from
cell surfaces
•Flagella and cilia can propel cells
or they can move substances
across a cell’s surface
•Cilia in lungs sweep mucus and
debris away and in your ears they
conduct sound vibrations
Cytoskeleton
• The cytoskeleton is a web of protein fibers
• It holds the cell together and keeps cell
membranes from collapsing
• Anchored to cell membrane
• It links one region to another
• Anchors nucleus and organelles to fixed
locations
• 3 different kinds—microfilaments,
microtubules, and intermediate filaments
Microfilaments
• Long and slender, made of actin
• Network beneath cell’s surface that is
anchored to the membrane proteins
• Determines the shape of the cell
Microtubules
• Hollow tubes of tubulin
• Within the cytoskeleton, microtubules
act as the highway for transportation of
information from the nucleus out
• RNA/protein complexes are transported
along the “tracks” of microtubules by
motor proteins
Cell Membrane
• Cell membranes are made up of
phospholipids, which are a phosphate
group and two fatty acids
• Phospholipids are made up of a polar
“head” and two nonpolar “tails”
• Phospholipids form a phospholipid
bilayer
Cell Membrane
• Cell membranes have selective permeability
• The lipid bilayer allows lipids and substances
that dissolve in lipids to pass through
• Membrane proteins are also part of the
membrane—some are for transport
Cell Membrane
• There are several types of membrane
proteins, including:
– Marker proteins
– Transport proteins
– Enzymes
– Receptor proteins
• Proteins move, because phospholipids
are constantly in motion
Nucleus
• Houses most of the DNA, which controls
the cell’s functions
• Surrounded by a double membrane,
called the nuclear envelope or nuclear
membrane
• The nuclear envelope is made of two
lipid bilayers
• Why do you think that there are 2?
Nucleus
• Nuclear pores are small channels through
the nuclear envelope
• What are the pores for?
• The nucleolus is an area of the nucleus
where ribosomes are partially assembled
• Eukaryotic DNA is tightly wound around
proteins, and appears as a dark mass under
magnification most of the time
Ribosomes
• Made up of dozens of proteins and RNA
• Cells make proteins on ribosomes
• Some are suspended in the cytosol. These
are “free” ribosomes. “Free” ribosomes
make proteins that remain in the cell.
• Proteins that leave the cell are made on
ribosomes on the surface of the
endoplasmic reticulum
Endoplasmic Reticulum
• An extensive system of internal
membranes that move proteins and
other substances through the cell
• The membrane of ER is a lipid bilayer
with embedded
proteins
Rough Endoplasmic Reticulum
• The Rough ER has ribosomes attached
–It helps transport proteins made on the
attached ribosomes
–The proteins enter the ER and a small,
membrane-bound sac, or vesicle, pinches
off
–Proteins made on ribosomes on
the rough ER stay separate from
proteins made on free ribosomes
Smooth Endoplasmic Reticulum
• The Smooth
Endoplasmic Reticulum
lacks ribosomes, so it
appears smooth under
an electron microscope
• The smooth ER makes
lipids and breaks down
toxic substances
Golgi Apparatus
• A flattened, membranebound sac that serves as
the packaging and
distribution center of
the cell
• Enzymes in the Golgi
Apparatus modify
proteins from the ER
Lysosomes
• Lysosomes are small, spherical organelles
that contain the cell’s digestive enzymes
Mitochondria
• Organelle that uses
organic compounds to
make ATP, the primary
energy source of cells
• Cells with high energy
requirements, like
muscle cells, may contain
hundreds or thousands
or mitochondria
Mitochondria
• The mitochondria has two membranes
–The outer membrane is smooth
–The inner membrane is greatly folded, so
that it has a lot of surface area
–The two membranes
form two compartments
Mitochondria
• The mitochondria also
contain DNA and
ribosomes, because they
make some of their own
proteins
• Most mitochondrial
proteins are made in the
cytosol
Organelles Only Found in Plants
• Plants have 3
unique organelles
–Cell wall
–Chloroplasts
–Central vacuole
Cell Wall
• Plants’ cell membranes are surrounded by
cell walls
• Plant cell walls are made of proteins and
carbohydrates, including cellulose
• Helps support and protect the cells
• Connects cells to one another
Chloroplasts
• Chloroplasts are organelles that use light to
make carbohydrates from CO2 and H2O
• Found in algae as well as plants
• Surrounded by 2 membranes
• Contain their own DNA
Central Vacuole
•
•
•
•
The central vacuole stores water
It may contain ions, nutrients, and wastes
It makes the cell rigid, when it is full
Enables plants to stand upright
Let’s Review
• We use microscopes to look at cells that
are too small to see with the naked eye
• The Cell Theory
• What is a cell? What do all cells share?
• Prokaryotes vs. Eukaryotes
• Nucleus, Organelles, and Cytoplasm, oh
my!
• What separates plants from other
eukaryotes?
The Cell
contains
Cytoplasm
1.
Function as
Ribosomes
Function as
3.
ER & Golgi
apparatus
Function as
4.
5.
Function as
Support/
structure
6.
Function as
Power
Plants
2.