Cell Structure and Function Quiz

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Questions and Answers

What is the primary function of ribosomes in eukaryotic cells?

Ribosomes are responsible for protein synthesis.

How are prokaryotic cells structurally different from eukaryotic cells?

Prokaryotic cells lack a nucleus and membrane-bound organelles.

Explain the importance of the surface area to volume ratio in cells.

A higher surface area to volume ratio allows for more efficient exchange of materials.

What distinguishes the rough endoplasmic reticulum from the smooth endoplasmic reticulum?

Rough ER has ribosomes on its surface, while smooth ER lacks ribosomes. Signup and view all the answers

Describe the structure of the plasma membrane.

The plasma membrane is composed of a double layer of phospholipids with embedded proteins. Signup and view all the answers

What role do fluorescent dyes play in microscopy?

Fluorescent dyes absorb ultraviolet radiation and emit visible light to label molecules. Signup and view all the answers

What are the two basic types of electron microscopes?

The two types are scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs). Signup and view all the answers

What is the function of the nucleolus within the nucleus?

The nucleolus is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly. Signup and view all the answers

What is the fluid mosaic model?

The fluid mosaic model describes the plasma membrane as a flexible structure with diverse proteins embedded within it. Signup and view all the answers

How does the nuclear envelope contribute to cellular processes?

The nuclear envelope separates the nucleus from the cytoplasm and regulates molecular entry and exit. Signup and view all the answers

What component of the endomembrane system is primarily involved in modifying and packaging proteins?

The Golgi apparatus is responsible for modifying and packaging proteins. Signup and view all the answers

Why do eukaryotic cells have internal membranes?

Internal membranes partition the cell into organelles for specialized functions. Signup and view all the answers

What is meant by 'magnification' in microscopy?

Magnification is the ratio of an object's image size to its real size. Signup and view all the answers

Distinguish between the two categories of cells in the three domains of life.

The two categories are prokaryotic and eukaryotic cells, with prokaryotic cells lacking a nucleus. Signup and view all the answers

What role does the Golgi apparatus play in the modification of glycoproteins?

The Golgi apparatus modifies the carbohydrate portions of glycoproteins by removing some sugar monomers and substituting others. Signup and view all the answers

Describe the primary function of lysosomes in a cell.

Lysosomes digest macromolecules and recycle the cell's own organelles through processes like autophagy. Signup and view all the answers

How do vacuoles function in plant cells?

Vacuoles in plant cells store organic compounds and water, and they can also form through phagocytosis, acting in various maintenance roles. Signup and view all the answers

What is the significance of the Endosymbiont Theory regarding mitochondria and chloroplasts?

The Endosymbiont Theory suggests that mitochondria and chloroplasts originated from engulfed prokaryotic cells that formed symbiotic relationships with early eukaryotic cells. Signup and view all the answers

Explain the structure and function of microtubules.

Microtubules are hollow rods that shape the cell, guide organelle movement, and assist in chromosome separation during cell division. Signup and view all the answers

What are the main roles of microfilaments in cellular function?

Microfilaments bear tension and help support the cell's shape, also playing a role in muscle contraction and cellular movements. Signup and view all the answers

How do plant cell walls differ from animal cell structures?

Plant cell walls are composed of cellulose fibers and provide protection, shape, and prevent excessive water uptake, unlike animal cells which lack walls. Signup and view all the answers

Identify and describe one type of intercellular junction.

Gap junctions are cytoplasmic channels that allow for communication between adjacent cells. Signup and view all the answers

What is the function of peroxisomes in the cell?

Peroxisomes contain enzymes that transfer hydrogen to oxygen, producing hydrogen peroxide, which they convert to water. Signup and view all the answers

What is the primary function of the extracellular matrix (ECM) in animal cells?

The extracellular matrix provides structural and biochemical support to surrounding cells and helps regulate their behavior. Signup and view all the answers

How do chloroplasts capture light energy?

Chloroplasts contain chlorophyll, which absorbs light energy for photosynthesis, converting it into chemical energy. Signup and view all the answers

Describe the structure of the cytoskeleton and its main components.

The cytoskeleton is a network of fibers including microtubules, microfilaments, and intermediate filaments that organize cellular activities. Signup and view all the answers

What is the role of centrosomes in cellular organization?

Centrosomes serve as microtubule-organizing centers critical for the formation and organization of microtubules during cell division. Signup and view all the answers

How do cilia and flagella contribute to cell movement?

Cilia and flagella, composed of microtubules, create wave-like motions that propel cells through fluids. Signup and view all the answers

Study Notes

Lecture 1: Cell Structure and Function

All living organisms are composed of cells
The cell is the basic unit of life
Cell structure is intricately linked to its function

Microscopy

Light microscopy (LM) uses visible light to magnify specimens
Lenses refract light to create a magnified image
Important parameters include magnification, resolution, and contrast
Magnification is the ratio of image size to real size
Resolution is the clarity of the image; lower values mean better resolution (Lower resolution in light microscopy than electron microscopy)
Contrast is the difference in visible parts of a sample
Resolution is limited by the wavelength of the radiation used
Numerical Aperture (NA) describes the ability of a lens to collect light
Different wavelengths of light provide different levels of resolution
Various organisms have diverse sizes, from atoms to humans
Most cells have a size range of 1-100 μm
Using microscopy helps visualize structures within cells
Fluorescence uses fluorescent dyes that absorb UV light and emit visible light, allowing scientists to visualize structures
The fluorescent protein GFP (Green Fluorescent Protein) exhibits bright green fluorescence when exposed to light, making it a very useful tool in biology
It forms internal chromophores without requiring cofactors or enzymes
Electron microscopy (EM) provides higher resolution than LM
Two types exist: Scanning EM (SEM) and Transmission EM (TEM)
SEM produces 3D images of the specimen's surface
TEM produces 2D images showing internal structures

Three Domains of Life and the Two Types of Cells

Life is categorized into three domains: Bacteria, Archaea and Eukarya
Prokaryotic cells lack internal membrane-bound organelles and a nucleus
Eukaryotic cells have internal membrane-bound organelles and a nucleus
Examples of prokaryotic organisms are bacteria and archaea
Organisms in the domains Protists, Fungi, Plants, and Animals belong to the domain Eukarya

Comparing Prokaryotic and Eukaryotic Cells

All cells share common features
- Plasma membrane
- Cytosol (Semifluid interior)
- Chromosomes (carry genes; DNA)
- Ribosomes (synthesize proteins)
Prokaryotic cells have no nucleus or membranous organelles
Eukaryotic cells have a nucleus and membranous organelles.

The Cytoplasm and Cytosol

Cytoplasm is the entire region between the nucleus and the plasma membrane.
Cytosol is the jelly-like substance within the cytoplasm of the cell

Plasma Membrane

A selective barrier that regulates what enters and leaves the cell
Composed of a phospholipid bilayer
Contains embedded proteins.

Fluid Mosaic Model

Phospholipids are amphipathic molecules—both hydrophobic and hydrophilic.
Membranes are fluid structures with various proteins embedded within the lipids.

Surface Area to Volume Ratio

Cell size is constrained by its surface-to-volume ratio.
Smaller cells have a larger surface area-to-volume ratio than larger cells.
This is important for efficient exchange of materials.

Increasing Surface Area: Volume Ratio

Specialized cells and tissues increase their surface area through folds, villi, and microvilli, optimizing material transfer.

A Panoramic View of the Eukaryotic Cell

Eukaryotic cells contain internal membranes that segregate organelles
Plants and animal cells share many organelles but have differences

Animal Cell

Illustrates the internal structures and organelles of an animal cell

Plant Cell

Illustrates the internal structures and organelles of a plant cell
- The components and processes that are unique to plant cells

The Nucleus

Houses the cell's DNA (genetic instructions)
Enclosed by a double membrane (nuclear envelope)
Pores regulate material transport
The nuclear lamina provides structural support
Contains the nucleolus, site of rRNA synthesis.

Ribosomes

Protein synthesis occurs at ribosomes.
Ribosomes are found in two locations; free ribosomes in the cytosol or attached to the Endoplasmic Reticulum (ER)

The Endomembrane System

The endomembrane system regulates protein traffic and performs metabolic functions
Components include the nuclear envelope, ER, Golgi, lysosomes, vacuoles, and plasma membrane

Endoplasmic Reticulum

The ER is a network of membranes that is continuous with the nuclear envelope
Two types of ER exist: Smooth and Rough
Smooth ER lacks ribosomes, and functions in lipid synthesis and detoxification of poisons
Rough ER is studded with ribosomes, performing protein synthesis and modification

Golgi Apparatus

Modifies, sorts, packages, and ships proteins and other macromolecules synthesized in the ER
Processes and modifies products from the ER and other parts of the cell

Lysosomes

Digestive compartments containing enzymes that degrade macromolecules
Catalyze the breakdown of molecules
Involved in cell's recycling (autophagy)
Participate in phagocytosis and macromolecule digestion

Vacuoles

Large sacs used for storage and maintenance
Plant cells typically have a large central vacuole containing water, salts, proteins, and carbohydrates

Mitochondria

Site of cellular respiration where chemical energy from the breakdown of sugar is converted into ATP
Double membrane structure with cristae for increased surface area

Chloroplasts

Site of photosynthesis where sunlight energy is converted into chemical energy (sugar)
Contains chlorophyll, a green pigment that absorbs sunlight

Peroxisomes

Specialized metabolic compartments bounded by a single membrane
Perform various functions, often involving oxidation
These functions are connected to other organelles in many cases

Cytoskeleton

Network of fibers that organizes structures and regulates activities in the cell
Three types include microtubules, microfilaments, and intermediate filaments
This complex system provides structure and enables essential functions like cell motility.

Microtubules

Hollow, cylindrical structures that are part of the cytoskeleton
Essential during cell division for chromosome separation
Used in cell motility (cilia and flagella)

Microfilaments (Actin Filaments)

Important for cell shape, muscle contraction, and intracellular movements (like amoeboid movement)
Key roles in maintaining cell shape and enabling other specialized cellular processes

Intermediate Filaments

Provide mechanical support; they help maintain cell shape and coordinate with other organelles

Centrosomes and Centrioles

Microtubule organizing center
Plays a crucial role in cell division and the growth of microtubules

Cilia and Flagella

Locomotor appendages of cells; composed of microtubules arranged in a 9+2 pattern
Both are motor proteins that drive the bending movements.

Microfilaments (Actin filaments)

Solid rods built of actin subunits in a twisted double chain
Helps maintain cell shape and enables various functions, such as muscle contraction and amoeboid movement

Extracellular Components and Connections

Some cells are surrounded by an extracellular matrix, which helps coordinate activities between neighboring cells
Cell walls are common in plant and some other eukaryotic cells

Cell Walls of Plants

Support and maintain shape; made primarily of cellulose

Plasmodesmata (Plant Cells)

Channels that perforate cell walls to allow for the passage of various molecules

Extracellular Matrix (ECM) of Animal Cells

A mixture of glycoproteins and fibers that provide structure and support for animal cells

Cell Junctions

Structures that connect cells to each other within tissues

Tight Junctions, Desmosomes, and Gap Junctions

Intercellular junctions that join neighboring cells to each other and enable communication

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Description

Test your knowledge on cell structure and its functions with this quiz. Explore concepts related to microscopy, including magnification, resolution, and contrast. Dive into the details of how cells are the fundamental units of life and how microscopy aids in their study.