Cell Biology: Organelles and Structures
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Questions and Answers

Which of the following statements accurately describes mitochondrial structure?

  • Mitochondria possess a single membranous layer.
  • The outer mitochondrial membrane is smooth and permeable. (correct)
  • The inner mitochondrial membrane is rigid and inflexible.
  • Mitochondria contain no DNA.

What is the primary function of lysosomes among membranous organelles?

  • Storage and breakdown of cellular waste. (correct)
  • Synthesis of proteins.
  • Regulating cell membrane permeability.
  • Energy production through oxidative phosphorylation.

Which characteristic distinguishes non-membranous organelles from membranous organelles?

  • Presence of metabolic enzymes.
  • Absence of a surrounding membrane. (correct)
  • Involvement in energy production.
  • Ability to self-replicate.

How do mitochondria contribute to cellular energy production?

<p>By producing ATP through oxidative phosphorylation. (B)</p> Signup and view all the answers

In what way do ribosomes and mitochondria differ functionally?

<p>Ribosomes synthesize proteins, while mitochondria are responsible for ATP generation. (A)</p> Signup and view all the answers

What type of membrane structure is the cell membrane classified as?

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

Which component of the cytoskeleton is primarily involved in providing structural support?

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

What is the primary function of microfilaments in cells?

<p>Acting as a cytoskeleton (A)</p> Signup and view all the answers

In which form are carbohydrates stored in cells?

<p>In the form of glycogen (C)</p> Signup and view all the answers

Which type of pigment is classified as endogenous?

<p>Hemoglobin in red blood cells (C)</p> Signup and view all the answers

What type of structure do tonofibrils represent in epithelial cells?

<p>Connection between adjacent cells (B)</p> Signup and view all the answers

How do microfilaments appear under a light microscope when stained?

<p>As minute dots and fine lines (A)</p> Signup and view all the answers

Which statement correctly describes the function of the Rough Endoplasmic Reticulum?

<p>Synthesis of proteins for secretion and hydrolytic enzymes. (B)</p> Signup and view all the answers

What microscopy characteristic distinguishes the Smooth Endoplasmic Reticulum from the Rough Endoplasmic Reticulum?

<p>Formation of branching and anastomosing tubules. (D)</p> Signup and view all the answers

In which type of cells is the Rough Endoplasmic Reticulum most prevalent?

<p>Cells responsible for protein secretion, such as pancreatic cells. (B)</p> Signup and view all the answers

Which of the following is NOT a function of the Golgi Apparatus?

<p>Detoxification of drugs and chemicals. (A)</p> Signup and view all the answers

What is the significance of the 'negative Golgi image' observed in plasma cells?

<p>It signifies an area characterized by diffuse basophilia. (C)</p> Signup and view all the answers

Which of the following statements best explains the structural appearance of the Rough Endoplasmic Reticulum under electron microscopy?

<p>Contains parallel flattened membranous sacs with attached ribosomes. (B)</p> Signup and view all the answers

What type of substances can the Smooth Endoplasmic Reticulum assist in managing during muscle contractions?

<p>Calcium ions for muscle contraction. (A)</p> Signup and view all the answers

Which of the following cells would contain a well-developed Smooth Endoplasmic Reticulum?

<p>Adrenal cortex cells producing steroid hormones. (D)</p> Signup and view all the answers

What is the primary role of the Rough Endoplasmic Reticulum in relation to the Golgi apparatus?

<p>To package and transport proteins to the Golgi apparatus. (D)</p> Signup and view all the answers

What is the primary role of lysosomal enzymes released during autolysis?

<p>To hydrolyze cell constituents after cell death (D)</p> Signup and view all the answers

Which statement accurately describes ribosomes?

<p>They can form polyribosomes by connecting multiple ribosomes with mRNA. (D)</p> Signup and view all the answers

In which form do ribosomes synthesize proteins used inside the cell?

<p>As free ribosomes scattered throughout the cytoplasm (D)</p> Signup and view all the answers

What is the composition of microtubules?

<p>Alpha and beta tubulin proteins arranged into protofilaments (D)</p> Signup and view all the answers

Which of the following is NOT a function of microtubules?

<p>Initiating autolysis in dead cells (D)</p> Signup and view all the answers

How do attached ribosomes primarily function?

<p>To synthesize proteins secreted as hormones or enzymes outside of cells (C)</p> Signup and view all the answers

What tissue observation indicates a high concentration of ribosomes?

<p>Cytoplasmic basophilia, as seen in pancreatic cells (A)</p> Signup and view all the answers

Which statement best describes the structure of a ribosome?

<p>Features a large subunit that houses the polypeptide chain (C)</p> Signup and view all the answers

Which of the following correctly describes the cytoskeleton?

<p>A complex network of microtubules and microfilaments (A)</p> Signup and view all the answers

What is the primary function of secretory vesicles produced from the mature concave surface of the Golgi apparatus?

<p>To bud off carrying protein ready for secretion. (C)</p> Signup and view all the answers

Which type of vesicle is formed when a primary lysosome fuses with a phagocytic vesicle containing bacteria?

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

What role do transfer vesicles play in the function of Golgi apparatus?

<p>They carry crude protein from the rough endoplasmic reticulum to the immature surface of Golgi. (C)</p> Signup and view all the answers

What typically differentiates primary lysosomes from secondary lysosomes in terms of appearance?

<p>Primary lysosomes are homogeneous in electron density, while secondary lysosomes are heterogeneous. (C)</p> Signup and view all the answers

What is a residual body in the context of lysosomal function?

<p>An undigested material that is expelled from the cell. (C)</p> Signup and view all the answers

Which of the following processes do lysosomes primarily contribute to?

<p>Cellular digestion and waste removal. (B)</p> Signup and view all the answers

Which type of lysosome arises from the fusion of primary lysosomes with old organelles?

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

Which statement best describes the origin of hydrolytic enzymes found in lysosomes?

<p>They are synthesized in the rough endoplasmic reticulum and then transferred to the Golgi for packaging. (D)</p> Signup and view all the answers

What is the overall importance of the Golgi apparatus in protein processing?

<p>It participates in the modification, sorting, and packaging of proteins for secretion. (B)</p> Signup and view all the answers

How do secondary lysosomes differ in internal composition compared to primary lysosomes?

<p>Secondary lysosomes contain both digested and undigested materials. (C)</p> Signup and view all the answers

Flashcards

Organelles

A vital and permanent intracellular structure that performs essential functions. They are classified into membranous (with membrane, metabolic enzymes) and non-membranous (without membrane, no enzymes).

Membranous Organelles

A type of organelle that is enclosed by a membrane, allowing it to compartmentalize and carry out specialized biochemical processes. They are rich in enzymes, facilitating various metabolic activities.

Non-Membranous Organelles

A type of organelle that lacks a membrane and is directly in contact with the cytoplasm. They are involved in essential processes like protein synthesis and structural support.

Cell Membrane

The outermost layer of the cell, acting as a barrier to control what enters and exits the cell. It also plays a role in communication with other cells.

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Mitochondria

The powerhouse of the cell, responsible for generating energy through ATP production. They can replicate themselves to increase their number as needed.

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Rough Endoplasmic Reticulum (RER)

A network of interconnected sacs and tubules that are involved in protein synthesis, folding, and transportation within the cell. It has a rough appearance due to the presence of ribosomes attached to its surface.

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Smooth Endoplasmic Reticulum (SER)

A network of interconnected sacs and tubules that are involved in lipid synthesis, detoxification, and calcium storage. It lacks ribosomes attached to its surface, giving it a smooth appearance.

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Golgi Apparatus

A network of parallel, flat, and curved sacs within the cell that play a role in protein modification, sorting, and packaging.

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Polyribosomes

Ribosomes attached to the surface of the rER.

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Transfer Vesicles

Small, membrane-bound vesicles that transport proteins from the rER to the Golgi apparatus.

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Basophilia

The appearance of rER under a light microscope, characterized by densely stained regions in protein-producing cells.

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Cisternae

The appearance of rER under an electron microscope, where the membranous sacs appear as flattened, interconnected structures.

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Negative Golgi Image

The appearance of the Golgi apparatus under a light microscope, appearing as a network of brownish granules and fibers.

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Golgi Stacks

The appearance of the Golgi apparatus under an electron microscope, where the network appears as stacked, flattened, and curved membrane-bound sacs.

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Golgi apparatus Immature surface

The immature surface of the Golgi apparatus receives protein-filled vesicles from the rough endoplasmic reticulum (rER).

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Golgi apparatus mature surface

The mature surface of the Golgi apparatus is where packaged proteins are released in secretory vesicles for export out of the cell.

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Secretory Vesicles

Large vesicles that bud off from the Golgi apparatus and release protein for secretion outside the cell.

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Golgi Apparatus: Protein Processing

This process involves modifying, concentrating, and sorting proteins received from the rER.

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Golgi Apparatus Conjugation

The Golgi apparatus adds carbohydrates, sulfates, and salts to proteins, attaching them to specific sites.

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Golgi Apparatus: Vesicle Formation

The Golgi apparatus creates small membrane-bound sacs that transport materials for various cellular functions.

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Golgi Apparatus: Membrane Renewal

The Golgi apparatus contributes to the renewal and maintenance of the cell membrane by producing and delivering membrane components.

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Lysosomes: Definition

Lysosomes are membrane-bound organelles containing hydrolytic enzymes responsible for cellular digestion.

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Primary Lysosomes

These are lysosomes that haven't yet fused with other vesicles. They contain a uniform mixture of enzymes.

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Autolysis

Process where lysosomes break down cell components after cell death, releasing their enzymes to digest cellular constituents.

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Acrosomal reaction

The process where acrosomal enzymes released by sperm cells help in breaking down the protective layers of the egg, enabling fertilization.

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Ribosome

Non-membranous structures composed of rRNA and proteins, responsible for protein synthesis. They are found in all cells but are more numerous in protein-producing cells.

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Free Ribosomes

Ribosomes that are dispersed throughout the cytoplasm and synthesize proteins for use within the cell.

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Attached Ribosomes

Ribosomes attached to the endoplasmic reticulum, responsible for producing proteins to be secreted outside the cell.

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Cytoskeleton

A network of interconnected microtubules and microfilaments that provides structural support, shape, and movement to cells.

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Microtubules

Hollow tubes made of tubulin protein that contribute to cell shape, movement, and organelle transport.

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Microtubule Dynamics

The dynamic assembly and disassembly of microtubules, allowing cells to move and change shape.

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Organized Microtubules

Stable and organized microtubular structures involved in cell division, movement of cilia and flagella, and maintaining cell shape.

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Microfilaments

Thread-like structures found throughout the cytoplasm, forming part of the cytoskeleton. They are responsible for maintaining cell shape, aiding in movement, and facilitating intracellular transport.

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Myofibrils

Organized bundles of microfilaments found in muscle cells, responsible for muscle contraction.

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Tonofibrils

Organized bundles of microfilaments found in epithelial cells, connecting adjacent cells together.

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Cytoplasmic Inclusions

Metabolically inactive materials stored within the cytoplasm. They include stored food, pigments, and secretory granules.

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Endogenous Pigments

Pigments produced by the cell itself, such as hemoglobin in red blood cells, melanin in skin cells, or lipofuscin in heart and nerve cells.

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Study Notes

Cell Organelles

  • Cells are living, permanent intracellular structures crucial for cell function.
  • Organelles are classified as membranous or non-membranous based on their membrane presence.

Membranous Organelles

  • Enclosed by a membrane
  • Contain metabolic enzymes
  • Examples:
    • Cell membrane (plasma membrane/plasmalemma)
    • Mitochondria
    • Rough endoplasmic reticulum
    • Smooth endoplasmic reticulum
    • Golgi apparatus
    • Lysosomes

Non-Membranous Organelles

  • Lack a surrounding membrane
  • Do not contain enzymes
  • Examples:
    • Ribosomes
    • Cytoskeleton (microtubules and microfilaments)

The Cell Membrane

  • A thin membrane (7.5-10nm) surrounding the cell cytoplasm.
  • Not visible under light microscopy (LM).
  • Appears as a trilaminar membrane under electron microscopy (EM).
  • Consists of two dark lines separated by a clear line

Mitochondria

  • Vital for energy production (the "powerhouse" of the cell)
  • Located in areas of high energy demand (e.g., muscle cells).
  • Appear as dark blue dots (LM) or green dots, using specific stains.
  • Have a double membrane structure (outer and inner).
  • Inner membrane folds (cristae) maximize surface area for energy production.
  • Contain DNA and RNA
  • Involved in ATP production via Krebs cycle and oxidative phosphorylation.

Rough Endoplasmic Reticulum (rER)

  • Membrane-bound organelles involved in protein synthesis.
  • Located near the nucleus.
  • Appears as a network of flattened sacs (cisternae).
  • Studded with ribosomes (giving the rough appearance).
  • Involved in protein synthesis and processing for export out of the cell.

Smooth Endoplasmic Reticulum (sER)

  • Membrane-bound system of tubules involved in steroid synthesis.
  • Abundant in steroid hormone-producing cells (e.g., adrenal cortex, testes).
  • Involved in detoxification, lipid synthesis, and calcium ion release.

Golgi Apparatus

  • Involved in secretion (abundant in cells specializing in secretion).
  • Composed of flattened sacs (cisternae).
  • Processes, sorts, and packages proteins and lipids.

Lysosomes

  • Membrane-bound organelles containing hydrolytic enzymes.
  • Responsible for cellular digestion.
  • Found in large numbers in phagocytic cells (e.g., macrophages, neutrophils).
  • Involved in breakdown of cellular debris and waste

Ribosomes

  • Non-membranous organelles crucial for protein synthesis.
  • Composed of ribosomal RNA and proteins.
  • Appear as small granular structures (LM).
  • May be free-floating or bound to the rough endoplasmic reticulum (rER).

Cytoskeleton

  • Network of microtubules and microfilaments.
  • Involved in cell shape maintenance and intracellular transport.
  • Essential for cell movement, division, and various cellular processes.

Centrioles

  • Non-membranous organelles found near the nucleus.
  • Involved in cell division (mitosis).
  • Composed of microtubules

Cilia and Flagella

  • Motile cellular extensions.
  • Composed of microtubules.
  • Involved in cell movement or transporting substances along cell surfaces.

Cytoplasmic Inclusions

  • Non-living, nonessential components found in the cytoplasm.
  • Examples:
    • Stored food (carbohydrates, fats)
    • Pigments (endogenous/exogenous)
    • Secretory granules.

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Test your knowledge on the structure and function of various organelles in cells, including mitochondria, lysosomes, and the endoplasmic reticulum. This quiz covers key concepts related to cellular components and their roles in maintaining cell functionality. Perfect for students studying cell biology at any level.

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