Cytology: The Cell Structure and Function
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Questions and Answers

What are the two basic parts of the cell?

  • Nucleus and Golgi apparatus
  • Ribosomes and Cell membrane
  • Cytoplasm and Nucleus (correct)
  • Mitochondria and Cytoplasm

Which of the following is NOT a membranous organelle?

  • Mitochondria
  • Golgi apparatus
  • Ribosomes (correct)
  • Lysosomes

The cell membrane is also known as the plasma membrane.

True (A)

What is the trilaminar appearance of the cell membrane due to?

<p>Arrangement of lipid molecules (A)</p> Signup and view all the answers

The head end of a phospholipid is _____, while the tail end is _____.

<p>Hydrophilic, Hydrophobic (A)</p> Signup and view all the answers

Which of the following is NOT a function of protein in the cell membrane?

<p>Produce energy for cellular functions (B)</p> Signup and view all the answers

What is the layer of carbohydrates that is present at the surface of the cell membrane?

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

Which of the following is a major type of endocytosis?

<p>All of the above (D)</p> Signup and view all the answers

Which of the following describes the process by which large molecules move out of the cell?

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

Which of the following is a non-membranous organelle?

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

Ribosomes are composed of rRNA and proteins.

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

What is the function of ribosomes?

<p>Ribosomes play an essential role in protein synthesis.</p> Signup and view all the answers

The endoplasmic reticulum appears rough due to the presence of:

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

Smooth endoplasmic reticulum lacks ribosomes.

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

What is NOT a function of smooth endoplasmic reticulum?

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

What is the function of mitochondria?

<p>Mitochondria are the power house of the cell. They contain many enzymes including some that play an important part in Kreb's cycle.</p> Signup and view all the answers

What is the name of the folds in the inner membrane of the mitochondria?

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

The Golgi apparatus is most highly developed in secretory cells.

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

What is the function of the Golgi apparatus?

<p>The Golgi apparatus modifies, concentrates, and packages synthesized proteins into secretory granules.</p> Signup and view all the answers

Lysosomes are membrane-bound vesicles containing enzymes that break down unwanted material.

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

What is the name of the primary lysosome that combines with a phagosome?

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

What is the fate of lysosomes?

<p>Residual Bodies are those lysosomes in which only indigestible food materials have been left.</p> Signup and view all the answers

Peroxisomes detoxify substances by oxidizing them.

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

What is NOT one of the three major components of the cytoskeleton?

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

Microtubules are about 25nm in diameter.

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

Which of the following is a function of microtubules?

<p>All of the above (D)</p> Signup and view all the answers

Microfilaments are about 5nm in diameter and are made of the protein actin.

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

Intermediate filaments are so called because their diameter is intermediate between microtubules and microfilaments.

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

Which of these statements about intermediate filaments is FALSE?

<p>They directly produce energy for cellular functions. (B)</p> Signup and view all the answers

The nucleus is the central, denser, part of the cell.

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

Mature red blood cells do not have a nucleus.

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

Flashcards

What is a cell?

The basic, functional units of tissues and the fundamental unit of life.

What is cytoplasm?

The cell's internal environment, containing organelles, inclusions, cytoskeleton, and cytosol.

What are organelles?

Specialized structures within the cytoplasm that perform specific functions.

What are membranous organelles?

Organelles enclosed by a membrane, separating their internal environment from the cytoplasm.

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What are non-membranous organelles?

Organelles that lack a surrounding membrane and are directly exposed to the cytoplasm.

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What is the cell membrane?

The outer boundary of the cell, regulating the passage of substances in and out.

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What creates the trilaminar appearance of the cell membrane?

The arrangement of lipid molecules, mainly phospholipids, that forms the basic structure of the membrane.

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What is the hydrophilic end of a phospholipid?

The polar head of a phospholipid, facing the watery environment of the cell.

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What is the hydrophobic end of a phospholipid?

The non-polar tail of a phospholipid, repelling water and interacting with the hydrophobic tails of adjacent molecules.

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What is the function of lipids in the cell membrane?

They prevent the passage of water-soluble substances and ions, but allow the passage of fat-soluble substances and small non-polar molecules.

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What are proteins in the cell membrane?

Irregularly shaped masses embedded within the membrane, playing various roles in cell function.

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What are transmembrane proteins?

Proteins that span the entire thickness of the membrane, potentially projecting outwards on both sides.

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What are the functions of proteins in the cell membrane?

They help maintain cell structure, provide adhesion, facilitate transport, act as receptors, and act as enzymes.

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What are carbohydrates in the cell membrane?

Sugar molecules attached to proteins (forming glycoproteins) or lipids (forming glycolipids), creating a layer on the external surface of the cell membrane.

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What is the glycocalyx?

Also known as the cell coat, it contains adhesion molecules, blood group antigens, and other cell surface markers.

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What is endocytosis?

The process by which large molecules enter the cell through inward folding and pinching off of the plasma membrane, creating cytoplasmic vesicles.

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What is phagocytosis?

The ingestion of large particles, such as bacteria or dead cell remnants, enclosed in a phagosome that fuses with a lysosome for degradation.

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What is pinocytosis?

The engulfment of extracellular fluid and dissolved contents into small invaginations of the cell membrane, creating pinocytotic vesicles.

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What is receptor-mediated endocytosis?

A specialized type of endocytosis where specific ligands bind to receptors on the cell surface, triggering the formation of vesicles.

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What is exocytosis?

The process by which large molecules are released from the cell through fusion of a cytoplasmic vesicle containing the molecules with the plasma membrane.

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What is cytosol?

The fluid component of the cytoplasm where organelles are distributed.

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What are ribosomes?

Small, non-membranous particles made of rRNA and proteins, responsible for protein synthesis.

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What are attached ribosomes?

Ribosomes attached to the rough ER, synthesizing proteins for the ER, Golgi apparatus, cell membrane, lysosomes, and for export.

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What are free ribosomes?

Ribosomes located freely in the cytoplasm, synthesizing proteins for use within the cytosol or nucleus, and for other organelles.

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What is the endoplasmic reticulum (ER)?

An interconnected network of channels and sacs (cisternae) involved in protein synthesis, modification, and transport.

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What is rough endoplasmic reticulum (RER)?

The ER that has ribosomes attached to its surface, giving it a rough appearance.

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What is smooth endoplasmic reticulum (SER)?

The ER lacking ribosomes on its surface, giving it a smooth appearance.

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What are mitochondria?

Organelles involved in cellular respiration, producing ATP for the cell's energy needs.

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What is the Golgi apparatus?

A stack of flattened, disc-like sacs involved in modifying and packaging proteins into secretory granules.

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What are lysosomes?

Membrane-bound vesicles containing hydrolytic enzymes that degrade unwanted material within the cell.

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What are peroxisomes?

Membrane-bound vesicles containing enzymes that convert substances into hydrogen peroxide for detoxification.

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Study Notes

Cytology: The Cell

  • Cells are the fundamental, functional units of tissues and the fundamental unit of life.
  • A cell is composed of two main parts: cytoplasm and nucleus.

Cytoplasm Components

  • Cell organelles: Structures within the cytoplasm with specific functions.
  • Cell inclusions: Non-membrane-bound substances, like pigments or stored nutrients.
  • Cytoskeleton: Provides structural support and facilitates movement within the cell.
  • Cytosol: The fluid portion of the cytoplasm.

Organelle Classification

  • Organelles are classified based on the presence or absence of membranes.

I. Membranous Organelles

  • Cell membrane: Separates the cell's cytoplasm from its surroundings, controlling the entry and exit of substances.
  • Mitochondria: Powerhouse of the cell, involved in energy production (ATP).
  • Rough endoplasmic reticulum (RER): Synthesizes proteins destined for secretion or insertion into membranes. Ribosomes on its surface are responsible for this.
  • Smooth endoplasmic reticulum (SER): Synthesizes lipids, steroid hormones, and detoxifies substances.
  • Golgi apparatus: Processes, packages, and modifies proteins and lipids.
  • Lysosomes: Contain enzymes to break down waste materials and cellular debris.
  • Peroxisomes: Break down fatty acids and other substances.
  • Secretory vesicles: Store and release substances outside of the cell.

II. Non-membranous Organelles

  • Ribosomes: Sites of protein synthesis.
  • Proteasomes: Degrade damaged or unnecessary proteins.
  • Cytoskeleton: Provides structural framework and facilitates cell movement.

The Cell Membrane

  • Structure: The cell membrane is a thin structure separating the cytoplasm from the surrounding environment.
  • Composition: The cell membrane is primarily composed of lipids (phospholipids), proteins, and carbohydrates.
  • Function: Controls the entry and exit of substances into and out of the cell; it is selectively permeable.
  • Molecular structure: A trilaminar appearance, having a lipid bilayer with proteins embedded in it. The heads are hydrophilic (water-loving), and the tails are hydrophobic (water-fearing). Carbohydrates are also attached to proteins and lipids.

Vesicular Transport

  • Endocytosis: The process by which cells absorb external substances by engulfing them in vesicles.
    • Phagocytosis: Ingesting larger particles like bacteria.
    • Pinocytosis: Ingesting fluid droplets.
    • Receptor-mediated endocytosis: Ingesting specific molecules targeted by receptors.
  • Exocytosis: The process in which cells expel substances from their internal environment.

Nucleus

  • The nucleus is the largest organelle, usually centrally located, and responsible for storing genetic material.
  • Structure: It has four main components:
    • Nuclear membrane: Double-layered membrane enclosing the nucleus and continuous with the endoplasmic reticulum.
    • Chromatin: DNA organized with proteins forming a complex structure.
    • Nucleolus: A dense area within the nucleus where ribosomal RNA is produced.
    • Nucleoplasm: The semi-fluid substance within the nucleus.

Other Cellular Components

  • Ribosomes: Composed of RNA and proteins, ribosomes are the sites of protein synthesis.
  • Mitochondria: Crucial for energy production.
  • Golgi Apparatus: Processes, packages, and modifies proteins and lipids.
  • Lysosomes: Digestive compartments of the cell.
  • Peroxisomes: Involved in various metabolic reactions.
  • Proteasomes: Involved in protein degradation.
  • Cytoskeleton: Framework for cell support, intracellular transport, and cell shape maintenance. The cytoskeleton includes microtubules, microfilaments, and intermediate filaments.
  • Cytoplasmic Inclusions: These are non-membrane-bound substances. Examples include lipid droplets, glycogen granules, pigments (like melanin) and crystals.

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Structure & Function Handbook 2024-2025 S1 Theoretical PDF

Description

Explore the fundamental concepts of cytology, focusing on the cell as the basic unit of life. This quiz covers key components such as the cytoplasm, organelles, and their classifications. Test your knowledge on how these structures contribute to cellular function and organization.

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