Secondary Active Transport Mechanisms

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Questions and Answers

What surrounds the organelles in a cell?

  • Nuclear envelope
  • Cytosol (correct)
  • Cell membrane
  • Cytoplasm

Where are many chemical reactions within a cell typically located?

  • In the cytoplasm
  • In the mitochondria
  • In the cytosol (correct)
  • In the nucleus

What provides the building blocks for cell maintenance, structure, function, and growth?

  • Ribosomes
  • Lysosomes
  • Mitochondrial DNA
  • Chemical reactions in the cytosol (correct)

Which specialized structures are found within a cell?

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

What is usually released by the chemical reactions in the cytosol?

<p>Energy (C)</p> Signup and view all the answers

What is phagocytosis primarily responsible for?

<p>Engulfing large particles such as viruses, bacteria, or dead cells (D)</p> Signup and view all the answers

Which two main types of cells are involved in phagocytosis?

<p>Macrophages and Neutrophils (C)</p> Signup and view all the answers

In the process of phagocytosis, what structure is formed after the plasma membrane extends pseudopods to envelope the microbe?

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

What happens to the microbe after a lysosome fuses with the phagosome?

<p>The microbe is digested by lysosomal enzymes (C)</p> Signup and view all the answers

What is the final result of the phagocytosis process?

<p>The digested products are released from the cell (C)</p> Signup and view all the answers

What are cilia?

<p>Short, hair-like projections that move fluids along a cell surface (D)</p> Signup and view all the answers

What is the function of flagella?

<p>Move the entire cell (C)</p> Signup and view all the answers

Which of the following cells typically have flagella?

<p>Sperm cells (B)</p> Signup and view all the answers

How do cilia differ from flagella in terms of length?

<p>Cilia are shorter than flagella (D)</p> Signup and view all the answers

Which of the following best describes the movement of cilia?

<p>Move fluids along a cell surface (D)</p> Signup and view all the answers

What is the primary function of ribosomes?

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

What type of RNA do ribosomes contain in large amounts?

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

Where are ribosomes commonly attached?

<p>Outer surface of nuclear membrane and Endoplasmic Reticulum (B)</p> Signup and view all the answers

Which cellular process are ribosomes directly involved in?

<p>Translation (C)</p> Signup and view all the answers

Which of the following statements about ribosomes is true?

<p>They contain rRNA and facilitate protein synthesis. (A)</p> Signup and view all the answers

Which protein is a component of microfilaments?

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

What is the primary role of intermediate filaments?

<p>Stabilise organelle position (C)</p> Signup and view all the answers

Where are microtubules located within the cell?

<p>Throughout the cell (C)</p> Signup and view all the answers

Which protein makes up the structure of microtubules?

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

Which type of cytoskeletal filament is most associated with the cell membrane?

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

What is the main purpose of microfilaments in cells?

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

Which process involves materials moving into a cell in a vesicle?

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

What is the correct term for a small spherical sac formed by budding off from a membrane?

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

Which process combines endocytosis and exocytosis?

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

Which type of endocytosis involves the ingestion of liquid into a cell by the budding of small vesicles?

<p>Bulk-phase endocytosis (pinocytosis) (C)</p> Signup and view all the answers

In which process do vesicles fuse with the plasma membrane to release their contents into the extracellular fluid?

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

What is the role of secondary active transport mechanisms?

<p>To use energy stored in Na+ or H+ gradients to transport solutes (B)</p> Signup and view all the answers

What do antiporters do?

<p>Carry two substances across the membrane in opposite directions (D)</p> Signup and view all the answers

Which ions are often involved in establishing the gradients used in secondary active transport?

<p>Na+ and H+ (C)</p> Signup and view all the answers

In the context of secondary active transport using symporters, which of the following is moved into the cell along with Na+?

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

What is hydrolyzed to indirectly provide energy for secondary active transport mechanisms?

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

What direction does Ca2+ move relative to the concentration gradient in the primary example of antiporters?

<p>Against its concentration gradient (B)</p> Signup and view all the answers

What triggers the fusion of synaptic vesicles with the presynaptic membrane during exocytosis?

<p>Influx of calcium ions (A)</p> Signup and view all the answers

Which channels open in response to the nerve impulse in the presynaptic membrane?

<p>Voltage-gated calcium channels (B)</p> Signup and view all the answers

During exocytosis, what occurs immediately after the nerve impulse reaches the synaptic end bulb?

<p>Ca2+ ions influx into the synaptic end bulb (B)</p> Signup and view all the answers

What is the final step in the exocytosis process at the synapse?

<p>Neurotransmitter is broken down or taken back up (A)</p> Signup and view all the answers

Which event causes ligand-gated channels to open on the postsynaptic neuron?

<p>Binding of neurotransmitter to receptors (C)</p> Signup and view all the answers

What results from the flow of ions through ligand-gated channels in the postsynaptic neuron?

<p>Change in membrane potential (A)</p> Signup and view all the answers

Which neuron is responsible for releasing the neurotransmitter in the synaptic cleft?

<p>Presynaptic neuron (B)</p> Signup and view all the answers

What is the role of neurotransmitter binding to receptors on the postsynaptic neuron?

<p>Opening ligand-gated channels on postsynaptic neuron (B)</p> Signup and view all the answers

What happens first in receptor-mediated endocytosis?

<p>Binding of LDL particle to the receptor (D)</p> Signup and view all the answers

Which particle is recognized and bound by receptor proteins in receptor-mediated endocytosis?

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

What structure forms on the cytosolic side of the membrane during receptor-mediated endocytosis?

<p>Clathrin-coated vesicle (B)</p> Signup and view all the answers

After the clathrin-coated vesicle forms, what is the next step?

<p>Uncoating of the vesicle (D)</p> Signup and view all the answers

In receptor-mediated endocytosis, what is the fate of LDL particles after fusion with an endosome?

<p>The particles are degraded in a lysosome (A)</p> Signup and view all the answers

During receptor-mediated endocytosis, what is the role of the receptors after they are internalized?

<p>They are recycled back to the plasma membrane (D)</p> Signup and view all the answers

What process is depicted by the cell engulfing extracellular fluid?

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

Which of the following is not involved in bulk-phase endocytosis?

<p>Receptor proteins (B)</p> Signup and view all the answers

What occurs immediately after the vesicle containing extracellular fluid is formed?

<p>Fusion with the lysosome (B)</p> Signup and view all the answers

What role do lysosomal enzymes play in pinocytosis?

<p>Digesting the fluid inside the vesicle (B)</p> Signup and view all the answers

What is released into the cell cytoplasm after the digestion of fluid in pinocytosis?

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

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Study Notes

Secondary Active Transport Mechanisms

  • Use energy stored in Na+ or H+ concentration gradients to drive transport of other solutes against their concentration gradients
  • These gradients are already established by primary active transport
  • Indirectly use energy from ATP hydrolysis

Antiporters

  • Carry two substances across the membrane in opposite directions
  • Use Na+ gradients for transport, e.g., Ca2+ out of the cell, Na+ into the cell

Symporters

  • Carry two substances across the membrane in the same direction
  • Use Na+ gradients for transport, e.g., glucose into the cell, Na+ into the cell

Phagocytosis

  • Form of endocytosis where cells engulf large particles like viruses, bacteria, or dead cells
  • Involves macrophages and neutrophils
  • Process:
    • Microbe attaches to receptor on cell membrane
    • Plasma membrane extends pseudopods that envelope the microbe, forming a phagosome
    • Lysosome fuses with the phagosome, and digestive enzymes break down the microbe
    • Digested products are released from the cell

Ribosomes

  • Sites of protein synthesis
  • Contain large amounts of ribosomal RNA (rRNA)
  • Attached to outer surface of nuclear membrane and Endoplasmic Reticulum

Cytoplasm

  • Contains:
    • Cytosol (intracellular fluid surrounding organelles)
    • Organelles (specialized structures within the cell)

Exocytosis

  • Releases materials from cells
  • Important for neurotransmitter signaling
  • Steps:
    1. Nerve impulse travels down presynaptic neuron
    2. Ca2+ influx triggers synaptic vesicles to fuse with presynaptic membrane
    3. Neurotransmitter is released into the synaptic cleft
    4. Neurotransmitter binds to receptors on postsynaptic neuron
    5. Ligand-gated channels open, allowing ions to flow across the postsynaptic membrane

Cilia and Flagella

  • Motile projections of the cell surface
  • Cilia: short, hair-like projections that move fluids along a cell surface
  • Flagella: longer, move an entire cell (e.g., sperm cell's tail)

Cytoskeleton

  • Network of protein filaments throughout the cytosol
  • Provides structural support for the cell
  • Three types:
    • Microfilaments (actin, associated with cell membrane and inside the cell)
    • Intermediate Filaments (keratin or other proteins, around nucleus)
    • Microtubules (tubulin, throughout the cell, attached to centrosome)

Vesicular Transport

  • Vesicle: small spherical sac formed by budding off from a membrane
  • Endocytosis: materials move into a cell in a vesicle
    • Receptor-mediated endocytosis
    • Phagocytosis
    • Bulk-phase endocytosis (pinocytosis)
  • Exocytosis: vesicles fuse with the plasma membrane, releasing their contents
  • Transcytosis: combination of endocytosis and exocytosis

Bulk-phase Endocytosis (Pinocytosis)

  • No receptor proteins involved
  • Transport of extracellular fluid
  • Process:
    1. Cell membrane invaginates, forming a pocket surrounding the fluid
    2. Pocket pinches off, creating a vesicle with the fluid
    3. Lysosome fuses with the vesicle
    4. Lysosome enzymes digest the fluid
    5. Digested solutes are released into the cell cytoplasm

Receptor-mediated Endocytosis

  • Binding: LDL particle binds to a receptor on the plasma membrane
  • Invagination: receptor-LDL complex internalized, forming a clathrin-coated pit
  • Vesicle formation: clathrin-coated pit pinches off, forming a clathrin-coated vesicle
  • Uncoating: clathrin coat is removed
  • Fusion with endosome: uncoated vesicle fuses with an endosome
  • Recycling: receptor proteins are recycled back to the plasma membrane
  • Degradation: LDL particle is degraded in a lysosome

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