Unit 3 and 4 Biology Review
Building Molecules That Store Energy
• Metabolism involves either using energy to build
molecules or breaking down molecules in which energy
is stored.
• Photosynthesis: process by which light energy is
converted to chemical energy.
• Autotrophs: organisms that use energy from sunlight
of from chemical bonds in inorganic substances to
make organic compounds.
– Most Autotrophs are photosynthetic organisms.
Breaking Down Food For Energy
• Chemical energy in organic compounds can be
transferred to other organic compounds or to
organisms that consume food.
• Heterotrophs: organisms that must get energy from
food instead of directly from sunlight or inorganic
substances. Heterotrophs get energy from food
using cellular respiration.
• Cellular respiration: a metabolic process that
releases energy in food to make ATP which can
provide the cell with the energy it needs.
ATP
• ATP or Adenosine triphosphate is a nucleotide with two extra
energy-storing phosphate groups.
• The phosphate groups store energy like a compressed
spring—the energy is released when the bonds holding the
phosphate groups together is broken.
• The removal of a phosphate group from ATP makes ADP, or
Adenosine diphosphate in the following reaction:
H20 + ATP  ADP + P + ENERGY!!!
Photosynthesis: Using the Energy in Sunlight
• There are three stages in Photosynthesis:
– Stage 1: Absorption of Light Energy—Energy is captured
from sunlight.
– Stage 2: Conversion of Light Energy—Light energy is
converted to chemical energy, which is temporarily
stored in ATP and the energy carrier molecule NADPH.
– Stage 3: Storage of Energy—The chemical energy
stored in ATP and NADPH powers the formation of
organic compounds, using carbon dioxide.
• Stages 1 and 2 of photosynthesis are light-dependent
reactions.
6 CO2 + 6H2O  C6H12O6 + 6O2
Carbon
dioxide
Sunlight
Water
Glucose
(sugar)
Oxygen
gas
Stage 1: Absorption of
Light Energy—Energy
is captured from
sunlight.
Stage 2: Conversion of
Light Energy—Light
energy is converted
to chemical energy,
which is temporarily
stored in ATP and the
energy carrier
molecule NADPH.
Stage 3: Storage of
Energy—The
chemical energy
stored in ATP and
NADPH powers the
formation of organic
compounds, using
carbon dioxide.
The Stages of
Photosynthesis
Stage One: Absorption of Light Energy
• Stage one is LIGHT DEPENDENT!
• Pigments: structures that absorb light in
certain wavelengths and reflect all others.
• Chlorophyll: primary pigment involved in
photosynthesis; absorbs blue and red light
and reflects green and yellow light. Two
types: chlorophyll a and chlorophyll b
• Cartenoids: pigments that produce fall
colors.
Factors that Affect Photosynthesis
• Photosynthesis is directly affected by various
environmental factors.
– The rate of photosynthesis increases as light
intensity increases until all pigments are being
used, when the Calvin cycle cannot proceed any
faster
– The carbon dioxide concentration affects the
rate of photosynthesis.
– Photosynthesis is also more efficient within a
certain range of temperatures (enzymes are
involved!)
Cellular Energy
• Your cells transfer the energy in organic
compounds, like glucose, to ATP through a process
called cellular respiration.
• Oxygen you breath in air makes the production of
ATP more efficient, although some ATP is made
without oxygen.
• Aerobic: metabolic processes that require oxygen
• Anaerobic: metabolic process that do not require
oxygen.
The Stages of Cellular Respiration
• Stage 1: Glucose is converted
to pyruvate, producing a small
amount of ATP and NADH.
• Stage 2: Pyruvate an NADH are
used to make a large amount
of ATP in a process called
aerobic respiration, occurring
in mitochondria.
– Krebs cycle and electron
transport chain take place,
making more ATP.
Glucose
(sugar)
Oxygen
Gas
Carbon
Dioxide
Water
C6H12O6 + 6O2  6CO2 + 6H2O + ATP energy
Respiration in the
Absence of Oxygen
• If there is not enough
oxygen for aerobic
respiration to occur, there is
no electron transport chain
• Under anaerobic
conditions, fermentation
occurs.
– Lactic Acid Fermentation
– Alcoholic Fermentation
Production of ATP
Total ATP Production
• Glycolysis: 2 ATP
• Krebs Cycle: 2 ATP
• Electron Transport Chain: Up to 34 ATP
The Path of Air
Alveoli: tiny air sacs in the
lungs where oxygen and
carbon dioxide gases are
exchanged.
• Air enters the respiratory
system through the nose
or mouth. About 21% is
oxygen gas.
• Air passes through the
pharynx and continues to
the larynx, or voice box.
• Air then passes into the
trachea, or windpipe
which divides into two
smaller tubes called
Bronchi, which branch
into the lungs.
• Within the lungs, smaller
tubes called bronchioles
divide off.
• Finally, the smallest
bronchioles reach air sacs
called alveoli where
gasses are actually
exchanged.
1. Oxygen reaches lungs.
2. Oxygen diffuses from alveoli
to capillaries (tiny blood
vessels surrounding alveoli).
3. Oxygen rich blood travels to
the heart.
4. Oxygen diffuses from the
blood into the cells for
aerobic respiration.
5. Carbon dioxide diffuses to
the blood from cells.
6. Most carbon dioxide travels
to the heart.
7. The heart pumps blood to
lungs. Carbon dioxide is
released to the alveoli.
8. Carbon dioxide is expelled in
exhalation.
Gas Transport:
Oxygen Transport
• Carbon dioxide is also
taken in by blood in
three forms.
– 7% is dissolved in
blood plasma.
– 23% is attached to
hemoglobin
molecules inside red
blood cells.
– 70% is carried in the
blood as bicarbonate
ions (H2CO3).
Gas Transport: Carbon
Dioxide Transport
Is a Virus Alive?
• Living things are made of cells, are able to grow and
reproduce, and are guided by information store in their
DNA.
• Virus: segments of nucleic acids contained in a protein
coat.
– Viruses are not cells and are even smaller than prokaryotes.
– Viruses replicate by infecting cells and using the cell to make
more viruses.
• Pathogens: agents that cause disease.
– Viruses are pathogens.
• Viruses do not have all the properties of life, and are
subsequently not considered to be living.
• Viruses do not grow, do not have homeostasis, and do
not metabolize.
Discovery of Viruses
• Scientists trying to find the
cause of the tobacco mosaic
disease found that if they
strained infected sap, they
could still infect plants. This
told scientists that the
pathogen was smaller than a
bacterium.
• For many years, viruses were
thought to be tiny cells.
• Eventually, Wendell Stanley
concluded that TMV is a
chemical rather than an
organism—each particle is
composed of RNA or DNA and a
protein.
Viral Structure
• Capsid: virus protein coat, which contains RNA or DNA.
• Envelope: structure surrounding capsid which allows
viruses to enter cells. Made of:
– Proteins, Lipids, and Glycoproteins
• Bacteriophage: a virus that enters bacteria that has a
complex structures.
Viral Replication
• Viruses lack the enzymes necessary for
metabolism and have no structures to make
protein.
• Viruses must rely on living cells (host cells) for
replication. Before a virus and replicate, it
must infect a living cell.
• An animal virus enters its host through
endocytosis.
• Bacteriophages punch holes in cell walls and
inject DNA
Lytic Cycle
• Lytic Cycle: the cycle of viral infection, replication, and
cell destruction.
• After viral genes have entered the cell, they use the cell
to replicate viral genes and to make viral proteins which
are then assembled to make complete viruses. The
host cell is broken open and releases newly made
viruses.
Lysogenic Cycle
• Lysogenic Cycle: the viral genome replicates
without destroying the host cell.
– Provirus: a virus that stays inside a cell but does not
make new viruses; instead the viral gene is inserted into
the chromosomes of a host cell, making a provirus.
Whenever the cell divides, the provirus also divides.
• Many viruses such as Influenza
and HIV have an envelope.
• In many cases the envelope is
composed of a lipid bilayer
derived from the membrane of
the host cells with glycoproteins
embedded within the envelope.
• Within the envelope lies the
capsid, which encloses the genetic
material.
• Viruses are often restricted to
certain kinds of cells. This may be
due to viruses’ origin.
• Viruses may have originated from
fragments of host genes escaped
or were expelled from cells.
• There are many kinds of viruses—
possibly as many kinds of viruses
as kinds of organisms!
HIV: Structure
HIV: Infection
• HIV entry is a two-step process. The viruses attaches to
the cell and then the envelope fuses with the
membrane.
• Attachment: spikes composed of a glygoprotein fits a
human cell receptor and binds to human cells.
• Entry into Macrophages: HIV binds to a receptor and a
co-receptor which allows the capsid to enter the cell.
• Replication: Once inside, the HIV capsid comes apart
and releases its components including viral RNA. New
viruses are assembled and released by exocytosis.
• AIDS: HIV continues to replicated and take over cells
they could not before. HIV starts to reproduce in T
Cells and destroy them.
HIV: Infection
Viral Diseases
Emerging Viruses
• Newly recognized viruses or reappearing
viruses are called emerging viruses.
• In 1999 a mosquito-borne virus called West
Nile began to spread across the U.S., probably
brought by infected birds.
• People who are infected typically experience
mild flulike symptoms. However, sometimes
fatal inflammation of the brain may occur.
Prions and Viroids
• In addition to viruses and bacteria, scientists are
now recognizing new classes of pathogens.
• Prions: composed of proteins but have no nucleic
acid.
– A disease-causing prion is folded into a shape that does
not allow the prion to function. Contact with a prion
causes a normal version of the protein to misfold, too.
This causes a chain reaction.
– Prions are linked to Mad Cow disease and the human
Creutzfeldt-Jakob.
• Virod: a single strand of RNA with no capsid.
– Important infectious agents in plants.
Change in Chromosome
Structure
• Mutations: changes in an organism’s
chromosome structure.
• Breakage of a chromosome can lead to
four types of mutation.
• Deletion: a piece breaks off completely,
the new cell will lack a set of genes.
• Duplication: a chromosome fragment
attaches to its homologous
chromosome, which will then carry two
copies of genes.
• Inversion: chromosome reattaches to
the original chromosome in reverse.
• Translocation: chromosome reattaches
to a nonhomologous chromosome.
Buck 2011
Primary Tissue Layers
• There are three primary tissue layers, described in
the table below.
• The cells of all animals except sponges are
organized into units called tissues, which are cells
with a common structure that work together to
perform a function.
Buck 2011
The Cell Cycle
• Cell Cycle: a repeating sequence of cellular growth
and division during the life of an organism. A cell
spends ninety percent of its time in the first three
phases, known together as interphase.
• The cell will enter the last phases
of interphase only if the cell is about
to divide. There are five phases of
the cell cycle, listed below and
summarized on the next slide:
1. First growth 2. Synthesis, 3. Second
growth 4. Mitosis 5. Cytokinesis.
Buck 2011
When Control is Lost: Cancer
• Certain genes contain the information to make
proteins that regulate cell growth and division.
• If one of these genes is mutation, the protein may
not function, and regulation of cell growth and
division can be disrupted.
• Cancer: the uncontrolled growth and division of
cells.
– A disorder of cell division; cancer cells do not respond
normally to the body’s control mechanisms.
– Some mutations cause cancer by over-producing
growth-promoting molecules, speeding up the cell cycle.
Buck
– Others cause cancer by inactivating control proteins. 2011
Mitosis
Buck 2011
Mitosis
1. Prophase: Chromosomes coil up and become visible
during prophase. The nuclear envelope dissolves and a
spindle forms.
2. Metaphase: Chromosomes move to the center of the
cell and line up along the equator. Spindle fibers link
the chromatids of each chromosome to opposite poles.
3. Anaphase: Centromeres divide during anaphase. The
two chromatids (now called chromosomes) move
toward opposite poles as spindle fibers shorten.
4. Telophase: A nuclear envelope forms around the
chromosomes at each pole—chromosomes are now at
opposite poles.
Buck 2011
A Winding Staircase
• Watson and Crick determined that DNA is a double
helix. Each strand is made of linked nucleotides,
the subunits that made up DNA—made of a sugar
(deoxyribose), a nitrogen base, and a phosphate
group.
Buck 2011
Purines and
Pyrimidines
• The sugar and the phosphate
group are the same for each
nucleotide. However, there
are four different nitrogen
bases: adenine, guanine,
thymine, and cytosine.
• Adenine and guanine are
Purines.
• Thymine and Cytosine are
Pyrimidines.
• Nitrogen bases of nucleotides
face each other in the double
helix and are held together by
weak hydrogen bonds. Buck 2011
Pairing Between Bases
• A Purine on each strand (A or G) is always paired with a
pyrimidine on the other strand (C or T)
• A pairs with T
• G pairs with C
• Two strands contain complementary base pairs—the
sequence of bases on one strand determines the
sequence on the other strand.
Determine the complementary
strand for the following
sequences:
TCGAACT
CCAGATTG
Buck 2011
Roles of Enzymes in DNA Replication
• DNA Replication: The process of making a copy of
DNA
• DNA Helicases: open the double helix by breaking the
hydrogen bonds that link the complementary nitrogen
bases between the two strands
• Replication Fork: The area where the double helix
separates
• DNA Polymerase: enzymes that move along the strands
of DNA and add new nucleotides to the new nitrogen
bases
• When replication is complete, there are two
identical DNA molecules, each made of a new
strand and an old strand.
Buck 2011
Steps of DNA Replication
Buck 2011