Cell Theory and Microscopy

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Questions and Answers

What is the primary function of flagella in bacteria?

Movement of the cell (correct)

Attachment to surfaces

Protein synthesis

DNA replication

Which of the following structures is responsible for genetic information storage in eukaryotic cells?

Endoplasmic reticulum

Cytoplasm

Ribosomes

Nucleus (correct)

What is the function of pili in bacterial cells?

Energy production

Movement

Attachment and conjugation (correct)

Transfer of nutrients

What structure provides structural support in eukaryotic cells?

Cytoskeleton Signup and view all the answers

Which of the following is NOT an organelle found in eukaryotic cells?

Capsule Signup and view all the answers

In what form is DNA organized within the nucleus of eukaryotic cells?

Chromatin Signup and view all the answers

What role do proteins play in enzymatic reactions?

Catalyzing biochemical reactions Signup and view all the answers

Which of the following best describes the function of the capsule in bacterial cells?

Protects the cell and aids in adhesion Signup and view all the answers

What is meant by the statement 'all living organisms are composed of one or more cells'?

Every living thing is made up of cells. Signup and view all the answers

Which aspect of microscopy defines the ability to distinguish two points as separate entities?

Resolution Signup and view all the answers

What is a primary limitation of light microscopes compared to electron microscopes?

Light microscopes typically have lower magnification capabilities. Signup and view all the answers

Which of the following accurately describes a characteristic of prokaryotic cells?

They have plasmids that can replicate independently. Signup and view all the answers

What is the primary role of ribosomes in prokaryotic cells?

Protein synthesis Signup and view all the answers

How does a scanning electron microscope (SEM) differ from a transmission electron microscope (TEM)?

SEM provides 3D images, while TEM provides detailed internal images. Signup and view all the answers

Which of the following components of prokaryotic cells provides shape and protection?

Cell wall Signup and view all the answers

What does magnification refer to in the context of microscopy?

The process of enlarging an object's appearance. Signup and view all the answers

What is the primary function of the Rough Endoplasmic Reticulum (ER)?

Involved in protein synthesis. Signup and view all the answers

Which organelle is responsible for the conversion of light energy into chemical energy?

Chloroplasts Signup and view all the answers

Which is a defining characteristic of plant cells that distinguishes them from animal cells?

Presence of a cell wall made of cellulose Signup and view all the answers

What role do motor proteins Kinesin and Dynein play in the cell?

Transport organelles along microtubules. Signup and view all the answers

What function do Lysosomes serve within the cell?

Contain digestive enzymes. Signup and view all the answers

Which structure is NOT part of the cytoskeleton?

Ribosomes Signup and view all the answers

What type of cell contains a large central vacuole?

Plant Cell Signup and view all the answers

Which aspect supports the Endosymbiosis Theory?

Both organelles have DNA similar to bacterial DNA. Signup and view all the answers

What characteristic is common to both mitochondria and chloroplasts?

They reproduce independently through binary fission. Signup and view all the answers

Which statement regarding the fluid mosaic model of the cell membrane is true?

Phospholipids can move laterally within the same leaflet. Signup and view all the answers

Which type of membrane protein spans the entire lipid bilayer?

Integral proteins Signup and view all the answers

How do unsaturated fatty acids affect the fluidity of the membrane?

They increase fluidity by preventing tight packing of phospholipids. Signup and view all the answers

What was observed when mouse and human cells were fused in the lateral movement experiment?

Labeled proteins mixed over time. Signup and view all the answers

Which process describes the movement of water across a semipermeable membrane?

Osmosis Signup and view all the answers

What is required for active transport?

Energy input, usually from ATP Signup and view all the answers

What defines passive transport?

Movement of molecules without energy input, down their concentration gradient Signup and view all the answers

What is the primary role of aquaporins in cellular function?

Facilitating water transport across the membrane Signup and view all the answers

Which type of transporter is characterized by moving two different types of molecules in the same direction?

Symporter Signup and view all the answers

What process involves cells engulfing large particles?

Phagocytosis Signup and view all the answers

Which is NOT a step in the process of exocytosis?

Engulfing solid particles Signup and view all the answers

How does a channel differ from a transporter?

Channels facilitate diffusion while transporters bind and transport molecules Signup and view all the answers

Study Notes

Cell Theory

All living organisms are composed of one or more cells.
The cell is the fundamental building block of all organisms, responsible for structure and function.
New cells are produced from pre-existing cells through cell division, ensuring the continuity of life.

Microscopy

Magnification enlarges the appearance of an object using lenses.
Resolution determines how clearly two points are distinguished as separate entities.
Contrast refers to the difference in light intensity between the image and the background, enhancing structure visibility.

Light Microscopes

Use visible light and glass lenses for image magnification.
Types include compound microscopes (multiple lenses) and stereo microscopes (3D view).
Suitable for viewing live cells and tissues, but limited to about 2000x magnification and 200 nm resolution.

Electron Microscopes

Use electron beams and electromagnetic lenses.
Scanning Electron Microscope (SEM) provides detailed 3D surface images.
Transmission Electron Microscope (TEM) provides detailed images of internal structures.
Offer significantly higher magnification (up to 2 million times) and resolution (up to 0.1 nm) compared to light microscopes.

Prokaryotic Cells

Nucleoid: Region containing the cell's DNA, not enclosed by a membrane.
Plasmids: Small, circular DNA molecules separate from the chromosomal DNA.
Ribosomes: Smaller than eukaryotic ribosomes (70S), involved in protein synthesis.
Cell Wall: Composed of peptidoglycan (bacteria) or other materials (archaea), providing shape and protection.
Flagella: Long, whip-like structures for movement.
Pili: Hair-like structures for attachment and conjugation (DNA transfer).

Eukaryotic Cells

Nucleus: Enclosed by a nuclear envelope, contains the cell's DNA organized into chromosomes.
Membrane-bound Organelles: Includes mitochondria, chloroplasts (plants), endoplasmic reticulum, Golgi apparatus, lysosomes, and peroxisomes.
Cytoskeleton: Network of protein filaments (actin filaments, intermediate filaments, microtubules), provides structural support and facilitates movement.
Larger Size: Typically 10-100 µm in diameter, enabling compartmentalization of functions.

Proteome and Cell Structure/Function

The proteome represents the complete set of proteins expressed by a cell, tissue, or organism at a given time.
Enzymatic Reactions: Proteins catalyze biochemical reactions.
Structural Support: They form the cytoskeleton and extracellular matrix.
Transport: Proteins move molecules across membranes.
Signaling: They facilitate communication between and within cells.
Defense: Proteins play critical roles in immune responses and protection against pathogens.

General Features of a Bacterial Cell

Capsule: A gelatinous outer layer protecting the cell and aiding in surface adhesion.
Cell Wall: Provides structural support and shape, composed of peptidoglycan in bacteria.
Plasma Membrane: A lipid bilayer regulating substance movement in and out of the cell.
Cytoplasm: Gel-like substance where metabolic reactions occur.
Nucleoid: Region containing the cell's DNA.
Ribosomes: Sites of protein synthesis, smaller than eukaryotic ribosomes.
Flagella: Tail-like structures enabling movement.
Pili: Hair-like structures assisting in attachment and DNA transfer during conjugation.

Four Main Regions of Eukaryotic Cells

Cytosol: Fluid component of the cytoplasm where metabolic reactions occur.
Nucleus: Houses the cell's genetic material (DNA) and acts as the control center for cellular activities.
Endomembrane System: Includes the endoplasmic reticulum (ER), Golgi apparatus, lysosomes, and vesicles.
Semi-autonomous Organelles: Mitochondria and chloroplasts possess their own DNA and can replicate independently.

Organelle Locations and Functions

Nucleus: Located within the nucleus, stores genetic information and coordinates cellular activities.
Endoplasmic Reticulum (ER): Rough ER (with ribosomes) is involved in protein synthesis; Smooth ER (without ribosomes) is involved in lipid synthesis and detoxification.
Golgi Apparatus: Located within the endomembrane system, modifies, sorts, and packages proteins and lipids for transport.
Lysosomes: Located within the endomembrane system, contain digestive enzymes for breaking down macromolecules.
Mitochondria: Located in the cytosol, produce ATP through cellular respiration.
Chloroplasts: Located in the cytosol of plant cells, conduct photosynthesis to convert light energy into chemical energy.

Key Differences Between Animal and Plant Cells

Animal Cells

Lack a cell wall, allowing for various shapes.
Do not possess chloroplasts, as they do not perform photosynthesis.
Have small, temporary vacuoles.
Contain centrioles, involved in cell division.

Plant Cells

Have a rigid cell wall composed of cellulose, providing structural support.
Contain chloroplasts for photosynthesis.
Have a large central vacuole for maintaining cell turgor and storing nutrients.
Lack centrioles.

Cytoskeleton and Motor Proteins

Cytoskeleton:
- Actin Filaments (Microfilaments): Thin filaments involved in cell movement and shape changes.
- Intermediate Filaments: Provide mechanical support and maintain cell integrity.
- Microtubules: Thick, hollow tubes that guide organelle movement and are involved in cell division.
Motor Proteins:
- Myosin: Interacts with actin filaments for muscle contraction and other cellular movements.
- Kinesin: Moves along microtubules, transporting vesicles and organelles towards the cell periphery.
- Dynein: Moves along microtubules, transporting vesicles and organelles towards the cell center.
Cilia and Flagella: Hair-like structures extending from the cell surface, involved in movement; cilia are short and numerous, while flagella are longer and fewer.

Endosymbiosis Theory

Proposes that mitochondria and chloroplasts originated from free-living bacteria engulfed by ancestral eukaryotic cells.
Evidence:
- Both organelles have their own DNA, similar to bacterial DNA.
- Both possess double membranes, consistent with the engulfing mechanism.
- Both reproduce independently within the cell through a process similar to binary fission.

Fluid Mosaic Model and Membrane Dynamics

Describes the cell membrane as a fluid combination of phospholipids, cholesterol, and proteins that move laterally within the layer.
Phospholipid Movement: Phospholipids move laterally within the same leaflet of the bilayer; flip-flop movement between leaflets is rare and requires enzymes called flippases.

Types of Membrane Proteins

Integral Proteins: Embedded within the lipid bilayer, often spanning the entire membrane.
Peripheral Proteins: Attached to the surface of the membrane, on either the cytoplasmic or extracellular side.
Lipid-anchored Proteins: Covalently attached to lipids within the membrane.

Membrane Fluidity

Influenced by the types of fatty acids in phospholipids (saturated vs. unsaturated) and the presence of cholesterol.
Unsaturated fatty acids increase fluidity by preventing tight packing of phospholipids.
Cholesterol stabilizes membrane fluidity, making it more resistant to changes in temperature.

Experiment on the Lateral Movement of Membrane Proteins

Procedure: Mouse and human cells were fused, and their membrane proteins were labeled with different fluorescent markers.
Observation: Over time, the labeled proteins mixed, demonstrating that membrane proteins can move laterally within the lipid bilayer.

Definitions of Key Terms

Gradient: A difference in concentration, pressure, or electrical charge between two regions.
Passive Transport: Movement of molecules across a membrane without energy input, down their concentration gradient.
Passive Diffusion: Movement of molecules directly through the lipid bilayer without the aid of proteins.
Facilitated Diffusion: Movement of molecules across a membrane via transport proteins, down their concentration gradient.
Active Transport: Movement of molecules against their concentration gradient, requiring energy (usually ATP).

Osmosis

The diffusion of water across a semipermeable membrane from a region of lower solute concentration to a region of higher solute concentration.
Importance: Maintains cell turgor in plants and regulates fluid balance in animal cells.

Aquaporin Experiment

Procedure: Cells with and without aquaporins were compared for water permeability.
Results: Cells with aquaporins showed significantly higher water permeability, confirming the role of aquaporins in water transport.

Channels vs. Transporters

Channels: Provide a passageway for molecules to diffuse through the membrane. Examples include ion channels and aquaporins.
Transporters: Bind and transport molecules across the membrane. Examples include glucose transporters and sodium-potassium pumps.

Types of Transporters

Uniporter: Transports one type of molecule in one direction.
Symporter: Transports two types of molecules in the same direction.
Antiporter: Transports two types of molecules in opposite directions.

Endocytosis and Exocytosis

Endocytosis: The process by which cells internalize substances by engulfing them in a vesicle.
- Phagocytosis: "Cell eating," engulfing large particles.
- Pinocytosis: "Cell drinking," engulfing fluids and dissolved substances.
- Receptor-mediated Endocytosis: Specific molecules are taken in after binding to receptors on the cell surface.
Exocytosis: The process by which cells expel materials by fusing a vesicle with the plasma membrane.
- Steps: Vesicle formation, transport to the membrane, fusion with the membrane, and release of contents outside the cell.

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Description

Explore the fundamental concepts of cell theory and the use of microscopy in biology. Understand how cells are the building blocks of life, and learn the differences between light and electron microscopes. This quiz will test your knowledge on magnification, resolution, and the importance of microscopy in studying cellular structures.