Cell Biology: Mitochondria and Peroxisomes
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Questions and Answers

What is the primary function of microtubules in a cell?

  • Cell shape maintenance
  • Support and maintain organelle position (correct)
  • Movement of the cell
  • Protein synthesis

    • Which structure is primarily responsible for increasing the absorptive area of a cell?

  • Cilia
  • Flagellum
  • Microvilli (correct)
  • Centrioles

    • What role do centrioles play during mitosis?

  • Separate chromosomes (correct)
  • Synthesize proteins
  • Detoxify free radicals
  • Move particles across the cell surface

    • Which of the following best describes the term 'semipermeable' in relation to cell membranes?

    <p>Allows some molecules to pass while inhibiting others</p> Signup and view all the answers

    Which structure enables sperm to swim?

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

    What is the primary function of mitochondria within a cell?

    <p>Energy production</p> Signup and view all the answers

    Which of the following is a role of peroxisomes in the cell?

    <p>Lipid metabolism</p> Signup and view all the answers

    What severe condition can Reactive Oxygen Species (ROS) contribute to?

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

    Which structure in the cell is critical for supporting cell movement?

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

    How do antioxidants help the body in relation to ROS?

    <p>They neutralize reactive molecules</p> Signup and view all the answers

    Which of the following is NOT a cause of oxidative stress?

    <p>Chemical detoxification</p> Signup and view all the answers

    What is the role of the electron transport chain in mitochondria?

    <p>Convert glucose to ATP</p> Signup and view all the answers

    What happens when a cell undergoes apoptosis?

    <p>It undergoes programmed cell death</p> Signup and view all the answers

    What is the primary function of a gene?

    <p>To code for a single protein</p> Signup and view all the answers

    What role does helicase play in DNA replication?

    <p>It unwinds and separates the DNA strands</p> Signup and view all the answers

    How are the nitrogenous bases of DNA paired?

    <p>Adenine pairs with Thymine, Cytosine with Guanine</p> Signup and view all the answers

    What is the role of the centromere during cell division?

    <p>It attaches two sister chromatids together.</p> Signup and view all the answers

    Which phase of the cell cycle involves the actual division of the cell's nucleus?

    <p>M Phase</p> Signup and view all the answers

    What happens to chromatin during cell division?

    <p>It condenses to form chromosomes</p> Signup and view all the answers

    What is produced during the second step of DNA replication?

    <p>Two duplicate DNA strands</p> Signup and view all the answers

    During which phase do spindle fibers align chromosomes at the cell equator?

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

    What is the main function of the S phase in the cell cycle?

    <p>To replicate DNA.</p> Signup and view all the answers

    What is contained within a chromosome?

    <p>Condensed DNA and associated proteins</p> Signup and view all the answers

    What is the significance of the S phase in the cell cycle?

    <p>It is when DNA replicates itself</p> Signup and view all the answers

    What happens during the telophase of mitosis?

    <p>The nuclear membrane reforms around the chromosomes.</p> Signup and view all the answers

    What is the sugar component found in DNA?

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

    Which type of cell is described as having two copies of a chromosome?

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

    What is the primary event that occurs during anaphase?

    <p>Centromeres divide and sister chromatids are pulled apart.</p> Signup and view all the answers

    Which phase is considered the resting phase of the cell cycle?

    <p>G0 Phase</p> Signup and view all the answers

    What is the primary role of tRNA in the translation process?

    <p>To carry amino acids to the ribosome</p> Signup and view all the answers

    Which of the following statements is true regarding mRNA?

    <p>mRNA is produced during the transcription process</p> Signup and view all the answers

    What initiates the transcription process?

    <p>RNA polymerase attaching to a gene</p> Signup and view all the answers

    What is the role of the start codon in the translation process?

    <p>It encodes the first amino acid in the protein sequence</p> Signup and view all the answers

    Which statement correctly describes the difference between DNA and RNA?

    <p>DNA is single-stranded, RNA is double-stranded</p> Signup and view all the answers

    During transcription, what is the function of the template strand of DNA?

    <p>It is the strand that is copied into mRNA</p> Signup and view all the answers

    What is the process of building proteins from amino acids called?

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

    Which component of the ribosome is primarily responsible for reading the mRNA?

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

    Study Notes

    Mitochondrion

    • The mitochondria is the powerhouse of the cell.
    • It produces energy for the cell through cellular respiration.
    • Cellular respiration is the process of burning carbohydrates to make energy for the cell.
    • Mitochondria produce 95% of the ATP a cell uses.
    • The inner membrane of the mitochondria performs oxidative phosphorylation.
    • Oxidative phosphorylation makes ATP with the electron transport chain.
    • Mitochondria are self-replicating.
    • Mitochondria have their own DNA and ribosomes to make needed proteins.
    • Cells with high energy needs have many thousands of mitochondria.

    Peroxisome

    • Peroxisomes perform many functions in the cell including:
      • Lipid metabolism
      • Chemical detoxification
    • Peroxisomes contain enzymes that produce hydrogen peroxide (H2O2).
    • Peroxisomes then reduce H2O2 to water to reduce oxidative stress from free radicals.

    Oxidative Stress

    • Reactive Oxygen Species (ROS) are unstable molecules containing oxygen.
    • ROS try to donate extra electrons to other molecules, leading to damage.
    • Free radicals steal or donate electrons, which can cause cell damage.
    • ROS are responsible for the aging process, atherosclerosis, neuronal diseases, mutations, and cancer.
    • Examples of ROS include:
      • Hydroxyl radical (OH)
      • Hydrogen Peroxide (H2O2)
      • Superoxide

    Sources of ROS

    • Oxidative phosphorylation in the mitochondria
    • Inflammatory pathways
    • Respiratory burst by neutrophils
    • Ischemia (lack of blood flow)

    External Factors that Create Free Radicals

    • Smoking
    • Drugs and alcohol
    • Pollution
    • Chemicals like pesticides
    • UV radiation

    Cytoskeleton

    • The cytoskeleton provides structural support, aids in cell motility, cell reproduction, and transportation of substances within the cell.
    • The cytoskeleton is made of three fibrous proteins:
      • Microtubules
      • Intermediate filaments
      • Microfilaments
    • Microtubules support and maintain organelle position.
    • Intermediate filaments provide cell shape and support.
    • Microfilaments are involved in cell movement.

    Microvilli

    • Microvilli are made of microfilaments of the cytoskeleton.
    • Microvilli increase a cell's absorptive area.

    Flagellum

    • The only human cell that uses flagella are sperm cells.
    • Flagella are made of microtubules of the cytoskeleton.
    • They propel sperm cells.
    • Flagella are longer than cilia.

    Cilia

    • Cilia are made of microtubules of the cytoskeleton.
    • Cilia have the motility to move substances across cell surfaces.
    • Cilia are longer than microvilli.

    Centriole

    • Centrioles make microtubules.
    • Microtubules help separate chromosomes during mitosis.

    Ribosomes

    • Ribosomes make proteins.

    Lysosomes

    • Lysosomes are digestive sacs.

    Golgi Apparatus

    • The Golgi apparatus modifies, sorts, and packages material for export.

    Smooth ER

    • Smooth ER makes cell membrane lipids.

    Rough ER

    • Rough ER makes protein within a membrane for export.

    Nucleus

    • The nucleus holds the genome of the cell.

    Cytosol

    • Cytosol is the liquid-like portion of the cytoplasm absent the organelles.

    Cell Membrane and Active and Passive Transport

    • The cell membrane acts as:
      • A barrier
      • A self-identifier
      • Contains receptors for hormones
    • The cell membrane is semipermeable.
      • Some molecules are allowed to pass through the membrane, while others are not.
    • Hydrophobic means non-polar and fears water.
    • Hydrophilic means polar and likes water.
    • Amphipathic means containing both hydrophobic and hydrophilic parts.
    • The cell membrane is amphipathic.

    DNA and DNA Replication

    • A gene is a sequence of DNA that codes for a single protein.
    • Chromatin refers to loose strands of DNA.
    • Chromosomes are condensed structures of DNA and proteins formed during cell division.
    • Human chromosomes are organized in 23 pairs.

    Nitrogenous Bases

    • DNA is a nucleic acid made of nucleotides containing nitrogenous bases.
    • The nitrogenous bases are arranged in complimentary base pairs.
    • The two strands of DNA form a double-helix.
    • The nitrogenous bases are:
      • Adenine (A)
      • Thymine (T)
      • Cytosine (C)
      • Guanine (G)
    • DNA also contains deoxyribose and phosphate groups.
    • Complementary bases are:
      • A-T
      • C-G
    • Bases are held together by hydrogen bonds.

    Chromatin

    • DNA is usually found in loose strands called chromatin.
    • Chromatin is wound around proteins (histones) for packaging, and called a nucleosome.

    Chromosome

    • During cell division, chromatin condenses into a visible structure, known as a chromosome.
    • Humans have 23 pairs of chromosomes, totaling 46 chromosomes.

    Genes

    • Both forms of DNA, loose chromatin and densely coiled chromosomes, hold the genes each cell needs to operate.
    • A gene is a segment of DNA that codes for a product, usually a protein.
    • The sequence of bases found on DNA is the genetic code that is read to make a protein.
    • Before a cell can divide, the DNA needs to be replicated.

    Helicase

    • Helicase is an enzyme needed for replication.
    • Helicase separates the hydrogen bonds between base pairs.

    DNA Polymerase

    • DNA polymerase is a DNA replication enzyme.
    • DNA polymerase brings in the complementary base to build a new strand.
    • Once two new strands are built, the process stops.

    DNA Replication

    • The process of DNA duplicating itself.
    • Occurs during the S phase of the cell cycle.
    • Needed to produce identical daughter cells during mitotic cell division.
    • Unwound DNA strands serve as templates for new complementary strands.
    • DNA polymerase and other enzymes add nucleotides to the template strands following the base pair rule.

    Steps of DNA Replication

    1. Unwinding of the DNA strand by the helicase enzyme. Breaks hydrogen bonds between nitrogenous bases.
    2. Creation of two new identical strands by DNA polymerase. Two duplicate DNA molecules are produced.

    Phases of the Cell Cycle and Potential Disruptions

    • Diploid: A cell with two copies of each chromosome.
    • Homologous: A pair of chromosomes, one from each parent.
    • Sister Chromatid: Exact copies of DNA molecules found during mitosis.
    • Centromere: The structure that attaches two sister chromatids together.
    • Somatic Cell: Normal body cell (does not include sex cells: eggs or sperm).
    • Sex Cell: Cells containing one half (haploid) of the somatic cells.

    Cell Cycle

    • The lifespan of a eukaryotic somatic (any cell besides sex cells) cell.
    • Happens in 4 phases:
      • Interphase
      • M Phase (Cell Division)

    Interphase

    • Occurs when a cell is not dividing.
    • The cell performs normal functions and prepares for division.
    • Consists of G0, G1, S, and G2 phases.
    • G0: Resting phase of the cell cycle.
    • G1: First growth phase, the cell is growing and performing normal functions.
    • S: Cell enters S (Synthesis) phase when it grows too large to function well, and needs to divide. A copy of DNA is being made (DNA replication).
    • G2: Growth 2/Gap Phase 2. Further cell division preparation (Mitosis).

    M Phase (Cell Division)

    • Consists of Mitosis and Cytokinesis.

    Mitosis

    • The division of the cell's nucleus.
    • Further divided into 4 phases:
      • Prophase
      • Metaphase
      • Anaphase
      • Telophase

    Prophase

    • The longest phase of mitosis.
    • Chromatin begins to condense into the shape of chromosomes.
    • The nucleolus and nuclear membrane disappear.
    • Chromosomes begin to appear.
    • Spindle fibers begin to form.
    • Sister chromatids are held together by centromeres in the middle.

    Metaphase

    • Centrioles complete movement and chromosomes line up to the middle of the cell (equator).
    • Spindle fibers align the chromosomes in the middle.

    Anaphase

    • The spindle fibers separate the sister chromatids at their centromere into two separate groups of chromosomes. Pull towards poles.
    • Now individual chromosomes, spindle fibers shorten, and they are a V shape.
    • Move to opposite sides of the pole towards the centrioles. Centrioles are at the poles.

    Telophase

    • The nuclear membrane and nucleolus reforms around chromosomes, then chromosomes spread out into chromatin.

    Cytokinesis

    • The division of the cytoplasm.

    Codon

    • Part of a gene containing the code for each specific amino acid in a protein (3 nitrogenous bases).

    Triplet

    • The process of protein synthesis starts in the nucleus and ends at the ribosome.
    • Proteins are shape dependent and run many of the cells function as enzymes.
    • Protein synthesis is called gene expression.
    • Not all genes are expressed at all times.
    • DNA > RNA > Protein
    • Triplet > Codon > Amino Acid
    • Most types of RNA, including mRNA, are single-stranded and contain no complementary strand.
    • RNA is important for building proteins.
    • RNA contains ribose, whereas DNA has deoxyribose.
    • Instead of thymine, RNA contains the base uracil.
    • Adenine will always pair up with uracil during the protein synthesis process.

    Transcription

    • Transcription is the process of building messenger RNA.
    • Transcription takes place in the nucleus.
    • Transcription is not related to replication.
    • Transcription is the process of copying genetic ‘code’ into mRNA.

    Transcription Process

    • The first step in the process of using the genetic code in DNA to synthesize different proteins.
    • Proteins are made outside the nucleus (in ribosomes).
    • DNA uses mRNA (messenger RNA) to carry the genetic code from the nucleus to the ribosome.
    • Transcription begins when the enzyme RNA polymerase attaches to a gene.
    • The gene contains the code to build protein.
    • RNA polymerase causes a specific area of a DNA strand to unwind and separate into two strands.
    • Template strand- transcribed by RNA, contains complementary bases.
    • Non-template strand- not transcribed.
    • DNA is written in three base groups called a triplet.
    • RNA is written in three bases called codons.
    • mRNA is a copy of the non-template strand with uracil instead of thymine.

    Translation

    • Uses the mRNA and ribosomes to create a protein.
    • Begins at a start codon (AUG) and ends when it reaches a stop codon.
    1. mRNA leaves the nucleus through a pore and associates with a ribosome (made of rRNA) either in the cytoplasm or attached to the endoplasmic reticulum.
    2. The ribosome “reads” the mRNA, and tRNA carries in the complimentary anticodon that matches the codon on mRNA. If the codon is AUG then the anticodon is UAC.
    3. Each tRNA drops off the amino acid it carries, and the amino acids are joined together by peptide bonding.

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    Description

    Explore the fascinating functions of mitochondria and peroxisomes in cellular biology. This quiz covers energy production, oxidative phosphorylation, lipid metabolism, and the role of reactive oxygen species. Test your knowledge of these essential organelles and their importance in maintaining cellular health.

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