Category: 2nd Semester

Chromatography of Simulated Plant Pigments

 

Chromatography of Simulated Plant Pigments

 

Introduction
    This experiment is conducted to investigate the components Plant Pigments separating visibly. There are a couple of different types of components in plant pigments, and they became clearly visible during this lab. The most important and abundant chemical pigment found in plants is chlorophyll. This pigment exists in two forms; chlorophyll a and chlorophyll b. Chlorophyll absorbs two main colors from light quite well. These are blue, and red. The chlorophyll reflects green light very well, however, the two different types of chlorophyll have their maximum absorption at different wavelengths of light. Chlorophyll a, being the main photosynthetic pigment, has a primary purpose to convert light energy to chemical energy used by the plant itself. Chlorophyll b absorbs light in a region of the spectrum apart from the dominant chlorophyll, and transfers the energy it produces to chlorophyll a. Along with chlorophyll b in transferring their energy produced to the dominant chlorophyll, two other pigments that are found in plants are carotenes and xanthophylls, which are orange and yellow respectively. Since chlorophyll is such a dominant pigment in green plants, this domination hides the color of the carotenes and xanthophylls in the leaves. This causes most plant leaves to appear green most of the time. During the autumn, however, the chlorophyll starts to break down, causing the carotenes and xanthophylls to show their bright red, orange and yellow colors.
These brilliant colors can be separated another way. This different technique, known as paper chromatography, separates mixtures in a liquid into individual components. The technique is based on the fact that each substance in a mixture has a specific affinity for a solid surface and a specific solubility in different solvents. By this method, the solid surface is the cellulose fibers in the chromatography paper, and the solvent is the solution that was placed in the bottom of the developing chamber.
 This separation takes place through a process of absorption and capillary action. Just a small drop of the mixture, in this case plant pigment to be separated, is placed at the bottom of the strip of chromatography paper. The chromatography paper is then placed in the developing chamber with a solvent, which wicks up the paper, pulling the solvent up the paper by capillary action, and the mixture of pigments is dissolved as the solvent passes over it. The different components of the mixture move upward at different rates. A compound with greater solubility will travel farther than one with less solubility. The pigments then show up as color streaks on the chromatography paper. These substances have formed a pattern called a chromatogram on the chromatography paper.
The Rf values for each pigment is calculated to establish the relative rate of migration for each pigment. This value represents the ratio of the distance a pigment traveled on the chromatogram relative to the distance the solvent front moved. Scientists use the Rf value of a sample to identify the molecule. Any molecule in a given solvent matrix system has a uniquely consistent Rf value. The formula for this value is as follows:

Rf = Distance each pigment traveled ¸ Distance solvent front traveled

 

Hypothesis
    Using paper chromatography, the pigments that give a leaf its color can be separated and observed to determine the Rf value of each pigment and their function during photosynthesis.

 

Materials
For this experiment the following items are used — one chromatography reaction chamber, one paper chromatography strip, one capillary pipette, a pencil and paper, calculator, ruler, 50 ml beaker, colored pencils, approximately 10 ml of solvent depending on the size of the reaction chamber, scissors, and simulated plant pigment.

 

Procedure
Use scissors to cut the bottom of the chromatography paper to a tapered end. Measure the strip and cut the length to equal slightly longer than the reaction chamber. Draw a faint pencil line at the bottom of the tapered end and use a capillary pipette to add some simulated plant pigment to this line. Add 5-10 ml of solvent to the reaction chamber. Extend the chromatography strip through the slit in the lids of the reaction chamber and carefully lower the strip into the chamber so the tapered end is in the solvent and the pencil line is above the solvent level. Make sure the strip does not touch the walls of the chamber and do not bump the chamber as the pigments begin to separate. After the pigments have completely separated and the solvent front has reached the top of the chamber, remove the strip and mark the solvent front with a pencil line before it evaporates. Measure and record the distance the solvent and each pigment traveled. Use a calculator to determine the Rf values for each pigment.

 

Data

 

Table 1
Band # Pigment Color Migration distance (mm) Rf value
1 Carotene Orange 59mm .94
2 Xanthophyll Yellow 56mm .89
3 Chlorophyll a Light green 29mm .46
4 Chlorophyll b Dark green 14mm .22
Solvent 63mm

Questions
1. Describe what happened to the original spot of simulated plant pigments?  The solvent separated  the original spot by wicking up the solvent while dissolving the various pigments in the spot.
2. List some other uses of chromatography?  Chromatography can be used to separate various mixtures of subtances, liquids and gases.
3. Which of the 4 pigments migrated the furthest and why?  carotene ( orange) because it was the most soluble in the solvent
4. Which type of chlorophyll was the most soluble?  chlorophyll a
5. Explain why leaves change color in the fall?  In Autumn, chlorophyll starts to break down which allows the other brilliant plant pigment colors to show. These pigments include the red, orange, and yellow colors.
6. What is the function of plant pigments in photosynthesis?  Plant pigments trap light energy and convert it into chemical energy that can be used by the plant to make glucose or sugar.

Error Analysis
The chromatography paper touched the sides of the chamber during the waiting time which caused the migration to go slightly to the side instead of straight to the top. Also the strip was bent at the top so there could have been a slight error in measuring the migration of the solvent  front.

Conclusion
Paper chromatography proved to be an accurate method of separating and observing the various colors of plant pigments. The pigments dissolved in the solvent and migrated upward. The colors were observed and their migration distances measured & recorded. The Rf value of each pigment was determined by dividing its migration by the migration of the solvent.  It was determined that 4 pigments were present in the original spot — carotene, xanthophyll, chlorophyll a, and chlorophyll b. Carotene was the most soluble, while chlorophyll b was the least soluble.

Chapter 46 AP Obj Animal Reproduction

 

 

Chapter 46   Animal Reproduction
Objectives
Overview of Animal Reproduction
1. Distinguish between asexual and sexual reproduction.
2. List and describe four mechanisms of asexual reproduction.
3. Describe several adaptive advantages of asexual reproduction. Discuss the conditions that may favor the occurrence of asexual reproduction.
4. Explain the advantages of periodic reproduction. Describe factors that may control the timing of reproductive events.
5. Describe an example of an animal life cycle that alternates between asexual and sexual reproduction.
6. Define parthenogenesis and describe the conditions that favor its occurrence. Note examples of invertebrate and vertebrate species that use this form of reproduction.
7. Explain how hermaphroditism may be advantageous in sessile or burrowing animals that have difficulty encountering a member of the opposite sex.
8. Distinguish between male-first and female-first sequential hermaphroditism. Note the adaptive advantages of these reproductive systems.
Mechanisms of Sexual Reproduction
9. Describe mechanisms that increase the probability that mature sperm will encounter fertile eggs of the same species in organisms that use external fertilization.
10. Explain the function of pheromones in mate attraction.
11. Compare reproductive systems using internal and external fertilization on the basis of the relative number of zygotes and protection of the embryos.
12. List and describe various methods of egg and embryo protection.
13. Compare the reproductive systems of a polychaete worm, a parasitic flatworm, an insect, a common nonmammalian vertebrate, and a mammal.
Mammalian Reproduction
14. Using a diagram, identify and give the function of each component of the reproductive system of the human male.
15. Using a diagram, identify and give the function of each component of the reproductive system of the human female.
16. Describe the two physiological reactions common to sexual arousal in both sexes.
17. Describe the four phases of the sexual response cycle.
18. Compare menstrual cycles and estrous cycles.
19. Describe the stages of the human female reproductive cycle.
20. Explain how the uterine cycle and ovarian cycle are synchronized in female mammals. Note in detail the functions of the hormones involved.
21. Describe human oogenesis.
22. Describe spermatogenesis and the structure and function of mature sperm.
23. Describe three major differences between oogenesis and spermatogenesis.
24. Describe human menopause. Describe a possible evolutionary explanation for human menopause.
25. Describe the influence of androgens on primary and secondary sex characteristics and behavior.
26. Compare the patterns of hormone secretion and reproductive events in male and female mammals.
27. Define conception, gestation, and parturition.
28. Compare the length of pregnancies in humans, rodents, dogs, cows, and elephants.
29. Describe the changes that occur in the mother and the developing embryo during each trimester of a human pregnancy.
30. Explain the role of embryonic hormones during the first few months of pregnancy.
31. Describe the stages of parturition.
32. Describe the control of lactation.
33. Describe mechanisms that may help prevent the motherÕs immune system from rejecting the developing embryo.
34. List the various methods of contraception and explain how each works.
35. Describe techniques that allow us to learn about the health and genetics of a fetus.
36. Explain how and when in vitro fertilization, zygote intrafallopian transfer, and gamete intrafallopian transfer may be used.
BACK

 

Chapter 47 AP Obj Animal Development

 

 

Chapter 47    Animal Development
Objectives
The Stages of Embryonic Development in Animals
1. Compare the concepts of preformation and epigenesis.
2. List the two functions of fertilization.
3. Describe the acrosomal reaction and explain how it ensures that gametes are conspecific.
4. Describe the cortical reaction.
5. Explain how the fast and slow blocks to polyspermy function sequentially to prevent multiple sperm from fertilizing the egg.
6. Describe the changes that occur in an activated egg and explain the importance of cytoplasmic materials to egg activation.
7. Compare fertilization in a sea urchin and in a mammal.
8. Describe the general process of cleavage.
9. Explain the importance of embryo polarity during cleavage. Compare the characteristics of the animal hemisphere, vegetal hemisphere, and gray crescent in amphibian embryos.
10. Describe the formation of a blastula in sea urchin, amphibian, and bird embryos. Distinguish among meroblastic cleavage, holoblastic cleavage, and the formation of the blastoderm.
11. Describe the product of cleavage in an insect embryo.
12. Describe the process of gastrulation and explain its importance. Explain how this process rearranges the embryo. List adult structures derived from each of the primary germ layers.
13. Compare gastrulation in a sea urchin, a frog, and a chick.
14. Describe the formation of the notochord, neural tube, and somites in a frog.
15. Describe the significance and fate of neural crest cells. Explain why neural crest cells have been called a “fourth germ layer.”
16. List and explain the functions of the extraembryonic membranes in reptile eggs.
17. Describe the events of cleavage in a mammalian embryo. Explain the significance of the inner cell mass.
18. Explain the role of the trophoblast in implantation of a human embryo.
19. Explain the functions of the extraembryonic membranes in mammalian development.
The Cellular and Molecular Basis of Morphogenesis and Differentiation in Animals
20. Describe the significance of changes in cell shape and cell position during embryonic development. Explain how these cellular processes occur. Describe the process of convergent extension.
21. Describe the role of the extracellular matrix in embryonic development.
22. Describe the locations and functions of cell adhesion molecules.
23. Describe the two general principles that integrate our knowledge of the genetic and cellular mechanisms underlying differentiation.
24. Describe the process of fate mapping and the significance of fate maps.
25. Describe the two important conclusions that have resulted from the experimental manipulation of parts of embryos and the use of fate maps.
26. Explain how the three body axes are established in early amphibian and chick development.
27. Explain the significance of SpemannÕs organizer in amphibian development.
28. Explain what is known about the molecular basis of induction.
29. Explain pattern formation in a developing chick limb, including the roles of the apical ectodermal ridge and the zone of polarizing activity.
30. Explain how a limb bud is directed to develop into either a forelimb or a hind limb.
BACK

 

Chapter 48 AP Obj Nervous Systems

 

 

Chapter 48     Nervous Systems
Objectives
An Overview of Nervous Systems
1. Compare and contrast the nervous systems of the following animals and explain how variations in design and complexity relate to their phylogeny, natural history, and habitat: hydra, sea star, planarian, insect, squid, and vertebrate.
2. Name the three stages in the processing of information by nervous systems.
3. Distinguish among sensory neurons, interneurons, and motor neurons.
4. List and describe the major parts of a neuron and explain the function of each.
5. Describe the function of astrocytes, radial glia, oligodendrocytes, and Schwann cells.
The Nature of Nerve Signals
6. Define a membrane potential and a resting potential.
7. Describe the factors that contribute to a membrane potential.
8. Explain why the membrane potential of a resting neuron is typically around 260 to 280 mV.
9. Explain the role of the sodium-potassium pump in maintaining the resting potential.
10. Distinguish between gated and ungated ion channels and among stretch-gated ion channels, ligand-gated ion channels, and voltage-gated ion channels.
11. Define a graded potential and explain how it is different from a resting potential or an action potential.
12. Describe the characteristics of an action potential. Explain the role of voltage-gated ion channels in this process.
13. Describe the two main factors that underlie the repolarizing phase of the action potential.
14. Define the refractory period.
15. Explain how an action potential is propagated along an axon.
16. Describe the factors that affect the speed of action potentials along an axon and describe adaptations that increase the speed of propagation. Describe saltatory conduction.
17. Compare an electrical synapse and a chemical synapse.
18. Describe the structures of a chemical synapse and explain how they transmit an action potential from one cell to another.
19. Explain how excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) affect the postsynaptic membrane potential.
20. Define summation and distinguish between temporal and spatial summation. Explain how summation applies to EPSPs and IPSPs.
21. Explain the role of the axon hillock.
22. Describe the role of signal transduction pathways in indirect synaptic transmission.
23. Describe the specific properties of the neurotransmitters acetylcholine and biogenic amines.
24. Identify and describe the functions of the four amino acids and several neuropeptides that work as neurotransmitters.
25. Explain how endorphins function as natural analgesics.
26. Describe the roles of nitric oxide and carbon monoxide as local regulators.
Vertebrate Nervous Systems
27. Compare the structures and functions of the central nervous system and the peripheral nervous system.
28. Distinguish between the functions of the autonomic nervous system and the somatic nervous system.
29. Describe the embryonic development of the vertebrate brain.
30. Describe the structures and functions of the following brain regions: medulla oblongata, pons, midbrain, cerebellum, thalamus, epithalamus, hypothalamus, and cerebrum.
31. Describe the specific functions of the reticular system.
32. Explain how the suprachiasmatic nuclei (SCN) function as a mammalian biological clock.
33. Relate the specific regions of the cerebrum to their functions.
34. Distinguish between the functions of the left and right hemispheres of the cerebrum.
35. Describe the specific functions of the brain regions associated with language, speech, emotions, memory, and learning.
36. Explain the possible role of long-term potentiation in memory storage and learning in the vertebrate brain.
37. Describe our current understanding of human consciousness.
38. Explain how research on stem cells and neural development may lead to new treatments for injuries and disease.
39. Describe current treatments for schizophrenia.
40. Distinguish between bipolar disorder and major depression.
41. Describe the symptoms and brain pathology that characterize Alzheimer’s disease. Discuss possible treatments for this disease.
42. Explain the cause of Parkinson’s disease.
BACK

 

Chapter 43 AP Obj Body Defenses

 

 

Chapter 43    Body’s Defenses
Objectives
Nonspecific Defenses Against Infection
1. Explain what is meant by nonspecific defense and list the nonspecific lines of defense in the vertebrate body.
2. Distinguish between:
a. innate and acquired immunity
b. humoral and cell mediated response
3. Explain how the physical barrier of skin is reinforced by chemical defenses.
4. Define phagocytosis. Name four types of phagocytic leukocytes.
5. Explain how interferon limits cell-to-cell spread of viruses.
6. Describe the inflammation response, including how it is triggered.
7. Describe the factors that influence phagocytosis during the inflammation response.
8. Explain how the action of natural killer cells differs from the action of phagocytes.
9. Explain what occurs during the condition known as septic shock.
10. Describe the roles of antimicrobial proteins in innate immunity.
How Specific Immunity Arises
11. Distinguish between antigens and antibodies.
12. Distinguish between antigen and epitope.
13. Explain how B lymphocytes and T lymphocytes recognize specific antigens
14. Explain how the particular structure of a lymphocyte’s antigen binding site forms during development. Explain the role of recombinase in generating the staggering variability of lymphocytes.
15. Explain why the antigen receptors of lymphocytes are tested for self-reactivity during development. Predict the consequences that would occur if such testing did not take place.
16. Describe the mechanism of clonal selection. Distinguish between effector cells and memory cells.
17. Distinguish between primary and secondary immune responses.
18. Describe the cellular basis for immunological memory.
19. Describe the variation found in the major histocompatibility complex (MHC) and its role in the rejection of tissue transplants. Explain the adaptive advantage of this variation.
20. Compare the structures and functions of cytotoxic T cells and helper T cells.
21. Compare the production and functions of class I MHC and class II MHC molecules.
Immune Responses
22. Distinguish between humoral immunity and cell-mediated immunity.
23. Describe the roles of helper T lymphocytes in both humoral and cell-mediated immunity.
24. Describe the functions of the proteins CD4 and CD8.
25. Explain how cytotoxic T cells and natural killer cells defend against tumors.
26. Distinguish between T-dependent antigens and T-independent antigens.
27. Explain why macrophages are regarded as the main antigen-presenting cells in the primary response but memory B cells are the main antigen-presenting cells in the secondary response.
28. Explain how antibodies interact with antigens.
29. Diagram and label the structure of an antibody and explain how this structure allows antibodies to (a) recognize and bind to antigens, and (b) assist in the destruction and elimination of antigens.
30. Distinguish between the variable (V) and constant (C) regions of an antibody molecule.
31. Describe the production and uses of monoclonal antibodies.
32. Compare the processes of neutralization, opsonization, and agglutination.
Immunity in Health and Disease
33. Distinguish between active and passive immunity and describe examples of each.
34. Explain how the immune response to Rh factor differs from the response to A and B blood antigens.
35. Describe the potential problem of Rh incompatibility between a mother and her unborn fetus and explain what precautionary measures may be taken.
36. Explain what is done medically to reduce the risk of tissue transplant rejection due to differences in the MHC. Explain what is unique about the source of potential immune rejection in bone marrow grafts.
37. Describe an allergic reaction, including the roles of IgE, mast cells, and histamine.
38. Explain what causes anaphylactic shock and how it can be treated.
39. List three autoimmune disorders and describe possible mechanisms of autoimmunity.
40. Distinguish between inborn and acquired immunodeficiency.
41. Explain how general health and mental well-being might affect the immune system.
42. Describe the infectious agent that causes AIDS and explain how it enters a susceptible cell.
43. Explain how HIV is transmitted and describe its incidence throughout the world. Note strategies that can reduce a person’s risk of infection.

.
BACK