Cell Biology Quiz: Organelles and Functions

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Questions and Answers

What is a primary function of the rough endoplasmic reticulum?

Synthesis of steroids

Synthesis of proteins for export (correct)

Detoxification of harmful substances

Transport of molecules through cisternal space

Which of the following correctly describes the structure of the Golgi complex?

A single large sac-like structure

An irregular structure with no defined shape

A network of tubular vesicles

A series of stacked, flattened cisternae (correct)

Which function is primarily associated with the smooth endoplasmic reticulum?

Protein transport to the Golgi apparatus

Synthesis of ribosomal RNA

Glycogen breakdown (correct)

Production of neurotransmitters

What is the characteristic appearance of rough endoplasmic reticulum under light microscopy?

Basophilic patches Signup and view all the answers

Which surface of the Golgi complex is known as the 'cis face'?

The surface closest to the nucleus Signup and view all the answers

Which component contributes to the asymmetry of the cell membrane?

Different composition of lipids Signup and view all the answers

What role do organelles serve within the cytoplasm?

Performing various cellular functions Signup and view all the answers

Which of the following structures is NOT considered an organelle?

Lipids Signup and view all the answers

What is the primary component of cytosol within the cytoplasm?

Water Signup and view all the answers

Which type of endoplasmic reticulum is characterized by the presence of ribosomes?

Rough endoplasmic reticulum Signup and view all the answers

What is the primary function of the Golgi complex?

Synthesizes polysaccharides and packages secretory products Signup and view all the answers

Which type of enzyme is primarily found in lysosomes?

Proteases and nucleases Signup and view all the answers

How do peroxisomes replicate?

By budding of precursor vesicles from the ER or fission of preexisting peroxisomes Signup and view all the answers

What is the primary role of the mitochondrial inner membrane?

To form cristae which increase surface area Signup and view all the answers

Which of the following components is found in the mitochondrial matrix space?

Circular DNA, mRNA, tRNA, and rRNA Signup and view all the answers

What distinguishes phagosomes from endosomes?

Phagosomes are involved in the ingestion of materials, while endosomes transport materials within the cell Signup and view all the answers

Which enzyme is not typically found in lysosomes?

Peroxidase Signup and view all the answers

What characteristic of mitochondria allows them to rapidly change shape?

Presence of multiple membranes Signup and view all the answers

What is the primary function of proteasomes?

Degrade damaged or misfolded proteins Signup and view all the answers

Which component is found in larger quantities in attached polyribosomes compared to free polyribosomes?

Proteins for secretion and those associated with the ER Signup and view all the answers

Which of the following accurately describes microtubules?

Form tubular structures made of tubulin heterodimers Signup and view all the answers

What is the role of kinesin proteins?

Transport vesicles toward the plus end of microtubules Signup and view all the answers

What do intermediate filaments primarily contribute to in a cell?

Mechanical stability and tensile strength Signup and view all the answers

The structure of ribosomes includes distinct subunits. Which statement is true regarding these subunits?

They include several types of ribosomal RNA and specific proteins. Signup and view all the answers

Microtubules are described as having a specific diameter. What is their outer diameter?

24 nm Signup and view all the answers

Which type of protein is primarily involved in sliding microtubules relative to each other?

Dynamin Signup and view all the answers

Which protein is specifically found in muscle cells?

Desmin Signup and view all the answers

What is the primary function of microfilaments in cells?

Facilitate transport of organelles and movement Signup and view all the answers

What structural feature characterizes centrioles?

Formed by 9 triplets of microtubules Signup and view all the answers

Which type of inclusion is most abundant in hepatocytes?

Glycogen granules Signup and view all the answers

What is the composition of microfilaments?

Polymers of globular G-actin monomers Signup and view all the answers

What is a primary role of the pericentriolar bodies (MTOCs)?

Control microtubule polymerization Signup and view all the answers

Which of the following statements correctly describes neurofilaments?

Present in neurons Signup and view all the answers

Hemosiderin, found in macrophages, is a breakdown product of which biological component?

Hemoglobin Signup and view all the answers

What is lipofuscin primarily associated with?

Accumulation with increasing age Signup and view all the answers

Which type of cells primarily contain melanin?

Melanocytes and keratinocytes Signup and view all the answers

What structure separates the outer and inner membranes of the nuclear envelope?

Perinuclear cisternal space Signup and view all the answers

What is the primary function of the inner nuclear membrane?

Regulation of gene expression and cell-cycle Signup and view all the answers

What composes a nucleosome?

146-166 base pairs of DNA and histone proteins Signup and view all the answers

Which type of pigment is carotenoid primarily derived from?

Vegetables and fruits Signup and view all the answers

During which phase is chromatin generally identified as less condensed?

Interphase Signup and view all the answers

What type of crystal is found in the Sertoli cells of the testis?

Crystals of Charcot-Böttcher Signup and view all the answers

Study Notes

Cytology Lecture Two

Cells are the basic structural and functional unit of living organisms.
They exhibit diverse functional specializations for organism survival, growth, and reproduction.
Cells are self-replicating, self-regulating, and self-governing biological systems.
Key cell activities include metabolism (e.g., absorption, synthesis, respiration, excretion), growth and regeneration, irritability (excitability), movement, and reproduction. Aging and death are also part of the cell cycle.
Cell numbers are estimated to be around 100 trillion (10¹²).
There are over 250 different named cell types.
Cell shapes include round, oval, columnar, multipolar, polygonal, cylindrical, fusiform, pyramidal, and pyriform.
Cell sizes range from 5µm to 120µm in diameter.
Cells perform various functions depending on their type and location in the body.

Cell Structure (Diagram)

Microtvillus
Plasma membrane
Nuclear envelope
Golgi apparatus
Microtubules
Nucleolus
Rough endoplasmic reticulum
Centrosome
Lysosome
Mitochondrion

Specialized Cell Functions

Movement: Muscle cells
Synthesis and secretion of enzymes: Pancreatic acinar cells
Synthesis and secretion of mucous substances: Mucous-gland cells
Synthesis and secretion of steroids: Cells in the adrenal glands, testes, and ovaries
Ion transport: Cells of the kidney and salivary glands
Intracellular digestion: Macrophages and other white blood cells
Transformation of stimuli into nervous impulses: Sensory cells
Metabolites absorption: Cells in the intestine

Cells — Light Microscope View

Cell nucleus (chromatin)
Cell cytoplasm
Cell boundary
Cell shape
Interstitial space
Red blood cell

Components of Eukaryotic Cells

Cell membrane
Cytoplasm
Karyoplasm (nucleus)
Centrioles
Secretory granules
Microtubules
Nuclear membrane
Chromatins
Golgi Apparatus
Nucleolus
Glycogen
Ribosomes
Lysosomes
Mitochondrion
Rough endoplasmic reticulum
Microfilaments
Smooth endoplasmic reticulum

Cell Membrane

The cell membrane's structure appears as a trilaminar layer, each layer 2.5 nm in diameter.
This appearance makes it known as the "unit membrane".
It is composed of lipids (approx. 90% by volume, 50% by weight), proteins (10% by volume, 50% by weight) and carbohydrates.
Phospholipids contain a hydrophilic polar phosphate-containing head and hydrophobic nonpolar fatty acid tails. This arrangement creates the lipid bilayer.
Cholesterol regulates membrane fluidity and structural integrity.
Integral proteins (intrinsic) transverse the membrane, while peripheral proteins (extrinsic) are located on one surface.

Membrane Proteins

Pumps, channels, receptors, linkers, enzymes and structural proteins are functional categories of membrane proteins.

Carbohydrates

Occur as oligosaccharides, attached to plasma membrane proteins (glycoproteins) and lipids (glycolipids).
Project from the outer surface of the outer leaflet of the plasma membrane.
Contribute to the glycocalyx (cell coat), responsible for cell adhesion, enzyme and antigen binding, and cell-to-cell recognition.

Cytoplasm

The cytoplasm is the cellular material outside the nucleus but within the plasma membrane.
It is composed of cytosol (cellular fluid), organelles, cytoskeleton, and inclusions.

Organelles

Endoplasmic reticulum (RER, SER)
Golgi complex (body or apparatus)
Lysosomes
Peroxisomes (microbodies)
Mitochondria
Endosomes and phagosomes
Proteasomes
Ribosomes

Ribosomes

About 20 × 30 nm in size.
Composed of ribosomal RNA (rRNA) and specific ribosomal proteins.
Exist in large and small subunits occurring as free ribosomes and polyribosomes (polysomes).

Polyribosomes

Occur as clusters along a single strand of mRNA.
Free polyribosomes synthesize structural proteins and enzymes for intracellular use.
Attached polyribosomes produce proteins to be secreted or destined for the ER, Golgi apparatus, lysosomes, or cell membrane.

Cytoskeleton

A gel-like network composed of protein filaments.
Three filament types are microtubules, intermediate filaments and microfilaments

Microtubules

Tubular, with 24nm outer diameter and 5nm wall thickness.
Built from tubulin heterodimers (a and b).
Include 13 protofilaments.
Contain microtubule-associated proteins (MAPs) which include Kinesin (towards plus end), and Dynein (towards minus end).
Microtubules are involved in intracellular transport, maintaining cell shape, intracellular compartmentalization and cell migration.

Intermediate Filaments

Characterized by width between microtubules and microfilaments (10-12nm).
Stable and contribute to cell mechanical strength.
Formed from tetramers of rod-like proteins.
Include various types, most common are Lamins, Keratin/Cytokeratin, Vimentin, Desmin, Neurofilaments and Glial fibrillary acid protein.

Microfilaments (Actin Filaments)

Measure 5–7 nm in diameter and composed of polymers of globular G-actin monomers, assembling as a double-stranded helix of filamentous F-actin.
G-actin is continually added to preexisting filaments to regulate growth and branching.
Involved in intracellular transport, cytokinesis, endocytosis, muscle contraction and cytoplasmic streaming

Centrioles

Cylindrically shaped structures found in pairs, perpendicular to one another.
Constructed from nine triplets of microtubules.
Associated with centrosomes, they control microtubule polymerization, transmit physical organizing forces, control movements of organelles and vesicles, and form basal bodies of cilia and flagella..

Inclusions

Metabolically inactive materials located in the cytoplasm.
Types include lipid droplets, glycogen granules, pigments (e.g., hemosiderin, lipofuscin, melanin), and crystals

Nucleus

Oval, elongated, or flattened.
Roughly 5-10 µm in diameter.
Composed of nuclear envelope, chromatin, nucleolus, and nucleoplasm

Nuclear Envelope

Double membrane separated by the perinuclear cisternal space (~30 - 50 nm).
Outer membrane is continuous with the endoplasmic reticulum, often displaying ribosomes.
Inner membrane is associated with structural proteins (lamins).

Chromatin

Composed of DNA and associated proteins (histones and nonhistones).
Organized into nucleosomes.
Exists in two variations during interphase: heterochromatin (dense, transcriptionally inactive) and euchromatin (dispersed, transcriptionally active)

Nucleolus

Round, nonmembranous bodies.
Site of rRNA synthesis and ribosome assembly. Contains nucleostemin.

Nucleoplasm

Nuclear components besides chromatin and nucleolus, including proteins, metabolites and the intranuclear lamina/structures.

Cell Renewal

Somatic cells are categorized by mitotic activity as renewing (e.g., rapidly renewing cells, slowly renewing cells), stable (e.g., quiescent cells), and static (e.g., permanent cells).

Cell Cycle

A self-regulated series of events controlling cell growth and division.
Phases include Interphase (G1, S, G2) and Mitosis (M).

G1 Phase

Longest phase (variable hours to days).
Cell growth, nutrient gathering, RNA/protein synthesis and centriole duplication.
Governed by two checkpoints (DNA damage checkpoint, restriction checkpoint)

S Phase

DNA replication and histone synthesis occur (7.5 - 10 hours).
Checkpoint(s): DNA-damage

G2 Phase

Further cell growth and cytoplasmic organelle reorganization (~3.5 – 4.5 – 1 hrs).
Checkpoints (DNA damage, unreplicated DNA).

Mitosis

A phase of nuclear division

Other Information

Lysosomes - Contain hydrolytic enzymes, breakdown molecules, active at acidic pHs (-0.05 to 0.5 µm)
Peroxisomes - Oxidative enzymes, including catalase, produce H2O2; related to lipid metabolism and degradation. (0.2 – 0.5 µm)
Mitochondria - Double membrane structures with an inner membrane forming cristae; cellular respiration occurs here.

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Description

Test your knowledge on cell biology in this quiz focused on organelles and their functions. Questions cover rough and smooth endoplasmic reticulum, Golgi complex structure, and other essential cellular components. Perfect for students in biology courses!