Microscopy & Cell Theory Overview

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Questions and Answers

What is the role of peptidoglycan in prokaryotic cells?

It serves as a component of the cell wall. (correct)

It regulates transport across the plasma membrane.

It acts as the genetic material.

It functions as the primary site for energy production.

Which factor primarily limits the size of cells?

The density of the cytoplasm.

The availability of organelles.

The amount of genetic material present.

The surface area to volume ratio. (correct)

What structural feature distinguishes eukaryotic cells from prokaryotic cells?

Presence of chromosomal DNA.

Presence of ribosomes.

Presence of internal membranes. (correct)

Presence of a cell wall.

Which of the following is NOT a function of the plasma membrane in eukaryotic cells?

Energy production through cellular respiration. Signup and view all the answers

What structure is found in the cytoplasm of eukaryotic cells?

Organelles. Signup and view all the answers

In which way does a prokaryotic cell's size benefit its function?

It enables the efficient movement of materials across the membrane. Signup and view all the answers

Which organisms are categorized as prokaryotes?

Bacteria and archaea. Signup and view all the answers

What structures are found in plant cells but not in animal cells?

Chloroplasts Signup and view all the answers

What composition is typical for the eukaryotic plasma membrane?

A phospholipid bilayer with embedded proteins. Signup and view all the answers

What is the main function of the large central vacuole in plant cells?

Water regulation and cell expansion Signup and view all the answers

What are the components of the endomembrane system?

Nuclear envelope, lysosomes, vesicles, endoplasmic reticulum Signup and view all the answers

How do the centrioles in the centrosome differ in structure?

They are made up of nine triplets of microtubules Signup and view all the answers

What role does the rough endoplasmic reticulum (RER) serve in eukaryotic cells?

Modification of proteins Signup and view all the answers

What distinguishes plant cell walls from prokaryotic cell walls?

Plant cell walls are made of cellulose Signup and view all the answers

Which of the following encapsulates the digestive enzymes in animal cells?

Lysosomes Signup and view all the answers

What is the significance of non-tubulin proteins in the structure of centrioles?

They hold the microtubule triplets together Signup and view all the answers

What is the primary function of the nucleolus within the nucleus?

Assemble ribosomal RNA and ribosomes Signup and view all the answers

What does the nuclear envelope primarily do?

Separate DNA from the cytoplasm Signup and view all the answers

How do mitochondria and chloroplasts support the endosymbiotic theory?

They have their own DNA and ribosomes resembling prokaryotes Signup and view all the answers

Which part of the mitochondrion is responsible for increasing surface area for cellular respiration?

Cristae Signup and view all the answers

What role do chloroplasts play in plant cells?

Conduct photosynthesis Signup and view all the answers

What is one of the primary functions of the cytoskeleton?

It helps maintain the shape of the cell. Signup and view all the answers

Which type of filament is involved in cell movement and stabilization of shape?

Microfilaments Signup and view all the answers

What structure is primarily composed of 9 doublets of microtubules and 2 central microtubules?

Cilia Signup and view all the answers

Which component of the cytoskeleton provides mechanical strength?

Intermediate filaments Signup and view all the answers

What is a primary role of the extracellular matrix in animal cells?

Providing mechanical support Signup and view all the answers

How do tight junctions function in animal cells?

They form watertight seals between cells. Signup and view all the answers

Which of the following statements correctly describes microtubules?

They form a rigid internal skeleton for some cells. Signup and view all the answers

What function do plasmodesmata serve in plant cells?

Allow cell-to-cell communication Signup and view all the answers

Microfilaments are primarily made from which type of protein?

Actin Signup and view all the answers

In multicellular organisms, which component of the cytoskeleton aids in the movement of cells?

Microfilaments Signup and view all the answers

What is the primary advantage of using electron microscopes over compound light microscopes?

They achieve higher magnification and resolution. Signup and view all the answers

Which statement about cell theory is accurate?

All living organisms are made of cells. Signup and view all the answers

What characteristic is unique to prokaryotic cells?

They lack membrane-enclosed internal compartments. Signup and view all the answers

Which of the following components is NOT common to all cells?

Mitochondria Signup and view all the answers

What role does a chemical stain play when using compound light microscopes?

It enhances the color contrast between different parts of a transparent object. Signup and view all the answers

Study Notes

Microscopy & Resolution

Higher resolution images provide greater clarity and detail.
Different microscopes use different optical systems to visualize different structures.
Compound light microscopes utilize visible light to magnify images.
Stains are used to differentiate structures in transparent samples, such as cells.
Electron microscopes use beams of electrons to achieve higher magnification and resolution.
Transmission electron microscopes show fine details within cells.
Scanning electron microscopes provide 3-D exterior views of structures.

Cell Theory

Cells are the fundamental units of life.
All living organisms are composed of cells.
All cells arise from pre-existing cells.

Universal Cell Components

Plasma membrane: Encloses the cell, separating its interior from the environment.
Cytoplasm: Contains cytosol, the gel-like substance, where cell components are suspended.
DNA: Genetic material of the cell.
Ribosomes: Synthesize proteins.

Prokaryotic Cells

Found in the domains Archaea and Bacteria.
Lack membrane-enclosed internal compartments (e.g., nucleus).
Most have a cell wall containing peptidoglycan.
Believed to be similar to the first cells.

Prokaryotic Cell Structure

Chromosomal DNA: Localized in a nucleoid.
Ribosomes: Found in the cytoplasm.
Cell membrane: Surrounded by a cell wall.
Other structures, like flagella and pili, may be present in some bacteria.

Small Size of Prokaryotes

Prokaryotic cells are smaller than eukaryotic cells.
Surface area to volume ratio: Favors efficient movement of materials in and out of the cell.
Lack of internal transport modifications: Found in eukaryotes, limiting their size.

Factors Limiting Cell Size

Surface area to volume ratio: When cells grow larger, volume increases faster than surface area, making it less effective for material transport.
The cell membrane acts as the interface for transporting oxygen and carbon dioxide, requiring sufficient surface area.

Eukaryotic Cells

Organisms like plants, animals, fungi, and many microorganisms are eukaryotic.
Possess internal membranes, which compartmentalize their structures.

Eukaryotic Cell Structure

Plasma membrane: Phospholipid bilayer with embedded proteins.
Cytoplasm: Consists of organelles suspended in cytosol, including the cytoskeleton.
Nucleus: Typically one per cell, often the largest organelle, larger than most prokaryotic cells.

Components of the Nucleus

Nuclear envelope: Double membrane (two phospholipid bilayers) separating DNA from the cytoplasm.
Nuclear pores: Perforate the nuclear envelope, connecting nucleoplasm to cytoplasm and regulating molecule flow.
Nucleolus: Region within the nucleus where ribosomal RNA (rRNA) is synthesized and ribosomes assemble.

Ribosomes

Composed of two subunits of different sizes.
Made of rRNA and proteins.
Assemble amino acids into proteins during protein synthesis.

Mitochondria

Convert chemical energy in glucose into ATP (adenosine triphosphate), the usable form of energy, through cellular respiration.
Folded inner membrane called cristae, enclosed by the mitochondrial matrix.
Possess their own DNA and ribosomes, distinct from those in the cytoplasm and nuclear DNA.

Chloroplasts

Double-membrane organelles, containing their own ribosomes and DNA, similar to mitochondria.
Inner membrane encloses a fluid-filled space called the stroma, containing interconnected and stacked thylakoids.
Stacks of thylakoids form grana.
Site of photosynthesis in plants.

Endosymbiosis

Hypothesized that mitochondria and chloroplasts originated as independent prokaryotic organisms.
Became endosymbionts within the prokaryotic ancestors of eukaryotes.
Explains their distinct DNA and ribosomes with prokaryotic similarities.
Their size is comparable to that of independent prokaryotes.

Centrosome

Consists of two centrioles perpendicular to each other.
Each centriole is a cylinder composed of nine triplets of microtubules, held together by non-tubulin proteins.

Animal vs. Plant Cells: Differences

Plant cells: Possess cell walls, chloroplasts, and large central vacuoles.
Animal cells: Lack these structures.

Plant Cell Wall

Rigid protective structure external to the plasma membrane.
Composed of cellulose, unlike the peptidoglycan found in prokaryotic cell walls.

Central Vacuole

Large vacuole occupying most of the plant cell's area.
Regulates water concentration under changing conditions, contributing to cell expansion.

The Endomembrane System

Internal membranes and organelles work together to modify, package, and transport lipids and proteins.
Includes: nuclear envelope, lysosomes, vesicles, endoplasmic reticulum, Golgi apparatus, and plasma membrane.

Lysosomes

Contain digestive enzymes in animal cells.
Break down large biomolecules and old organelles.
Fuse with other organelles, digesting their contents.

Endoplasmic Reticulum (ER)

Network of interconnected membranous sacs and tubules.
The hollow portion of the ER tubules is called the lumen or cisternal space.
Membrane is continuous with the nuclear envelope.
Rough ER (RER): Modifies proteins.
Smooth ER (SER): Synthesizes lipids.

The Cytoskeleton

Network of protein fibers performing essential functions.
Maintains cell shape.
Holds organelles in specific positions.
Facilitates cytoplasm and vesicle movement.
Enables movement of cells within multicellular organisms.

Components of the Cytoskeleton

Microfilaments: Involved in movement, both cellular and internal. Determine and stabilize cell shape. Composed of actin monomers.
Intermediate filaments: Tough, flexible fibers formed from protein subunits, providing mechanical strength and cell shape stabilization.
Microtubules: Form a rigid internal skeleton, providing a framework for motor proteins to move structures within the cell. Composed of tubulin dimers, forming 13 chains around a central cavity.

Cilia & Flagella

Ultrastructure: Consists of a 9+2 array of microtubules - 9 doublets on the outside and 2 unfused microtubules in the center. Spokes connect the doublets to the center.
Cilia: Shorter and more numerous.
Flagella: Longer and fewer in number.

Extracellular Structures

Plant cell walls: Provide support, act as a barrier to infection, and connect cells via plasmodesmata.
Extracellular matrix in animals: Composed of collagen, other fibrous proteins, glycoproteins called proteoglycans, and linking proteins.

Cell Junctions

Tight junctions: Act as watertight seals between animal cells, preventing leakage of materials. Found in epithelial cells lining internal organs and cavities.
Desmosomes: Anchor cells together in strong sheets, providing structural support and preventing tearing.
Gap junctions: Channels between adjacent animal cells, allowing communication and passage of ions and small molecules.
Plasmodesmata: Channels connecting adjacent plant cells, facilitating communication and transport of substances.

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Description

This quiz covers key concepts in microscopy and cell theory, including the functions of various types of microscopes and the universal components of cells. Test your knowledge on how cells function as the basic units of life and the significance of different microscopy techniques in biological research.