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Biology Proctor Exam Study
Guide
SCI 120: Introduction to Biology Key Topics to Study by Lesson for Proctored Final Examination Below is a list of the main topics presented in this course by unit. Review the content as a method to prepare for the proctored examination and organize your notes. Information is organized by the main learning objectives for each module aligning with your course. Therefore, use the learning objectives within the main units to answer the questions. Good luck! The Cell Unit
- Identify and briefly describe the steps of the scientific method. Making observations- Asking questions- Formulating hypotheses, or testable explanations- Developing testable predictions- Designing an experiment- Conducting an experiment and collecting data- Analyzing data and drawing conclusions. The method starts with observations that you refine through questions, educated guesses, experimental design, experimentation, and analysis. The process is rarely linear and the period from experimentation to the final answer can be iterative,
meaning it requires multiple trials. Each step has an important purpose A controlled experiment requires a control group, which doesn’t receive the experimental treatment, and a experimental group, which does receive the experimental treatment. Besides the experimental treatment, all other conditions are kept the same. Variables are the factors that can influence the outcome of an experiment. Controlled variables don’t change and are the same between the control group and the experimental group, Manipulated or independent variables are intentionally changed in the experimental group. Responding variables are the results of the change in the experimental group
- What are the hierarchical levels of organization in biology? Atom, Molecule, Cell organelles, cell, tissue, Organ, System of Organs, Organism, Population, Biocenoses (Community), Ecosystem, Biome, Biosphere(Earth)
- Briefly identify the three domains of life. What are examples for each? (Note: this content is found in two different locations (also in the Evolution Unit) within the course. (Combine answers from both sections) Bacteria and Archaea are prokaryotic (single-cell organisms) Eukarya are multicellular and include humans
- How do enzymes work? Enzymes are a class of proteins that catalyze reactions. Enzymes
products packaging them into vesicles and sending them to other regions of the cell. Considered the shipping and receiving center of the cell. Mitochondria are often called the “powerhouse” of the cell because they’re the cellular energy production centers. They specialize in the generation of (ATP) adenosine triphosphate, an energy-carrying molecule produced by cellular respiration. Chloroplasts are a member of a family of related organelles called plastids. Chloroplasts contain chlorophyll, which absorbs sunlight. The nucleus stores cellular DNA and directs cellular activity by controlling DNA transcription and synthesis The rough endoplasmic reticulum appears rough because it has ribosomes studding its surface. This is the site of protein synthesis in eukaryotes. The smooth endoplasmic reticulum doesn’t have ribosomes on its surfaces or has very few. Its function is to synthesize lipids The Golgi apparatus processes and packages the proteins and lipids produced by the endoplasmic reticulum. Mitochondria are responsible for carrying out cellular respirations and thereby produce energy for the cell in the form of ATP. Lysosomes break down damaged cellular materials and salvage useful scraps of cellular material to be reused
- Define homeostasis. Why is this important? Homeostasis is the tendency of living things to maintain a steady state. It is important to keep functioning at an optimal level,
organisms need to remain relatively stable, despite whatever changes they may faces. Organisms and their cells are constantly responding to changing variables in both their internal and external environments to stay in harmony. The human body constantly works to maintain temperature homeostasis despite the external temperature, that’s why we sweat when it is hot and shiver when it is cold out. Homeostasis within a living system is the maintenance of dynamic equilibrium.
- Compare cell transport types- active, passive, diffusion, facilitated diffusion, and osmosis. What is an example of each? Diffusion is the process by which substances move from areas of high concentration to areas of low concentration. This process continues until the concentration becomes equal throughout space. Facilitated diffusion involves transport proteins that can function as either channels or carriers Osmosis is the diffusion of water from areas of high-water concentration to areas of low- water concentration across a selectively permeable membrane. Osmosis differs from diffusion in that osmosis is specifically associated with water. Osmosis causes water to move in whatever direction will equalize the concentration of water and any solutes present Diffusion, facilitated diffusion and osmosis are all forms of passive transport, meaning they require no energy input to occur. These are necessary and important for cellular function and the
set point- on a cold day the organism is too cold of after eating the blood sugar spikes. The body then uses a negative feedback loop to move value back toward set point and maintain homeostasis A negative feedback- loop is a process that changes the direction of or reduces the stimulus. With the example of increased blood sugar after eating, the feed back loop works to decrease blood sugar until homeostasis near the set point is restored A positive feedback loop maintains the stimulus and sometimes even enhances it. Such loops are rare within humans, but a good example involves labor and contractions during labor. When the uterus contracts, the pain receptor in the uterus prompts the production of oxytocin
- Review the purpose and structure of the plasma membrane and how substances get into the cell (i.e., what are the different types of membrane proteins). What model represents the cell (plasma) membrane that was discussed? The main function of the plasma membrane also called the phospholipid bilayer, is to control which substances can enter and exit the cells. There are two major populations of proteins in the cell membrane integral proteins, and peripheral proteins. Integral proteins often span the entire membrane and are also
called transmembrane proteins. The hydrophobic region of these proteins are in contact with the water on both sides of the cell membrane, but the interior hydrophobic region is between the lipids. These proteins have many roles but the most important is the transport of molecules and ions in and out of the cell Peripheral Proteins aren’t part of the cell membrane but are appendages to the surface of the cell. These proteins add structure to the cells by binding them with fibers. They also serve as attachment sites for enzymes or as cell-recognition sites 10.Briefly describe the four levels of cellular potency. Provide examples for each. There are four levels of cellular potency totipotent, pluripotent, multipotent, unipotent. Totipotent, having to do with cells that can develop into any type of cell found in the body. Examples are spores and zygotes A Pluripotent is a cell that can develop into many different types of cells or tissues in the body. Example Embryonic stem cells. Examples are adult stem cells and cord blood stem cells Multipotent cells that have the capacity to self-renew by dividing and then develop into multiple specialized cell types present in a specific tissue or organs Unipotent capable of developing into only one type of cell or tissue. An example is a skin cell A stem cell has a high level of potency because it’s undifferentiated or only partially differentiated. The function of stem cells is to differentiate into specialized cells and
carbon dioxide and water, sometimes with the help of oxygen molecules, to produce ATP Explain the function of the enzyme ribulose bisphosphate carboxylate, also called RuBisCO. What reactions does this enzyme catalyze, and why is this important RuBisCO catalyzes carbon fixation in plants, where carbon dioxide is added to a 5-carbon molecule to form 2 3-carbon molecules. The 5-carbon molecule is ribulose 1,5-bisphosphate and the 3-carbon molecules formed by this reaction are glyceraldehyde 3-phosphate. This is the step in the Calvin cycle, which is the light- independent reactions in photosynthesis. This is important because carbon fixation is how atmospheric carbon dioxide is converted into sugars 12.Analyze briefly the differences between new cells produced by both mitosis and meiosis. What mainly happens during each? Mitosis is part of the cell cycle in which replicated chromosomes are separated into two new nuclei. The major focus of mitosis is DNA. Mitosis is the type of cell division carried out by somatic cells. It involves the growth and maintenance of tissues such as lungs, intestines, skin, and other organs While mitosis is a method of cell division for the replacement of old or worn-out somatic cells, meiosis produces gametes. Gametes, or sex cells, have half the number of chromosomes of their parent cell. The phases of meiosis are like the phases of mitosis. However, meiosis is slightly more complex.
Meiosis generates four daughter cells, instead of two daughter cells as in mitosis. Meiosis is responsible for creating genetic diversity in multi- celled animals 13.Identify the types and functions of the major cell cycle regulators. Cyclin these proteins get their name from constantly changing concentrations within the cell. The levels of cyclins present at each stage determine whether the cell should proceed past a given checkpoint Cyclin-dependent kinases, depend on specific cyclins to function. The cyclin will only bind to a cyclin-dependent kinase only if the cell is well-supported and prepared for the next phase of the cell cycle Cancer occurs often because a cell cycle regulator is malfunctioning or a checkpoint is being ignored Checkpoints are ways that cells minimize the risk of an error being introduced during the cell cycle and propagated to future generations of cells. At the G1 checkpoint, cells must be ready to divide moving forward. At G2 checkpoint, cellular DNA needs to be intact and undamaged before moving forward. At M checkpoints, the spindle fibers must be properly attached to sister chromatids before the cell moves forward. Cell cycle regulators provide feedback that contributes to the decision of whether a cell proceeds past a check point. The function of the cell cycle check points and cell cycle regulators is to ensure that a cell can successfully divide and to minimize errors introduced
other, so one end of the bond develops a partial negative charge and the other end develops a partial positive charge. The bonds between hydrogen and oxygen in water provide a good example of a polar covalent bond. In nonpolar covalent bonds, the electrons are shared equally between two atoms so no partial charges are formed. A good example of a nonpolar covalent bond is the bond between Oxygen atoms in a molecule of oxygen Gas O2 or the bond between chlorine atoms in a molecule of chlorine gas CL When elements form Covalent bonds, they share electrons to achieve a full outer shell instead of gaining or losing. Covalent bonds can be single, double, or even triple bonds (involving one, two, or three electrons) A hydrogen bond is an attraction between 2 atoms that already participate in other chemical bonds. One of the atoms is hydrogen, while the other may be any electronegative atoms, such as oxygen, chlorine, or fluorine. Hydrogen bonds may form between atoms within a molecule or between two separate molecules
- Cellular respiration breaks down sugar (glucose) to form ATP. Anaerobic respiration turns fuel (glucose) into energy (ATP or other energy-carrying molecules) in the absence of oxygen.
- Aerobic respiration uses oxygen as a reactant to produce energy. Aerobic cellular respiration uses sugar and oxygen to produce carbon dioxide, water, and ATP.
- There are four stages of aerobic cellular respiration: glycolysis, pyruvate oxidation, the Krebs (citric acid) cycle, and the electron transport chain.
- Aerobic cellular respiration produces 38 molecules of ATP. Anaerobic cellular respiration, called fermentation, produces two molecules of ATP and either ethanol or lactic acid. Make sure to review the basics of nucleic acids to prepare for the Genetics unit. Nucleic Acids are the building blocks of genetic code; biologically important nucleic acids are the biopolymers DNA and RNA Genetics Unit
- Who is Gregor Mendel? What did he do with pea plants? Gregor Mendel was born in 1822 to a poor farming family in what is now the Czech Republic. Although is discoveries weren’t recognized until after his death he is today known as the father of modern genetics. Mendel is known as the father of modern genetics because of his important work in breeding pea plants and demonstrating the basic principles of heredity. For 8 years he studied the characteristics of pea plants and performed experiments on plants he bred in the monastery’s garden. Mendel used the concept of hybridization, or the crossing of two genetically different pea plants, to plant a third plant, called a hybrid, with a distinct, predictable set of traits obtained from its parent plants.
each trait, with one coming from each parent. The law derives its name from the fact that although living organisms possess two alleles for each trait, the alleles separate, or segregate, during reproduction. Therefore, each parent contributes only one of its two alleles for any given trait in a seemingly random fashion. The laws of Dominance establishes which genes manifest as traits in the new organism. To understand the law of dominance, it’s helpful to understand the terms dominant and recessive. A dominant gene will always be completely expressed if it's present in the organism's genetic code, even if only one parent contributed a dominant allele. A recessive allele will only be completely expressed if both parents contributed recessive alleles. In other words, to see a recessive trait, both parents must have the recessive allele for that trait, and they must both pass on that allele. Some alleles aren’t strictly dominant or recessive 6.What are the exceptions to Mendel’s laws? (Hint: Describe incomplete dominance, codominance, and environmental factors influencing genes). The concept of incomplete dominance is an exception. In incomplete dominance, one phenotype doesn’t prevail over the other. Instead, there’s an intermediate phenotype that’s a mix of both parents’ phenotypes for a given trait. A simple example would be crossing a red snapdragon with a white snapdragon, resulting in a pink
snapdragon. Incomplete dominance leads to a blending of the two alleles passed down from the parents for a given characteristic. Codominance both the recessive and the dominant traits are expressed together in an organism’s phenotype. For example, if one parent has 2 alleles for type A blood and the other parent is homozygous for type B blood the offspring will have a new phenotype- type AB, both phenotypes of the parents are expressed in the offspring. Environmental influences are another exception to Mendel’s principles. Environmental influences refer to how the external world in which the organisms lives or develops affects the organisms. For example, an organism that inherits both recessive genes may not be abel to withstand the environment that it’s living in and may not survive to reproduce. This lessens the number of organisms with recessive genes in a population and the dominant gene predominates. These three concepts demonstrate that the genetic influences on phenotypes are often very complex 7.What is the difference between transcription and translation? Briefly describe each. Transcription and translation are both involved in the process of gene expressions required for cell functioning. Transcription is the copying down of genes in the genome in RNA pieces. The translation is the decoding of the mRNA into proteins. The transcription of DNA into RNA and the translation of RNA into proteins are considered as the central dogma of biology. The main difference is that transcription involves
Base pairs of DNA are Adenine and Thymine pair, and Cytosine and Guanine pair, RNA base pairs are Adenine and Uracil pair, and Cytosine and Guanine pair. DNA is found in the nucleus with a small amount of DNA also present in mitochondria. RNA forms in the nucleolus, and then move to specialized regions of the cytoplasm depending on the type of RNA Formed. DNA is a more stable molecule than RNA, which is useful for a molecule which has the task of keeping genetic information safe. RNA, containing ribose sugar, is more reactive than DNA and is not stable in alkaline conditions. RNA’s larger helical grooves mean it is more easily subject to attack by enzymes. DNA is vulnerable to damage by ultraviolet light, and RNA is more resistant to damage from UV light than DNA 9 What is the central dogma? The central dogma of the molecular biology provides a framework of how to understand the two-step process of gene expression. More specifically , the central dogma explains how DNA’s instructions are translated into RNA that’s used to produce proteins that are essential for the cells function.
- Briefly identify and describe the different types of RNA. Messenger RNA(mRNA) copies portions of genetic code, a process called transcription, and transports these copies to ribosomes, which are the cellular factories that facilitate the production of proteins from this code. Transfer RNA(tRNA) is responsible for bringing amino acids, basic protein building blocks, to these protein factories, in response to the
coded instructions introduced by mRNA. This protein- building process is called translation. Ribosomal RNA (rRNA) is a component of the ribosome factory itself without which protein production would not occur
- What is the Meselson-Stahl experiment? Describe semi- conservative replication. The experiment done by Meselson and Stahl demonstrated that DNA replicated semi- conservatively, meaning that each strand in a DNA molecule serves as a template for the synthesis of a new, complementary strand. Although Meselson and Stahl did their experiments in the bacterium E.
- How is an individual strand of DNA replicated (review the process and proteins/enzymes involved, for example- Helicase)? What is complementary base pairing? Replication is the process by which DNA is copied to make DNA for new cells. Each strand of DNA serves as a template for DNA replication. During replication, the enzyme , helicase, separates the DNA strands into a lagging strand and a leading strand, which unzips the double helix. The leading strand is easily replicated because it runs in the same direction as the original DNA. It’s replicated continuously. And an RNA primer is added to the strand and then the DNA polymerase adds the appropriate base pairs to reconstruct the ladder. The laggings strand is in reverse and can’t be replicated easily. In this case, RNA primer attaches, and the DNA polymerase adds small groups of base pairs one at a time. These
