Cell Biology: Lysosomes and Organelles

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Questions and Answers

What is the primary function of lysosomes in a cell?

Energy production

Protein synthesis

Genes expression regulation

Utilizing nutrients and destroying dead cells (correct)

How are primary lysosomes formed?

Through the degradation of other organelles

By ribosomal activity in the nucleus

From the Golgi complex as secretory vesicles (correct)

By fusing with phagocytic vesicles

What is a secondary lysosome?

A vesicle formed exclusively from the Golgi complex

A primary lysosome that has fused with a phagocytic vesicle (correct)

A lysosome that has not yet fused with any vesicle

A lysosome involved in protein synthesis

What structure gives the rough endoplasmic reticulum its characteristic appearance?

Attached ribosomes Signup and view all the answers

Which of the following processes do lysosomes participate in?

Carbohydrate metabolism Signup and view all the answers

What characterizes the rough endoplasmic reticulum in a nerve cell?

Nissl's body Signup and view all the answers

What type of enzymes fill the lysosome's cavity?

Hydrolytic enzymes Signup and view all the answers

What is the general diameter of a lysosome?

800 nm Signup and view all the answers

Which organelle is NOT a membranous organelle found in eukaryotic cells?

Centriole Signup and view all the answers

Which theory describes the structure of the cell membrane as having proteins that float and change positions?

Fluid Mosaic Theory Signup and view all the answers

What is the primary composition of the cell membrane?

Phospholipids and proteins Signup and view all the answers

What type of granules are considered inclusions within the cytoplasm?

Secretory granules Signup and view all the answers

What distinguishes the hydrophilic and hydrophobic regions of phospholipids in the cell membrane?

Hydrophilic heads facing outward, tails facing inward Signup and view all the answers

Which component of the nucleus is responsible for producing ribosomes?

Nucleolus Signup and view all the answers

Which type of proteins are loosely attached to the cell membrane and can move laterally?

Peripheral proteins Signup and view all the answers

What is the function of lysosomes in eukaryotic cells?

Digestion of macromolecules Signup and view all the answers

What is the primary function of microtubules in dividing cells?

Form the mitotic spindle Signup and view all the answers

Which structure is formed from tubulin molecules and organized around the centrosome?

Microtubules Signup and view all the answers

What component do cilia and flagella share at their base for support?

Centriole Signup and view all the answers

How many microtubules are found in the arrangement of cilia and flagella?

9 doublets and 2 single Signup and view all the answers

What role do microtubules play in the process of mitosis?

Pulling chromosomes apart during anaphase Signup and view all the answers

Which of the following is NOT a function of microtubules?

Synthesis of ATP Signup and view all the answers

What is the diameter of microtubules?

24 nm Signup and view all the answers

During which cellular process do microtubules aggregate extensively?

Cell division Signup and view all the answers

What is the primary function of ribosomes in a cell?

Synthesis of intracellular protein Signup and view all the answers

Which description best defines smooth endoplasmic reticulum (sER)?

A ribosome-free, membranous network involved in lipid biosynthesis Signup and view all the answers

What role does the Golgi apparatus play in cellular function?

It transports and modifies proteins from the endoplasmic reticulum Signup and view all the answers

Which of the following is a function of the smooth endoplasmic reticulum?

Glycogen synthesis Signup and view all the answers

How does the structure of the Golgi apparatus change in response to physiological states?

It assumes a fragmented state in aging cells Signup and view all the answers

Which process does the smooth endoplasmic reticulum NOT participate in?

Protein synthesis Signup and view all the answers

What describes microsomes in the context of the endoplasmic reticulum?

Vesicles resulting from ER fragmentation Signup and view all the answers

What is a key function of the Golgi apparatus that is particularly important for certain cells?

Modification and secretion of proteins Signup and view all the answers

What is the primary function of myofilaments in muscle cells?

Facilitating muscular contraction Signup and view all the answers

Which type of filament is specifically found in nerve cells?

Neurofilament Signup and view all the answers

What is the role of catalase in peroxisomes?

To split H2O2 into H2O and O2 Signup and view all the answers

What is the primary role of the cytoskeleton?

Maintaining cell shape and organization Signup and view all the answers

What type of cilia is known to be motile?

Kenocilia Signup and view all the answers

Which type of filament is involved in forming a contractile ring during cell division?

Myofilament Signup and view all the answers

Which types of inclusions are described as non-living and transitory in cells?

Cytoplasmic inclusions Signup and view all the answers

What connects adjacent epithelial cells through junctional complexes?

Tonofilaments Signup and view all the answers

What is the primary storage form of carbohydrates in liver and muscle cells?

Glycogen Signup and view all the answers

Which stain is used to identify lipid storage in tissues?

Sudan black Signup and view all the answers

What color does lipofuchsin appear in its fresh state?

Brown Signup and view all the answers

What component of the cytosol is responsible for holding numerous organelles and inclusions?

Cytoplasmic matrix Signup and view all the answers

Which type of chromatin is usually transcriptionally inactive and attached to the nuclear envelope?

Constitutive heterochromatin Signup and view all the answers

What is the role of the nucleolus within the nucleus?

Synthesis of ribosomal RNA Signup and view all the answers

Which of the following statements about exogenous pigments is true?

They originate from outside the body. Signup and view all the answers

Which component of the cell contains densely packed DNA and is associated with mRNA synthesis?

Euchromatin Signup and view all the answers

Study Notes

Cytology

Cytology is a biological science studying cell structure, histochemistry, and ultrastructure. It also focuses on immunohistochemistry and cell genetics.
Key cellular components are studied including organelles and inclusions. Cell membranes are also an essential component for study, including their structure and function.

Cell Membrane

Also known as plasmalemma or plasma membrane, this membrane has a trilaminar structure.
It's composed of a dense layer of cytoplasm surrounding eukaryotic cells.
It is made up of two layers of dense protein with phospholipids between them.
The membrane's thickness ranges from 8 to 10 nm and can only be seen with electron microscopy (EM).
The structure appears as proteins swimming in a lipid sea.
Theories of cell membrane structure include linear theory, molecular theory, and the fluid mosaic theory

Mitochondrial Structures

Mitochondria: plural term, not always a single mitochondrion, or sometimes called a chondriosome.
Mitochondria are power centers of cells
They are approximately the size of bacteria but can have varied shapes based on the cell type.
They are membranous organelles that can be viewed under a light microscope using Janus green stain.
They are enclosed by two membranes separated by an intermembranous space.
Morphology may appear as short rods, threads or granules.
The number of mitochondria in a cell can increase depending on the metabolic activity of that cell (ranging from 2500-3000).
The structures comprise an outer membrane, inner membrane, cristae, matrix, intermembrane space, ribosomes, granules, and DNA.

Lysosome

Lysosomes are membranous organelles, containing hydrolytic enzymes, that operate at an acidic pH.
Lysosomes serve to break down cellular nutrients and destroy the cell after death.
These structures are often implicated in diseases that cause break down of cell processes in living cells and have a diameter of 800nm.
Derived from the Golgi complex. Viewed at the light microscope (LM) level, they appear as vesicles in basophils, eosinophils, and neutrophils.
The EM image of a lysosome shows a homogenous, round vesicle with a thin membrane, containing proteins/enzymes.
Lysosomes are formed from the rough endoplasmic reticulum (rER) and can fuse with other vesicles, like phagosomes in phagocytosis, or damaged organelles to form secondary lysosomes.

Endoplasmic Reticulum

The rough endoplasmic reticulum (rER) is a membranous organelle that's a system of membranes, involved in protein and lipid production.
It is marked by the presence of ribosomes on its surface- hence the name rough ER.
It also appears as a three-dimensional branching and anastomosing network of membranes.
The smooth endoplasmic reticulum (SER) is a membranous network lacking ribosomes.
The SER's cisternae are more tubular and interconnected; they communicate with the rER and nuclear envelope.
It's thought that smooth ER arises from the rough ER after it has lost its ribosomes.
Functions for the SER include lipid and fatty acid synthesis, synthesis of cholesterol and steroid hormones, metabolism of cholesterol, drug detoxification, and muscle contraction.

Golgi Apparatus

The Golgi apparatus, also called the Golgi network, is a membrane-bound organelle composed of plate-like sacs (cisternae) stacked together and connected to the endoplasmic reticulum (ER).
The Golgi modifies, categorizes, and transports proteins and lipids originating in the ER.
The Golgi apparatus is considered the "post office" of the cell for its role in packaging and transportation.
Morphological differences exist depending on the cell type or physiological state.
The Golgi apparatus is known to vary in shape (ranging from a dense body in intestinal cells to a net-like structure in neuron axon poles).
Other forms include flattened saccules, vesicles, and cisternae.
The Golgi apparatus has various functions including the concentration of proteins from transfer vesicle, polysaccharide synthesis ("hexosamine"), protein conjugation to polysaccharide ("glycoproteins"), concentration of hydrolytic enzymes, role in exocytosis, glycocalyx formation and membrane renewal.
Gerl is an area near Golgi that may connect with ER, serving a function related to protein modification and lysosome production.

Ribosomes

Free ribosomes are small electron-dense particles (15-20 nm in size) composed of rRNA and protein.
They exist either on the rough endoplasmic reticulum (RER) or in the cytoplasm as polysomes.
Ribosomes play a critical role in interpreting cellular information (from the nucleus) to synthesize proteins.
Ribosomes are composed of two subunits, held together by mRNA.
The protein and rRNA of ribosomes are synthesized in the nucleoli, then transported to the cytoplasm to form ribosomes.
Ribosomes are also found in eukaryotic cells, but also in prokaryotic cells (mitochondria and chloroplasts).

Centrioles (Centrosomes)

Centrioles are non-membranous structures found in most cells (except nerve cells and red blood cells).
The term "centrosphere" describes the clear dark body that surrounds a centriole.
A centrosome has two centrioles that are perpendicular to each other and composed of nine triplets of hollow microtubules together with associated fibrils and arms
Centrioles are involved in cell division (mitosis), sperm tail formation, and cilia formation.

Components of the Cytoplasm

Cytosol: The cytoplasmic matrix, a solution containing water, proteins, enzymes, nutrients, inorganic substances, and all cytoplasmic organelles.
Cytoplasmic Inclusions: Non-living, transitory structures in the cell made of accumulated metabolites or deposits of varying natures. These primarily include secretory granules, stored food (glycogen in liver and muscle cells), and pigments (e.g., lipochrome, lipofuscin, melanin).

Cytoskeleton

Cytoskeleton: A complex three-dimensional network of filamentous structures in the cytoplasm.
Microtubules, intermediate filaments, and microfilaments are components that help in maintaining cell shape, transport, and cell division.
Cytoskeleton structures link microtubules to other filament-like structures.

Cell Cycle

The cell cycle is the sequence of events in a cell's life, divided into stages like gap 1, synthesis, gap 2, and mitosis.
Different cells have different durations in their cell cycle, regulated by a mechanism that stops mitosis at times of unfavorable cell conditions.

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Description

Test your knowledge on the functions and structures of lysosomes and various cell organelles. This quiz covers topics such as the formation of primary lysosomes, characteristics of the rough endoplasmic reticulum, and the components of the cell membrane. Whether you're preparing for an exam or just want to reinforce your understanding of cell biology, this quiz is for you.