Biology

  1. Nucleus:

    • Function: Control center of the cell, contains genetic material (DNA), regulates gene expression.

    • Specific Terms: Chromatin (DNA-protein complex), nucleolus (site of ribosome synthesis), nuclear envelope (double membrane surrounding nucleus).

  2. Mitochondria:

    • Function: Powerhouse of the cell, produces ATP through cellular respiration.

    • Specific Terms: Cristae (inner membrane folds), matrix (innermost compartment containing enzymes for respiration).

  3. Endoplasmic Reticulum (ER):

    • Function: Site of protein and lipid synthesis, transport of molecules within the cell.

    • Specific Terms: Rough ER (studded with ribosomes for protein synthesis), smooth ER (lacks ribosomes, synthesizes lipids).

  4. Golgi Apparatus:

    • Function: Modifies, sorts, and packages proteins and lipids for transport.

    • Specific Terms: Golgi vesicles (membrane-bound sacs for transport), cis face (receiving side), trans face (shipping side).

  5. Lysosomes:

    • Function: Contains enzymes for digestion of macromolecules, cellular waste, and pathogens.

    • Specific Terms: Acidic pH (maintained by proton pumps), hydrolytic enzymes.

  6. Ribosomes:

    • Function: Site of protein synthesis, reads mRNA and assembles amino acids into polypeptide chains.

    • Specific Terms: Large and small subunits (composed of rRNA and protein), free ribosomes (in cytoplasm), bound ribosomes (attached to ER).

  7. Vacuoles:

    • Function: Storage of water, nutrients, ions, and waste products.

    • Specific Terms: Contractile vacuole (pumps excess water out of cell in some organisms), central vacuole (found in plant cells, maintains turgor pressure).

  8. Chloroplasts:

    • Function: Site of photosynthesis, converts light energy into chemical energy (glucose).

    • Specific Terms: Thylakoids (membrane-bound compartments containing chlorophyll), stroma (fluid-filled matrix), grana (stacks of thylakoids).

  9. Cell Membrane:

    • Function: Regulates the passage of substances in and out of the cell, maintains cell shape and integrity.

    • Specific Terms: Phospholipid bilayer (main structural component), integral proteins (embedded in the membrane), peripheral proteins (attached to membrane surface), cholesterol (helps stabilize membrane fluidity).

  10. Cell Wall:

    • Function: Provides structural support and protection for plant cells.

    • Specific Terms: Primary cell wall (outermost layer), secondary cell wall (inner layer in some cells), middle lamella (adhesive layer between plant cells).

  11. During which stage of the cell cycle does replication of the DNA occur?

    • DNA replication occurs during the S phase of the cell cycle.

  12. Why is it necessary that the cell copies its DNA?

    • DNA replication is necessary for cell division and growth. It ensures that each daughter cell receives an identical copy of the genetic material, allowing for the transmission of genetic information to offspring cells.

  13. Why are chromosomes visible during mitosis but not at other times?

    • Chromosomes are condensed and visible during mitosis because they have undergone replication and are tightly coiled. During other times in the cell cycle, such as interphase, chromosomes are less condensed and appear as chromatin, making them less visible under a microscope.

  14. Under a microscope, some cells can appear to be between metaphase and anaphase. Explain this observation.

    • Cells that appear to be between metaphase and anaphase may be experiencing a delay or disruption in the normal progression of mitosis. This could be due to factors such as DNA damage, spindle checkpoint activation, or regulatory protein malfunction.

  15. Which stage or phase of the cell cycle corresponds to each of the descriptions below?

    • A new cell wall begins to form: Cytokinesis

    • The membrane of the nucleus dissolves: Prophase

    • Daughter chromosomes begin to separate: Anaphase

    • The cell begins to pinch together along its centre: Telophase

    • Thick chromosome threads are visible in two distinct regions of the cell: Metaphase

  16. Create a table to summarize what happens during the three stages of the cell cycle.

    Stage

    Description

    Interphase

    Cell grows, DNA replicates, prepares for cell division

    Mitosis

    Nuclear division, chromosomes condense, separate, and reform nuclei

    Cytokinesis

    Cytoplasm divides, two daughter cells are formed

  17. Biology books used to describe interphase as the "resting phase." Based on what we know now, what was wrong with this term?

    • Interphase is not a resting phase but rather an active period of the cell cycle where the cell undergoes growth, DNA replication, and preparation for cell division. Cells are actively synthesizing proteins, organelles, and other cellular components during interphase, making it a crucial and dynamic stage of the cell cycle. Therefore, describing it as a "resting phase" is inaccurate and misleading.

  18. Here are some key differences between plant cells and animal cells:

    1. Cell Wall:

      • Plant cells have a rigid cell wall made of cellulose outside the cell membrane, providing structural support and protection.

      • Animal cells lack a cell wall; instead, they have a flexible cell membrane that maintains cell shape and regulates the passage of substances.

    2. Chloroplasts:

      • Plant cells contain chloroplasts, which are organelles responsible for photosynthesis, converting light energy into chemical energy (glucose).

      • Animal cells do not contain chloroplasts and cannot perform photosynthesis.

    3. Vacuoles:

      • Plant cells typically have one large central vacuole filled with water, nutrients, and waste products, helping maintain turgor pressure and store substances.

      • Animal cells may have small vacuoles, but they are generally less prominent and serve various functions such as storage, digestion, and waste removal.

    4. Shape:

      • Plant cells are often rectangular or polygonal in shape due to the presence of a cell wall, which maintains cell structure.

      • Animal cells are typically round or irregular in shape, with no fixed structure imposed by a cell wall.

    5. Centrioles:

      • Animal cells contain centrioles, which are involved in organizing microtubules during cell division (mitosis and meiosis).

      • Plant cells do not have centrioles, although they can still undergo cell division.

    6. Lysosomes:

      • Animal cells contain numerous lysosomes, which are membrane-bound organelles containing digestive enzymes for breaking down macromolecules and cellular waste.

      • Plant cells have fewer lysosomes, and their functions may be performed by other organelles such as vacuoles.

    7. Golgi Apparatus:

      • The Golgi apparatus in plant cells tends to be larger and more numerous than in animal cells, reflecting the need for extensive protein processing and secretion in plant cells.

      • In animal cells, the Golgi apparatus is typically smaller and less extensive.

    8. Three reasons for cell division are:

      1. Growth: As an organism grows, its body increases in size due to an increase in the number of cells. Cell division allows for the formation of new cells to accommodate this growth.

      2. Repair: Cell division plays a crucial role in repairing damaged tissues and replacing old or dying cells. When tissues are injured or worn out, cell division helps regenerate new cells to restore function and integrity.

      3. Reproduction: In multicellular organisms, cell division is essential for the reproduction of new individuals. During sexual reproduction, specialized cells divide to form gametes (sperm and egg cells), which then fuse during fertilization to produce a new organism. In asexual reproduction, a single parent organism produces offspring genetically identical to itself through mitotic cell division.

      4. Regarding the cleaning product claiming to kill "99.9% of all bacteria," a cleaned surface will not stay bacteria-free forever. Despite the high efficiency of the cleaning product, it is nearly impossible to completely eliminate all bacteria from an environment. Some bacteria may survive or be reintroduced to the surface after cleaning, leading to eventual bacterial colonization.

      Three differences between asexual reproduction and sexual reproduction are:

      1. Genetic Variation: Asexual reproduction produces offspring that are genetically identical to the parent organism, whereas sexual reproduction produces offspring with genetic variation due to the combination of genetic material from two parent organisms.

      2. Involvement of Gametes: Asexual reproduction does not involve the fusion of gametes, whereas sexual reproduction requires the fusion of specialized reproductive cells (gametes) from two parent organisms.

      3. Number of Parents: Asexual reproduction typically involves only one parent organism, while sexual reproduction involves two parent organisms, each contributing genetic material to the offspring.

      The processes responsible for chemicals moving into, throughout, and out of cells include:

      • Diffusion: The movement of molecules from an area of high concentration to an area of low concentration, down the concentration gradient.

      • Active Transport: The movement of molecules against the concentration gradient, requiring energy in the form of ATP.

      • Osmosis: The movement of water molecules across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.

      Cells divide instead of just getting bigger as an organism grows because larger cells would have difficulty efficiently transporting materials, such as nutrients and waste products, throughout the cell. By dividing into smaller cells, each cell maintains a high surface area-to-volume ratio, allowing for more efficient exchange of substances with the external environment.

      A minor wound heals over time through a process called wound healing, which involves three main phases: inflammation, proliferation, and remodeling. In the inflammation phase, blood vessels constrict to stop bleeding, and immune cells remove debris and pathogens from the wound site. In the proliferation phase, new tissue forms as cells divide and migrate to the wound site to fill the gap. In the remodeling phase, the new tissue matures and remodels to restore strength and function to the healed tissue.

    9. he cell theory:

      The cell theory states that:

      1. All living organisms are composed of one or more cells.

      2. The cell is the basic unit of structure and function in organisms.

      3. Cells arise from pre-existing cells through cell division.

      As for your cells, they are eukaryotic. Eukaryotic cells have a true nucleus, which contains the genetic material (DNA) surrounded by a nuclear membrane. They also have membrane-bound organelles such as mitochondria, endoplasmic reticulum, and Golgi apparatus.

    10. The most obvious difference between prokaryotic and eukaryotic cells is the presence of a nucleus. Prokaryotic cells do not have a true nucleus and lack membrane-bound organelles, while eukaryotic cells have a nucleus and membrane-bound organelles.

      The nucleus coordinates cell activities by controlling gene expression and directing the synthesis of proteins. It contains the cell's genetic material (DNA), which serves as instructions for building and maintaining the cell's structures and functions.

    11. When you exercise and breathe harder and faster, it's because your cells need more oxygen to produce energy. Mitochondria, known as the powerhouse of the cell, use oxygen to generate ATP (adenosine triphosphate), the cell's energy currency, through cellular respiration.

    12. Not all plant cells contain chloroplasts because chloroplasts are primarily found in cells that perform photosynthesis, such as the cells in leaves. Other plant cells, such as root cells, may not contain chloroplasts because they do not carry out photosynthesis.

    13. The function of the cell wall in plant cells is to provide structural support and protection. It helps maintain the shape of the cell and prevents it from bursting due to osmotic pressure.

    14. While plant cells can make their own glucose through photosynthesis, they still need mitochondria to produce ATP through cellular respiration. Even though they can generate energy through photosynthesis, mitochondria provide additional energy for cellular processes and activities.

    15. Cellular Respiration: The overall equation for cellular respiration is: 𝐢6𝐻12𝑂6+6𝑂2β†’6𝐢𝑂2+6𝐻2𝑂+energyΒ (ATP)C6​H12​O6​+6O2​→6CO2​+6H2​O+energyΒ (ATP) In words, glucose (C6H12O6) and oxygen (O2) are converted into carbon dioxide (CO2) and water (H2O), releasing energy in the form of ATP (adenosine triphosphate).

      Photosynthesis: The overall equation for photosynthesis is: 6𝐢𝑂2+6𝐻2𝑂+lightΒ energy→𝐢6𝐻12𝑂6+6𝑂26CO2​+6H2​O+lightΒ energyβ†’C6​H12​O6​+6O2​ In words, carbon dioxide (CO2) and water (H2O), in the presence of light energy, are converted into glucose (C6H12O6) and oxygen (O2).

    16. Cell Cycle:

      • Interphase:

        • G1 Phase (Gap 1): During G1 phase, the cell grows in size, synthesizes proteins, and carries out its normal metabolic functions. The nuclear membrane is intact, and the chromatin is dispersed throughout the nucleus. Centrosomes replicate in preparation for mitosis.

        • S Phase (Synthesis): In the S phase, DNA replication occurs within the nucleus. Each chromosome is replicated to form two sister chromatids held together at the centromere. The nuclear membrane remains intact, allowing the replication machinery access to the DNA.

        • G2 Phase (Gap 2): G2 phase is a period of further growth and preparation for cell division. The cell synthesizes additional proteins, organelles, and cytoplasmic components needed for mitosis. The nucleus continues to grow, and the nuclear membrane remains intact.

      • Mitosis:

        • Prophase: As the cell enters prophase, chromatin condenses into visible chromosomes, each consisting of two sister chromatids. The nuclear membrane begins to disintegrate, allowing spindle fibers to access the chromosomes. Centrosomes move to opposite poles of the cell, and spindle fibers begin to extend from the centrosomes.

        • Prometaphase: The nuclear envelope fully disintegrates, and spindle fibers attach to the centromeres of each chromosome. The chromosomes are now fully condensed and are free to move within the cell.

        • Metaphase: Chromosomes align along the metaphase plate, a plane equidistant between the two spindle poles. The nuclear membrane is completely dissolved, and the spindle fibers extend from the centrosomes to the chromosomes' kinetochores, ensuring proper alignment.

        • Anaphase: Sister chromatids separate and move towards opposite poles of the cell, pulled by the shortening spindle fibers. As the chromatids are pulled apart, each chromatid is now considered a separate chromosome. The nuclear membrane may begin to reform around the separated chromosomes.

        • Telophase: Chromosomes arrive at the opposite poles of the cell, and decondense into chromatin. The nuclear membrane reforms around each set of chromosomes, enclosing them in separate nuclei. The spindle fibers disassemble, and the nucleoli reappear.

      • Cytokinesis:

        • Animal Cells: In animal cells, cytokinesis involves the formation of a cleavage furrow, a contractile ring of actin and myosin filaments that forms around the cell's equator. The cleavage furrow gradually deepens, pinching the cell into two daughter cells.

        • Plant Cells: In plant cells, cytokinesis involves the formation of a cell plate, composed of Golgi-derived vesicles containing cell wall materials. The vesicles fuse at the metaphase plate, forming a new cell wall between the daughter nuclei. As the cell plate expands outward, it fuses with the existing cell membrane, dividing the cell into two daughter cells.

      Cellular Respiration: The overall equation for cellular respiration is: 𝐢6𝐻12𝑂6+6𝑂2β†’6𝐢𝑂2+6𝐻2𝑂+energyΒ (ATP)C6​H12​O6​+6O2​→6CO2​+6H2​O+energyΒ (ATP) In words, glucose (C6H12O6) and oxygen (O2) are converted into carbon dioxide (CO2) and water (H2O), releasing energy in the form of ATP (adenosine triphosphate).

      Photosynthesis: The overall equation for photosynthesis is: 6𝐢𝑂2+6𝐻2𝑂+lightΒ energy→𝐢6𝐻12𝑂6+6𝑂26CO2​+6H2​O+lightΒ energyβ†’C6​H12​O6​+6O2​ In words, carbon dioxide (CO2) and water (H2O), in the presence of light energy, are converted into glucose (C6H12O6) and oxygen (O2).


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