Cell Biology: Cytoskeleton and Energy Use
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Questions and Answers

What is the primary function of microtubules in cells?

  • Formation of daughter cells
  • Providing structural strength
  • Energy transformation during photosynthesis
  • Movement of cilia and flagella (correct)

    • Which of the following correctly describes heterotrophs?

  • Organisms that perform chemosynthesis in harsh environments
  • Net consumers of CO2 and must consume other organisms (correct)
  • Organisms that produce their own food from sunlight
  • Organisms that can synthesize complex organic molecules

    • Which of the following components do plant cells possess that animal cells do not?

  • Cell wall (correct)
  • Nucleus
  • Ribosomes
  • Mitochondria

    • What substances are produced during photosynthesis?

    <p>Oxygen and glucose</p> Signup and view all the answers

    What is the role of chloroplasts in plant cells?

    <p>Photosynthesis</p> Signup and view all the answers

    Which process allows some autotrophs to derive organic material from chemicals?

    <p>Chemosynthesis</p> Signup and view all the answers

    What is the primary characteristic of diffusion?

    <p>It seeks to achieve equilibrium between intra and extra cellular fluids.</p> Signup and view all the answers

    In cell biology, what is the primary function of intermediate filaments?

    <p>Provide structural strength</p> Signup and view all the answers

    Which of the following statements about energy transformation is true?

    <p>Energy is only transformed, never created</p> Signup and view all the answers

    Which of the following statements regarding osmosis is true?

    <p>Osmosis does not require energy.</p> Signup and view all the answers

    What happens to an animal cell placed in a hypotonic solution?

    <p>It swells and may burst.</p> Signup and view all the answers

    What is the function of channel proteins in facilitated diffusion?

    <p>To facilitate the movement of larger molecules.</p> Signup and view all the answers

    Which term describes the ability of an extracellular solution to influence water movement in a cell?

    <p>Tonicity.</p> Signup and view all the answers

    What is required for active transport mechanisms?

    <p>ATP energy.</p> Signup and view all the answers

    In which situation will an animal cell be in an isotonic solution?

    <p>It maintains its current shape with no net change in water.</p> Signup and view all the answers

    What specific molecule is transported by the sodium-potassium pump?

    <p>Sodium and potassium.</p> Signup and view all the answers

    What are homologous chromosomes?

    <p>Chromosomes that have two copies of each gene</p> Signup and view all the answers

    What is the main purpose of meiosis?

    <p>To form haploid gametes for sexual reproduction</p> Signup and view all the answers

    What occurs during Prophase I of meiosis?

    <p>Bivalents form through synapsis</p> Signup and view all the answers

    Which statement is true regarding somatic cells?

    <p>They have a diploid number of chromosomes</p> Signup and view all the answers

    What is a key difference between sexual and asexual reproduction?

    <p>Asexual reproduction does not involve the combination of cells</p> Signup and view all the answers

    What is the result of meiosis?

    <p>Four genetically non-identical daughter cells</p> Signup and view all the answers

    During which stage of meiosis does the reduction in chromosome number occur?

    <p>Meiosis I</p> Signup and view all the answers

    What process allows genetic information exchange between homologous chromosomes?

    <p>Crossing over</p> Signup and view all the answers

    What is the primary function of exocytosis in cells?

    <p>To remove waste products</p> Signup and view all the answers

    Which process allows nerve cells to exchange sodium and potassium ions?

    <p>Active transport</p> Signup and view all the answers

    What type of molecule is typically transported into cells via phagocytosis?

    <p>Large solid particles</p> Signup and view all the answers

    Why do smaller cells have a higher surface area to volume ratio?

    <p>They are more efficient at exchanging materials</p> Signup and view all the answers

    Which type of transport requires channel proteins due to the charge of the molecule?

    <p>Facilitated diffusion for ions</p> Signup and view all the answers

    What is the role of enzymes in metabolic pathways?

    <p>To catalyze biochemical processes</p> Signup and view all the answers

    Which type of endocytosis is specifically used for the uptake of liquids?

    <p>Pinocytosis</p> Signup and view all the answers

    What structure within mitochondria contains enzymes necessary for ATP synthesis?

    <p>Cristae</p> Signup and view all the answers

    What is the primary outcome of fertilisation in terms of genetic variation?

    <p>It combines DNA from different parents, increasing gene pool.</p> Signup and view all the answers

    What process occurs during prophase 1 to increase genetic variation?

    <p>Crossing over</p> Signup and view all the answers

    Which statement best describes independent assortment?

    <p>It occurs randomly during metaphase 1.</p> Signup and view all the answers

    How do mutations contribute to variation in sexually reproducing organisms?

    <p>By introducing new genetic variations in the gene pool.</p> Signup and view all the answers

    During which stage of meiosis do homologous chromosomes exchange genetic material?

    <p>Prophase 1</p> Signup and view all the answers

    What best characterizes daughter cells produced by meiosis compared to those produced by mitosis?

    <p>They are genetically similar but not identical.</p> Signup and view all the answers

    Which factor does NOT contribute to genetic variation in sexually reproducing organisms?

    <p>Genetic cloning</p> Signup and view all the answers

    What role do enzymes play during crossing over?

    <p>They cut and swap DNA sections between chromatids.</p> Signup and view all the answers

    Study Notes

    Microfilaments

    • Made of actin protein
    • Are assembled into long filaments
    • Used in movement, such as the formation of daughter cells during cytokinesis

    Microtubules

    • Made of tubulin protein
    • Are assembled into long filaments
    • Involved in the movement of cilia and flagella
    • Also help to hold organelles in place within cells

    Intermediate filaments

    • Made of multiple proteins
    • Provide strength and structural support to cells

    Animal vs Plant Cells

    • Animal cells lack a cell wall and chloroplasts
    • Plant cells have a larger vacuole and a cell wall
    • Plants can undergo photosynthesis, making them autotrophs. Animals lack this ability and are heterotrophs
    • Plants have a more rigid shape due to their cell walls

    Uses for Energy

    • Energy is needed for essential cellular processes, such as:
      • Synthesis of molecules
      • Movement
      • Cell division
      • Active transport
    • Energy cannot be created nor destroyed, only transformed from one form to another

    Autotrophs

    • Produce their own food through the conversion of external energy sources into usable energy
    • Are producers in ecosystems
    • Examples include plants
    • Can synthesize complex organic molecules, like glucose, from external energy sources, such as sunlight
    • Take in carbon dioxide and water, releasing oxygen and glucose
    • Are net consumers of carbon dioxide

    Heterotrophs

    • Obtain energy by consuming other organisms
    • Are net producers of carbon dioxide
    • Cannot synthesize their own complex organic molecules, relying on autotrophs for nutrition
    • Gain energy through eating other organisms, ultimately depending on autotrophs for all nutrients

    Chemosynthesis

    • Some autotrophs use external energy sources from chemicals to produce organic material
    • Commonly occurs in environments without sunlight, such as hydrothermal vents

    Photosynthesis

    • Occurs in plants, specifically within chloroplasts
    • Converts carbon dioxide and water into oxygen and glucose using sunlight as the energy source
    • Cells involved in photosynthesis contain numerous chloroplasts, giving them a green color due to chlorophyll
    • Specialised leaf structures maximise the rate of photosynthesis
    • Chloroplasts can move within cells to reach optimal light conditions

    Diffusion

    • Passive process, requiring no energy
    • Movement of molecules across the cell membrane, between phospholipid molecules
    • Travels with the concentration gradient, from high to low concentration
    • Aims to reach equilibrium between the intra and extra cellular fluids
    • Example: Gas exchange in the lungs

    Facilitated Diffusion

    • Passive process, requiring no energy
    • Works with the concentration gradient to reach equilibrium
    • Utilises channel proteins to facilitate the movement of larger molecules across the membrane
    • Example: Transport of glucose

    Osmosis

    • Passive transport that specifically moves water across the membrane
    • Travels through aquaporins, proteins specifically designed for water transport
    • Direction of travel is determined by the solute concentration
    • Aims to reach equilibrium
    • Hypotonic: Less concentrated solution, causing water to move into the cell
    • Isotonic: Equal concentration, no net movement of water
    • Hypertonic: More concentrated solution, causing water to move out of the cell
    • Tonicity: The ability of an extracellular solution to make water move into or out of a cell via osmosis
    • Osmolarity: The concentration of a solution expressed as the total number of solute particles per liter

    Active Transport

    • Requires energy to move molecules across the membrane
    • Utilizes protein pumps
    • Movement usually occurs against the concentration gradient
    • Transport proteins are located in the cell membrane
    • Specialized for specific molecules
    • Requires ATP to operate
    • Example: Sodium potassium pump, which occurs in nerve cells to maintain electrochemical gradients

    Exocytosis

    • A type of cytosis used to move large substances across the membrane by forming vesicles
    • Exo = exit, meaning substances are released from the cell
    • Often used for the removal of waste products
    • Vesicles containing substances from the Golgi apparatus fuse with the membrane to release their contents

    Endocytosis

    • The opposite of exocytosis, bringing substances into the cell
    • The cell membrane engulfs particles, forming a vesicle that brings the substance into the cell
    • Two types:
      • Pinocytosis: For liquids
      • Phagocytosis: For solids/food, used by white blood cells to engulf pathogens

    SA/V Ratio

    • Represents the ratio between the surface area of a cell and its volume
    • Smaller cells have a higher SA:V ratio, making them more efficient
    • Part of the reason cells divide is to maintain an efficient SA:V ratio

    Examples of Molecule Transport across the Membrane

    • Small hydrophobic molecules: (e.g. CO2 and O2) can passively diffuse across the membrane without needing additional energy or special proteins
    • Small hydrophilic molecules: (e.g. water) passively diffuse but require aquaporins for transport
    • Ions: Possessing a charge, require channel proteins for facilitated diffusion
    • Large hydrophilic molecules: (e.g. glucose and amino acids) cannot passively cross but need channel proteins or active transport depending on the concentration gradient

    Cell Metabolism

    • Refers to the biochemical processes that occur within a cell
    • Essential for cell survival
    • Highly influenced by enzymes
    • Metabolic pathways exist, with specific steps facilitated by enzymes
    • Many processes occur within membrane-bound structures
    • Membranes often contain enzymes that facilitate the metabolic pathway

    Internal membrane of mitochondria

    • Inner membrane is highly folded to form cristae
    • The membrane contains enzymes that assist in ATP synthesis, including ATP synthase

    Chromosome

    • Condensed strands of DNA and proteins that carry genetic information

    Cytokinesis

    • The last stage of the cell cycle where the cytoplasm splits

    Cytoplasm

    • The entire internal environment of a cell, including the cytosol and organelles

    Cytosol

    • The liquid component of the cytoplasm

    Cristae

    • Folded inner membrane of a mitochondria

    Somatic vs Germline/Gametes

    • Somatic cells are all body cells, containing a diploid number of chromosomes
    • Germline cells are sex cells/gametes (egg and sperm), containing a haploid number of chromosomes

    Homologous Chromosomes

    • Chromosomes of the same type, carrying the same genes but potentially different alleles (e.g., chromosome 1 from the mother and father)

    Sexual Reproduction vs Asexual Reproduction

    • Sexual reproduction involves the combination of two different cells (usually from different parents) to form a new organism
    • Asexual reproduction does not require the fusion of two cells
    • Sexual reproduction requires fertilization
    • Some plants can self-fertilize, involving one parent organism but still requiring the fusion of two cells

    Meiosis

    • Cell division that forms haploid cells with half the number of chromosomes
    • Results in four genetically non-identical daughter cells
    • In animals, occurs in the gonads
    • Two stages:
      • Meiosis I: Reduction stage, halves the number of chromosomes
      • Meiosis II: Similar to mitosis, separates chromatids

    Meiosis I: Reduction Stage

    • Prophase I:
      • Chromosomes condense and become visible
      • Sister chromatids pair up
      • Homologous chromosomes also pair, a process called synapsis, forming structures called bivalents (four chromatids together)
      • Nuclear membrane dissolves
      • Spindle fibres start to form
      • Genetic information is exchanged between homologous pairs through crossing over

    Variation

    • Due to differences between meiosis and mitosis, the daughter cells produced from meiosis are not genetically identical
    • This genetic variation is essential for evolution, allowing populations to adapt to changing environments

    Crossing Over

    • Occurs during prophase I when bivalents form
    • Genetic material is swapped between homologous chromosome pairs
    • The point of swapping is called a chiasmata
    • Regions of DNA from different chromosomes are cut and exchanged, creating recombinant DNA
    • This process is completely random, occurring 2-3 times per chromosome

    Independent Assortment

    • Occurs during metaphase I
    • Homologous pairs align at the metaphase plate (center of the cell)
    • The orientation of each pair is random, determining which pole the maternal and paternal chromosomes will face
    • Increases variation in daughter cells as the homologous pairs are pulled apart during anaphase.

    Fertilization

    • Random process where the sperm and egg fuse
    • Increases genetic variability, as it is impossible to predict which specific sperm and egg will combine

    Mutations

    • Can occur in both sexually and asexually reproducing organisms
    • Rare but introduce new variations into the genome
    • The only source of variation in asexually reproducing organisms

    Cell Division

    • Process by which cells split and duplicate
    • Occurs through mitosis, binary fission, or meiosis
    • Essential for growth, repair, and reproduction.

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    Description

    Explore the fascinating structures of the cytoskeleton including microfilaments, microtubules, and intermediate filaments. Learn about the key differences between animal and plant cells, and discover how energy is utilized in various cellular processes such as movement and cell division.

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