CYTOLOGY
CHAPTER 5
CELL MODELS
The idea of the hasn’t
always existed.
The invention of the
allowed
scientists to study plants and
animals in a new way.
What they saw
popular theories.
CELL MODELS
The idea of the cell hasn’t
always existed.
The invention of the
allowed
scientists to study plants and
animals in a new way.
What they saw
popular theories.
CELL MODELS
The idea of the cell hasn’t
always existed.
The invention of the
microscope allowed
scientists to study plants and
animals in a new way.
What they saw
popular theories.
CELL MODELS
The idea of the cell hasn’t
always existed.
The invention of the
microscope allowed
scientists to study plants and
animals in a new way.
What they saw disproved
popular theories.
PREFORMATION
The idea that eggs and sperm
contain miniature that
increase in size after conception.
PREFORMATION
The idea that eggs and sperm
contain miniature people that
increase in size after conception.
MAJOR CONTRIBUTIONS TO THE CELL THEORY
Year Scientist Contribution
1665 Robert Hooke First used the term “cell” when looking at cork
under magnification. Beginning of cytology.
1682 Antonie van
Leeuwenhoek
Each cell had a central part. Living things
didn’t arise from nonliving materials.
1831 Robert Brown Named the nucleus.
1837 Matthias Schleiden
Theodor Schwann
Proposed that all plants and animals are
made of cells.
1855 Robert Remak Cells divide to produce new cells.
1858 Rudolf Virchow All cells come from preexisting cells.
MODERN CELL THEORY
1. Living things are composed of one or
more .
2. The cell is the basic unit of .
3. Cells come from cells.
The model we
use now!
MODERN CELL THEORY
1. Living things are composed of one or
more cells.
2. The cell is the basic unit of .
3. Cells come from cells.
The model we
use now!
MODERN CELL THEORY
1. Living things are composed of one or
more cells.
2. The cell is the basic unit of life.
3. Cells come from cells.
The model we
use now!
MODERN CELL THEORY
1. Living things are composed of one or
more cells.
2. The cell is the basic unit of life.
3. Cells come from preexisting cells.
The model we
use now!
CELL THEORY
Cell theory is a very reliable and predictable model that explains
the way cells work.
TRUE OR FALSE:
The cell theory is so foundational to biology that it may not ever
need to be changed.
CELL THEORY
Cell theory is a very reliable and predictable model that explains
the way cells work.
TRUE OR FALSE:
The cell theory is so foundational to biology that it may not ever
need to be changed.
FALSE
WHAT MAKES A GOOD MODEL?
A model is only useful if it can:
1. what we have already observed.
2. Make .
3. Be to account for new observations.
WHAT MAKES A GOOD MODEL?
A model is only useful if it can:
1. Explain what we have already observed.
2. Make .
3. Be to account for new observations.
WHAT MAKES A GOOD MODEL?
A model is only useful if it can:
1. Explain what we have already observed.
2. Make predictions.
3. Be to account for new observations.
WHAT MAKES A GOOD MODEL?
A model is only useful if it can:
1. Explain what we have already observed.
2. Make predictions.
3. Be modified to account for new observations.
WAYS TO CLASSIFY ORGANISMS
1. How the cells work together
organism- an
organism that is made of only
one cell.
Can fully function without help
from other cells.
Examples: bacteria, protozoans,
several algae and fungi
WAYS TO CLASSIFY ORGANISMS
1. How the cells work together
Unicellular organism- an
organism that is made of only
one cell.
Can fully function without help
from other cells.
Examples: bacteria, protozoans,
several algae and fungi
UNICELLULAR ORGANISMS
Some unicellular organisms work
together in a .
cells take on specific tasks.
cells can break away from the colony
and function on their own.
algae
bacteria
UNICELLULAR ORGANISMS
Some unicellular organisms work
together in a colony.
cells take on specific tasks.
cells can break away from the colony
and function on their own.
algae
bacteria
MULTICELLULAR ORGANISM
Made of two or more cells that
on each other to
function.
Example: some algae and fungi, all
plants, animals, and humans.
Most cells are highly
and can’t function without the
support of other cells.
Example: blood cells, skin cells.
MULTICELLULAR ORGANISM
Made of two or more cells that
depend on each other to
function.
Example: some algae and fungi, all
plants, animals, and humans.
Most cells are highly
and can’t function without the
support of other cells.
Example: blood cells, skin cells.
MULTICELLULAR ORGANISM
Made of two or more cells that
depend on each other to
function.
Example: some algae and fungi, all
plants, animals, and humans.
Most cells are highly specialized
and can’t function without the
support of other cells.
Example: blood cells, skin cells.
Organization of cells in organisms
unicellular
colony
multicellular
tissue
organ
organ system
made of one cell made of more than one cell
cells work together in a cells work together to form a
which work together for a specific function in an
which work together for a specific function in an
WAYS TO CLASSIFY ORGANISMS
2. By the kinds of parts
they have
The parts inside a cell are
called .
Many organelles are
surrounded by a .
WAYS TO CLASSIFY ORGANISMS
2. By the kinds of parts
they have
The parts inside a cell are
called organelles.
Many organelles are
surrounded by a .
WAYS TO CLASSIFY ORGANISMS
2. By the kinds of parts
they have
The parts inside a cell are
called organelles.
Many organelles are
surrounded by a membrane.
CELL ORGANELLES
An organism with cells that contain
membrane-bound organelles is
.
Examples: humans, animals, plants,
fungi, and protists.
An organism whose organelles
lack surrounding membranes is
.
Example: bacteria
CELL ORGANELLES
An organism with cells that contain
membrane-bound organelles is
eukaryotic.
Examples: humans, animals, plants,
fungi, and protists.
An organism whose organelles
lack surrounding membranes is
.
Example: bacteria
CELL ORGANELLES
An organism with cells that contain
membrane-bound organelles is
eukaryotic.
Examples: humans, animals, plants,
fungi, and protists.
An organism whose organelles
lack surrounding membranes is
prokaryotic.
Example: bacteria
PROKARYOTIC CELLS
1. CYTOPLASM
consists of everything within the cell
membrane except the nucleus
contains cytosol, the fluid in which the
organelles are suspended
has molecules used for building structures
in the cell
2. CYTOSKELETON
a system of fibers in the cytosol that helps
maintain the cell’s shape
provides protein motors and a track to
move substances around the cell in a
process called cytoplasmic streaming
3. CAPSULE
Found only in bacteria/prokaryotes
Located outside the cell membrane and
cell wall
Protects the cell
Contains water to keep the cell from
drying out, often making it feel slimy
4. NUCLEOID
Found only in bacteria/prokaryotes
Contains the genetic material for the cell
Floats freely in the cytosol (no membrane)
5. FLAGELLUM
extension of the cytoskeleton
usually only one or a few per cell
propels the cell through its
environment using a protein
motor
6. CHLOROPLAST
A type of pigmented plastid
Found only in plants and algae
converts light energy from the sun into
chemical energy
7. GRANUM
Found inside the chloroplasts
Made of stacks of thylakoids
Thylakoids contain the green pigment
chlorophyll to carry out photosynthesis
8. RIBOSOME
found in both prokaryotes and eukaryotes
because it’s not surrounded by a
membrane
contains protein and RNA
“reads” RNA and assembles amino acids
into proteins
either attached to the endoplasmic
reticulum or floating in the cytosol
9. ROUGH ENDOPLASMIC RETICULUM
transports compounds around the cell
helps maintain the cell’s shape
is studded with ribosomes
processes the proteins made by ribosomes
10. SMOOTH ENDOPLASMIC RETICULUM
transports compounds around the cell
helps maintain the cell’s shape
processes fats and breaks down toxic
substances in liver cells
11. CENTRAL VACUOLE
Found mostly in plants
Stores water, salts, sugars, and proteins
Maintains turgor pressure- the water pressure
inside the central vacuole that keeps the cell
rigid
12. LEUKOPLAST
A type of colorless plastid
found only in plants and algae
stores starches, lipids and proteins
13. CELL WALL
Found in plants, fungi, algae and
bacteria
Provides strength and rigidity to the cell
contains pores so that material can
pass through
1. NUCLEUS
found only in eukaryotic cells
“control center” of the cell
contains the cell’s genetic material
2. NUCLEOLUS
contains RNA and proteins
area of the nucleus where ribosomes
are assembled
3. CHROMATIN
the genetic material of the nucleus
contains DNA, RNA, and proteins
4. LIPID BILAYER
Lipids have a hydrophilic (water-loving) end
and a hydrophobic (water-fearing) end.
They arrange themselves into two layers
The hydrophilic ends face the watery
environments inside and outside the cell
The hydrophobic ends face each other to
escape the water
5. LYSOSOME
a type of vacuole found in humans, animals,
and protozoans
contains digestive enzymes that digest food, kill
bacteria and viruses, and recycle old cell parts
6. GOLGI APPARATUS
“post office” of the cell
receives substances from the ER and
packages them into membrane sacs
called vesicles
sends vesicles either to places within
the cell or to the cell membrane to
deliver their cargo outside the cell
7. CENTROSOME
found in animal and human cells
absent in plants and fungi
builds parts for the cytoskeleton
8. MITOCHONDRION
“powerhouse” of the cell
transforms energy from sugars into usable
energy for the cell (ATP)
Has an inner membrane that contains folds
(cristae) to increase surface area and
increase energy output.
9. CELL MEMBRANE
found in both prokaryotes and eukaryotes
surrounds the cell and protects it
allows certain materials to move through it-
semipermeable
10. CILIA
extensions of the cytoskeleton
often cover an entire cell or a portion of a cell
(many per cell)
shorter than flagella
propel the cell through its environment
move particles past the cell (mucus out of the
lungs)
smooth ER
chromatinnucleus
nuclear pore
nucleolus
cell membrane
lysosome mitochondrion
Golgi apparatuscilium
rough ER
TYPICAL ANIMAL CELL
ribosome
WHY STUDY CELLS?
The model of cells is still
developing.
The vesicle that makes unripe fruit
taste bitter was discovered in
2013.
There is much more to be
discovered about cells!
WHY STUDY CELLS?
It helps us to fulfill the Creation
Mandate and to love others.
BALANCE IN THE CELL
- the process by which a cell
maintains stable conditions in its internal
environment.
BALANCE IN THE CELL
Homeostasis- the process by which a cell
maintains stable conditions in its internal
environment.
- the
balance of changes and
motions in a system.
Dynamic equilibrium- the
balance of changes and
motions in a system.
What can affect homeostasis?
temperature
nutrition
illness
: ideal conditions, cells don’t have to work hard.
: cells can handle with extra work.
: beyond what cells can handle, cells die.
Examples: frostbite, sunburn
Optimal range: ideal conditions, cells don’t have to work hard.
: cells can handle with extra work.
: beyond what cells can handle, cells die.
Examples: frostbite, sunburn
Optimal range: ideal conditions, cells don’t have to work hard.
Range of tolerance: cells can handle with extra work.
: beyond what cells can handle, cells die.
Examples: frostbite, sunburn
Optimal range: ideal conditions, cells don’t have to work hard.
Range of tolerance: cells can handle with extra work.
Limit of tolerance: beyond what cells can handle, cells die.
Examples: frostbite, sunburn
How do cells regulate the speed of
processes?
How do cells start and stop
processes?
Signaling occurs through two
important processes:
feedback
feedback
Signaling occurs through two
important processes:
Positive feedback
Negative feedback
- occurs when a substance involved
in a cellular process causes the process to speed up.
Example: oxygen with hemoglobin
Positive Feedback- occurs when a substance involved
in a cellular process causes the process to speed up.
Example: oxygen with hemoglobin
- occurs when a substance
produced by a cellular process causes the process to
slow down or stop.
Example: ATP and Phosphofructokinase (PFK)
Negative Feedback- occurs when a substance
produced by a cellular process causes the process to
slow down or stop.
Example: ATP and Phosphofructokinase (PFK)
SOLUTIONS AND THE CELL
WHAT IS A SOLUTION?
A solution is a homogeneous of two or
more substances (solvent and solute).
A solution may exist in any (solid, liquid,
or gas).
WHAT IS A SOLUTION?
A solution is a homogeneous mixture of two or
more substances (solvent and solute).
A solution may exist in any (solid, liquid,
or gas).
WHAT IS A SOLUTION?
A solution is a homogeneous mixture of two or
more substances (solvent and solute).
A solution may exist in any phase (solid, liquid,
or gas).
SOLUTIONS
: the substance in a solution that does the dissolving.
Water is the universal solvent.
: the substance in a solution that is being dissolved.
SOLUTIONS
Solvent: the substance in a solution that does the dissolving.
Water is the universal solvent.
: the substance in a solution that is being dissolved.
SOLUTIONS
Solvent: the substance in a solution that does the dissolving.
Water is the universal solvent.
Solute: the substance in a solution that is being dissolved.
SOLUTIONS
- the amount of solutedissolved in a solvent.
- the spreading of solutes throughout a solution until they reach equilibrium. (Brownian motion)
SOLUTIONS
Concentration- the amount of solutedissolved in a solvent.
- the spreading of solutes throughout a solution until they reach equilibrium. (Brownian motion)
SOLUTIONS
Concentration- the amount of solutedissolved in a solvent.
Diffusion- the spreading of solutes throughout a solution until they reach equilibrium. (Brownian motion)
MEMBRANE
a membrane that allows some substances to
pass through it, but not others.
Example: The membrane
SEMIPERMEABLE MEMBRANE
a membrane that allows some substances to
pass through it, but not others.
Example: The membrane
SEMIPERMEABLE MEMBRANE
a membrane that allows some substances to
pass through it, but not others.
Example: The cell membrane
OSMOSIS
the diffusion of a through a semipermeable membrane.
OSMOSIS
the diffusion of a solvent through a semipermeable membrane.
DIFFUSION VS. OSMOSIS
Diffusion Osmosis
It involves movement of solute
molecules
It involves movement of solvent
molecules
Molecules move from higher
concentration of solute to lower
concentration of solute
Molecules move from lower
concentration of solute to higher
concentration of solute
Produces equal solution
concentrations
Does not produce equal solution
concentrations
Does not require a
semipermeable membrane
Requires a semipermeable
membrane
SOLUTIONS
: a solution that is more
concentrated than the cytoplasm of the cell.
: a solution that is less
concentrated than the cytoplasm of the cell.
: a solution that has the same
concentration of solutes as the cell.
SOLUTIONS
Hypertonic solution: a solution that is more
concentrated than the cytoplasm of the cell.
: a solution that is less
concentrated than the cytoplasm of the cell.
: a solution that has the same
concentration of solutes as the cell.
SOLUTIONS
Hypertonic solution: a solution that is more
concentrated than the cytoplasm of the cell.
Hypotonic solution: a solution that is less
concentrated than the cytoplasm of the cell.
: a solution that has the same
concentration of solutes as the cell.
SOLUTIONS
Hypertonic solution: a solution that is more
concentrated than the cytoplasm of the cell.
Hypotonic solution: a solution that is less
concentrated than the cytoplasm of the cell.
Isotonic solution: a solution that has the same
concentration of solutes as the cell.
SOLUTIONS
same lower higher
TRANSPORT ACROSS THE MEMBRANE
- The movement of molecules across a
membrane without the use of chemical energy.
TRANSPORT ACROSS THE MEMBRANE
Passive Transport- The movement of molecules across a
membrane without the use of chemical energy.
PASSIVE TRANSPORT
The particle’s own natural motion causes it to
move from an area of concentration to an
area of concentration.
Cells don’t have to expend any energy to get
these particles across their membranes.
Examples:
Diffusion
Osmosis
Facilitated diffusion
PASSIVE TRANSPORT
The particle’s own natural motion causes it to
move from an area of high concentration to an
area of low concentration.
Cells don’t have to expend any energy to get
these particles across their membranes.
Examples:
Diffusion
Osmosis
Facilitated diffusion
PASSIVE TRANSPORT
Four factors determine whether a particle can be
passively transported across a membrane:
1. Particle size
2. Particle shape
3. Particle polarity
4. Membrane composition
PARTICLE SIZE
Very small particles can pass through the
pores of a cell membrane easily.
Examples:
water
oxygen
carbon dioxide
nitrogen
PARTICLE SHAPE
Even if a particle is small enough, it may still
not be able to pass through an opening in the
cell membrane.
A round particle will not fit into a square hole
and vice versa!
PARTICLE POLARITY The cell membrane only allows nonpolar molecules to
pass through easily.
Only very small polar molecules like water can pass
through the membrane using passive transport.
Ions cannot pass through the membrane passively.
MEMBRANE COMPOSITION
The lipid bilayer contains different
proteins and different-size openings that
affect what can get through a cell
membrane.
Example: liver cells have large openings in
their cell membranes to process toxins that
enter the body.
PASSIVE TRANSPORT- FACILITATED DIFFUSION
Molecules move through the cell membrane with the
help of without expending energy
(ATP).
Molecules are moved from areas of concentration
to concentration.
PASSIVE TRANSPORT- FACILITATED DIFFUSION
Molecules move through the cell membrane with the
help of transport proteins without expending energy
(ATP).
Molecules are moved from areas of concentration
to concentration.
PASSIVE TRANSPORT- FACILITATED DIFFUSION
Molecules move through the cell membrane with the
help of transport proteins without expending energy
(ATP).
Molecules are moved from areas of high concentration
to low concentration.
ACTIVE TRANSPORT- PROTEIN PUMP The movement of molecules across a
membrane using (ATP).
Molecules are moved from areas of
concentration to concentration.
ACTIVE TRANSPORT- PROTEIN PUMP The movement of molecules across a
membrane using chemical energy (ATP).
Molecules are moved from areas of
concentration to concentration.
ACTIVE TRANSPORT- PROTEIN PUMP The movement of molecules across a
membrane using chemical energy (ATP).
Molecules are moved from areas of low
concentration to high concentration.
ACTIVE TRANSPORT- ENDOCYTOSIS AND EXOCYTOSIS
Two kinds of active transport to handle large particles.
: the process by which large molecules are taken
into the cell using vesicles.
: Transportation of material from inside the cell to
outside the cell using vesicles.
ACTIVE TRANSPORT- ENDOCYTOSIS AND EXOCYTOSIS
Two kinds of active transport to handle large particles.
Endocytosis: the process by which large molecules are taken
into the cell using vesicles.
: Transportation of material from inside the cell to
outside the cell using vesicles.
ACTIVE TRANSPORT- ENDOCYTOSIS AND EXOCYTOSIS
Two kinds of active transport to handle large particles.
Endocytosis: the process by which large molecules are taken
into the cell using vesicles.
Exocytosis: Transportation of material from inside the cell to
outside the cell using vesicles.