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Questions and Answers
What distinguishes temperate phages from virulent phages based on their replication cycle?
What distinguishes temperate phages from virulent phages based on their replication cycle?
Which of the following outcomes is characteristic of the lytic cycle of a bacteriophage?
Which of the following outcomes is characteristic of the lytic cycle of a bacteriophage?
The presence of a 'prophage' is a defining characteristic of which viral replication cycle?
The presence of a 'prophage' is a defining characteristic of which viral replication cycle?
How does phage genome replication differ between the lytic and lysogenic cycles?
How does phage genome replication differ between the lytic and lysogenic cycles?
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During which cycle does the phage genome exert complete control over the host cell's cellular mechanisms?
During which cycle does the phage genome exert complete control over the host cell's cellular mechanisms?
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What is the relative productivity of phage genomes in the lytic cycle compared to the lysogenic cycle?
What is the relative productivity of phage genomes in the lytic cycle compared to the lysogenic cycle?
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Considering the duration, how do the lytic and lysogenic cycles compare?
Considering the duration, how do the lytic and lysogenic cycles compare?
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Under what conditions, as indicated in the text, can a lysogenic cycle transition into a lytic cycle?
Under what conditions, as indicated in the text, can a lysogenic cycle transition into a lytic cycle?
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Which metabolic process yields the highest net ATP production from a single glucose molecule?
Which metabolic process yields the highest net ATP production from a single glucose molecule?
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In contrast to aerobic cellular respiration, anaerobic cellular respiration utilizes which of the following as a final electron acceptor?
In contrast to aerobic cellular respiration, anaerobic cellular respiration utilizes which of the following as a final electron acceptor?
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How is photosynthesis primarily related to cellular respiration based on the provided information?
How is photosynthesis primarily related to cellular respiration based on the provided information?
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What is the primary function of chlorophyll in the process of photosynthesis?
What is the primary function of chlorophyll in the process of photosynthesis?
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If an organism is described as heterozygous at a specific locus, what does this indicate about its alleles for that locus?
If an organism is described as heterozygous at a specific locus, what does this indicate about its alleles for that locus?
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What is a defining characteristic shared by all protists?
What is a defining characteristic shared by all protists?
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Which process directly converts solar energy into a usable form of energy for living organisms?
Which process directly converts solar energy into a usable form of energy for living organisms?
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Maintaining a stable internal environment in an organism is best described as:
Maintaining a stable internal environment in an organism is best described as:
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Facilitated diffusion is a type of:
Facilitated diffusion is a type of:
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Which of the following is an example of negative feedback in biological systems?
Which of the following is an example of negative feedback in biological systems?
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In the context of energy transformation in cells, photosynthesis is considered:
In the context of energy transformation in cells, photosynthesis is considered:
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Cellular respiration is described as:
Cellular respiration is described as:
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What is the primary role of ATP in cells?
What is the primary role of ATP in cells?
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What is the primary distinction between prokaryotic and eukaryotic cells?
What is the primary distinction between prokaryotic and eukaryotic cells?
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Which stage of aerobic respiration occurs before the transition reaction?
Which stage of aerobic respiration occurs before the transition reaction?
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Which of the following describes the function of topoisomerases in prokaryotic cells?
Which of the following describes the function of topoisomerases in prokaryotic cells?
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In aerobic respiration, oxygen is directly required for which process?
In aerobic respiration, oxygen is directly required for which process?
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What is the main function of rhizoids in bryophytes?
What is the main function of rhizoids in bryophytes?
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Which structural feature of mitochondria is directly involved in increasing the efficiency of ATP production?
Which structural feature of mitochondria is directly involved in increasing the efficiency of ATP production?
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Besides ATP production, what is another crucial function of mitochondria within eukaryotic cells?
Besides ATP production, what is another crucial function of mitochondria within eukaryotic cells?
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How do enzymes accelerate biochemical reactions?
How do enzymes accelerate biochemical reactions?
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In the 'induced fit' model of enzyme-substrate interaction, what occurs upon substrate binding?
In the 'induced fit' model of enzyme-substrate interaction, what occurs upon substrate binding?
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Mitosis and meiosis are two types of cell division. What is the key distinction between them in terms of offspring genetic similarity to the parent cell?
Mitosis and meiosis are two types of cell division. What is the key distinction between them in terms of offspring genetic similarity to the parent cell?
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Lysogenic conversion, caused by a prophage, results in which type of change in a host cell?
Lysogenic conversion, caused by a prophage, results in which type of change in a host cell?
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Which of the following is NOT a characteristic of the nucleoid region in prokaryotic cells?
Which of the following is NOT a characteristic of the nucleoid region in prokaryotic cells?
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Which of the following accurately describes the outcome of meiosis in sexually reproducing organisms?
Which of the following accurately describes the outcome of meiosis in sexually reproducing organisms?
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A plant species can reproduce both sexually and asexually. Under which condition would asexual reproduction likely be favored over sexual reproduction?
A plant species can reproduce both sexually and asexually. Under which condition would asexual reproduction likely be favored over sexual reproduction?
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In nonflowering plants like bryophytes, what is the function of the antheridium?
In nonflowering plants like bryophytes, what is the function of the antheridium?
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During the alternation of generations in plants, which phase is characterized by haploid cells and the production of gametes?
During the alternation of generations in plants, which phase is characterized by haploid cells and the production of gametes?
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How do the daughter cells produced in mitosis compare to the parent cell in terms of chromosome number and genetic information?
How do the daughter cells produced in mitosis compare to the parent cell in terms of chromosome number and genetic information?
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In which stage of mitosis do sister chromatids separate and move towards opposite poles of the cell?
In which stage of mitosis do sister chromatids separate and move towards opposite poles of the cell?
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What is the primary significance of crossing over during prophase I of meiosis?
What is the primary significance of crossing over during prophase I of meiosis?
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During which phase of the cell cycle does DNA replication occur?
During which phase of the cell cycle does DNA replication occur?
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Which of the following mitotic errors results in a cell having an abnormal number of chromosomes, which is not an exact multiple of the haploid set?
Which of the following mitotic errors results in a cell having an abnormal number of chromosomes, which is not an exact multiple of the haploid set?
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Protista are characterized by their polyphyletic nature. What does 'polyphyletic' imply about the Kingdom Protista?
Protista are characterized by their polyphyletic nature. What does 'polyphyletic' imply about the Kingdom Protista?
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Study Notes
Viral Replication Cycles
- Viruses are acellular, parasitic particles, considered non-living until they invade a host for growth and reproduction.
- Bacteriophages (phages) infect bacteria only. Their structure includes a capsid head containing the nucleic acid genome, a tail sheath, and tail fibers.
- Phages can undergo lytic or lysogenic cycles, classified as temperate (non-virulent) or virulent phages respectively.
Lytic Cycle
- Temperate phages follow this cycle.
- Host bacterium is killed by cell lysis.
- No prophage stage.
- Phage genome replicates independently of host DNA.
- Phage genome completely controls host mechanisms.
- High phage genome productivity.
- Quick cycle with progeny virus production.
- Does not involve a lysogenic cycle.
- Five steps: adsorption (attachment), penetration (entry), phage replication/biosynthesis, maturation (assembly), and lysis (release).
Lysogenic Cycle
- Virulent phages follow this cycle.
- Host cell is not harmed initially.
- Phage genome integrates into host genome as a prophage. Bacteria with a prophage are called lysogens.
- Phage genome replicates along with host DNA.
- Phage genome does not fully take over host mechanisms.
- Low phage genome productivity.
- Time-consuming process; no immediate progeny production.
- Can transition to lytic cycle with induction (e.g., UV light, chemical treatment).
Phenotypes and Ghosts
- Prophage presence can cause changes to host phenotype, called lysogenic conversion.
- The empty phage particle outside the host bacterium is called a ghost.
Prokaryotic and Eukaryotic Cells
- All living things are composed of cells classified as prokaryotic or eukaryotic.
- Prokaryotic cells lack membrane-bound organelles, including a nucleus.
- Eukaryotic cells possess membrane-bound organelles, including a nucleus.
- Prokaryotic cells have DNA located in the nucleoid region.
- The nucleoid is a region within the cytoplasm, lacking a membrane and containing DNA, proteins (including enzymes), and RNA.
- DNA in the nucleoid is organized by associating with proteins called histones.
- Supercoiling compacts DNA for fitting within the nucleoid.
- Topoisomerases nick DNA to relax supercoiling (for processes like transcription).
Rhizoids
- Rhizoids are filamentous structures on non-vascular plants (mosses, liverworts, hornworts) and some fungi and algae.
- Their primary function is anchoring to a substrate, and in some species, also absorbing water and nutrients through capillary action (osmosis and diffusion).
- Rhizoids grow from epidermal cells of the gametophyte.
- Rhizoids are ancient structures likely preserved from when plants transitioned to terrestrial life from aquatic life.
Mitochondria
- Mitochondria are double-membrane organelles found in eukaryotic cells (like human cells) in the cytoplasm.
- Mitochondria are thought to have originated from bacteria, evidenced by their double membrane and binary fission reproduction.
- Outer mitochondrial membrane has porins for mineral and protein passage.
- Inner mitochondrial membrane has enzymes for ATP production and is highly folded (cristae).
- The mitochondrial matrix contains mitochondrial DNA and enzymes involved in energy production, as well as calcium storage.
- Intermembrane space is the space between the membranes.
- Mitochondria produce ATP (energy currency) including processes like the citric acid cycle (Krebs cycle).
- Mitochondria also regulate apoptosis by releasing cytochrome C.
- Mitochondria store calcium; they regulate calcium levels in cells.
Enzymes
- Enzymes are specialized proteins that catalyze reactions by lowering activation energy.
- Activation energy is the minimum energy needed for a reaction to occur.
- Enzymes bind to substrates at the active site, forming an enzyme-substrate complex. The lock-and-key or induced fit model describes how this occurs.
- Products are formed and released, leaving the enzyme unchanged to repeat the process.
Sexual and Asexual Reproduction
- Reproduction can be sexual (two parents) or asexual (one parent).
- Offspring result from reproduction.
- Mitosis creates identical daughter cells (asexual).
- Meiosis produces gametes (sex cells) for sexual reproduction.
- Gametes are oocytes (female) and spermatocytes (male).
- Meiosis halves the genetic information during gamete formation.
- Zygote formation (fertilization of gametes) yields a cell with all parental DNA.
- A zygote develops into an embryo via mitosis, creating genetically similar (but not identical) offspring.
- Sexual reproduction increases survival chances for a species.
Plant Reproductive Structures
- Antheridium is the male reproductive structure in many plants (flowering and non-flowering).
- Antheridium produces sperm cells in spermatogenesis.
- Archegonia are the female reproductive structures which produce egg cells.
- Gametophytes are the sexual phase of alternation of generations. They have a haploid number of chromosomes.
- Antheridia are found in Bryophytes and cryptogams (nonflowering plants).
- Plants have alternation of generations life cycles, alternating between sexual and asexual phases.
- Water is needed for sperm to reach eggs for fertilization in some plants.
Mitosis and Meiosis
- Mitosis is a single cell division process producing two identical daughter cells from one parent cell (somatic cells).
- Meiosis is a two-round cell division process that produces four different daughter cells (reproductive cells).
- Crossing over occurs during prophase I of meiosis, leading to genetic variation.
- Key stages in mitosis and meiosis include prophase, metaphase, anaphase, and telophase.
Cell Cycle
- The cell cycle is a process of cell division resulting in two genetically identical daughter cells.
- Interphase, mitosis, and cytokinesis are the three main stages of the cell cycle.
Interphase, Mitosis and Cytokinesis in Detail
- Interphase prepares the cell for mitosis, comprising G1, S, and G2 phases.
- G1: cell growth, basic metabolism, G1 checkpoint.
- S: DNA synthesis and duplication.
- G2: production of intracellular materials and organelles, G2 checkpoint (checks for DNA damage).
- M: Mitosis (prophase, prometaphase, metaphase, anaphase, telophase, and cytokinesis).
- Prophase: chromosome formation. Chromosomes appear as X shapes under microscope
- Prometaphase: nuclear envelope breakdown.
- Metaphase: chromosomes align at metaphase plate.
- Anaphase: sister chromatids separate.
- Telophase: nuclear membrane reassembles, cell splits.
- Errors in mitosis can result in aneuploidy, nondisjunction, and trisomy.
- Endoreplication is a form of mitosis used by some organisms in response to stress.
Protista
- Protista kingdom encompasses single-celled, eukaryotic organisms that aren't plants, animals, or fungi.
- Protists are polyphyletic (don't share a single ancestry).
- Protists share the characteristic of being eukaryotic cells, meaning they have membrane-bound organelles, including a nucleus.
Energy and Matter
- All living organisms need constant energy and matter input for survival and reproduction.
- The sun provides ultimate energy via photons.
- Plants (autotrophs) use photosynthesis to convert sunlight to usable energy.
- Photosynthesis uses carbon dioxide and water to produce sugar and oxygen.
- Consumers (heterotrophs) obtain energy from plants or other animals.
- Energy and matter are recycled in ecosystems when organisms die.
Homeostasis
- Homeostasis is maintaining a stable internal environment, crucial for biological function.
- Cell membranes help maintain homeostasis through molecular transport (passive and active transport).
- Passive transport (diffusion, facilitated diffusion): no energy required.
- Active transport: energy required.
Feedback Mechanisms
- Feedback mechanisms maintain homeostasis through responses to changes.
- Negative feedback maintains a target level (e.g., body temperature).
- Positive feedback amplifies changes away from a target level (e.g., fruit ripening).
Energy Transformation
- Organisms need energy for survival and reproduction.
- The sun provides energy for photosynthesis, an endergonic reaction.
- Cellular respiration, an exergonic reaction, breaks down sugar to make ATP. ATP is the usable energy for cells.
- Photosynthesis and cellular respiration are linked, creating a continuous energy cycle.
Cellular Respiration
- Cells, particularly eukaryotes, need oxygen to produce ATP (energy) from food molecules like glucose.
- Cellular respiration is the breakdown of organic molecules to produce ATP.
- Aerobic respiration, which requires oxygen, involves glycolysis, the transition reaction, Krebs cycle, and oxidative phosphorylation.
- Anaerobic respiration, which occurs without oxygen, uses a different electron acceptor instead of oxygen and may involve fermentation.
Photosynthesis
- Photosynthesis is the process where plants and some protists and bacteria use sunlight to convert energy into food (sugar).
- Chlorophyll absorbs light, especially blue and red wavelengths (reflects green). Chlorophyll is located in the thylakoid membrane of chloroplasts.
- Chlorophyll energizes electrons, which is critical to the steps of photosynthesis.
- In essence, photosynthesis is cellular respiration in reverse, transforming sunlight into energy storage.
Genetics
- Homozygous: an organism has two identical alleles for a particular gene. Example: BB, bb.
- Heterozygous: an organism has two different alleles for a particular gene. Example: Bb.
- Dominant trait: expressed in heterozygous genotypes.
- Recessive trait: not expressed in heterozygous genotypes.
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Description
Test your knowledge on the lytic and lysogenic cycles of viral replication. This quiz covers the characteristics and processes involved in how viruses, particularly bacteriophages, infect and reproduce within host cells. Understand the differences between temperate and virulent phages as you answer the questions.
