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Biology: the study of life
Organism: an individual life-form
Species: organisms that can interbreed and produce fertile
offspring
Environment: an area made up of air, water, weather,
temperature, any other organisms in the area and many
other factors
Stimulus: anything in an organism's external or internal
environment that causes the organism to react
Homeostasis: an organism's ability to regulate its own
internal environment to maintain conditions suitable for its
survival
Adaptation: any inherited structure, behavior, or internal
process that enables an organism to respond to
environmental factors and live to produce offspring
Evolution: the gradual change in a species through
adaptations over time
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Biology - the study of life
◦ Organism – an individual life form
◦ Species – a group of organisms that can breed
to produce fertile offspring
Biology studies:
◦ The diversity of life on earth
◦ How organisms interact with their environment
◦ How organisms interact with each other
◦ Specific characteristics make up what is
defined as a “living” thing.
 There are four major descriptions:
 Orderly structure
 Produce offspring
 Grow and develop
 Adjust to changes in the environment
◦ All living things show an orderly structure
or organization
 This is seen in:
 Shape of organism
 Shape of organs
 The interactions between organs
 While living things are very diverse they
all have cellular organization.
 Simple organisms have similar
structure
 Complex organisms have similar
structures
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The most important characteristic of life is reproduction
◦ This is the production of offspring
◦ Organisms don't live forever so they need to replace
themselves
All organisms begin life as a single cell
◦ Growth results in an increase in the amount of living
material and the formation of new structures
◦ Single cell organisms may change little but they do
grow
◦ More complex organisms go through many different
stages throughout their lives and any of those changes
are call development.
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Environment – an area made up of air, water, weather,
temperature, any other organisms in the area and many
other factors
◦ Stimulus - anything in an organism's external or
internal environment that causes the organism to react
◦ Response - a reaction to a stimulus
◦ Organisms that do not respond to stimuli are more
likely not to survive.
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Homeostasis - an organism's ability to regulate its
own internal environment to maintain conditions
suitable for its survival
◦ This is a characteristic of life because it is a
process that occurs in all organisms.
 Energy is the ability to cause change and it
fuels reproduction, growth, and development.
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Adaptation - any inherited structure, behavior, or internal
process that enables an organism to respond to
environmental factors and live to produce offspring
◦ Adaptations are inherited from previous generations.
◦ Evolution - the gradual change in a species through
adaptations over time
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Scientific methods: the steps used to answer questions in the
scientific community
Hypothesis: an explanation for a question or a problem that
can be formally tested
Experiment: an investigation that tests a hypothesis by the
process of collecting information under controlled conditions
Control: the group in which all conditions are kept the same
Independent variable: the condition in an experiment that is
changed
Dependent variable: the condition that relies on changes made
to the independent variable and is more often measured by
scientists
Data: information obtained from investigation
Theory: an explanation of a natural phenomenon that is
supported by a large body of scientific evidence
Law: certain facts of nature that are provable
Ethics: the moral principles and values held by humans
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Curiosity is often what motivates
biologists to try and answer
simple questions about everyday
observations.
◦ To answer these questions there
are many different approaches
but scientists all follow the
same basic steps.
◦ Scientific method – the steps
used to answer questions in the
scientific community
 The scientific method begins
with identifying a problem.
 Hypothesis - an explanation
for a question or a problem
that can be formally tested
 Before making a hypothesis,
one should have developed
some idea of what the
answer to the question
might be through
observations, research, or
previous experience.
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Experiment - an investigation
that tests a hypothesis by the
process of collecting information
under controlled conditions
◦ There are usually two groups in
an experiment, the control
group and the experimental
group.
◦ Control - the group in which
all conditions are kept the
same
◦ Independent variable - the
condition in an experiment that
is changed
◦ Dependent variable - the
condition that relies on
changes made to the
independent variable and is
more often measured by
scientists
◦ Not all investigations are
controlled and most biological
investigations are straight field
work.
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Safety symbol - a symbol that warns you about danger that
may exist from chemicals, electricity, eat, or procedures you
will use
◦ Experiments are designed to be safe and using such
methods ensures no one will be hurt.
Data -information obtained from investigation
◦ Data can also be referred to as experimental results.
◦ Data is often in numerical form and can appear in verbal,
written, and graphical form.
◦ Data does not end the scientific process.
 Often at the end of an experiment, scientists have more
questions, but it is important to remain on task.
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◦ Most scientific reports and conclusions are reported to the
scientific community through journals.
◦ Once data and conclusions are shared it is important to have
additional investigations attempt to achieve the same
results.
 This verifies and validates the initial investigation.
Theory - an explanation of a natural phenomenon that is
supported by a large body of scientific evidence
Law (principle) - certain facts of nature that are provable
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Sharing information is important to the scientific community
and there are different types of information as well as different
types of technology and uses.
◦ Scientific information is either qualitative or quantitative.
 Quantitative data - numerical data, such as numbers and
graphs
 This is easy to understand information that can easily be
displayed.
 Qualitative data - observational information such as
descriptions and other information that is not easily
graphed
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Scientists provide society with
important information that can
be put to practical use.
◦ Ethics - the moral principles
and values held by humans
 Scientists may not consider
all the possible applications
for the products of their
research and society must
take responsibility for the
ethical use of scientific
discoveries.
 Examples:
 Nuclear bombs
 Cloning
◦ Science cannot answer all
questions: good and evil,
beautiful and ugly.
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Element: the materials that make up everything
Atom: the smallest particle of an element that has the
characteristics of that element
Nucleus: the center of an atom
Isotope: atoms of the same element that have different
numbers of neutrons
Compound: a substance that is composed of atoms of two or
more different elements that are chemically combined
Covalent bond: the force that holds two atoms sharing
electrons together
Molecule: a group of atoms held together by covalent bonds
Ionic Bond: the attractive force between two ions of opposite
charge
Metabolism: all of the chemical reactions that occur within an
organism
Mixture: a combination of substances in which the individual
components retain their own properties
Solution: a mixture in which one or more substances are
distributed evenly in another substance
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In understanding life you must understand the very basic
components that make up life.
◦ Elements - the materials that make up everything and
25 of them are essential to living organisms
◦ There are four major elements and they make up
roughly 96% of the human body.
 Carbon
 Hydrogen
 Oxygen
 Nitrogen
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The other elements that make up life are called trace
elements.
◦ These are usually essential for keeping the cells of
the body healthy.
Atom - the smallest particle of an element that has
the characteristics of that element
◦ They are the basic building block of all matter.
◦ The structure of the atom dictates their properties
and chemical behavior.
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Nucleus - the center of an atom
◦ Protons - positively charged particles contained in the
nucleus
◦ Neutrons - particles that have no charge located in the
nucleus
◦ Nuclei are all positively charged because of the
presence of the protons.
◦ The number of protons in each element is different for
that specific element.
◦ Electrons - small, negatively charged particles that
move around the nucleus
◦ Electrons are always moving and are very hard to
locate.
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Electrons exist in energy levels and
each level is different, but you will
learn more about this in chemistry.
◦ The number of electrons and
protons should be equal so that the
atom has no charge.
Isotopes - atoms of the same element
that have different numbers of
neutrons
◦ This is important to scientists
because some isotopes can be used.
 Carbon-14 is an unstable isotope
that breaks apart over time.
 There is radiation released when
the isotope breaks and it can be
detected.
 Carbon-14 is used to tell how old
some objects are using the
radiation.
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Compound - a substance that is
composed of atoms of two or more
different elements that are
chemically combined
◦ The properties of a compound
are different from the individual
properties of the elements that
make it up.
◦ Most elements in nature are
found combined in the form of
compounds.
 Atoms combined with other
atoms only when the resulting
compound is more stable than
the individual atoms.
 This happens when the
outermost energy level is full.
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Each atom becomes stable by sharing its electrons with
another atom.
◦ The shared electrons move around the nuclei of both atoms.
Covalent bond - the force that holds two atoms sharing
electrons together
◦ Most compounds in organisms have covalent bonds.
Molecule - a group of atoms held together by covalent bonds
◦ It has no overall charge.
Ion - an atom that has gained or lost electrons and has
electrical charge
◦ A different type of chemical bond holds ions together.
◦ Ionic bond - the attractive force between two ions of
opposite charge
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Chemical reactions occur when bonds are formed or
broken, causing substances to recombine into different
substances.
◦ Metabolism - all of the chemical reactions that occur
within an organism
◦ These reactions break down and build molecules that
are important for the functioning of organisms.
◦ Reactants - substances that undergo chemical reactions
◦ Products - substances formed by chemical reactions
◦ No atoms are created or destroyed in a chemical
reaction they are simply rearranged.
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Mixture - a combination of substances in
which the individual components retain their
own properties (Like a salad)
◦ Neither component of the mixture changes
and can be removed from the other.
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Solution - a mixture in which one or more substances are
distributed evenly in another substance
◦ What is being mixed into a solution is a solute.
◦ What something is being mixed in is a solvent.
Solutions are important to organisms because many
substances are dissolved in water.
◦ Living things need certain substances at a specific
concentration range.
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Many chemical reactions
are dependent on special
circumstances.
◦ pH is the measure of
how acidic or basic a
solution is.
◦ An acid is any
substance that forms
hydrogen ions in water.
◦ A base is any substance
that forms hydroxide
ions in water.
◦ Acids and bases are
important to living
systems, but strong
acids and bases can be
dangerous.
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Polar molecule: the bond formed when atoms in a
covalent bond do not share the electrons equally
Hydrogen bond: a weak bond that forms when the
attraction of opposite charges between hydrogen
and oxygen occur
Diffusion: the net movement of particles from an
area of higher concentration to an area of lower
concentration
Dynamic equilibrium: when there is continuous
movement but concentration remains the same
Isomer: compounds that have the same chemical
formula but different three-dimensional shape
Polymer: a large molecule formed when many
smaller molecules bond together
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Carbohydrate: a biomolecule composed of carbon,
hydrogen, and oxygen with a ratio of two hydrogen
atoms and one oxygen atom for every carbon atom
Lipid: large biomolecules that are made mostly of
carbon and hydrogen with a small amount of oxygen
Protein: a large, complex polymer composed of carbon,
hydrogen, oxygen, nitrogen, and sometimes sulfur
Amino Acid: molecules containing an amine group,
carboxylic acid group, and a side-chain
Enzyme: proteins that change the rate of a chemical
reaction
Nucleic acid: a complex biomolecule that stores cellular
information in the form of a code
Nucleotide: made up of carbon, hydrogen, oxygen,
nitrogen, and phosphorous arranged in a nitrogenous
base, a simple sugar, and a phosphate group
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Water is the most important
compound in living organisms and
in fact, makes up 70-95% of most
organisms.
◦ Water does not share the
electrons equally because the
oxygen atom attracts the
electrons greater than the
hydrogen atoms.
◦ Polar bond - the bond formed
when atoms in a covalent bond do
not share the electrons equally
 A polar molecule is a molecule
with an unequal distribution of
charge, each molecule has a
positive end and a negative end.
 Polar water molecules attract
ions as well as other polar
molecules.
 Because of this water can
dissolve many ionic
compounds such as salt and
sugar.
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Water molecules attract
other water molecules
because of the positively
and negatively charged
atoms.
◦ Hydrogen bond - a weak
bond that forms when the
attraction of opposite
charges between
hydrogen and oxygen
occur
◦ Water also has the unique
property of being able to
creep up thin tubes.
 This is used by plants to
collect water through
their roots and is called
capillary action.
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Water resists temperature
changes.
◦ It takes more energy than
most common liquids to
heat water.
 This is important
because water is an
insulator and cells can
maintain homeostasis
easier in a water rich
environment.
◦ Water is one of the few
substances that expands
when it freezes.
 This is why ice floats.
The properties of water
make it an excellent vehicle
for carrying substances in
living systems.
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All objects in motion have energy of motion called kinetic
energy.
◦ In 1827, Robert Brown noticed that grains of pollen would
move constantly in water.
 He thought this was due to a life force hidden within the
pollen.
 He tested this by putting dye into the water and saw the
same motion.
 This motion is Brownian Motion and while Brown did not
know what caused it, it has been discovered that the
random motion is because of the random motion of atoms
and molecules.
 This happens in gases, liquids, and solids.
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Diffusion - the net movement of particles from an area of
higher concentration to an area of lower concentration
◦ This results because of the random movement of
particles (Brownian Motion).
◦ Diffusion is a slow process because it relies on the
random motion of atoms and molecules.
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The three key factors of diffusion are:
◦ Concentration of the substances is the most important of the
factors.
 The more concentrated the substance the more rapidly
diffusion takes place because there are more collisions
between particles.
◦ Increase temperature increases the particle motion and
increases diffusion.
◦ Increasing pressure will increase particle collision and
increase diffusion.
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Dynamic equilibrium - when there is continuous
movement but concentration remains the same
Most substance in and around a cell are in water
solutions where the ions and molecules of solute are
distributed evenly among water molecules.
◦ Concentration gradient - the difference in
concentration of a substance across space
Diffusion is one of the methods by which cells move
substances in and out of the cell.
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Carbon is very important to living organisms.
◦ Carbon atoms have four electrons available for bonding.
◦ When carbon atoms bond to each other they can form
straight chains, branched chains, or rings.
 This ability to bond in so many ways makes a huge number
of carbon structures possible.
 Isomers - compounds that have the same chemical formula
but different three-dimensional shape
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Carbon compounds vary in size.
◦ Polymer - a large molecule
formed when many smaller
molecules bond together
Carbohydrate - a biomolecule
composed of carbon, hydrogen,
and oxygen with a ration of two
hydrogen atoms and one oxygen
atom for every carbon atom
◦ 2 Hydrogen:Oxygen:Carbon
◦ Starch consists of branched
chains of glucose units and is
used as energy storage by plant
cells and as food reservoirs in
seeds and bulbs.
◦ Mammals store energy in the
liver in the form of glycogen.
◦ Cellulose is another glucose
polymer that forms the cell
walls of plants and gives plants
structural support.
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Lipids - large biomolecules that are made mostly of
carbon and hydrogen with a small amount of oxygen
◦ Lipids are fats, oils, waxes, and steroids.
◦ Lipids are important for the proper functioning of
organisms.
 They make up the membranes that surround all
living cells.
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Protein - a large, complex polymer composed of
carbon, hydrogen, oxygen, nitrogen, and sometimes
sulfur
◦ Proteins are made up of amino acids.
 Amino acids - molecules containing an amine
group, carboxylic acid group, and a side-chain
◦ Peptide bonds - covalent bonds that form between
amino acids
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Number and sequence of amino acids that make up a
protein are important to determine its shape.
◦ The shape of a protein is extremely important, if the
shape is wrong the protein cannot carry out the proper
function.
Enzymes - proteins that change the rate of a chemical
reaction
◦ Enzymes are involved in nearly all metabolic processes.
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Nucleic acid - a complex biomolecule that stores cellular
information in the form of a code
◦ Nucleic acids are polymers made of smaller subunits
called nucleotides.
◦ Nucleotides - made up of carbon, hydrogen, oxygen,
nitrogen, and phosphorous arranged in a nitrogenous
base, a simple sugar, and a phosphate group
◦ Nucleic acids make up DNA and RNA.
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Cell: the basic unit of living organisms
Compound light microscope: a microscope that
uses a series of lenses to magnify objects
Cell Theory: the theory that describes what cells
are and what defines a cell
Electron Microscope: a microscope that uses a
beam of electrons instead of light to magnify
structures
Organelle: small specialized structures within all
cells
Prokaryote: cells that do not have membranebound organelles
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Eukaryote: cells that contain membrane-bound
organelles
Nucleus: the central membrane-bound organelle
that manages or controls cellular functions
Plasma Membrane: the flexible boundary between
the cell and its environment
Selective Permeability: a process in which a
membrane allows some molecules to pass through
while keeping others out
Phospholipid: a molecule with a glycerol backbone,
two fatty acid chains, and a phosphate group
Transport Protein: are proteins that move needed
substances or waste materials through the plasma
membrane
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Until the development of the
microscope, human beings did not
know about the causes of illnesses
and disease.
◦ Cells - the basic unit of living
organisms
◦ The microscope was invented in
the 1600s by Anton van
Leeuwenhoek and was used to
view objects.
 Over the following 200 year
scientists would improve
microscopes by grinding higher
quality lenses and developing
the compound light microscope.
 Compound light microscopes
- a microscope that uses a
series of lenses to magnify
objects
 They can magnify objects up
to 1500 times.
 With microscopes the
organization of life was seen.
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Robert Hooke studied cork and he observed small geometric
shapes.
◦ Hook called the structures cells because the cork cells
reminded him of the small rooms that monks lived in.
Hooke’s observations were expanded on by many other
scientists.
◦ Matthias Schleiden observed plants and concluded that all
plants were composed of cells.
◦ Theodor Schwann observed animals and concluded that all
animals were composed of cells.
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The cell theory is made up of three main ideas:
◦ All organisms are composed of one or more cells.
◦ The cell is the basic unit of structure and
organization of organisms.
◦ All cells come from preexisting cells.
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In the 1930-1940’s the electron microscope was
developed.
◦ Electron microscope - a microscope that uses a beam
of electrons instead of light to magnify structure up to
500,000 times their actual size
◦ This allowed scientists to see inside of cells.
◦ This also gave a three dimensional image.
◦ Organelles - small specialized structures within all
cells
 Most organelles are surrounded by membranes.
 Each organelle has a specific function within the
cell.
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Cells are divided up into
two broad groups:
◦ Prokaryote cells - cells
that do not have
membrane-bound
organelles
◦ Eukaryote cells - cells
that contain membranebound organelles
◦ Prokaryotes are mostly
unicellular organisms
while Eukaryotes are
mostly multicellular
organisms.
 Some prokaryotes have
more than one cell while
come eukaryotes are
single cells.
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When comparing prokaryotes and eukaryotes the
important thing to notice is the organelles.
◦ Organelles benefit the eukaryotic cells.
 They perform chemical reactions that would not occur
in the same area.
◦ Organelles can be identified and some are rather
prominent to the cell.
 Nucleus - the central membrane-bound organelle that
manages or controls cellular functions
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Living cells must maintain a balance regardless of internal and
external conditions.
◦ Plasma membrane - the flexible boundary between the cell
and its environment
 The plasma membrane allows nutrients like glucose,
amino acids, and lipids into the cell.
 Too many nutrients can be harmful to the cell.
 Waste and other products leave the cell through the
plasma membrane.
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Selective permeability - a process in which a membrane allows
some molecules to pass through while keeping others out
◦ This helps with homeostasis.
◦ Molecules like water can freely enter the cell through the
plasma membrane.
◦ Particles such as sodium and calcium ions must be allowed
into the cell at only certain times, in certain amounts, and
through certain channels.
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Phospholipid - a molecule
with a glycerol backbone,
two fatty acid chains, and a
phosphate group
◦ Phospholipids make up
the plasma membrane by
making two layers of
phospholipids back-toback.
◦ The phospholipid group is
critical for the formation
and function of the plasma
membrane.
 The polar phosphate
group allows the cell
membrane to interact
with its watery
environment (because
water is polar).
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◦ The phospholipid membrane
is special because while water
can pass easily through the
polar layers, the lipid layers
can stop anything that is
water-soluble
 If something that is watersoluble means that it is
something dissolved in
water.
 So if something is bonded
to the water molecule it
cannot slip through the
phospholipid layers.
The fluid mosaic model is a
model of the plasma
membrane.
◦ Proteins are located
throughout the plasma
membrane giving the mosaic
appearance.
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Cholesterol is also found in the plasma membrane because it
helps to stabilize the phospholipids by preventing their fatty
acid tails from sticking together.
◦ Like many substances people need, if a person has too much
cholesterol there is a health risk, however, without any
cholesterol there are still great health risks.
◦ Transport proteins - are proteins that move needed
substances or waste materials through the plasma
membrane
 Waste goes out, needed substances go in.
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Other proteins and carbohydrates that stick out from the
cell are to identify chemical signals and each other.
◦ This is important to protect cells from infection.
Proteins on the inside of the plasma membrane play a
role attaching the plasma membrane to the cell’s internal
support structure giving the cell its flexibility.
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Cell wall: a fairly rigid structure located outside the
plasma membrane that provides additional support
and protection in plants
Nucleolus: the structure that makes ribosomes
Ribosome: the sites where the cell produces
proteins according to the directions of DNA
Cytoplasm: the clear gelatinous fluid inside a cell
Endoplasmic reticulum: the site of cellular chemical
reactions
Golgi apparatus: the organelle that sorts proteins
into packages and packs them into membranebound structures
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Vacuole: structures that are temporary storage
sites for materials
Lysosome: organelles that contain digestive
enzymes
Chloroplast: cell organelles that capture light
energy and convert it to chemical energy
Chlorophyll: the green pigment that traps light
energy and give leaves and stems their color
Mitochondria: organelles that transform energy for
the cell
Cytoskeleton: the support structure within the cell
Centrioles: organelles found in animals and
protists which are important in cell division
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Eukaryote cells are made up of many parts, those parts
can identify what types of cells that are being dealt with:
plant or animal.
◦ The fluid mosaic model describes the plasma
membrane as a flexible boundary of a cell, however
many other cells have an additional boundary, the cell
wall.
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Cell wall - a fairly rigid structure located outside the
plasma membrane that provides additional support and
protection in plants
It forms an inflexible barrier that protects the cell and
gives it support.
This wall is very porous and allows molecules to enter
◦ Unlike the plasma membrane, it does not select which
molecules can enter into the cell.
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The nucleus is the leader of the eukaryotic cell because it
contains the directions to make proteins.
◦ The nucleus controls the activity of the organelles
◦ The master set of directions for making proteins is
contained in chromatin, which are strands of DNA.
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Inside the nucleus is the
nucleolus.
◦ Nucleolus - the structure
that makes ribosomes
◦ Ribosomes - the sites
where the cell produces
proteins according to the
directions of DNA
 Ribosomes are not
bound in a membrane
◦ For proteins to be made,
ribosomes must move out
of the nucleus and into
the cytoplasm.
 Cytoplasm - the clear
gelatinous fluid inside a
cell
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Endoplasmic reticulum (ER) - the
site of cellular chemical reactions
◦ Ribosomes in the cytoplasm are
attached to the surface of the
endoplasmic reticulum, called
rough endoplasmic reticulum,
and they carry out the function
of protein synthesis
◦ Each protein made in the rough
ER has a particular function:
 Becoming part of the plasma
membrane
 Part of another organelle
◦ The smooth ER is involved in
numerous biochemical activities
such as the production and
storage of lipids.
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Golgi apparatus - the organelle that sorts proteins into
packages and packs them into membrane-bound
structures called vesicles
◦ The Golgi’s vesicles are like envelopes being sent
through the mail to specific locations.
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Vacuoles - structures that are temporary storage sites for
materials
◦ Vacuoles are basically sacks with food, enzymes, and
other materials.
◦ Some contain waste.
◦ Vacuoles are massive in plants but small in animals.
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Lysosomes - organelles that contain digestive enzymes
◦ They digest excess or worn out organelles, food, and
engulf viruses/bacteria.
◦ They can fuse with the vacuoles and dispense their
enzymes to digest the vacuole’s contents.
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Chloroplasts - cell organelles that capture light
energy and convert it to chemical energy
◦ These are plant organelles and are called plastids
◦ Plastids are used for storage and can store lipids or
starches.
◦ Plastids are named for their color pigment
◦ Chlorophyll - the green pigment that traps light
energy and give leaves and stems their color
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Mitochondria - in both plants and animals, organelles
that transform energy for the cell
◦ Energy produced here will be stored in the bonds of
other molecules that the cell organelles can access
easily and quickly when energy is needed.
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Cytoskeleton - the support structure within the cell
◦ Microtubules are thin, hollow cylinders made of protein
◦ Microfilaments are smaller, solid protein fibers.
◦ Microtubules and microfilaments act as a scaffold to
maintain the shape of the cell like the poles in a tent.
Centrioles - organelles found in animals and protists which are
important in cell division

Some cells require special organelles to move and there are
two main types
◦ Cilia - short, numerous projections that look like hairs and
their motion is like that of a rowboat
◦ Flagella - longer projections that move with a whip-like
motion
 A cell only has one or two flagella.
◦ In single cell organisms cilia and flagella are the major
means of locomotion.
1) Cell Membrane
2) Cytoplasm
3) Nucleus
4) Chromosomes
5) Nucleolus
6) Ribosomes
7) Endoplasmic reticulum
8) Mitochondria
9) Vacuoles
10) Golgi apparatus
11) Centrioles