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Pre-AP Biology Bellwork
September 24th
1. What is a cell?
2. What is “cell theory”
3. Why are cells considered the building
blocks of all living things?
Definition of Cell
A cell is the smallest unit that is
capable of performing life functions.
It is the basic building block of all
living things.
Cell Theory
• All living things are made up of one or
more cells.
• Cells are the smallest working units of all
living things.
• All cells come from preexisting cells
through cell division.
Why is it a “building block”?
REVIEW
• Organism – group of organ systems
functioning together.
• Organ System – group of organs
functioning together.
• Organ – group of tissues functioning
together.
• Tissue – group of cells functioning
together.
• Cell – the foundation of all of the
above! IE a “building block”
The Microscopic World of Cells
– Organisms are either:
• Single-celled, such as most bacteria and protists
• Multicelled, such as plants, animals, and most fungi
History
of the Cell
Cell size
Figure 4.3
Microscopes as a Window on
the World of Cells
– The light microscope is used by many scientists.
• Light passes through the specimen.
• Lenses enlarge, or magnify, the image.
• Magnification
– Is an increase in the specimen’s apparent size.
• Resolving power
– Is the ability of an optical
instrument to show two
objects as being separate.
Euglena
1. The electron microscope (EM) uses a beam of
electrons.
• It has a higher resolving power than the light
microscope.
• The electron microscope can magnify up to
100,000X.
– Such power reveals the diverse parts within a cell.
2. The scanning electron microscope (SEM) is
used to study the detailed architecture of the
surface of a cell.
3. The transmission electron microscope (TEM) is
useful for exploring the internal structure of a
cell.
Microscopes and Cells
• 1600’s.
–Anton van
Leeuwenhoek
first described
living cells as
seen through a
simple
microscope.
Microscopes and Cells
–In 1665 Robert Hooke used
the first compound
microscope to view thinly
sliced cork cells.
•Compound scopes
use a series of lenses
to magnify in steps.
•Hooke was the first
to use the term “cell”.
Microscopes and Cells
• 1830’s.
–Mathias Schleiden
identified the first plant cells
and concluded that all plants
made of cells.
-Thomas Schwann
made the same
conclusion about
animal cells.
Examples of Cells
Amoeba Proteus
Plant Stem
Bacteria
Red Blood Cell
Nerve Cell
Cell Structure
& Function
Two Types of Cells
1. Prokaryotic
2. Eukaryotic
Prokaryotic
• Do not have structures surrounded by
membranes
• Do not have
structures
surrounded by
membranes
• NO TRUE
NUCLEUS
• Few internal
structures
• Examples: unicellular organisms,
archaebacteria & eubacteria
Eukaryotic
•
•
•
•
•
Contain organelles surrounded by membranes
Most living organisms
Contains a true nucleus
Unicellular or multicellular
Examples: Protista, Fungi, Plants, Animals
Plant
Animal
In your notes…
• Compare and contrast a prokaryotic cell
and a eukaryotic cell
Two Basic Cell Types
• Prokaryotes
– Small
– no not contain any
membrane-bound
organelles
– No true nucleus
– Bacteria
• Eukaryotes
– Do contain membranebound organelles
– Most multicellular (also
amoebas, some algae)
– Contain a Nucleus (Robert
Brown and Rudolf
Virchow)
Figure 4.4
Parts of the Cell
I. Surrounding the Cell
Cell Boundries
1. Cell Membrane
• The outer layer of
animal cells, found
inside cell walls
(in plants)
• Double layer (bi-lipid
layer)
• Function: Controls what
goes in and out of a cell.
The Cell Membrane
The Plasma Mosaic Membrane Model
Membrane Structure
– The plasma membrane separates the living cell
from its nonliving surroundings.
– The membranes of cells are composed mostly
of:
• Lipids
• Proteins
Why Cells Must Control Materials
Cells need nutrients (glucose, AA, lipids etc)
• Plasma Membrane controls what goes in and what
goes out
• Waste removed through membrane
• Selectively Permeable
–
–
–
–
Allows some things through,
keeps others out
Water – osmosis
Ca+2, Na+ - only certain times
Let’s Draw It Together!
Study!
STUDY THE DIAGRAM YOU JUST DID
ON THE CELL MEMBRANE. THERE
WILL BE A QUIZ THE NEXT CLASS
WHERE YOU WILL DRAW, LABEL AND
EXPLAIN THE FUNCTION OF THE
PARTS OF THE PLASMA MOSAIC
MEMBRANE
A Better Rendition…
Phospholipid Bilayer
• Lipids – nonpolar
– Makes it difficult for water to get
through
– HYDROPHOBIC
• Phosphate head – polar
– Face inside and outside of cell
– Work well with water – water
soluble barrier
– HYDROPHILIC
• Fluid Mosaic Model
– Phospholipids move within
membrane
– Proteins create mosaic
Other Components of the
Membrane
• Cholesterol
– Stabilize phospholipids
by preventing fatty
acid tails from sticking
together – the glue
– Holds it all!
• Transport Proteins
– Move substances in
and out of membrane
Membrane Proteins - Examples
Evolution Connection:
The Origin of Membranes
– Phospholipids were probably among the organic
molecules on the early Earth.
– When mixed with water, phospholipids
spontaneously form membranes.
Cell Surfaces
– Most cells secrete materials for coats of one
kind or another
• That are external to the plasma membrane.
– These extracellular coats help protect and
support cells
• And facilitate interactions between cellular neighbors
in tissues.
– Plant cells have cell walls,
• Which help protect the cells, maintain their shape,
and keep the cells from absorbing too much water.
– Animal cells have an extracellular matrix,
• Which helps hold cells together in tissues and
protects and supports them.
2. Cell Wall
• Most commonly found
in plant cells &
bacteria
• NOT FOUND IN
ANIMAL CELLS!
• Rigid layer of non
living material
• Function: Protection &
Support
II. Inside the Cell
3. Cytoplasm / Cytosol
• Gel-like mixture
– water (70%)
– Proteins, fats,
carbohydrartes,
nucleic acids, ion
(30%)
• Surrounded by cell
membrane
4. Nucleus
• The boss!
– The nucleus is the manager of the cell.
• Genes in the nucleus store information necessary to
produce proteins.
• Directs cell activities
• Contains genetic material
– DNA
– The nucleus is bordered by a double
membrane called the nuclear envelope.
• It contains chromatin.
• It contains a nucleolus.
5. Nuclear Envelope
• Also known as the
nuclear mebrane
• Surrounds nucleus
• Made of two layers
• Openings allow
material to enter and
leave nucleus through
large pores
Figure 4.8
6. Chromosomes
•
•
•
•
The blueprints!
In nucleus
Made of DNA
Contain instructions
for traits &
characteristics
7. Nucleolus
• The “secretary”
• Contains RNA copy of
the DNA to build
proteins
• Inside nucleus
• Responsible for
ribosome production
8. Ribosomes
• Protein factory
• Responsible for
protein synthesis
• Each cell contains
thousands
• Make proteins
• Found on
endoplasmic
reticulum & floating
throughout the cell
How DNA Controls the Cell
– DNA controls the cell by transferring its coded
information into RNA.
• The information in the RNA is used to make proteins.
Figure 4.9
The Endomembrane System:
Manufacturing and Distributing
Cellular Products
– Many of the membranous organelles in the cell
belong to the endomembrane system.
9. Endoplasmic Reticulum
•
•
•
•
Produces an enormous variety of molecules.
Moves materials such as protein around in cell
Smooth type: lacks ribosomes
Rough type: ribosomes embedded in surface
Figure 4.10
Rough ER
– The “roughness” of the rough ER is due to
ribosomes that stud the outside of the ER
membrane.
– The functions of the rough ER include:
• Producing two types of membrane proteins
• Producing new membrane
– After the rough ER synthesizes a molecule, it
packages the molecule into transport vesicles.
Figure 4.11
Smooth ER
– The smooth ER lacks the surface ribosomes of
ER and produces lipids, including steroids.
10. Golgi Body (Golgi Apparatus)
• Works with ER
• Protein 'packaging
plant‘
• Packages proteins
with lipids
– Refines, stores, and
distributes the chemical
products of cells.
• A series of flattened
sacs where newly
made lipids and
proteins from the
E.R. are repackaged
and shipped to the
plasma membrane.
Figure 4.12
11. Lysosome
• A lysosome is a membraneenclosed sac.
• Garbage bag of the cell!
• Digestive 'plant' for proteins, fats,
and carbohydrates
– Contains digestive enzymes
– These enzymes break down
macromolecules
• Lysosomes have several types of
digestive functions
– They fuse with food vacuoles to digest
the food.
– Transports undigested material to cell
membrane for removal
Lysosome Formation
•More numerous in ANIMAL cells
•Contain enzymes that function in digestion of food and
dead cell parts
•Also known as “suicide sacs” because they can destroy
the whole cell: Cell breaks down if lysosome explodes
Figure 4.13a
– They break down damaged organelles.
12. Vacuoles
• Vacuoles are membranous sacs.Contains water
solution
• Two types are the contractile vacuoles of
protists and the central vacuoles of plants.
– MUCH larger in plants
– Small in animal cells
• FUNCTION: Membrane-bound sacs for storage of food
and water, digestion, and waste removal. Help plants
maintain shape (support)
Paramecium Vacuole
Figure 4.14
– A review of the endomembrane system
Chloroplasts and Mitochondria:
Energy Conversion
– Cells require a constant energy supply to do all
the work of life.
13. Chloroplast
• Site of photosynthesis
• Usually found in plant
cells
• NOT FOUND IN ANIMAL
CELLS!
• Contains green
chlorophyll in the
thylakoid membrane
• Turn the Sun’s energy
into food through
photosynthesis
– They do not make energy,
they convert it
Figure 4.16
14. Mitochondria
• Mitochondria are the sites of
cellular respiration, which
involves the production of ATP
from food molecules.
• The “powerhouse” of the cell
• Produces energy in the form of
ATP through chemical reactions
– breaking down fats &
carbohydrates
• Controls level of water and
other materials in cell
• Recycles and decomposes
proteins, fats, and
carbohydrates
• Has a highly folded inner
membrane (cristae).
Figure 4.17
– Mitochondria and chloroplasts share another
feature unique among eukaryotic organelles.
• They contain their own DNA.
– The existence of separate “mini-genomes” is
believed to be evidence that
• Mitochondria and chloroplasts evolved from
free-living prokaryotes in the distant past.
15. Cytoskeleton
The cytoskeleton is an infrastructure of the cell
consisting of a network of fibers.
•A network of thin,
fibrous materials that
act as a scaffold and
support the organelles.
•Microtubules – hollow
filaments of protein.
Produced in
centrosome
•Microfilaments – solid
filaments of protein.
Maintaining Cell Shape
– One function of the cytoskeleton
• Is to provide mechanical
support to the cell and
maintain its shape.
– The cytoskeleton can change the shape of a
cell.
• This allows cells like amoebae to move.
16. Cilia
• Short, numerous,
hair-like projections
from the plasma
membrane.
• Move with a
coordinated beating
action.
Figure 4.19c
17. Flagella
 Longer, less
numerous
projections from
the plasma
membrane.
 Move with a
whiplike action.
Cilia and Flagella
– Cilia and flagella are motile appendages
– Flagella propel the cell in a whiplike motion.
– Cilia move in a coordinated back-and-forth
motion.
– Some cilia or flagella extend from nonmoving
cells.
• The human windpipe is lined with cilia.
Cilia and Flagella
Paramecium Cilia
18. Centrosome
• Microtubles are produced here
• The centrosome contains a pair of small
organelles, the centrioles in animal cells
ONLY
• Plant cells have centrosomes BUT no
CENTRIOLES!
19. Centriole
Made of protein.
Play a role in the splitting of
the cell into two cells (cell
division).
Found in animal and fungi
cells. NEVER IN PLANTS!
Made of microtubules
Draw a Generalized Cell
Please use all 19 parts mentioned we just went over
Study!
STUDY THE DIAGRAM YOU JUST DID
OF A GENERALIZED CELL. THERE
WILL BE A QUIZ THE NEXT CLASS
WHERE YOU WILL DRAW, LABEL AND
EXPLAIN ALL OF THE PARTS OF A
GENERALIZED CELL.
...
Composite Animal Cell
Composite PLANT Cell
Cell Project!
Please see the rubric handed out in class for specifics on this project.
Liver Cell
Lily Parenchyma Cell
Specialized Cells
• Muscle Cells
–Long, slippery and
elastic so that they can
slide past one another
upon expansion and
contraction
Specialized Cells
• Red Blood Cell
–Has no nucleus so that
it can carry more
oxygen
Specialized Cells
• Nerve cells
–Can be several feet
long
–pass chemical and
electrical signals
throughout the body
Cellular Transport
Cellular Transport
Osmosis: Review
• Osmosis – diffusion of
water across a
selectively permeable
membrane
• Plasma membrane
does NOT limit water
movement
Osmosis
If two solutions are separated by a selectively
permeable membrane….
Only water can flow from side to side to make the
concentrations equal
Isotonic
The concentration of solute in the solution can be equal
to the concentration of solute in the cells. The cell is in
an isotonic solution. (iso = same as normal)
The concentration
of solutes is the
same inside and
outside of the cell.
So the same
amount of water
that enters the cell,
leaves the cell.
Hypotonic: “below strength”
The concentration of solute in the solution can be less
than the concentration of solute in the cells. The cell is
in an hypotonic solution. (hypo = less than normal)
Solution has a
lower solute
concentration than
the cell. So the
water will move in.
Hypertonic: “above strength”
The concentration of solute in the solution can be
greater than the concentration of solute in the cells. The
cell is in an hypertonic solution. (hyper = more than
normal)
Solution has a
higher solute
concentration than
the cell. So water
will leave the cell.
Osmotic Relationships in Blood Cells
Summary
• Isotonic Solution
– Concentration of dissolved substances in solution is
same as dissolved substances inside cell
• Hypotonic Solution
– Concentration of substances is lower in solution
– Water flows out of solution into cell to lower
concentration in cell
• Hypertonic
– Concentration of substances is higher in solution
– Water flows into solution and out of cell to raise
concentration in cell
Passive Transport
• Cells don’t use energy to move things across
the plasma membrane
• Facilitated diffusion
–
–
–
–
Passive transport using proteins
Channel proteins
Carrier Proteins
With the concentration gradient
Active Transport
• Moving things from lower to
higher concentration
• Against diffusion
• Carrier Proteins
Transport of Large Particles
• Endocytosis
– Cell surrounds and
takes in material
– phagocytosis: solid
material is taken in
– Pinocytosis: liquid is
taken in
• Exocytosis
– Expulsion or secretion
of materials
Transport of Large Particles
Endocytosis
Exocytosis