Locating the Specimen under the Microscope
1. Place the slide on the stage with the specimen over the
beam of light.
2. Always begin at the lowest power (scanning- 4x) with the
stage at its highest point.
3. While looking through the microscope, slowly lower the
stage using the course adjustment knob until the sample
comes into focus.
4. Use the fine adjustment knob to sharpen the image.
5. Turn to the low power (10x) objective and fine focus the
image.
6. Turn to the high power (40x) objective and fine focus
until the image is clear.
Unit 3C
Cell Structure and Function
2 Main Categories of Cells
1. Prokaryotic Cells- DO NOT have
“membrane bound” organelles and DO
NOT have a nucleus to hold the DNA
2. Eukaryotic Cells- contain membrane
bound organelles including a nucleus to
hold the DNA
Euk
examples:
Prok
examples:
-Bacteria
(Eubacteria,
archaebacteria)
-Protists
(paramecium/
amoeba)
-Fungi
(mushrooms/
yeast)
-Plants
-Animals
Differences and Similarities Between the
Two Cell Types: (+ present, - absent)
Cell Characteristics
Prokaryotic Cell
Outer Cell Membrane
+
+
Cytoplasm-Cell Fluid
+
+
+ smaller
+ larger
Nucleus
-
+
Chromosomes (DNA/RNA)
+
+
Membrane Bound Organelles
-
+
Average Size of Cells
1-10 μm
2-1000 μm and larger
Time of Evolution
3.5 Billion Years Ago
1.5 Billion Years Ago
Ribosome (structures which form
proteins)
Organisms Exhibiting this type of Cell
General Shape of the Cell
Bacteria
Spherical, rod-shaped, spiral
Eukaryotic Cell
Protists, plants,
fungi, animals
Wide variety of shapes
depending on function
Eukaryotes
• Are organisms that have
eukaryotic cells
(prokaryotes do not)
• Examples: animals,
plants, fungi, protists
• We will mainly be
discussing the parts of
eukaryotic cells and
comparing prokaryotic
and eukaryotic cells to
each other.
Cell Organization
•
The Nucleus (Euk only)
1.
Controls all of the cell’s
activities because it…
Contains and protects the
DNA
Surrounded by the nuclear
envelope double lipid
bilayer with pores that
regulates what enters/exits
the nucleus
Contains the nucleolus
area of the nucleus that
makes ribosomes
2.
3.
4.
Cell Organization (continued)
• Cytoplasm- the portion of Shade in the
region
the cell outside of the
showing the
cytoplasm
nucleus
• Found in both prok and euk
• Contains an aqueous
Shade in the
solution called cytosol
region
the
containing solutes needed showing
cytosol
for metabolic reactions
• Contains the organelles (in
euk)
Cell Organization (continued)
• Organelles- specialized structures
inside the cell (“Little Organs”)
• Mostly found in the cytoplasm
• If membrane bound (surrounded by a
membrane)- only found in euk
• Summarize cell organization at the bottom
of pg. 2
Organelles and Cell Structures
• The following slides discuss the organelles
of a cell, they fall into the following
categories:
1. Cellular boundaries
2. Organelles that capture and release
energy
3. Organelles that store, clean up, and
support
4. Organelles that build proteins
Cellular Boundaries
Boundaries keep certain things inside and
certain things outside of the cell.
• Cell Walls
• Cell Membranes
A. Cell Walls
• Support, shape, and protect the cell
• Lie outside the cell membrane
• Have openings allowing small molecules in and
out (semipermeable, not selectively permeable).
• Found in most prokaryotes, many eukaryotes
(protists, fungi, and plant cells), but NOT in
animal cells
– Why not?
– We need to move/be flexible
Cell Wall Composition
• In bacteria- contains various
carbohydrates
• In protists- carbs and silica (SiO2)
• In fungi- chitin (a type of carb)
• In Plants- mostly cellulose (polysaccharide
made of glucose monomers)
B. Cell (or Plasma) Membranes
•
•
•
•
Found surrounding all cells (prok or euk)
Made of a lipid bilayer
Protects and supports the cell
Regulates what comes in and out of the
cell- selectively permeable
The Fluid Mosaic Model
• Flexible and contains many transport
proteins that help move materials in and
out and help cells communicate.
• Carbs on the outer surface help with
communication and identification of the
cell.
Carbohydrates
attached to
proteins
Proteins in
Membrane
Summarize cellular boundaries at the
bottom of pg. 4.
Organelles that Capture and
Release Energy
Are membrane bound and thus found in
eukaryotic cells only
• Chloroplasts- found in plant cells; are the
location of photosynthesis
• Mitochondria- found in both plant and animal
cells; location of energy production (ATP)
A. Chloroplasts and Photosynthesis
• Contain a green colored
pigment called chlorophyll
which captures light energy to
power photosynthesis
• Have two membranes (inner
and outer).
• Contain a fluid called stroma,
stacks called grana of folded
structures called thylakoids
surrounded by thylakoid
membranes.
Photosynthesis: 6CO2 + 6H2O→ C6H12O6 + 6O2
Label the chloroplast
• If the pigment chlorophyll causes the
green color in plants, do all plant parts
contain chlorophyll? Support your answer.
• Some prokaryotic bacteria are
photosynthetic. Do They contain
chloroplasts?
B. Mitochondria and Cellular
Respiration
• Contain its own unique DNA, proteins, and
ribosomes; can self replicate
• Contains an outer membrane, and a fluid
called matrix inside a highly folded inner
membrane.
• This creates folds called cristae for the
reactions of cellular respiration.
Cellular Respiration: 6O2 + C6H12O6 → 6CO2 + 6H2O + ATP
Label the Mitochondria
Mitochondria and Cellular
Respiration
• Which do you think would contain more
mitochondria, a heart muscle cell or a skin
cell?
• Why?
• Summarize energy organelles at the
bottom of pg. 5
Organelles that Store, Clean up,
and Support
• Storage: vacuoles (store material) and vesicles
(move materials around the cell)
– Vacuoles form by the combining of many vesicles
• Clean up: lysosomes- contain enzymes to
digest materials
• Support: the cytoskeleton- meshwork that
allows for movement of the cell and materials
throughout the cell
– Contains the centrioles (help the cell divide)
A. Vacuoles
“Storage”
• Membrane bound organelles
found in eukaryotic cells
• In Plant cells- typically have
one large central vacuole to
store water, nutrients, wastes,
and enzymes.
– Helps maintain turgor pressurethe pressure from inside the full
vacuole that pushes the cell
membrane against the cell wall
and helps the plant cell stay
rigid
Vacuoles
“Storage” (cont.)
• In Animal cells- have
varying numbers of small
vacuoles that function to
store large molecules like:
– food brought in by a
vesicle during endocytosis
– Molecules waiting to be
released by exocytosis
Vacuoles
“Storage” (cont.)
• In Unicellular aquatic organisms- there
are specialized vacuoles called contractile
vacuoles which function to pump excess
water from the cell’s cytoplasm
• Think back to the unit on cell transport
– Why are contractile vacuoles necessary in
unicellular aquatic organisms?
– Without them, cells would swell and explode
due to water rushing in from the hypotonic
environment of the pond
B. Lysosomes
“Clean up”
• Found in eukaryotes,
though mainly in animal
cells (rare in plant cells)
• Membrane bound sacks
that are the site of
hydrolysis (digestion)
• Have an acidic pH and are
filled with digestive
enzymes
• Produced by the golgi
apparatus
Lysosomes
“Clean up”
• Why is it important for the digestive
enzymes to be bound by the lysosome,
rather than being in the cytoplasm?
– If the enzymes were free in the cytoplasm
then they could break down other molecules
and even organelles that need to stay intact.
• Summarize storage and clean up at the
bottom of pg. 6
C. Cytoskeleton
“Support”
• Just like your body depends on your skeleton
(bones) to keep your shape, so do cells.
• Not membrane bound so also in prokaryotes
• Consist of long networks of protein strands
called microfilaments and microtubules.
-Thicker strandsmicrotubules
-Thinner strandsmicrofilaments
The Cytoskeleton
“Support”(continued)
microfilaments – provide a framework and
The amazing
help move the cell
marching
proteins!
- made of the protein actin
Intermediate filaments – help anchor cells in
place using a variety of proteins
microtubules – Act as tracks for organelles to
travel on as they move throughout the cell
- help in cell reproduction and division by
forming centrioles (not found in prok or plant
cells)
- made of proteins called tubulins
More on Microtubules
• May extend outside of the cell to form cilia
(tiny hairs) or flagella (long tail-like hairs)help the cell move
Ex: sperm
cell- one
flagella
Other
microorganismsone or more
flagella
Cilia
Ex: Paramecium
Flagella
• Summarize the cytoskeleton at the bottom
of pg. 7
Organelles that build Proteins
• Ribosomes
• Rough Endoplasmic Reticulum (ER)
• Golgi Apparatus
Ribosomes
make proteins
and insert
them into the
Rough ER
Rough ER
tags and
modifies the
proteins and
sends them to
the Golgi in
vesicles
The Golgi
packages the
proteins and
sends them off in
vesicles to where
they are needed
Ribosomes
NOT membrane bound- so also found in
prokaryotes
Produced by the nucleolus (which is where?)
There are two types of Ribosomes
Free Ribosomes – move around in the
cytoplasm
ER Ribosomes – are attached to the
rough endoplasmic reticulum
Chloroplasts and mitochondria have their own
ribosomes! (remember endosymbiosis?)
Ribosome Structure
• Two parts (subunits)
• One large subunit and one small subunit
that fit together
• Both made of RNA bound with proteins
Endoplasmic Reticulum (ER)
• Network of membrane bound tubes and sacks.
Constantly forming and breaking down.
Endoplasmic Reticulum (ER)
There are two types of ER
1. Rough ER- has ribosomes on its surface
-
Proteins are made at the ribosomes and inserted
into the rough ER.
The rough ER tags/modifies the proteins; telling
the cell where to send them
ER (continued)
2. Smooth ER- no ribosomes on its surface
- NOT involved in the synthesis of
proteins
- Helps make lipids
- Site of detoxification of drugs like
alcohol and sedatives
- cells in people who use
these drugs from large
amounts of smooth ER.
Golgi Apparatus
• Series of sack-like membranes, drawn
like a stack of pita bread
• Found between the rough ER and cell
membrane
• Modifies, sorts, and packages proteins
coming from the rough ER
• Sends the finished proteins to their
destination by vesicles which bubble off
of the main stacks. (Proteins may be sent
either elsewhere in the cell or to its surface to
leave the cell)
• Lysosomes are formed from golgi
vesicles
– The “FedEx” of the cell
• Summarize protein synthesis at the bottom
of pg. 9
Differences between Plant and Animal
Cells
Plant cells share all the common features of animal cells,
but also contain some additional organelles.
• chloroplasts to convert sunlight into food
chloroplast
vacuole
• Every plant cell is
surrounded by a cell
wall, and typically
contains large central
vacuole.
• Plant cells do NOT have centrioles
cell wall
Plant cells vs. Animal cells
Label the following Eukaryotic Cells
A
B
C_______________________
D
E
AB
AC
AD
AE
BC
BD
BE
CE
Which cell – the one on the right or the left – is the Animal cell?_________
Plant cell?___________
Cells can function individually
and work together in order for
the organism to function as a
whole
Homeostasis in
Unicellular Organisms
• Unicellular organism- an organism made
of just 1 cell.
– Can perform all necessary functions for life
– Must maintain homeostasis
• By growing, responding to their environment,
transforming energy, and reproducing.
Homeostasis in Multicellular Life
• Multicellular organisms are made of
many cells that work together
• Also must maintain homeostasis
– To do this, cells become specialized for
certain tasks and communicate with
each other.
Cell Specialization
• Different cells take on different roles
• The process by which cells specialize is
called cell differentiation
Cell Specialization (cont.)
– Example: human tracheal cells- millions of cilia
sweep out debris that you breathe in. Filled with
mitochondria because need constant supply of ATP
to do this day and night!
– What other cells are specialized in the human
body?
Cell Specialization (cont.)
• Pick any two cell types from the diagram– compare and
contrast their specialized structure, and relate this to the
cells’ function in the body.
Levels of Organization
• Cells that work together form tissues
• Tissues that work together form organs
• Organs that work together form organ
systems
• Organ systems work together to make a
fully functioning organism
• Example 1:
Levels of Organization
• Example 2:
Levels of
Organization
(continued)
Cellular Communication
• How do cells interact to form tissues
and organs?
• Cells of the same tissue are connected
by an extracellular matrix (ECM) and…
• communicate by sending chemical
signals to one another.
Extracellular Matrix (ECM)
• The ECM is a meshwork of proteins and
polysaccharides located between cells that
plays a role in
1) connecting cells into tissues through cell
junctions and
2) sending chemical signals between cells
using receptor proteins.
1) Cell Junctions
• Cell Junctions are connections between two
cells, or between a cell and the ECM
– Hold cells together
– Allow signaling molecules to pass between cells
– Anchor the cell to the ECM
Many types of
cell junctions
ECM
2) Receptor Proteins
• To respond to a signal,
the cell must have a
receptor for that signal
• These receptors are
proteins and may be in
the cell membrane or in
the cytoplasm
• When bound by a
signaling molecule, the
receptor will cause
changes within the cell
Cell Signaling Is Complex!!