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Anatomy & Physiology: Cell Structure, Membrane Potential, and Protein Synthesis

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  • What is resting membrane potential (RMP)?

    Resting membrane potential is the electrical potential energy produced by the separation of oppositely charged particles across the plasma membrane in all cells, typically ranging from –50 to –100 mV.

  • Which ion is the key player in establishing the resting membrane potential?

    Potassium (K+) diffuses out of the cell through leakage channels, making the inside of the cell more negative and establishing the RMP around –90 mV.

  • How does sodium (Na+) influence the resting membrane potential?

    Na+ is attracted to the negative interior of the cell and can raise the RMP to about –70 mV, but the membrane is more permeable to K+, so K+ has the primary influence.

  • What role does the Na+-K+ pump play in maintaining RMP?

    The Na+-K+ pump actively ejects 3 Na+ ions out and brings 2 K+ ions in, maintaining the electrochemical gradients and steady state of the resting membrane potential.

  • What are the two main types of endoplasmic reticulum (ER) and their functions?

    Rough ER has ribosomes and synthesizes proteins; Smooth ER synthesizes lipids, absorbs and transports lipids, and stores/releases calcium.

  • What is the function of mitochondria in the cell?

    Mitochondria produce most of the cell's ATP via aerobic respiration and have their own DNA, RNA, and ribosomes.

  • What are ribosomes and their two forms?

    Ribosomes are nonmembranous organelles that synthesize proteins; they exist as free ribosomes in the cytosol or membrane-bound on the rough ER.

  • What is the Golgi apparatus responsible for?

    The Golgi apparatus modifies, concentrates, and packages proteins and lipids received from the rough ER for transport or secretion.

  • What are lysosomes and their function?

    Lysosomes are membranous sacs containing digestive enzymes that degrade bacteria, viruses, toxins, and nonfunctional organelles.

  • Describe the cytoskeleton and its role.

    The cytoskeleton is a network of protein rods that provide structural support, aid in cell movement, and organize cell components.

  • What is the centrosome and what do centrioles do?

    The centrosome is the microtubule organizing center near the nucleus; centrioles help organize microtubules and form the bases of cilia and flagella.

  • What are microvilli and their function?

    Microvilli are fingerlike projections of the plasma membrane that increase the cell's surface area for absorption.

  • What are the main components of the nucleus?

    The nucleus contains the nuclear envelope, nucleoli (for rRNA synthesis), and chromatin (DNA, RNA, and proteins).

  • What is chromatin and how is it organized?

    Chromatin is DNA wrapped around histone proteins forming nucleosomes; condensed chromatin forms chromosomes during cell division.

  • What are the two major periods of the cell cycle?

    Interphase (cell growth and DNA replication) and mitotic phase (cell division including mitosis and cytokinesis).

  • List the four stages of mitosis.

    1. Prophase, 2. Metaphase, 3. Anaphase, 4. Telophase – stages ensuring equal DNA distribution to daughter cells.

  • What happens during prophase of mitosis?

    Chromatin condenses into chromosomes, centrosomes move to poles, nuclear envelope breaks down, and spindle fibers attach to chromosomes.

  • What occurs during metaphase?

    Chromosomes align at the cell's equator along the metaphase plate, preparing for separation.

  • Describe anaphase in mitosis.

    Sister chromatids separate at centromeres and are pulled toward opposite poles of the cell.

  • What are the key events in telophase?

    Chromosomes uncoil into chromatin, nuclear envelopes reform, nucleoli reappear, and the spindle disappears.

  • What is cytokinesis?

    Cytokinesis is the division of the cytoplasm, where a contractile ring pinches the cell into two daughter cells.

  • What signals regulate cell division?

    Go signals include surface-to-volume ratio and growth factors; stop signals include contact inhibition and space availability.

  • What is the role of DNA in protein synthesis?

    DNA holds the genetic code for proteins, with genes specifying amino acid sequences via triplet codes.

  • How does RNA differ from DNA?

    RNA uses uracil instead of thymine and ribose sugar instead of deoxyribose; it acts as a messenger and translator of DNA code.

  • What are the three types of RNA and their functions?

    mRNA carries the code from DNA, rRNA forms ribosomes, and tRNA delivers amino acids for protein assembly.

  • What are the two main steps of protein synthesis?

    Transcription copies DNA to mRNA; translation decodes mRNA to assemble amino acids into polypeptides.

  • What happens during transcription?

    DNA base sequence is copied into complementary mRNA, which then leaves the nucleus for protein synthesis.

  • Describe translation in protein synthesis.

    mRNA codons are read by ribosomes, and tRNA brings corresponding amino acids to form a polypeptide chain.

  • How are proteins processed in the rough ER?

    Proteins synthesized on rough ER ribosomes are enclosed in vesicles and sent to the Golgi apparatus for modification and packaging.