Unit 3 and 4 Biology Review Building Molecules

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: H 20 + ATP ADP + 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 CO 2 + 6 H 2 O C 6 H 12 O 6 + 6 O 2 Carbon dioxide Water Sunlight 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 C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + 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 (H 2 CO 3). 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 an old strand. Buck 2011

Steps of DNA Replication Buck 2011