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UNIT THREE: CELLULAR ENERGY AND REPRODUCTION
MAIN IDEA: ALL LIVING ORGANISMS USE ENERGY FOR BIOLOGICAL PROCESSES
OBJECTIVE 1: SUMMARIZE THE TWO LAWS OF THERMODYNAMICS
A. Cellular activities require energy, the ability to do work.
B. Thermodynamics is the study of flow and transformation of energy in the universe and consists of
two laws.
1. Law of Conservation of Energy – energy can be converted from one form to another but cannot
be created or destroyed.
2. Entropy increases – energy cannot be converted without the loss of useable energy, Energy that
is “lost” is usually converted to thermal energy.
OBJECTIVE 2: COMPARE AND CONTRAST AUTOTROPHS AND HETEROTROPHS
A. Directly or indirectly, nearly all the energy for life comes from the sun.
B. Autotrophs are organisms that make their own food.
1. Chemoautotrophs use inorganic substances like hydrogen sulfide as a source of energy.
2. Photoautotrophs convert light energy from the Sun into chemical energy.
C. Heterotrophs are organisms that need to ingest food to obtain energy.
OBJECTIVE 3: EXPLAIN THE NEED FOR ENERGY AND DESCRIBE METABOLIC PATHWAYS
A. Energy is essential to life.
B. All living organisms must be able to:
1. produce energy from the environment in which they live
2. store energy for future use
3. use energy in a controlled manner
C. Uses of energy may be physical or on the cellular level:
1. build molecules, membranes and organelles
2. maintain homeostasis
D. All the chemical reactions in a cell are called the cell’s metabolism.
E. Metabolic pathways are a series of reactions in which the product in one reaction is the substrate for
the next reaction. There are two types of metabolic pathways:
1. Catabolic: releases energy by breaking down larger molecules into smaller molecules
2. Anabolic: uses the energy released from catabolic pathways to build larger molecules from
smaller molecules.
F. Energy continually flows between the metabolic reactions of organisms in the ecosystem.
G. Photosynthesis is the anabolic pathway in which light energy from the sun is converted into
chemical energy for use by the cell.
1. Autotrophs use light energy, carbon dioxide, and water to form glucose and oxygen.
H. Cellular respiration is the catabolic pathway in which organic molecules are broken down to release
energy for use by the cell.
1. Oxygen is used to break down organic molecules resulting in the production of carbon dioxide
and water.
OBJECTIVE 4: DESCRIBE HOW ATP STORES AND RELEASES ENERGY AND WORKS IN A CELL
A. Energy for the cell is stored in chemical bonds of the energy molecule ATP (Adenosine
triphosphate).
B. ADP + P = ATP (high energy compound) See fig. 8.4 page 221
C. When bonds in food are broken, that energy is used indirectly to form ATP.
D. When the chemical bond between phosphate groups is broken, a great amount of energy is released
and the resulting molecule is ADP.
E. The formation/breakdown recycling activity keeps the cell from having to store all of the ATP it needs.
1. As long as phosphate molecules are available, the cell has an unlimited supply of energy.
2. ADP can also be used as an energy source.
F. To access the energy stored in ATP, proteins(enzymes) bind to ATP and allow the phosphate group
to be released. The ADP that is formed is released and the binding site can once again be filled by
ATP.
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MAIN IDEA: LIGHT ENERGY IS TRAPPED AND CONVERTED INTO CHEMICAL ENERGY DURING
PHOTOSYNTHESIS
OBJECTIVES 5: GIVE AN OVERVOEW OF PHOTOSYNTHESIS AND EXPLAIN THE LIGHT
DEPENDENT REACTIONS
A. Photosynthesis is the process plants use to trap the sun’s energy and build carbohydrates (glucose)
that store energy.
B. The process of photosynthesis occurs in two phases
1. The first phase (Light Dependent) converts light energy from the sun into chemical energy (ATP)
2. The second phase (Light Independent) uses the ATP to make glucose
3. Summary equation of photosynthesis:
6CO2 + 6 H2O ----LIGHT --- C6H12O6 + 6O2
C. First phase of photosynthesis is the light dependent reaction and it occurs in the thylakoid
membrane, flattened saclike membranes arranged in stacks, of the chloroplast
1. The thylakoids form stacks called grana.
2. Uses the pigment chorophyll within the organelles membrane to absorb the wavelengths from
the sun.
3. Chlorophyll a and b absorb most wavelengths of light but green. Green is reflected so the plant
appears green.
D. Most photosynthetic plants have other pigments to trap light.
1. Carotenoids reflect yellow, orange and red light and absorb blue and green regions of the
spectrum. These produce the colors of sweet potatoes and carrots.
2. Chlorophyll is most abundant, hiding the other pigments, but in some trees prepare for winter the
chlorophyll breaks down to reveal other colors.
E. Summary of light dependent reaction:
1. Energized or excited electrons in the pigments of the chloroplasts are used to generate ATP and
NADPH2. More electrons are supplied by H2O.
2. See page 225 in your textbook for diagram.
Photons
4e-
4ee-
ee-
ADP
ATP
ee-
ADP
e-
4e2H2O
4H+ + O2
ATP
ee-
4e-
e2NADP + 2H+
NADPH2
F. ATP is made during the electron transport chain by the process of chemiosmosis – the mechanism by
which ATP is produced as a result of the flow of electrons down a concentration gradient.
1. The breakdown of water is important for two reasons:
a. water provides the electrons that initiate the ETC
b. Water provides the protons (H+) needed to drive ATP synthesis during chemiosmosis
OBJECTIVE 6: DESCRIBE THE LIGHT-INDEPENDENT CALVIN CYCLE
A. The second phase of photosynthesis is called the Calvin Cycle in which energy is stored in organic
molecules like glucose.
1. Does not require light
2. Takes place in the stroma of the chloroplast
B. Uses the ATP and the NADPH2 from the light reaction and CO2 from the atmosphere to synthesize
carbohydrates (glucose).
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1. Although NADP and ATP provide cells with large amounts of energy, these molecules are not
stable enough to store chemical energy for long periods of time.
2. Resulting ADP and NADP can be reused in the light reaction.
3CO2
3C6
6C3
3C5
ATP
ADP + P
NADPH2
NADP + 2H
Calvin
Cycle
ATP
ADP + P
5C3
6C3
C3 (PGAL)
3. The enzyme rubisco converts the remaining gylceraldehyde (C3) into ribulose biphosphate (C5).
a. Because rubisco converts inorganic carbon dioxide into organic molecules that can be used
by the cell, rubisco is considered one of the most important biological enzymes.
MAIN IDEA: LIVING ORGANISMS GET ENERGY BY BREAKING DOWN ORGANIC MOLECULES
DURING CELLULAR RESPIRATION
OBJECTIVES 7: SUMMARIZE THE STAGES OF CELLULAR RESPIRATION AND IDENTIFY THE
ROLES OF ELECTRON CARRIERS IN EACH STAGE OF CELLULAR
RESPIRATION
A. Cellular respiration is the process by which the mitochondria, using many small steps, break down
nutrients to produce ATP (energy).
1. Electrons are harvested from carbon compounds, like glucose, to make ATP. ATP allows cells to
do work.
2. The overall equation for respiration is the opposite of the equation for photosynthesis.
C6H12O6 + O6  6CO2 + 6H2O + Energy
B. Cellular respiration occurs in three steps. The first step is glycolysis and is an anaerobic process
because it does not require oxygen. The second and third steps, Kreb’s Cycle and the Electron
Transport chain are aerobic respiration because both use oxygen.
1. Glycolysis (see page 229)
a. occurs in the cytoplasm
b. split glucose (C6) into two pyruvic acid molecules (C3)
c. costs 2 ATP to do the reactions but you make 4 ATP so the net gain is 2 ATP
d. reduce NAD (add H)  NADH2 (using electrons from glucose)
e. summary: the energy from glucose is transferred to ATP and NADH2
2H + NAD  NADH2
C6
2C3 (pyruvic acid/pyruvate)
2ADP + 2P  2ATP
f. convert pyruvic acid to acetyl CoA
NAD + 2H  NADH2
2C3
pyruvic acid
2C2 + 2CO2
acetyl CoA
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2. Kreb’s/Citric Acid Cycle/Tricarboxylic Cycle (see page 231)
a. occurs in the mitochondria
b. start with a C2 compound called acetyl CoA (small portion of glucose) and shift the energy to
NADH2, FADH2, and a little ATP. The carbons in the acetyl CoA will be released as CO 2.
C2 (acetyl CoA)
CO2
C6
NAD + 2H
NADH2
Kreb’s
Cycle
C4
C5
FAD + 2H
FADH2
NAD + 2H
NADH2
ADP + P
ATP
CO2
NAD + 2H
NADH2
C4
3. Electron Transport Chain (ETC) (see page 231)
a. occurs in the mitochondria
b. takes the energy stored in the NADH2 and the FADH2 and make ATP!
c. The ETC is a series of electron acceptors(proteins) in the membrane of the mitochondria.
d. NADH2 and FADH2 drop their electrons (held by H atoms) at the top of the chain. NAD and
FAD can now be reused in any of the first three steps.
e. The electrons are passed through the chain, with the acceptors gaining and losing the
Hydrogen atoms.
f. As the electrons are passed through the chain, ATP is made.
g. Oxygen catches (bonds) with the electrons at the end of the chain and forms H 20.
NADH2
NAD + 2H+
ee-
FADH2
FAD + 2H+
eeeADP + P
e-
ATP
ee2H+ + O  H2O
h. Overall the ETC makes 32 ATP molecules; it is very efficient!
C. Some prokaryotes also undergo aerobic respiration but because they have no mitochondria there are
some differences
1. The cell membrane is the site of the ETC as there is no mitochondria in prokaryotes
2. With no mitochondria, the pyruvate is not transported, saving the prokaryote 2 ATP and yielding a
net total of 38 ATP, not 36.
OBJECTIVE 8: COMPARE ALCOHOLIC FERMENTATION AND LACTIC ACID FERMENTATION
A. An anaerobic process (fermentation) can produce ATP for short periods of time in the absence of
oxygen, but it’s not efficient enough to generate sufficient quantities of ATP for all of a multicellular
organisms needs.
B. Anaerobic respiration begins with glycolysis just like before:
C6
2H + NAD  NADH2
2C3 (pyruvic acid)
2ADP + 2P  2ATP
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C. The second part of anaerobic respiration follows two pathways, lactic acid fermentation or
alcoholic fermentation. In both, NADH2 releases 2H to make NAD. NAD can be reused in
glycolysis.
2C3
pyruvic acid
NADH2
NAD + 2H
2C2 (ethanol) + 2CO2
lactic acid 2C3
1. Lactic acid fermentation supplies energy to your muscles when oxygen is scarce but only
makes 2 ATP. Lactic acid build up in your muscles will make them sore (muscle fatigue).
2. Alcoholic fermentation is used under normal conditions by simple organisms like yeast.E.
D. Compare aerobic to anaerobic respiration
Steps
# ATP
Organisms:
Aerobic respiration
Glycolysis
acetyl CoA
Kreb’s cycle
ETC
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Single-celled and a must for
multicellular organisms
Anaerobic respiration
Glycolysis
Fermentation
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Single-celled and a backup for
multicellular organisms
OBJECTIVE 9: COMPARE AND CONTRAST PHOTOSYNTHESIS AND CELLULAR RESPIRATION
A. See page 233
B. Similarities: Both are metabolic pathways thatuse electron carriers, ETC’s, and have cycles
C. One of the end products of cellular respiration is CO2, which is one of the beginning reactants for
photosynthesis. The oxygen produced during photosynthesis is a critical molecule necessary for
cellular respiration.
MAIN IDEA: CELLS GROW UNTIL THEY REACH THEIR SIZE LIMIT, THEN THEY EITHER STOP
GROWING OR DIVIDE
OBJECTIVE 10: DESCRIBE SEVERAL MECHANISMS THAT LIMIT CELL SIZE
A. Surface area-to- volume ratio (see page 244)
1. The key factor that limits cell size where surface area refers to the area covered by the plasma
membrane and volume refers to the space taken by the inner contents of the cell, including
organelles.
2. As the cell surface area grows, its volume increases dramatically. More resources are needed by
organelles and more waste is produced.
3. As a cell grows, it reaches a point where the surface area is not large enough to transport
resources and wastes to allow the cell to survive.
4. By remaining small, cells have a higher ratio of surface area to volume and can sustain
themselves more easily.
B. Transport of substances
1. Diffusion does not efficiently move nutrients and waste when cells are large. It would take too
long as it depends on random movement of molecules and ions.
2. The cytoskeleton transportation network is less efficient and motor proteins can’t pull substances
for long distances.
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C. Cellular communication
1. Cell size affects the ability of the cell to communicate instructions for cellular functions.
2. If the process for signaling proteins to move throughout the cell becomes too slow, the cell can’t
function.
OJECTIVE 11: SUMMARIZE THE PRIMARY STAGES OF THE CELL CYCLE
A. Once a cell reaches its size limit, it will stop growing or it will divide. Most cells eventually divide.
1. Dividing keeps the cell the right size and it is the way the cell reproduces so that organisms grow
and heal certain injuries.
B. Cells reproduce by a cycle of growing and dividing called the cell cycle. (see pages 246 and 249).
C. There are three main stages to the cell cycle:
1. Interphase is the stage during which the cell grows, carries our cellular functions, and makes
copies of DNA (replicates) as it prepares for the next stage of the cycle.
2. Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide.
3. Cytokinesis occurs near the end of mitosis and is when the cell’s cytoplasm divides.
D. Duration of the cell cycle varies, depending on the cell that is dividing.
1. For most normal, animal cells, the cycle takes about 12 to 24 hours.
OBJECTIVE 12: DESCRIBE THE STAGES OF INTERPHASE
A. Interphase is a period of active growth and development and divided into three stages.
1. G1 - occurs immediately after the cell divides; cell grows and performs normal functions,
prepares the cell for DNA replication.
2. S - second phase; the cell copies its DNA in preparation for cell division.
a. Chromosomes are the structures that contain the genetic material that is passed from
generation to generation of cells.
b. Chromatin is the relaxed form of DNA in the cell’s nucleus.
3. G2 - Follows the S stage and is when the cell prepares for the division of its nucleus, by making
special proteins and taking an inventory of its organelles and compounds.
MAIN IDEA: EUKARYOTIC CELLS REPRODUCE BY MITOSIS, THE PROCESS OF NUCLEAR
DIVISION, AND CYTOKINESIS, THE PROCESS OF CYTOPLASM DIVIDING
OBJECTIVE 13: DESCRIBE THE EVENTS IN STAGE OF MITOSIS
A. In mitosis the cell’s replicated genetic material separates and the cell prepares to split into two cells.
B. The key activity of mitosis is the accurate separation of the cell’s replicated DNA.
1. This enables the cell’s genetic information to pass into the new cells intact, resulting in genetically
identical daughter cells.
C. Mitosis increases the number of cells as young organisms grow into its adult size.
D. Mitosis is used by organisms to replace damaged cells.
E. Mitosis is divided into phases
1. Prophase:
a. stage during mitosis in which the cell spends most of its time
b. chromatin tightens (condenses) into chromosomes, shaped like an X
c. Each half of the X is a sister chromatid, structures that contain identical copies of DNA.
d. centromeres are at the center of the chromosome, to which the sister chromatids are
attached. Centromeres ensure that a complete copy of the replicated DNA will become part
of the daughter cells at the end of the cell cycle.
e. Nuclear membrane and nucleolus both disappear
f. spindle fibers begin to form between the poles
g. centrioles (animal cells only) begin to migrate toward the poles
2. Metaphase:
a. chromosomes attach to mitotic spindle and line up in the middle or equator of the cell
b. the centromeres duplicate
3. Anaphase:
a. chromatids move apart as microtubules of the spindle apparatus shorten
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4. Telophase:
a. Chromosomes arrive at the poles and begin to relax or decondense.
b. nuclear membrane begins to form around each nucleus and the nucleoli reappear
c. spindle apparatus disassembles
OBJECTIVE 14: EXPLAIN THE PROCESS OF CYTOKINESIS
A. Animals: begins during late anaphase, completed in telophase, microfilaments contract, pinching the
cytoplasm to create a furrow.
B. Plants: a cell plate forms across the middle with cell walls forming on either side of the cell plate.
C. Results of mitosis
1. Guarantees genetic continuity, resulting in two new cells with chromosomes that are identical to
those of the parent cell.
2. Cell growth and reproduction result in groups of cells that work together as tissue and perform a
specific function. Tissues organize in various combinations to form organs and organs work
together to form organ systems.
MAIN IDEA: THE NORMAL CELL CYCLE IS REGULATED BY CYCLIN PROTEINS
OBJECTIVE 15: SUMMARIZE THE ROLE OF CYCLIN PROTEINS IN CONTROLLING THE CELL
CYCLE
A. The timing and rate of cell division are important to the health of the organism.
B. A mechanism using proteins and enzymes control the cell cycle.
1. Proteins called cyclins bind to enzymes called cyclin-dependent kinases (CDKs) in the stages
of interphase and mitosis to start various activities that take place in the cell cycle.
a. In the G1 stage of interphase, cyclin and CDKs signal the start of the cell cycle.
b. Different cyclin/CDK combinations signal other activities:
(1) DNA replication
(2) protein sysnthesis
(3) nuclear division
(4) termination/end of cell cycle
c. Check points monitor the cell cycle for errors and can stop the cycle if an error occurs.
(1) monitors DNA damage at the end of G1
(2) spindle checkpoints can stop cytokinesis
OBJECTIVE 16: EXPLAIN HOW CANCER RELATES TO THE CELL CYCLE
A. Cancer is the uncontrolled growth and division of cells – a failure in the regulation of the cell cycle.
B. When unchecked, cancer cells can kill an organism by crowding out normal cells, resulting in loss of
tissue function.
C. Cancer cells spend less time in interphase than do normal cells, so cancer cells grow and divide
unrestrained as long as they have essential nutrients.
D. Enzyme production is directed by genes located on a chromosome.
1. Genes are segments of DNA that control the production of a protein.
E. Cells can lose control of the cell cycle if mutations or changes to the DNA occur.
F. Uncontrolled dividing of the cell may be caused by:
1. failure to make certain enzymes
2. overproduction of enzymes
3. production of enzymes at the wrong time.
G. Substances and agents that are known to cause cancer are called carcinogens
1. The Food and Drug Administration (FDA) works to make sure what you eat and drink are safe.
a. requires labels and warnings on products that might be carcinogens
2. Industrial laws can help limit exposure to carcinogens
3. Causes may be avoidable like avoiding tobacco of all kinds, including second hand smoke
4. Some causes are unavoidable like U.V. radiation from the sun…USE SUNSCREEN! Other forms
of radiation like x-rays are used for medical purposes and your exposure is relatively low.
H. More than one change in DNA is needd to change an abnormal cell into a cancer cell.
1. Over time, there might be many changes, so this may be why risk of cancer increases as we get
older.
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2.
Someone who inherits one or more changes from a parent is at higher risk for developing some
cancers and this might be why some forms of cancers run in some families.
OBJECTIVE 17: WAYS TO POTENTIALLY REDUCE CANCER
A. There is a clear link between a healthy lifestyle and the incidence of cancer.
B. Certain diets may reduce your risk of some cancers:
1. low fat; high fiber (fruits, vegetables, and grains)
2. Certain vitamins and minerals may also help to prevent cancer (carotenoids, vitamins A, C, E,
and calcium)
C. Healthy lifestyle may reduce risk
1. daily exercise
2. avoid tobacco
OBJECTIVE 18: DESCRIBE THE ROLE OF APOPTOSIS
A. Not every cell is destined to survive and when an embryo divides, some cells go through a process
called apoptosis, or programmed cell death.
1. Cells shrink and shrivel in a controlled process
2. Seen in human hands and feet…the webbing between our fingers and toes is not present in the
mature organism.
3. In plants, apoptosis is responsible for leaves falling from trees during autumn.
4. Occurs in cells that are damaged beyond repair, including those with DNA damage that could
lead to cancer, thus protecting organisms from cancerous growths.
OBJECTIVE 19: DESCRIBE THE TWO TYPES OF STEM CELLS AND THEIR POTENTIAL USES
A. While most of your cells are designed for a specialized function, stem cells are unspecialized
until the right conditions are met.
B. Stem cells can remain in an organism for many years while undergoing cell division
C. There are two types of stem cells:
1. Embryonic stem cells
a. After fertilization the zygote rapidly divides (mitosis) until there are about 100-150
unspecialized cells.
b. If separated, each of these cells have the capability of developing into a wide variety of
specialized cells. Left alone, the embryo continues to divide and the cells specialize into
various tissues, organs, and organ systems.
c. Embryonic stem cell research is controversial because of the ethical concerns about the
source of cells.
2. Adult stem cells
a. Found in various tissues in the body and might be used to maintain and repair the same kind
of tissue in which they were found. These stem cells are found even in newborns, not just
adults.
b. Certain kinds of adult stem cells also might be able to develop into different kinds of cells,
providing new treatments for many diseases and conditions.
c. Less controversial because the adult stem cells can be obtain with the consent of the owner.
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