Download What is Life?

Jay Phelan
What Is Life? A Guide To Biology
Second Edition
CHAPTER 3
Cells
© 2012 W. H. Freeman and Company
Cell History
Robert Hooke – coined term “cell”
Anton von Leuweenhoek – discovered
bacteria, blood, microorganisms
Robert Brown – discovered Nucleus
Mathias Schleiden – “All plants are made
up of cells”
Theodor Schwann – “All animals are
made up of cells”
Robert Virchow – Cells reproduce
FOUR STRUCTURES IN ALL PROKARYOTES
PLASMA MEMBRANE
Encloses cell contents: DNA,
ribosomes, and cytoplasm
CYTOPLASM
Jelly-like fluid inside cell
RIBOSOMES
Granular bodies in the cytoplasm
that convert genetic information
into protein structure
DNA
One or more circular loops
containing genetic information
ADDITIONAL STRUCTURES
CELL WALL
Protects and gives shape to the cell
CAPSULE
Protective outer coating
PILI
Hair-like projections that help cells
attach to other surfaces and
sometimes play a role in DNA
transfer
FLAGELLUM
Whip-like projection(s) that aids in
cellular movement
Cell Theory
All living things are made up of cells, and cell products.
All cells come from pre-existing cells
Where did the first cell come from?
Nucleus
Other
organelles
TYPICAL EUKARYOTIC CELL FEATURES
• DNA contained in nucleus.
• Larger than prokaryotes—usually at least 10 times bigger.
• Cytoplasm contains specialized structures called organelles.
TYPICAL PROKARYOTIC CELL FEATURES
• No nucleus—DNA is in the cytoplasm.
• Internal structures mostly not organized into compartments.
• Much smaller than eukaryotes.
Cell Types
Prokaryotes – no nucleus or organelles.
Eukaryotes – nucleus, organelles
STRUCTURES FOUND IN BOTH CELLS
Nucleus
Plasma membrane
Ribosomes
Mitochondria
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Cytoplasm
Cytoskeleton
Golgi apparatus
Lysosome
STRUCTURE NOT FOUND
IN PLANT CELLS
Centriole
STRUCTURES NOT FOUND
IN ANIMAL CELLS
Chloroplast
Cell wall
Vacuole (occasionally
found in animal cells)
Plasma membranes are made up of two
layers that are filled with a variety of pores,
molecules, and channels.
Plasma membrane
FUNCTIONS
• Holds contents of cell in place
• Takes in food and nutrients
• Aids in building and exporting
molecules
• Allows interactions with the
environment and neighboring cells
Inside cell 1
Inside cell 2
Plasma membranes are the
“gatekeepers” of the cell.
HYDROPHILIC HEAD
(POLAR)
• Attracted to water
• Composed of a
glycerol linked to a
phosphorus-containing
molecule
HYDROPHOBIC TAILS
(NONPOLAR)
• Not attracted to water
• Composed of carbonhydrogen chains
EXTRACELLULAR FLUID
Watery fluid outside cell
INTRACELLULAR FLUID
Watery fluid inside cell
Plasma membrane
Hydrophilic heads extend toward the
intracellular and extracellular fluid,
and hydrophobic tails are directed
away from these watery fluids.
Extracellular fluid
Hydrophilic region
Hydrophobic region
Carbohydrates
Plasma membrane
Transmembrane
protein
Lipids
Surface proteins
Intracellular fluid
Hydrophobic and hydrophilic forces
determine the orientation of proteins
in the plasma membrane.
Extracellular fluid
CARBOHYDRATE CHAINS
Provide a “fingerprint” for the
cell, so it can be recognized
by other cells
CHOLESTEROL
Helps the membrane
retain its flexibility
REACTIONS
REACTIONS
Intracellular fluid
RECEPTOR PROTEINS
Bind to external chemicals
in order to regulate
processes within the cell
RECOGNITION PROTEINS
Provide a “fingerprint” for
the cell, so it can be
recognized by other cells
TRANSPORT PROTEINS
Provide a passageway for
molecules to travel into
and out of the cell
ENZYMATIC PROTEINS
Accelerate intracellular and
extracellular reactions on
the plasma membrane
Cell Membrane
Double layer of Phospolipids – barrier
Proteins embedded in lipids
– Receptors for outside molecules
– Carriers for moving things in or out of cell
– Cell connections
Fluid Mosaic Model – membrane is a liquid with
proteins floating around in it.
Selectively permeable – only certain things can
pass in or out of the cell.
The nucleus: the cell’s genetic control
center
FIGURE 3-27 The nucleus: the cell’s genetic control center
FIGURE 3-27 The nucleus: the cell’s genetic control center
FUNCTIONS
• Acts as the genetic control
center of the cell
• Stores hereditary information
NUCLEOLUS
Area of the nucleus, where
ribosomal subunits are
assembled
CHROMATIN/
CHROMOSOMES
Thin fibers of DNA,
which carry all
hereditary information
NUCLEOLUS
Area of the nucleus,
where ribosomal
subunits are assembled
Pore
NUCLEAR MEMBRANE
Two bilayers, covered in pores,
that surround the nucleus
Pore
NUCLEAR MEMBRANE
Two bilayers, covered in pores,
that surround the nucleus
Nucleus
Control center of the cell
Double layered membrane
Large nuclear pores
Chromatin – DNA material (unraveled)
Chromosomes – Coiled DNA (visible)
Nucleolus – dark spot in nucleus, site of
and RNA synthesis
ribosome
FUNCTIONS
• Acts as the inner
scaffolding of the cell
• Provides shape and
support
• Controls intracellular
traffic flow
• Enables movement
Structural network of
intermediate filaments
THREE TYPES OF PROTEIN FIBERS IN THE CYTOSKELETON
MICROTUBULES
• Thick, hollow tubes
• The tracks to which molecules
and organelles within the cell may
attach and be moved along
INTERMEDIATE FILAMENTS
• Durable, rope-like systems
of numerous overlapping
proteins
• Give cells great strength
MICROFILAMENTS
• Long, solid rod-like fibers
• Help with cell contraction and
cell division
Cilia
Flagella
With gentle beating, cilia can move fluid
past cells, whereas flagella, with whip-like
motions, can move the cells themselves.
Cytoskeleton
Microfilaments –hair-like protein threads
Microtubules – hollow protein tubes
Involved with cell structure and movement
Cell structures made up of microtubules
– Centrioles – function in cell division
– Cilia – short, numerous, whip-like action
– Flagella – long, few, propeller action
FUNCTIONS
• Act as all-purpose
energy converters
• Harvest energy to be
used for cellular functions
DNA
Matrix
Outer
membrane
Inner
membrane
Intermembrane
space
Matrix
Outer
membrane
Inner
membrane
Intermembrane
space
Cells such as liver cells, which
use a lot of energy, can have up
to 2,500 mitochondria!
Liver cell
~2,500
Skeletal muscle cell
~1,200
White blood cell in lung
~700
Dermal cell (just under the skin)
~200
Cells with high
energy needs have
many times more
mitochondria than
cells with low
energy needs.
White adipose cell (fat storage)
~100
Red blood cell
0
Number of mitochondria per cell
Mitochondria
Power house of cell
Cell respiration – breaks down glucose to produce ATP
for cell activities
Double membrane with inner one folded to increase the
surface area (ISA)
Cristae – inner folded membrane, contains enzymes for
respiration
Contains some DNA
FUNCTION
• Act as floating garbage disposals
for cells, digesting and recycling
cellular waste products and
consumed material
Membrane
Digestive
enzymes
and acid
Partially
digested
organelle
Membrane
Digestive
enzymes
and acid
Partially
digested
organelle
Lysosomes
Single membrane bound sacs of digestive enzymes
within the cell
Suicide sacs – release of enzymes for programmed
self-destruction of the cell.
FUNCTIONS
• Produces and modifies molecules to be exported to other parts
of the organism
• Breaks down toxic chemicals and cellular by-products
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Golgi apparatus
Rough endoplasmic
reticulum
Smooth endoplasmic
reticulum
Golgi apparatus
FUNCTION
• Modifies proteins that will be
shipped to other locations in
the endomembrane system,
the cell surface, or outside
the cell
Ribosomes
Rough ER is covered in
ribosomes. Ribosomes are
protein-making machines.
Ribosomes
FUNCTIONS
• Synthesizes lipids such as fatty acids,
phospholipids, and steroids
• Detoxifies molecules such as alcohol,
drugs, and metabolic waste products
Smooth ER is called
“smooth” because it has no
ribosomes on its surface.
Liver cells are packed with huge
amounts of smooth ER, because the
liver is the primary site for detoxifying
harmful molecules.
Endoplasmic Reticulum
Double layered membranes
3-D system of canals folding back and forth around the
cell
Transports proteins within cell
2 Types of ER
– Rough ER – covered with ribosomes
– Smooth ER – no ribosomes
Ribosomes
Made up of protein and RNA
Produce all cell proteins
Proteins produced usually enter the ER to be
transported someplace
FUNCTION
• Processes and packages proteins, lipids,
and other molecules for export to other
locations in or outside of the cell
Transport
vesicle
Transport
vesicle
1 Transport vesicle buds from the
Smooth ER
Rough ER
smooth or rough ER.
2 Transport vesicle fuses with Golgi
apparatus, dumping contents inside.
3
Golgi apparatus modifies the
molecules as they move through
its successive chambers.
4 Modified molecules bud off from
the Golgi apparatus as a transport
vesicle.
5 Vesicle may fuse with the plasma
membrane, dumping contents
outside the cell for delivery
elsewhere in the organism.
Transport
vesicle
1
Transport
vesicle
Golgi
apparatus
2
3
Plasma
membrane
Transport
vesicle
4
5
Golgi
Flattened layers of double membrane sacs
Vesicles found around it
Package materials for secretion
FUNCTIONS
• Provides the cell with
structural strength
• Gives the cell increased
water resistance
• Provides some
protection from insects
and other animals that
might eat plant parts
Plasmodesmata allow water
and other molecules to pass
between adjacent cells.
Cell 1
Cell 2
Cell 3
Primary cell
wall
Secondary
cell wall
Plasmodesmata
Plasma
membrane
Vacuole
FUNCTIONS
• Stores nutrients
• Retains and degrades waste products
• Accumulates poisonous materials
• Contains pigments, enabling plants to attract
birds and insects that help the plant reproduce
• Provides physical support
Vacuoles
Single membrane bound storage sacs
Types:
– Water vacuoles
– Food vacuoles
– Contractile vacuoles
– Pigment storage
FUNCTION
• Site of photosynthesis—
the conversion of light
energy into chemical
energy
Light is collected for
photosynthesis on
the membranes of
the thylakoids within
the chloroplasts.
DNA
Thylakoid
Stroma
Chloroplasts
Only found in plant cells - Photosynthesis
Double layered membrane with inner one forming
multiple stacks (ISA)
Grana – inner membranes contain enzymes for
photosynthesis
Chlorophyll found on inner membrane
Contains some DNA
Nucleus
Cytoskeleton
Directs cellular activity
and stores hereditary
information
Provides structural
shape and support
and enables cellular
movement
Harvests energy for
cellular functions
Mitochondrion
Lysosome
Digests and recycles
cellular waste
products and
consumed material
Rough ER
Modifies proteins
that will be shipped
elsewhere in the
organism
Synthesizes lipids and
detoxifies molecules
Smooth ER
Golgi apparatus
Processes and
packages proteins,
lipids, and other
molecules
Cell wall
Stores nutrients,
degrades waste
products, provides
pigments and
structural support
Sometimes
Performs
photosynthesis
Vacuole
Chloroplast
Provides structural
strength, protection,
and increased resistance
to water loss
Q-animation
1
A solute, such as food
coloring, is dropped into
a solvent, such as water.
Food coloring
2
Food-coloring molecules
move about randomly,
bumping into each other.
Food-coloring
molecules
3
The random motion of the
food-coloring molecules
causes them to end up
evenly distributed.
Passive transport occurs when molecules move across a membrane
without energy input. Molecules move down their concentration
gradients.
Extracellular fluid
Molecules
Intracellular fluid
Channel or
carrier
molecule
SIMPLE DIFFUSION
Molecules pass directly through
the plasma membrane without the
assistance of another molecule.
Higher
concentration
of molecules
Lower
concentration
of molecules
FACILITATED DIFFUSION
Molecules move across the
plasma membrane with the
help of a channel or carrier
molecule.
Osmosis is a type of passive transport by which water diffuses
across a membrane, in order to equalize the concentration of water
inside and outside the cell. The direction of osmosis is determined
by the total amount of solutes on either side of the membrane.
ANIMAL CELL
PLANT CELL (RED BLOOD CELL)
ISOTONIC SOLUTION
• Solute concentrations
are balanced.
• Water movement
is balanced.
Extracellular fluid
Water
Water
Osmosis is a type of passive transport by which water
diffuses across a membrane, in order to equalize the
concentration of water inside and outside the cell. The
direction of osmosis is determined by the total amount of
solutes on either side of the membrane.
ANIMAL CELL
PLANT CELL (RED BLOOD CELL)
HYPOTONIC SOLUTION
• Solute concentrations
are lower in the
extracellular fluid.
• Water diffuses into cells.
Water
Water
Unlike plant cells,
animal cells may
explode in hypotonic
solutions because they
don’t have a cell wall to
limit cellular expansion.
Osmosis is a type of passive transport by which water
diffuses across a membrane, in order to equalize the
concentration of water inside and outside the cell. The
direction of osmosis is determined by the total amount of
solutes on either side of the membrane.
ANIMAL CELL
PLANT CELL (RED BLOOD CELL)
HYPERTONIC SOLUTION
• Solute concentrations
are higher in the
extracellular fluid.
• Water diffuses out
of cells.
Water
Water
Water will always move toward a region
having a greater concentration of solutes.
Dehydrated celery
Water
Dissolved
molecules
Dehydrated celery contains many
dissolved molecules (solutes)
relative to water molecules.
WHEN PLACED IN
DISTILLED WATER
Water
Distilled water contains
fewer dissolved molecules
than the celery cells.
Water molecules diffuse into the celery, equalizing
the water concentration inside and outside the
cells. The celery becomes crisp.
WHEN PLACED IN
SALT WATER
Water
Salt water contains more
dissolved molecules than
the celery cells.
Water molecules diffuse out of
the celery. The celery becomes
even more shriveled.
Active transport occurs when the movement of molecules into and out of a cell
requires the input of energy. For example, in response to eating, the cells lining
your stomach use ATP to pump large numbers of H+ ions into the stomach.
Inside a cell lining
the stomach
ATP
Outside the cell
(inside the
stomach)
Low
concentration
of molecules
H+ ions
ATP
High
concentration
of molecules
Active transport in the
stomach increases your
ability to digest food.
Phagocytosis is a type of endocytosis by which cells engulf
large particles.
Extracellular fluid
Intracellular
fluid
Large particle
Plasma
membrane
1
The plasma membrane
forms a pocket-like vesicle
around a large particle.
Vesicle
2
The particle is
transported into
the cell in a
vesicle.
Exocytosis is the method by which cells export
products for use in another location.
Extracellular fluid
Intracellular
fluid
Plasma membrane
1 Molecules are packaged in
Transport
vesicle
a vesicle within the cell.
Molecules
for export
2 The vesicle fuses with the
cell’s plasma membrane.
3 Vesicle contents are
released for use
throughout the body.
1. What are the variables in this graph?
2. What additional information would
make this figure more helpful? Why?
3. What can you conclude from this figure?
4. Is “number of mitochondria per cell”
the best measure of a cell’s “energygenerating capacity”? Can you think of
a reason why this might not be a perfect
measure? (Hint: muscle cells can be
much, much larger than liver cells.)
5. Based on these data, can you make
any of your own predictions?
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
ORGANELLE:
FUNCTION:
Which feature below is not found in a prokaryote?
1.
2.
3.
4.
5.
Plasma membrane
Nucleus
Ribosomes
Cell wall
Flagellum
Which answer below supports the theory
that mitochondria and chloroplasts were
originally bacteria?
1. Circular DNA is present in both
organelles.
2. Both organelles are larger than
other organelles in the cell.
3. Both organelles are surrounded
by a single lipid bilayer.
4. All of the above.
Why does oil not mix with water
but instead spontaneously forms
spheres?
1. The oil is maximizing the amount of surface
exposed to water.
2. The oil is minimizing the amount of surface
exposed to water.
3. The oil becoming less hydrophobic.
4. The oil is becoming more hydrophobic.
Which statement is false about the
fatty acid tails of a phospholipid?
1. They are hydrophobic.
2. They cannot interact with ions (Na+, K+).
3. Small molecules like oxygen can slip between
them.
4. They interact with water.
Which arrow indicates a protein or part
of a protein that is hydrophobic?
1.
2.
3.
4.
Arrow
Arrow
Arrow
Arrow
A
B
C
D
A
B
C
D
A normal cell has a high concentration of potassium on the
inside and a low concentration of potassium on the outside.
Also, a normal cell has a low concentration of sodium on the
inside and a high concentration on the outside. Yet, the net
movement of potassium is into the cell and the net movement
of sodium is out of the cell. What type of transport is
involved?
1.
2.
3.
4.
5.
Osmosis
Facilitated transport
Active transport
Simple diffusion
Secondary active
transport
An intestinal epithelial cell powers the movement of
glucose into the cell against its concentration gradient
by simultaneously transporting sodium down its
concentration gradient. Which transport mechanism is
responsible?
1.
2.
3.
4.
5.
Osmosis
Facilitated transport
Active transport
Simple diffusion
Secondary active transport
When a woman nurses her baby, proteins
are released from the mammary cells,
accumulate in the ducts of the breast, and
flow out of the nipple. Which process listed
below is involved?
1. Phagocytosis
2. Pinocytosis
3. Receptor-mediated
endocytosis
4. Exocytosis
Your skin cells form a waterproof barrier,
therefore they are held together by…
1.
2.
3.
4.
Tight junctions
Desmosomes
Gap junctions
Glue
When a blister forms, two layers of skin become
separated. Originally they were held together by…
1.
2.
3.
4.
Tight junctions
Desmosomes
Gap junctions
Lipid
Which statement about mitochondria is false?
1.
2.
3.
4.
Mitochondria are surrounded by two membranes.
Mitochondria make energy of the cell (ATP).
You inherited half of your mitochondria from your mother.
The characteristics of mitochondria can be explained by
endosymbiosis.
Which cell type contains the most mitochondria per cell?
1.
2.
3.
4.
5.
6.
Liver
Muscle
White blood cell
Dermal cell
White adipose cell
Red blood cell
Which cell type in the graph might require the most energy?
1.
2.
3.
4.
5.
6.
Liver
Muscle
White blood cell
Dermal cell
White adipose cell
Red blood cell
Which organ below is likely composed of cells with the greatest amount of SER?
1.
2.
3.
4.
5.
Heart
Lungs
Kidney
Liver
Brain
Almost all eukaryotic organisms derive
energy directly or indirectly from the
sun. Therefore, which organelle is the
most important for life as we know it?
1.
2.
3.
4.
5.
Nucleus
Endoplasmic reticulum
Golgi
Chloroplast
Mitochondria