Chapter 7
Lecture notes
Name _____________________
A VIEW OF THE CELL
Two scientists who invented the microscope are
a. Robert Hooke (Englishman) used a compound microscope with 30 X magnification.
looked at cork and gave us the term “cell” for the basic building blocks of living things.
b. Anton van Leeuwenhoek (Dutch) used a simple microscope with 400 X magnification
i. looked at water and saw protozoan (single cell organisms).
(Multicellular organisms are metazoans.)
ii. he discovered the “Protist Kingdom”
There are several types of microscopes:
1. optical microscopes (light microscopes)—use lenses to magnify light (up to 1,500 X)
a. simple light microscope—has one lens
b. compound light microscope—has two lenses (or multiple lenses)
i. ocular lens is near the eyes
ii. objective lens is near the object you are studying
Two things are important to the quality of the image
a. resolution—sharpness, clarity—ability to see two distinct points
b. magnification—how many times larger the image looks
i. um [micrometer] is a millionth of a meter (light microscope unit)
ii, nm [nanometer] is a billionth of a meter (electron microscope unit)
iii. Multiply the power of the two lenses to get the microscope’s magnification
a) low power = 1.5 mm or 1,500 um
b. high power =
375 um
Total magnification = Power of ocular lens X Power of objective lens
2. electron microscopes—use a beam of electrons to magnify an image on a computer
screen. (up to 500,000 X)
There are three basic types of electron microscopes:
a. Scanning electron microscopes (SEM)—show a three dimensional image of
the outside surface of the object. [60,000 X]
b. Transmission electron microscopes (TEM)—give a cross section showing
the internal structure of the organism. [500,000 X]
c. Scanning tunneling microscope (STM)—show the 3-D structure of atoms
on the surface of molecules. [2,000,000 X]
New techniques with light microscopes improve their images
a. polarized light, refracted light, fluorescing light, laser light…
b. new stains & dyes to stain different cell organelles differently
1
The Cell Theory
1. Three scientist helped us develop the “Cell Theory”.
a. Matthias Schleiden (German)—observed that all plants are made of cells.
b. Theodore Schwann (German)—observed that all animals are made of cells.
c. Rudolf Virchow (German)—observed that cells divide (mitosis) forming more
cells (daughter cells).
2. The cell theory states three things:
a. All living things are composed of one or more cells
b. The cell is the basic unit of organization in living things
(cells  tissue  organs  organ systems  whole organism)
c. All cells come from preexisting cells.
i. (by mitosis—cell division—passing on the genetic code God created and
put in the organism)
i. this contradicts the “theory of evolution” which states that living things
sprang to life from the non-living “primordial sea”.
There are two major types of cells (living organisms)
1. Prokaryotes (bacteria & archaebacteria)
a. do not have membrane bound organelles (internal membranes)
b. do not have a nuclear envelope (nuclear membrane)
(nucleoid region—the area where their one circular chromosome is found)
c. have a single circular chromosome
2. Eukaryotes (plants, animals, Protists, fungi)
a. have membrane bound cell organelles—mitochondria, lysosomes, chloroplasts…
b. have a nuclear envelope
c. have linear chromosomes
The study of cells is called cytology
PARTS OF A CELL
1. Plasma membrane (cell membrane)—separates the living cell from the non-living
environment
a. Is responsible for homeostasis—maintaining the right level of everything in the
cell within very narrow limits.
b. Is selectively permeable (semi-permeable)—it allows some things in but not others.
i. lets oxygen, water, sugar, amino acids, ions, carbohydrates, lipids…in
ii. lets out or actively pumps out
a) wastes
b) products made in the endoplasmic reticulum
c) excess ions.
c. The plasma membrane is a phospholipid bilayer (two layers thick, back to back)
2
d. Phospholipids are composed of
i. a glycerol backbone
(three carbon atoms each attached to a hydroxyl group—making an alcohol)
ii. two fatty acid chains—[carbohydrates]which are hydrophobic (water hating)
(really it is water that excludes them because water is polar and lipids are not)
iii. a phosphate group—[polar head] that is hydrophilic (water loving) or polar.
e. The phospholipid bilayer is like a sandwich
i.. The two water-loving phosphate heads are at the inner & outer surface
a) outer surface—faces the interstitial fluid (lymph) and other body cells.
b) inner surface—faces the cytosol (cell’s fluid interior)
ii. The two water-hating fatty acid tail layers are next to each other in the interior
This lipid (oil base) interior stops all polar substances from passing
through the plasma membrane.
iii. The fluid mosaic model of the plasma membrane indicates that
a) side by side phospholipid molecules move around and switch places
with each other thousands of times a second.
b) molecules rarely switch from the inside to the outside of the membrane.
f. Other components of the bilayer phospholipid membrane (plasma membrane)
i. Cholesterol molecules—lie between some of the phospholipid molecules.
a) its hydroxide functional group (—OH) is polar [hydrophilic] and lies at
the surface with the phosphate heads.
b) its four carbon rings and hydrocarbon tail extend in-between the
phospholipid fatty acid tails because they are non-polar [hydrophobic].
c) the cholesterol helps stabilize the plasma membrane
d) in eukaryotic plasma membranes there may be as many cholesterol
molecules as there are phospholipid molecules.
ii. Protein molecules are embedded in the plasma membrane.
a) Integral proteins (integrins, transmembrane proteins)—go all the way
through the plasma membrane and have three functions.
i) Transport—they act as gates to bring ionic molecules through
the non-polar fatty acid middle of the membrane.
These proteins often have a lot of α-helix spirals (α-helices).
ii) Enzymatic activity—they can instigate a metabolic reaction ot
the signal of an enzyme from outside the cell.
iii) Signal transduction—they can release a receptor into the
cytoplasm in response to a signal from
b) Associated proteins attach to the inner surface of the plasma
membrane and peripheral proteins attach to the outside surface.
i) associated proteins attach to the microfilaments of the
cytoskeleton (which goes all the way across the cell).
ii) peripheral proteins attach to fibronectin which attaches to the
other two members of the extracellular matrix which
connects every cell of the body to every other cell by a nonbone skeletal grid.
a. glycoproteins (feathery sugar-protein macromolecules)
b. collagen fibers and elastic fibers
3
iii. Glycolipids and glycoprotein molecules (branching carbohydrate chains)
serve as identification tags for cell-cell recognition.
Example: (Leukocytes (white blood cells) use this to know what is self
and what is foreign (like dirt or bacteria).
2. Protoplasm—general term for the chemical rich fluid in the cell. The average cell in your
body has 75,000 different complex organic macromolecules (chemicals) involved in
cellular metabolism.
a. Cytosol—the fluid in the cell but outside the nucleus
(Cytoplasm—is the cytosol + the cell organelles which is everything outside the
nucleus)
b. Nucleoplasm—the chemically rich fluid in the nucleus which contains the DNA.
3. Nucleus—the control center of the cell.
The nucleus contains the genetic material—chromatin which is strands of DNA
(deoxyribonucleic acid).
[During mitosis (cell division) chromatin shortens and thickens into visible
chromosomes.]
a. The DNA controls cell metabolism by sending messenger ribonucleic acid
(mRNA) to the factories (ribosomes) instructing them on what proteins, catalysts
and enzymes to make.
The sequence is:
DNA → mRNA → protein (enzymes)
b. The genetic material is the blueprint that
i. passes traits on from parents to offspring (ex. blue eyes, blond hair…)
ii. assures that when a cell divides the two daughter cells are the same type of
cell as the parent cell was—and at a higher level that offspring are the same
organism as their parents.
God commanded organisms to “reproduce after their own kind”
(Genesis 1:25).
4. Nuclear envelope—is the double membrane surrounding the nucleus and keeping its
chemical rich fluid separate from the cell fluid.
a. Nuclear pores (pore complexes)—are holes in the membrane that allow ribosomal
sub-units and mRNA to pass out.
b. Nuclear lamina—criss-crossing microfilament fibers (part of they cell cytoskeleton)
which line the inside of the nuclear envelope and help it hold its round shape.
c. Nuclear matrix—a network of fibers extending throughout the interior of the
nucleus-giving it structure.
5. Nucleolus—a chemically rich area within the nucleus which makes the ribosomes.
The ribosomes are made of large and small ribosomal subunits—which are shipped
separately through the pores of the nuclear envelope and put together out in the cytosol.
6. Ribosomes—are the factories in the cell which read mRNA (a single strand copy of the
nucleus’ DNA) and follow its instructions to assemble proteins, catalysts and enzymes.
a. a human pancreas cell can have over a million ribosomes
4
b. ribosomes do not have a membrane—
Prokaryotes (bacteria) have ribosomes
c. structurally similar ribosomes are found in two areas of the cell
i. Free ribosomes—are floating in the cytosol and make proteins the cell will
use in its metabolic reactions.
ii. Bound ribosomes—are attached to the walls of the endoplasmic reticulum and
make chemicals to be used by membranes or secreted out of the cell.
7. Endoplasmic reticulum—a series of folded membranes attached to and surrounding the
nucleus that provides a large working area for chemical reactions to occur and then
cisternea and tunnels to transport the reactants to where they need to go.
a. Rough ER is close to the nucleus and embedded with ribosomes.
i. The ribosomes make proteins.
ii. The proteins feed into a cistern or tunnel and are transported to where they
will be used.
b. Smooth ER is further from the nucleus and does not contain any ribosomes.
i. It produces lipids
ii. It detoxifies the cell of poisons (like alcohol & drugs)
8. Golgi apparatus—is an extension of the endoplasmic reticulum’s outermost surface. It is
a series of closely folded membranes.
a. Proteins made by the ribosomes of the Rough ER are processed and activated to
their final form by the Golgi apparatus.
b. Finished proteins are then labeled for shipping.
c. Sections of the Golgi apparatus’ membrane pinch off into vesicles which transport
the finished proteins to their destination within the cell or to the plasma
membrane to exit the cell by exocytosis.
d. The two sides of the stack of membranes making up the golgi apparatus have a
distinct polarity.
i. the cis face—is towards the nucleus and ER and is the receiving side
ii. the trans face—is towards the plasma membrane and is the shipping side
9. Vesicles—are membranous sacs which surround a substance containing it so it can be
shipped around in the cytosol of the cell.
a. They pinch off from the ER, Golgi apparatus or plasma membrane.
b. After their contents are released they join the new membrane at their destination.
Even though different cellular membranes differ in their proteins, amount of cholesterol…
they all form the endomembrane system because they exchange parts of membranes as
vesicles join and leave.
10. Vacuoles—are membranous sacs for storage of water, enzymes, protein, lipids, wastes…
Types of vacuoles and plastids (storage vacuoles in plants)
a. Chromoplasts—store pigments
Chloroplasts—store the green pigment chlorophyll for photosynthesis
Xanthrophylls—are yellow fall pigments
Carotenoids—orange
5
Phycobilins (Anthrocyanides)—reds & purples
Tannins—brown
b. Leucoplasts—store food (protein, lipids, carbohydrates…
Starch granules—store the carbohydrate starch in plants
c. The central vacuole is a large water storage vacuole in plants
i. it is surrounded by a membrane called the tonoplast
ii. it makes the cell turgid and this helps the plant’s branches stand out
against the pull of gravity.
d. In many single cell protests contractile vacuoles act as binge pumps and
collect and pump water out of the cells as it seeps in by osmosis from the
environment.
11. Lysosomes—are packages of hydrolytic enzymes (they carry out hydrolysis reactions—
as opposed the dehydration synthesis reactions) wrapped in a protective membrane.
a. They are the “garbage dispenser” units in the cell.
b. A lysosome can fuse with a vacuole and dispense its digestive enzymes into the
vesicle to digest away worn out cell organelles, food particles, viruses and
bacteria.
c. Groups of lysosomes can destroy a whole cell
i. apoptosis—good programmed cell death.
Example: to eat away the tissue between fingers in an embryo
Example: to eat away the tail of a tadpole as it is turning into a frog
ii. necrosis—bad cell death due to disease or genetic disorder
Example: when the body destroys virus infected cells
12. Peroxisomes—transfer hydrogen atoms to oxygen forming hydrogen peroxide [H2O2].
a. The hydrogen peroxide can be used to break fatty acids down into smaller
carbohydrates by the process of beta oxidation.
b. Often these are found in plant seeds to release sugar from storage for the seedling.
13. Mitochondria—are the “powerplants” of the cell.
a. These are the sites of cellular respiration where glucose sugar is burned with
oxygen to release energy.
C6H12O6 + 6O2 → 6CO2 + 6H2O + energy
b. This energy is used to recharge ADP to ATP (adenosine tri phosphate) the
energy storage molecules of cells.
c. The mitochondria have an outer membrane and a highly folded inner membrane
(cristae) which is where the enzymes controlling cellular respiration are
embedded in metabolic pathways.
d. The fluid in the mitochondria is called the mitochondrial matrix.
14. Chloroplasts—sites of photosynthesis. They produce glucose sugar and release oxygen
which meets the needs of animals.
Sunlight + 6CO2 + 6H2O → C6H12O6 + 6O2
6
a. Chloroplasts are found in the mesophyll layer of the leaf (palisade & spongy
layers) and in green stems in plants, as well as in algae, and some bacteria and
Protists.
b. The chlorophyll is embedded in the membranes of the thylakoids (flattened disks)
which are in stacks called grana in the chloroplasts.
The fluid in the chloroplast but outside the thylakoids is called stroma.
c. Chloroplasts have a double membrane like the nuclear envelope.
d. Chloroplasts can change shape and move around the cell in response to light
density changes.
15. Centrosome—is a microtubule organizing center.
a. In animal cells—it contains two centrioles lying at right angle to each other which
produce the spindle fibers chromosomes line up on during mitosis (celldivision).
In structure centrioles are like basal bodies with “nine sets of triplets”.
b. Plant cells do not have centrioles but the spindle still forms.
16. Cytoskeleton—a framework of three different types of fibers which gives structure and
organization to the cell.
a. microfilaments—are the smallest. (7 nm)
i. they are composed of two twisted strands of actin protein
ii. functions include
a) muscle contraction of thick myosin pulling on thin actin filaments
b) cytoplasmic streaming in plant cells
i. the outer “gel” is non-moving cytosol anchored to the plasma
membrane by criss-crossing actin filaments.
ii. the inner “sol” is circulating cytosol with loose parallel actin
filaments.
c) pseudopod mobility in ameoba
d) forming the cleavage furrow during cell division
e) tension bearing in holding cell shape
b. intermediate filaments—medium size (10nm)
i. they are composed of about eight fibrous keratin protein filaments twisted
together.
ii. functions include
a) anchor the nucleus in the middle of the cell
b) the nuclear lamina gives the nuclear envelope a rigid shape
c) tension bearing in holding cell shape
c. microtubules—are the largest in size (25 nm) and are hollow cylinders
(the lumen is 15 nm across)
i. they are composed of alternating strings of 13 spiraling ά tubulin and
β-tubulin and look somewhat like ears of corn.
ii. functions include
a) cell motility by flagella and cilia
b) chromosome movement during mitosis
c) in cell organelle movement motor proteins walk along the microtubule
highways powered by ATP
d) compression-resisting in holding cell shape
7
17. Two Structures for Locomotion and Movement of Particles:
a. Cilia—numerous, short hair like appendages
i. on the outer surface of cells
ii. used for locomotion or for feeding
iii. bend and move things by a wave-like motion perpendicular the the axis of
the cilia.
Example: cilia of trachea move dust & bacteria up to the throat and keep
the lungs clean
b. Flagella—a few, long hair like appendages
i. used primarily for locomotion
ii. have a whiplike motion in the same direction as the axis of the flagella
Example: sperm for swimming to fertilize the egg
c. Both flagella and cilia have the same “9 + 2 pattern” to their microtubule
structure.
i. A cross section shows nine doublets of microtubules around two singles
ii. The basal body which anchors the flagella or cilia within the plasma
membrane’s structure is different—nine triplets.
iii. Proteins called dynein arms “walk” one doublet along another to produce
bending movement in cilia.
18. Cell Walls—plants, algae, fungi, bacteria and some Protists have an additional
boundary-outside the plasma membrane for support and protection.
a. The cell wall is made of fibers of cellulose (long interconnected chains of glucose
molecules) glued together by the natural glues pectins and lignans.
b. Plants produce a thin, flexible primary cell wall first and then after cell growth is
done they produce a thicker,more rigid secondary cell wall that stops cell growth
and supports the woody plant.
c. The area between the two cell walls that glue them together is called the middle
lamella.
d. Channels called plasmodesmata perforate the cell walls and allow cytoplasm with
chemicals to flow from one plant cell to another.
(This unifies all of the cells in a plant into one living continuum!)
Comparison of Plant and Animal Cells.
1. Animal cells have three cell organelles plant cells do not have.
a. Lysosomes
b. Centrioles
c. Flagella (except for a few species of plant sperm)
2. Plant cells have three cell organelles animal cells do not have.
a. Chloroplasts
b. A large central vacuole with the tonoplast membrane
c. Cell wall
d. Plasmodesmata
8
Organization Within a Living Organism:
1.
2.
3.
4.
Cells are the basic unit of life.
Cells
(a) of the same type (b) doing the same job form tissue
Cells and tissue (a) of different types (b) doing the same job form organs
Organs and tissue (a) of different types (b) doing the same job form organ systems
Three Types of Junctions Hold Animal Cells Together Into Tissue
1. Tight junctions—made of protein join neighboring cells together so fluids can not
flow in-between in the epidermis (skin).
Example: car mechanics can wash their greasy hands in gasoline without any
gasoline entering the body through the skin.
2. Desmosomes—act like rivets to hold neighboring cells together so they do not rip
away under stress.
In structure at the desmosomes the cell membranes have thicker areas called
plaque which are stitched together by cross-linkage proteins.
3. Gap junctions—in animals (are similar to plasmodesmata in plants) and are tubes
between neighboring cells that allow nutrients and chemicals to flow from the cytosol
of one cell to another.
They are numerous in
a. heart cardiac muscle—where cells must communicate with each other so
the pacemaker can lead the millions of heart muscle cells to beat together
as one organ.
b. animal embryos—where stem cells communicate to tell other cells what
type of tissue to specialize into
Cells are Limited in the Size They Can Grow To
a. Virtually all cells are microscopic
Exception: a chicken egg is one cell and is large.
b. Cell membranes surface area increase with the square of the enlargement
Cell cytoplasm volume increases with the cube of the enlargement
Therefore: if a cell grew large it would die from
i. lack of surface area to absorb oxygen and nutrients & secrete wastes
ii. a large, person sized cell, would not have any organization into tissue,
organs or systems so it would have no bones for rigidness, muscles to
move, brain to think or sense organs to sense its environment.
c. Larger organisms therefore have more cells (not larger cells)
9