AP Biology Unit 2: The Cell
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Questions and Answers

What is the primary function of the nucleus in a cell?

  • Package and modify synthesized proteins
  • Synthesize proteins using ribosomes
  • Store genetic material and facilitate transcription (correct)
  • Detoxify harmful substances

    • Which structure is responsible for synthesizing proteins that will be secreted from the cell?

  • Smooth endoplasmic reticulum
  • Rough endoplasmic reticulum (correct)
  • Golgi apparatus
  • Nucleus

    • What role does the Golgi apparatus play in a cell?

  • Facilitate transcription of DNA
  • Package and modify proteins (correct)
  • Store calcium ions
  • Synthesize amino acids

    • What is a key function of the smooth endoplasmic reticulum?

    <p>Detoxification and lipid synthesis (D)</p> Signup and view all the answers

    Which part of the ribosome is responsible for binding to mRNA during translation?

    <p>Small subunit (A)</p> Signup and view all the answers

    What is the primary function of ribosomes in protein synthesis?

    <p>To read mRNA and synthesize amino acids. (D)</p> Signup and view all the answers

    Which part of the mitochondria is responsible for oxidative phosphorylation?

    <p>Inner membrane. (A)</p> Signup and view all the answers

    Which structure within the chloroplast is involved in capturing solar energy for photosynthesis?

    <p>Thylakoid. (D)</p> Signup and view all the answers

    What indicates that mitochondria may have originated from prokaryotes?

    <p>The presence of circular DNA. (C)</p> Signup and view all the answers

    What role do lysosomes play in the cell?

    <p>Digestion of macromolecules. (C)</p> Signup and view all the answers

    What type of molecules can primarily pass through the membrane via simple diffusion?

    <p>Small and non-polar molecules (B)</p> Signup and view all the answers

    How do facilitated diffusion and active transport differ fundamentally?

    <p>Facilitated diffusion occurs down a concentration gradient, while active transport moves against it. (D)</p> Signup and view all the answers

    What type of transport protein is responsible for binding and carrying substances across the membrane?

    <p>Carrier protein (B)</p> Signup and view all the answers

    Which process is specifically utilized for the intake of large particles into a cell?

    <p>Phagocytosis (A)</p> Signup and view all the answers

    What characterizes active transport in cellular processes?

    <p>It requires energy input to move substances against their concentration gradient. (D)</p> Signup and view all the answers

    What is the primary function of hydrolytic enzymes in cells?

    <p>To break down bacteria and recycle organic materials (C)</p> Signup and view all the answers

    What role does the central vacuole play in plant cells?

    <p>Provides structure by storing water and maintaining turgor pressure (A)</p> Signup and view all the answers

    Why is a high surface area to volume ratio considered favorable for cells?

    <p>It enables faster diffusion of materials across the cell membrane (B)</p> Signup and view all the answers

    What is the main purpose of cholesterol in the plasma membrane?

    <p>To act as a buffer, maintaining membrane fluidity at varying temperatures (B)</p> Signup and view all the answers

    Which of the following accurately describes simple diffusion?

    <p>It is a passive process where materials move down their concentration gradient (D)</p> Signup and view all the answers

    Study Notes

    Cell Structure and Function

    • Nucleus:
      • Contains DNA, the genetic material.
      • Composed of a double membrane (nuclear envelope) with pores.
      • Pores allow mRNA to exit for translation and proteins/enzymes to enter for transcription.
      • Stores genetic material (DNA/RNA).
      • Site of transcription (RNA synthesis).
      • Assembles ribosomes (using rRNA).
    • Rough Endoplasmic Reticulum (Rough ER):
      • Network of flattened sacs connected to the nuclear envelope.
      • Studded with ribosomes, facilitating protein synthesis within a membrane.
      • Synthesizes secreted proteins (exocytosis).
      • Important for cell compartmentalization and mechanical support.
      • Involved in intracellular transport (vesicle movement).
    • Smooth Endoplasmic Reticulum (Smooth ER):
      • Extension of Rough ER, no ribosomes.
      • Critical for detoxification of harmful substances.
      • Stores calcium ions (Ca²⁺) in muscle cells, acting as a secondary messenger in cell signaling pathways.
      • Site of lipid synthesis (steroids, other lipids).
    • Golgi Apparatus (Golgi):
      • Stacks of flattened sacs.
      • Packages and modifies proteins and other macromolecules (carbohydrates) made by the Rough ER.
      • Involved in protein transport to the plasma membrane for secretion.
    • Ribosomes:
      • Composed of a large and small subunit, both made of rRNA and proteins.
      • Synthesize proteins via translation, reading mRNA.
      • Can be free in the cytoplasm or bound to the Rough ER.
    • Mitochondria:
      • Double membrane: outer membrane and inner membrane (cristae).
      • Cristae are highly folded (increased surface area) for oxidative phosphorylation.
      • Contains its own DNA and ribosomes (endosymbiotic theory).
      • Site of oxidative phosphorylation (third step of cellular respiration).
      • Matrix (inner space of the cristae) is the site of the Krebs/citric acid cycle (second step of cellular respiration).
      • Glycolysis occurs in the cytoplasm.
    • Chloroplasts:
      • Triple membrane (outer, inner, thylakoid).
      • Thylakoids are stacks of sacs containing chlorophyll, which absorbs light energy for photosynthesis.
      • Stroma (fluid within chloroplast) contains the Calvin cycle.
      • Contains its own DNA and ribosomes (endosymbiotic theory).
      • Site of photosynthesis.
    • Lysosomes:
      • Membrane-bound sacs containing hydrolytic enzymes.
      • Function in intracellular digestion.
      • Recycles cell's organic material.
      • Involved in programmed cell death (apoptosis).
    • Vacuoles:
      • Membrane-bound sacs with diverse functions.
      • Storage of macromolecules and cellular waste products.
      • Central Vacuole (plants): Water retention, turgor pressure for rigidity.
      • Contractile Vacuole (single-celled organisms): Osmoregulation, expelling excess water from cells.
      • Food Vacuole: Formed by phagocytosis; fuses with lysosomes for digestion.

    Cellular Transport and Membranes

    • Plasma Membrane:

      • Phospholipid bilayer (hydrophilic heads, hydrophobic tails).
      • Cholesterol (buffers fluidity).
      • Proteins (facilitate transport).
      • Glycolipids and glycoproteins (cell communication).

    • Membrane Transport (Passive):

      • Simple Diffusion:
        • Movement of small, non-polar molecules (O₂, CO₂, steroids) down a concentration gradient, directly through the membrane.
        • Small amounts of water also move without aid of channels.
      • Facilitated Diffusion:
        • Movement of polar or charged molecules down a concentration gradient.
        • Channel proteins allow molecules to pass through the membrane.
        • Carrier proteins physically bind to molecules and carry them across.

    • Membrane Transport (Active):

      • Requires energy (ATP).
      • Moves molecules against their concentration gradient.
      • Often uses carrier proteins (pumps).

    • Bulk Transport:

      • Endocytosis: Bringing material into cell.
        • Phagocytosis (cellular eating): Ingesting large particles via pseudopods.
        • Pinocytosis (cellular drinking): Ingesting extracellular fluid.
        • Receptor-mediated endocytosis: Specific molecules bind to receptors to initiate engulfment.
      • Exocytosis: Materials transported out of cell using vesicles.

    • Osmosis:

      • Movement of water across a semi-permeable membrane.
      • Hypertonic: High solute concentration, low water potential; water moves out.
      • Hypotonic: Low solute concentration, high water potential; water moves in.
      • Isotonic: Equal solute and water concentrations; water moves in and out equally.

    Surface Area-to-Volume Ratio

    • Cells with a high surface area-to-volume ratio are more efficient for diffusion and exchange of materials

    Cell sizes

    • Smaller cells are more efficient for transport within the cell than larger cells

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    Description

    Dive into the intricacies of cell structure and function, exploring the roles of the nucleus, rough endoplasmic reticulum, and smooth endoplasmic reticulum. Understand how these components work together to maintain cellular processes such as transcription, protein synthesis, and detoxification. This quiz will test your knowledge on essential cell biology concepts.

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