Cell Biology Overview Quiz

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Questions and Answers

What is the smallest unit of life?

Molecule

Cell (correct)

Organism

Atom

What type of organisms obtain energy from sunlight?

Lithotrophic

Phototrophic (correct)

Heterotrophic

Organotrophic

What do prokaryotes lack compared to eukaryotes?

Nucleus (correct)

Ribosomes

Cell membranes

Cytoplasm

Which of the following statements correctly describes organotrophic organisms?

They obtain energy from other living things and their organic chemicals. Signup and view all the answers

Which group of bacteria is essential for fixing nitrogen and assisting plants?

Nitrogen-fixing bacteria Signup and view all the answers

What is the main focus of cell biology?

Examining the microscopic and molecular level of cells Signup and view all the answers

Why is it important for society to understand cell biology?

To make informed decisions about biotechnology and medicine Signup and view all the answers

Which characteristic is NOT associated with prokaryotic cells?

They have complex cellular structures. Signup and view all the answers

What is one of the impacts of lipids being added to proteins?

They can lead to changes in protein localization. Signup and view all the answers

How do individual protein kinases function in the cell?

They act as microprocessors integrating signals. Signup and view all the answers

What regulates the lifespan of proteins?

Regulated degradation pathways. Signup and view all the answers

What effect does the addition of phosphate groups have on proteins?

It alters structure and interacts for signaling. Signup and view all the answers

What lifespan is an example of a protein that lasts your entire life?

Crystallin in the lens of the eye Signup and view all the answers

What is the advantage of using cultured cells in research?

They allow for the study of important cell biological phenomena. Signup and view all the answers

Which technique provides a three-dimensional view of cellular structures?

Scanning Electron Microscopy (SEM) Signup and view all the answers

How are the images formed in an Electron Microscope?

By detecting scattered electrons after they pass through a specimen. Signup and view all the answers

Which staining method specifically targets nucleic acids?

Feulgen stain Signup and view all the answers

What is a characteristic of induced pluripotent stem cells (iPS cells)?

They do not require human oocytes for their production. Signup and view all the answers

Which microscopy technique involves a sample being surrounded by vitreous ice?

Cryoelectron Tomography Signup and view all the answers

What role does the numerical aperture play in microscopy?

It impacts the light gathering capacity of the lens. Signup and view all the answers

Which type of stem cells can differentiate into any cell type in the body?

Embryonic stem cells Signup and view all the answers

What happens to cellular macromolecules during staining for Transmission Electron Microscopy (TEM)?

They are cross-linked with glutaraldehyde. Signup and view all the answers

Which process describes changing the genetic makeup of embryonic stem cells to match a patient's DNA?

Customization of ES cells Signup and view all the answers

In freeze fracture techniques, what is the purpose of using heavy metals?

To create a replica of the fractured cellular structure. Signup and view all the answers

What is the primary use of the microtome in microscopy?

To prepare slides by thinly slicing tissue. Signup and view all the answers

What describes the process of transdifferentiation?

The transformation of one differentiated cell type directly into another. Signup and view all the answers

In the context of optical microscopy, what does resolution depend on?

The wavelength of light used and the numerical aperture. Signup and view all the answers

What is the primary purpose of ATP in cells?

Carrier of free energy Signup and view all the answers

Which of the following best describes endosymbiont theory?

A theory proposing eukaryotic cells evolved from prokaryotic cells living symbiotically Signup and view all the answers

How do prokaryotes and eukaryotes differ in terms of genome size and frequency of gene duplication?

Prokaryotes generally have smaller genomes with lower frequency of gene duplication Signup and view all the answers

What type of organism is Caenorhabditis elegans and what has it helped researchers understand?

A worm that has helped with understanding controls over cell division and death Signup and view all the answers

Which of the following is NOT a characteristic of eukaryotic cells?

All eukaryotic cells perform photosynthesis Signup and view all the answers

What is a significant advantage of zebrafish as a model organism?

They are transparent during early development phases, allowing easy observation of cell behaviors Signup and view all the answers

What is the main characteristic of a primary cell culture?

Obtained directly from the organism and has limited divisions Signup and view all the answers

Which of the following statements about differentiation in humans is correct?

It is the process by which unspecialized cells become specialized Signup and view all the answers

What is a characteristic of Drosophila melanogaster as a model organism?

It is primarily used for studies in invertebrate developmental biology Signup and view all the answers

How does cell culture in a 3-D format differ from 2-D culture methods?

3-D cultures allow better observation of individual cell interactions Signup and view all the answers

What role do membrane transport proteins serve in cells?

They maintain the semi-permeable nature of the cell membrane Signup and view all the answers

Which prokaryotic group is characterized as 'extremophiles'?

Archea Signup and view all the answers

What triggers the process of cell differentiation?

Environmental signals received by the cell Signup and view all the answers

What is a common method to observe details in unstained specimens?

Dark-field microscopy Signup and view all the answers

What role do chaperones play in protein folding?

They aid in the proper folding of proteins by preventing inappropriate interactions. Signup and view all the answers

Which statement best describes a secondary structure of proteins?

It includes structures such as alpha helices and beta-pleated sheets. Signup and view all the answers

What is the primary structure of a protein?

The sequence of amino acids in a polypeptide chain. Signup and view all the answers

What is a key feature of the tertiary structure of proteins?

It is characterized by the interactions between R-groups. Signup and view all the answers

Which of the following groups of amino acids can form hydrogen bonds?

Polar uncharged amino acids Signup and view all the answers

Which of the following statements is true regarding peptide bonds?

They create a linkage between the amino group of one amino acid and the carboxyl group of another. Signup and view all the answers

What can lead to dire consequences for protein function?

Changes in the primary structure of the protein. Signup and view all the answers

How is ATP primarily produced in cells?

By stepwise oxidation of glucose and other food sources. Signup and view all the answers

What is one of the roles of signaling proteins like kinases?

They communicate messages over long distances. Signup and view all the answers

Which of these is NOT considered a macromolecule stored for energy in cells?

NADH Signup and view all the answers

Which category of amino acids is most likely to be located in the interior of a protein structure?

Nonpolar amino acids Signup and view all the answers

What determines the specific sequence of amino acids in a protein?

The sequence of the gene encoding the protein Signup and view all the answers

In what direction do peptide chains typically travel?

N – C direction only Signup and view all the answers

What are beta-pleated sheets characterized by?

Side-by-side polypeptide segments Signup and view all the answers

Which factor primarily influences the formation of a protein's tertiary structure?

The interactions between the R-groups of amino acids Signup and view all the answers

Study Notes

Introduction to Cell Biology

Cells are the smallest unit of life and are fundamental to all living organisms.
Cell biology involves studying cellular structure, function, and behavior at microscopic and molecular levels.
Understanding cell biology benefits fields such as biotechnology, forensics, and medicine.

Importance of Cell Biology

Informed societal decisions depend on knowledge of cell biology, impacting GM plants, lab-grown organs, and genome editing.
Some cells specialize in essential processes, like nitrogen and carbon fixation which is crucial for plant life.

Types of Cells

Prokaryotes
- Defined as simple cells without a nucleus (e.g., bacteria).
- Includes Archaea known as extremophiles, which thrive in high temperatures.
- Bacteria encompass diverse forms such as spherical (Streptococcus) and rod-shaped (Escherichia coli).
Eukaryotes
- More complex cells with a nucleus.
- Can be unicellular (e.g., protists) or multicellular (e.g., humans).
- Eukaryotic cells are believed to have evolved from a symbiotic relationship between prokaryotic cells.

Model Organisms

Yeast
- Single-celled eukaryote that is easy to study due to its small genome and the ability for genetic modification.
Arabidopsis thaliana
- A quick-reproducing weed model used extensively in genetics studies.
Caenorhabditis elegans
- A nematode that has aided research in cell division and death mechanisms.
Drosophila melanogaster
- Fruit fly used to study genetic processes and development.
Xenopus laevis
- Frog model for vertebrate development, known for large, easily fertilized eggs.
Danio rerio
- Zebrafish offer transparency during early development, allowing observation of cellular behaviors.
Mus musculus
- Mouse model essential for genetic studies, mimicking human genetic conditions.

Cell Differentiation

Cell differentiation is the process through which unspecialized cells become specialized.
This process is influenced by environmental signals and varies depending on the cell's position in the embryo.

Cell Culture

Cells may be grown outside the body (in vitro) under controlled conditions, often in plastic flasks.
Primary Culture is directly harvested from organisms, typically embryonic tissues which can rapidly dissociate and divide.
Cell Lines are modified primary cultures that can proliferate indefinitely, often used for research (e.g., HeLa cells).

Cell Culture Techniques

2-D cell culture techniques monitor conditions like temperature and CO2.
3-D cell culture allows cells to grow in a manner more reflective of natural environments.

Microscopy Techniques

Various staining techniques allow for detailed observation of cellular structures.
Dark-field microscopy helps visualize unstained specimens by applying light at an angle.
Phase contrast and differential interference contrast microscopy enhance visibility in unstained specimens.### Cell Culture and Microscopy Techniques
Histological specimens involve lining of stomach, intestines, and bladder; one side is in gel culture while the other is submerged in water.
Cells are cultured in a gel-like environment, mimicking the extracellular matrix (ECM).
Two main methods for visualizing cell structure: phase contrast and differential interference contrast (DIC) microscopy.
Phase contrast microscopy relies on differing refractive indices across cell structures.
DIC microscopy enhances visualization by considering the rate of refractive index change for varying image brightness.

Advantages of Cultured Cells

Cultured cells can be obtained in large quantities and are often homogenous (one cell type).
Important biological processes such as cell movement and division can be studied.
Cultured cells are capable of differentiation and can be used to assess drug and hormone activity.
Prepping cells for microscopy involves fixation for structure preservation, staining for visibility (e.g., Feulgen stain for DNA), and mounting on slides.

Microscopy Techniques

Bright Field Light Microscopy: Enlarges images of objects, relies on light diffraction by cells with resolution determined by wavelength and lens numerical aperture.
Electron Microscopy (EM): Uses electrons for imaging, providing higher resolution due to shorter wavelengths.
- TEM requires specimens to be fixed, embedded, and sectioned; stained with heavy metals to visualize structures.
- Cryoelectron microscopy involves rapid freezing without chemical fixatives and achieves high resolution by combining multiple images.
- SEM provides detailed surface views by reflecting backscattered electrons from specimens.

Stem Cells

Stem Cells: Undifferentiated cells capable of self-renewal and differentiation into various cell types.
- Adult Stem Cells can possibly be transplanted for therapies.
- Embryonic Stem Cells (ES): Derived from embryos, pluripotent, and can differentiate into any cell type.
iPS cells (induced pluripotent stem cells) are created by reprogramming somatic cells for therapeutic use without embryos.
Ethical debates surround the use of ES cells, particularly regarding embryo creation.

Biological Macromolecules

Four primary types:
- Polysaccharides (sugars),
- Fats and lipids,
- Proteins (from amino acids),
- Nucleic acids (from nucleotides).
Macromolecules assemble to form larger structures through various chemical interactions, highlighting the interplay between structure and function.

Carbohydrates

Composed of monosaccharides, including aldoses (aldehyde group) and ketoses (internal carbonyl).
Linked by covalent bonds in disaccharides through reactions that either form or break polymers.
Structural nuances such as alpha and beta forms impact sugar interactions and biochemical properties.

Reprogramming and Transdifferentiation Strategies

Direct cell reprogramming can enable functionality shifts, demonstrated in type 1 diabetes treatment by converting pancreatic alpha cells to beta cells for insulin production.

ATP and Energy Transfer

Reaction coupling enables cells to drive energetically unfavorable reactions by pairing them with favorable ones.
Coenzymes, like coenzyme A (CoA), are formed when ATP combines with other groups.
The standard free energy change indicates the direction and feasibility of biological reactions.

Metabolism and Energy Production

Glucose and other dietary components undergo stepwise oxidation reactions.
These reactions generate ATP and NADH, providing chemical energy.
Small molecules produced during these reactions serve as substrates for macromolecule biosynthesis.
Stored macromolecules, including glycogen and fats, are significant energy reserves.

Proteins Overview

Approximately 10,000 proteins are synthesized in every mammalian cell.
Proteins execute nearly all cellular functions such as:
- Enzymatic activity to accelerate reactions.
- Signaling through molecules like kinases and phosphatases.
- Hormonal messaging over long distances.
- Growth factor functions.
- Membrane receptor communication.
- Facilitation of cell movement via the cytoskeleton.

Protein Structure

Proteins are polymers composed of 20 amino acids.
Each amino acid features an amino group, a carboxyl group, and a variable R group attached to an alpha carbon.
R groups categorize into four types:
- Polar charged: capable of ionic interactions.
- Polar uncharged: can form hydrogen bonds.
- Nonpolar: usually hydrophobic, situated in protein cores.
- Special cases: glycine, cysteine, and proline.

Peptide Bonds and Folding

Peptide bonds form between the carboxyl group of one amino acid and the amino group of another, leading to polypeptide chain formation.
Secondary structure stabilized by hydrogen bonds includes:
- Alpha helices: a cylindrical spiral with R groups projecting outward.
- Beta-pleated sheets: segments lying side by side, can be antiparallel or parallel.

Higher-order Protein Structure

Primary Structure: Sequence of amino acids determined by gene sequences.
Tertiary Structure: Overall 3-D conformation influenced by R-group interactions.
Stability can be impacted by:
- Hydrophobic interactions and van der Waals forces.
- Disulfide bridges linking cysteine residues.

Modifications and Regulation

Lipids can anchor proteins to cell membranes, influencing functions and localization.
Metal ions and phosphate groups are crucial for protein function, aiding in signaling and structural alterations.
Protein lifetime varies widely, from a few minutes to a lifetime (e.g., mitotic cyclins vs. crystallins in the eye lens).
Regulated degradation pathways maintain protein homeostasis by controlling protein lifespan through targeted degradation.

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Description

Test your knowledge of fundamental concepts in cell biology with this quiz. Questions cover the smallest units of life, energy acquisition in organisms, and distinctions between prokaryotes and eukaryotes. Challenge yourself on essential topics like organotrophic organisms and nitrogen-fixing bacteria.