Topic 2 A: Cell Structure and Division Flashcards
What is the primary function of the nucleus in a cell?
It controls cell activities by regulating DNA transcription.
Describe the structure of the mitochondrion.
Mitochondria are oval with a double membrane; the inner membrane is folded into cristae, with a matrix inside containing enzymes for respiration.
What is the role of the Golgi apparatus?
It processes, modifies, and packages new lipids and proteins and produces lysosomes.
How does rough endoplasmic reticulum (RER) differ from smooth endoplasmic reticulum (SER)?
RER has ribosomes attached and folds proteins, while SER synthesizes and processes lipids without ribosomes.
What is the function of lysosomes in the cell?
Lysosomes contain digestive enzymes to break down waste materials and cellular debris.
Explain the structural adaptation of red blood cells for oxygen transport.
Red blood cells lack a nucleus, maximizing space for hemoglobin to carry oxygen.
How does the cell membrane control cellular activity?
It regulates movement of substances in and out and responds to chemical signals.
Describe the structure and role of chloroplasts.
Chloroplasts contain thylakoids stacked into grana for photosynthesis, surrounded by stroma.
What is the purpose of the cell wall in plants, algae, and fungi?
It provides structural support and prevents cells from changing shape.
Define the function of ribosomes.
Ribosomes are the sites of protein synthesis in cells.
What is the role of the cell vacuole in plants?
It maintains cell pressure, keeps the cell rigid, and stores chemicals.
How do prokaryotic cells differ structurally from eukaryotic cells?
Prokaryotes lack a nucleus and membrane-bound organelles; they have smaller ribosomes and a cell wall made of murein.
Describe the function of plasmids in prokaryotic cells.
Plasmids are small DNA loops that often carry genes, like antibiotic resistance.
Explain the structure and function of viral capsids.
The capsid is a protein coat surrounding viral DNA or RNA, with attachment proteins for host cell binding.
What is the purpose of cell fractionation?
It isolates organelles by breaking cells apart, filtering, and centrifuging at various speeds.
How is the magnification of a microscope calculated?
Magnification = size of image ÷ actual size of object.
Describe the differences between magnification and resolution.
Magnification enlarges an image; resolution distinguishes two close points as separate.
What is the maximum resolution of an optical microscope?
Approximately 0.2 micrometers.
How does a transmission electron microscope (TEM) work?
TEMs use electrons to pass through a specimen, creating detailed images of cell interiors.
Why are electron microscopes better suited for studying small structures?
They offer much higher resolution than optical microscopes.
What is a limitation of transmission electron microscopes (TEM)?
TEMs cannot observe living specimens due to the vacuum requirement and specimen preparation.
How does a scanning electron microscope (SEM) differ from a TEM in function?
SEMs scan the surface of specimens to produce 3D images rather than viewing internal structures.
What is cell division, and why is it important?
Cell division is the process of creating new cells, essential for growth, repair, and reproduction.
Describe the basic stages of the cell cycle.
The cell cycle includes interphase (cell growth and DNA replication), mitosis (nuclear division), and cytokinesis (cytoplasmic division).
What occurs during interphase?
The cell grows, replicates DNA, and synthesizes necessary proteins and organelles.
What happens in prophase during mitosis?
Chromosomes condense, the nuclear envelope dissolves, and spindle fibers begin to form.
What key events occur during metaphase?
Chromosomes align at the cell’s equator, attached to spindle fibers by their centromeres.
Describe what happens in anaphase.
Centromeres split, and spindle fibers pull sister chromatids to opposite poles of the cell.
What occurs during telophase in mitosis?
Chromatids reach the poles, the nuclear envelope reforms around each set, and chromosomes decondense.
Define cytokinesis and its role in cell division.
Cytokinesis is the final division of the cytoplasm, resulting in two separate cells.
How is the cell cycle regulated?
Through checkpoints controlled by proteins that ensure each stage is completed accurately.
What is a tumor, and how does it relate to cell division?
A tumor is an uncontrolled mass of cells due to mutations in genes that regulate the cell cycle.
How do cancer treatments target cell division?
Treatments often disrupt DNA replication or mitosis, slowing tumor growth but also affecting healthy dividing cells.
Describe the process and purpose of mitosis.
Mitosis creates two genetically identical daughter cells, used for growth, tissue repair, and asexual reproduction.
What is binary fission, and in which organisms does it occur?
Binary fission is cell division in prokaryotes, resulting in two genetically identical cells.
How does DNA replication differ in prokaryotic cells?
Prokaryotes replicate DNA by copying a single circular chromosome before division.
What role do attachment proteins play in viruses?
They allow viruses to bind to host cells, enabling entry for infection.
Describe the process of ultracentrifugation.
Cells are fractionated, and organelles are separated by density through spinning at various speeds.
How does the S phase of the cell cycle relate to cancer development?
Mutations during the S phase (DNA replication) can lead to errors in genes that control cell division, promoting cancer.
What is an artefact in microscopy, and how can it affect observations?
Artefacts are distortions or misinterpretations in microscope images, which can be mistaken for real cell structures.
What is mitosis?
Mitosis is a type of cell division that results in two genetically identical daughter cells from a single parent cell.
In what type of organisms does mitosis primarily occur?
Mitosis occurs in eukaryotic organisms, used for growth, repair, and asexual reproduction.
What are the main stages of the cell cycle in order?
Interphase, mitosis (prophase, metaphase, anaphase, telophase), and cytokinesis.
What is the purpose of mitosis?
Mitosis ensures genetic consistency across cells, aiding in growth, tissue repair, and asexual reproduction.
What occurs during interphase before mitosis begins?
The cell grows, duplicates its DNA, and prepares for division by synthesizing proteins and organelles.
Describe prophase in mitosis.
Chromosomes condense and become visible, the nuclear envelope dissolves, and spindle fibers start to form from centrioles.
What is the role of spindle fibers in mitosis?
Spindle fibers attach to chromosomes at their centromeres and help separate sister chromatids during cell division.
What happens to chromosomes during metaphase?
Chromosomes align along the cell’s equator, with each centromere attached to spindle fibers from opposite poles.
Describe anaphase.
Centromeres divide, and spindle fibers pull sister chromatids toward opposite poles of the cell.
What changes occur during telophase?
Chromatids reach the cell poles, decondense into chromatin, and are enclosed by newly formed nuclear envelopes.
What is cytokinesis?
Cytokinesis is the division of the cytoplasm, which completes the cell division process, resulting in two separate cells.
How does cytokinesis differ between plant and animal cells?
In animal cells, a cleavage furrow forms and pinches the cell into two; in plant cells, a cell plate forms to separate the new cells.
What are sister chromatids?
Sister chromatids are identical copies of a chromosome, joined together at a centromere, produced during DNA replication.
What is the function of centromeres in mitosis?
Centromeres hold sister chromatids together and serve as attachment points for spindle fibers during mitosis.
How does mitosis ensure genetic consistency in daughter cells?
Each daughter cell receives an identical set of chromosomes, maintaining the same DNA as the parent cell.
What is the significance of G1, S, and G2 phases in relation to mitosis?
G1 (cell growth), S (DNA synthesis), and G2 (preparation for mitosis) are interphase stages where the cell readies for mitosis.
How do cancer treatments target mitosis?
Some treatments disrupt stages of mitosis to slow or stop the rapid cell division in tumors.
How long does mitosis typically take in comparison to interphase?
Mitosis is a shorter phase, with interphase taking up most of the cell cycle as the cell grows and prepares for division.
Why is mitosis important for multicellular organisms?
It supports growth, tissue maintenance, and repair by creating identical cells for the organism’s development and functioning.
What would happen if errors occurred during mitosis?
Errors can lead to abnormal chromosome numbers in cells, potentially resulting in conditions like cancer or genetic disorders.
What is the purpose of investigating mitosis?
To observe and analyze cell division stages in rapidly growing tissues, like plant root tips.
Describe the purpose of preparing a ‘root tip squash’ in mitosis experiments.
It spreads out cells thinly for easier microscopic viewing of mitotic stages.
Why are plant root tips used to study mitosis?
Root tips have actively dividing cells, making mitosis more observable.
What initial step is required in preparing a root tip squash?
Add 1 M hydrochloric acid to a boiling tube and heat it to 60°C in a water bath.
Why must the root tip be placed in hydrochloric acid?
Acid treatment softens the cell walls, making it easier to spread the cells.
What safety precautions should be taken during this experiment?
Wear safety goggles, a lab coat, and gloves when handling chemicals and stains.
What is the purpose of staining in a root tip squash?
Staining helps visualize chromosomes during mitosis.
Name common stains used for observing mitosis.
Examples include toluidine blue, ethano-orcein, and Feulgen stain.
What is the next step after staining in the root tip squash method?
Cover the sample with a coverslip, and use filter paper to apply even pressure without sideways movement.
Why is it essential to squash the tissue during slide preparation?
Squashing makes the tissue thinner, allowing light to pass through for clear microscopic imaging.
Describe the setup for viewing cells under an optical microscope.
Secure the slide on the microscope stage, select a low-power lens, and use the coarse and fine adjustment knobs to focus.
How do you calculate the mitotic index?
Divide the number of cells undergoing mitosis by the total number of cells observed.
Why is the mitotic index important?
It indicates the proportion of dividing cells, useful for assessing growth rate or abnormal tissue activity.
In what tissues would you expect a high mitotic index?
Rapidly growing tissues, like root tips, or tissues undergoing repair or cancerous growth.
How do you calculate the actual size of a cell observed under a microscope?
Use the formula: actual size = image size ÷ magnification.
What is an eyepiece graticule, and how is it used?
It’s a scaled ruler in the eyepiece that allows measurement of specimens by calibrating with a stage micrometer.
How can the magnification of a microscope be calculated?
Multiply the magnifications of the objective lens and the ocular lens.
What is the advantage of a high mitotic index in plant root tips?
Indicates active growth, which is vital for root expansion and nutrient absorption.
What might an unusually high mitotic index in other tissues indicate?
It may suggest tissue repair or potential cancerous growth.
How long does each stage of mitosis last in an experiment?
Duration varies by cell type; calculate specific times by observing cell cycle proportions under controlled conditions.
