Cytology and Histology Introduction B1100

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Questions and Answers

What is the primary function of the plasma membrane?

Enclosing the contents of the entire cell (correct)

Facilitating cellular respiration

Transcribing RNA from DNA

Synthesizing proteins

Which of the following correctly describes one of the roles of the plasma membrane?

Store genetic information

Facilitate the exchange of substances (correct)

Synthesize energy for the cell

Perform photosynthesis

What does compartmentalization refer to in the context of the plasma membrane?

Enclosing different cellular organelles (correct)

Organizing ribosomes within the nucleus

Facilitating transport across membranes

The separation of genetic material from cytoplasm

In terms of selective exchange, what is a key feature of the plasma membrane?

It filters substances based on size and charge Signup and view all the answers

How does the plasma membrane respond to external signals?

By stimulating or inhibiting cellular activities Signup and view all the answers

Which of the following statements about membrane functions is accurate?

Membranes assist in creating specific microenvironments within cells. Signup and view all the answers

What percentage of the total cellular RNA is ribosomal RNA (rRNA), which is associated with ribosomes?

82% Signup and view all the answers

Which of the following does NOT characterize the role of the plasma membrane?

It directly synthesizes new organelles. Signup and view all the answers

What is the approximate thickness of the plasma membrane?

5 to 10 nm Signup and view all the answers

Which component primarily makes up the majority of the chemical composition of the plasma membrane?

Lipids Signup and view all the answers

Which type of lipid is the most abundant in the plasma membrane of animal cells?

Phospholipids Signup and view all the answers

What feature characterizes the amphiphilic nature of membrane lipids?

One hydrophobic and one hydrophilic part Signup and view all the answers

Which type of component is primarily absent from the plasma membrane of plant cells?

Cholesterol Signup and view all the answers

Which characteristic pertains to the trilaminar appearance of the plasma membrane?

Three distinct layers with specific density properties Signup and view all the answers

The ratio of proteins to lipids in the plasma membrane is approximately:

1.5 Signup and view all the answers

Which feature is a primary function of cholesterol in the plasma membrane?

To provide rigidity and stability Signup and view all the answers

Which statement about the plasma membrane of prokaryotic cells is correct?

It has a structure similar to that of eukaryotic cells. Signup and view all the answers

What is the primary role of the plasma membrane in prokaryotic cells?

To protect the cell from environmental stress. Signup and view all the answers

Which of the following components is absent in the plasma membrane of prokaryotic cells?

Sterols Signup and view all the answers

Which structure is formed from infoldings of the plasma membrane in photosynthetic bacteria?

Lamella Signup and view all the answers

What distinguishes the plasma membrane of mycoplasma from other prokaryotes?

It contains sterols. Signup and view all the answers

How does the plasma membrane of prokaryotes differ from that of eukaryotes?

Prokaryotic membranes lack sterols in general. Signup and view all the answers

What occurs simultaneously in the cytoplasm of prokaryotic cells?

Replication, transcription, and translation. Signup and view all the answers

Which of the following describes the genetic material within prokaryotic cells?

It includes plasmids that aid in antibiotic resistance. Signup and view all the answers

Study Notes

Introduction to Cytology & Histology

Cytology is the study of cells, while histology is the study of tissues.
All living organisms are composed of cells.
The course, B1100, covers cytology and histology for 60 hours, with 30 hours allocated to each subject.
Assessments include a final exam, where 50 points are dedicated to cytology and 50 to histology.
The final exam score will be multiplied by 6 (the number of credits in the course).

About Organization

Organization occurs in 3 levels.
An organism is made of systems (e.g., digestive, respiratory).
Systems are composed of organs (e.g., heart, lungs).
Organs comprise tissues (e.g., muscular, epithelial).
Tissues consist of cells.
The cell is the fundamental morphological unit of an organism.

About Functional Properties

Cells exchange with the external environment to maintain life.
The exchange process involves assimilation (transforming external nutrients into intracellular components) and dissimilation (removing substances from the cell so that they cease functioning).
Reproduction enables species continuity.
Living organisms reproduce through sexual or asexual mechanisms.
Irritability is the capacity of cells to respond to stimuli (physical, chemical, or physiological). This response varies by organism.

Prokaryotic Cells

Prokaryotes are cells without a membrane-bound nucleus or other organelles (excluding some ribosomes). These cells contain a single circular DNA molecule.
Prokaryotes include bacteria and archaebacteria.
Archaebacteria live in extreme environments (e.g., hot springs, ocean trenches).
Eubacteria are the more common type and can be found in the environment and some are even living organisms (e.g., mycoplasma, cyanobacteria, etc…).
Bacteria are morphologically categorized into spherical (cocci), elongated (bacilli), or spiral (spirilla) forms.
Bacterial sizes vary, but the average is around 1-2 µm.
Some bacteria lack a cell wall and are very small. Mycoplasmas are an example.
Bacteria have different roles and can be both harmful (pathogenic) or beneficial.
Prokaryotic cells reproduce asexually by binary fission.
Classification depends on oxygen requirements (strictly aerobic, strictly anaerobic, facultative, or microaerophilic).

Eukaryotic Cells

Eukaryotes are cells containing a nucleus and other organelles, which are enclosed by membranes.
Eukaryotic cells consist of diverse sub-cellular components (e.g., endoplasmic reticulum, ribosomes, Golgi apparatus, lysosomes, mitochondria, cytoskeleton, and centrioles) that each have specialized functions.
Eukaryotes can be unicellular (such as yeast, amoeba, and paramecium) or multicellular (such as animals, plants, and humans).
Photoautotrophs produce their own food, while heterotrophs rely on consuming other organisms for sustenance.
Eukaryotes have a larger size range (10 to 100µm) compared to prokaryotes.

Viruses

Viruses are not cells; they are not living things, but multimolecular complexes.
Viruses are obligate intracellular parasites.
Viruses lack metabolic machinery; they cannot generate energy or synthesize proteins independently.
Virus reproduction relies on host cells.
Viruses are very small (20-200nm).
Viruses are pathogens, causing diseases like influenza, AIDS, and cancers.

Viral Structure

Viruses consist of a core of nucleic acid (DNA or RNA) surrounded by a protein coat called a capsid.
The capsid protects viral genetic material and is the vehicle for entering host cells.
Some viruses have an outer lipid bilayer.
Based on genetic material, there are DNA viruses/RNA viruses (riboviruses)/retroviruses.
A structurally mature and infectious viral particle is called a virion.
The viral capsid exhibits many shapes.

Viral Reproduction

Viral replication depends on host cell conditions.
A lytic cycle involves viral replication, assembly, and the release of new virions, generally resulting in cell lysis.
The lysogenic cycle involves the integration of viral DNA into the host cell's DNA, termed provirus, which remains dormant until specific triggers induce transition to lytic replication.
In retroviruses, RNA is initially converted to DNA (reverse transcription) before replication; then viral nucleic acid, proteins & other materials are released from the host cell.

Cells: Summary of Organelles

The cytoplasm contains numerous organelles.
Organelles have specialized functions.
The cytoplasm is composed of cytosol, organelles and a variety of organic & inorganic molecules to support metabolic activities.
The cell membrane is a boundary (a lipid bilayer).
Other organelles include ribosomes, Golgi apparatuses, lysosomes & peroxisomes, etc. The cytoskeleton forms a framework to maintain cell shape, and for organelle & cell movement. The centrosome is near the nucleus for cell division.

Plasma Membranes

The plasma membrane encloses the cell and regulates the passage of substances in and out of the cells.
The plasma membrane has a lipid bilayer structure, with hydrophilic heads facing the exterior and interior of the cell, and hydrophobic tails oriented toward the inside of the bilayer.
Membrane proteins are responsible for diverse functions, including transport and signal transduction.

Membrane Transport

Selective permeability is crucial for regulating what enters and exits the cell.
Passive transport (no energy required) includes simple and facilitated diffusion.
Active transport (energy required) employs carriers to move substances against their concentration gradient.
Vesicular transport encompasses endocytosis and exocytosis, which move large materials into and out of the cell, respectively.

Cell Surface Specializations

Microvilli increase the surface area of cells, which facilitates absorption and secretion.
Stereocilia are immotile, irregular-shaped protrusions.
Basal folds invaginate into the cell, maximizing the surface for material exchange (e.g. in filtering cells of kidneys).

Intercellular Connections

Cell-to-cell adhesions,
Tight junctions (preventing diffusion between cells)
Intermediate junctions (anchoring cells together)
Gap junctions (allowing small molecule passage).
Hemidesmosomes (attaches cell to basement membrane)

Intercellular Adhesion

CAMs and SAMs are responsible for cell-cell and cell-matrix attachments.
Cadherins, selectins, and integrins are examples of CAMs and SAMs, facilitating interactions.

Carbohydrates

Carbohydrates are abundant in the environment and are crucial energy sources.
Carbohydrates are classified into monosaccharides (simple sugars), disaccharides (double sugars), and polysaccharides (complex carbohydrates).
Monosaccharides (sugars) can form rings or linear shapes, and different positioning of the OH groups can create isomers (e.g., α-, β- forms).
Disaccharides are formed by dehydration reactions.
Polysaccharides are large polymers of monosaccharides, with variations in branching.

Lipids

Lipids are a class of biomolecules that are hydrophobic.
Lipids are crucial components of cell membranes.
Triglycerides are composed of glycerol and three fatty acids (triacylglycerols).
Phospholipids consist of glycerol, two fatty acids, and a phosphate group; they are crucial for cell membranes.
Sphingolipids have a sphingosine backbone and fatty acyl side chains.
Steroids are a diverse class of lipids; cholesterol is crucial for cell membranes.

Nucleic Acids

Nucleic acids like DNA and RNA are macromolecules used to store and transfer genetic instructions.
DNA carries the instructions; RNA carries out the instructions.
DNA and RNA are polymers of nucleotides.
Nucleotides have a base, a sugar (ribose or deoxyribose), and a phosphate group.
These bonds form a chain or polymers via phosphodiester bonds (covalent bonds).

DNA

DNA is a double-stranded helix.
The sequence of DNA nucleotides determines the genetic information contained in organisms.

RNA

RNA is generally single-stranded.
There are three main types of RNA: mRNA, rRNA, and tRNA; and other small RNAs such as snRNA.
These are crucial components of protein synthesis.

Other Important Cellular Components

Other components (e.g., viroids, prions) also play critical roles in cellular activities; and there are specialized types of structures such as cell membranes present in the variety of cells.

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Description

Explore the foundational concepts of cytology and histology in this quiz based on the B1100 course. Understand the organization of living organisms from cells to tissues and their functional properties. Prepare for your final exam and solidify your knowledge about the study of cells and tissues.