Name
Western Governors University
D311 Microbiology Lab Report: Identification Tests & Results
Prof. Name
Date
Which statement describes prokaryotic cells?
Prokaryotic cells are defined by their lack of a nucleus enclosed by a complex nuclear membrane. Unlike eukaryotic cells, prokaryotes do not possess membrane-bound organelles. Their genetic material typically exists as a single circular chromosome located in the nucleoid region. These cells can appear in various shapes, including spherical (coccus), often forming pairs, clusters, or chains. Prokaryotic cells do not have multiple rod-shaped chromosomes nor a nucleus with a nuclear membrane.
Answer: Prokaryotic cells lack a nucleus with a complex nuclear membrane and may exist in coccus form in pairs or clusters (a).
Which statement describes eukaryotic cells?
Eukaryotic cells contain a well-defined nucleus surrounded by a double membrane called the nuclear envelope. These cells feature multiple membrane-bound organelles such as mitochondria and the Golgi apparatus. Their genetic material is organized into multiple linear chromosomes. Structural support is provided by the cytoskeleton, which maintains cell shape and organelle positioning within the cytoplasm. They do not possess an exoskeleton.
Answer: Eukaryotic cell nuclei are enclosed by complex nuclear membranes (b).
Which statement describes eukaryotic flagella?
Eukaryotic flagella are flexible, whip-like appendages that enable cell movement. Unlike prokaryotic flagella, which rotate, eukaryotic flagella move by bending due to their internal “9+2” microtubule arrangement—nine pairs of microtubules surrounding two central microtubules. These flagella do not cover the entire cell surface.
Answer: Eukaryotic flagella are flexible, whip-like structures (d).
Which statement describes the endomembrane system?
The endomembrane system consists of interconnected membrane-bound organelles including the Golgi apparatus, lysosomes, rough and smooth endoplasmic reticulum, and vesicles. It facilitates the synthesis, modification, and transport of proteins and lipids within the cell. Protein synthesis occurs in the rough ER, and transport is mediated by vesicles rather than simple diffusion.
Answer: The system includes the Golgi apparatus, lysosomes, and vesicles (b).
| Question | Options | Answer | Explanation |
|---|---|---|---|
| Which organelle is involved in energy production? | a) Golgi apparatus b) Mitochondria c) Lysosome d) Ribosome | b) Mitochondria | Mitochondria generate ATP through cellular respiration. |
| What is the function of the rough endoplasmic reticulum? | a) Lipid synthesis b) Protein synthesis c) Detoxification d) Storage of genetic material | b) Protein synthesis | The rough ER has ribosomes for synthesizing proteins destined for membranes or secretion. |
| Which of these is NOT a feature of mitochondria? | a) Double membrane b) Own DNA c) Photosynthesis capability d) Production of ATP | c) Photosynthesis capability | Photosynthesis is performed by chloroplasts, not mitochondria. |
What type of macromolecule are enzymes?
Enzymes are primarily proteins that act as biological catalysts, speeding up biochemical reactions without being consumed, thereby facilitating essential metabolic processes.
Answer: Proteins (c).
Which molecule carries genetic information?
DNA (deoxyribonucleic acid) stores and transmits genetic information in all living organisms, while RNA mainly participates in gene expression.
Answer: DNA (a).
What is the primary structure of a protein?
The primary structure is the unique linear sequence of amino acids linked by peptide bonds. This sequence ultimately dictates the protein’s shape and function.
Answer: The sequence of amino acids (a).
Which cellular process involves movement of molecules from high to low concentration?
Diffusion is a passive process where molecules naturally move from an area of higher concentration to one of lower concentration without the input of energy.
Answer: Diffusion (b).
Which organelle is responsible for digesting cellular waste?
Lysosomes contain enzymes that break down cellular debris and waste, playing a key role in maintaining cell health.
Answer: Lysosome (a).
| Question | Options | Answer | Explanation |
|---|---|---|---|
| What is the function of ribosomes? | a) Synthesis of DNA b) Protein synthesis c) Lipid metabolism d) Energy production | b) Protein synthesis | Ribosomes translate messenger RNA to form polypeptides. |
| What part of the cell controls what enters and leaves? | a) Cytoplasm b) Cell membrane c) Nucleus d) Golgi apparatus | b) Cell membrane | The cell membrane regulates passage of substances in and out of the cell. |
What is the fluid mosaic model?
The fluid mosaic model explains the cell membrane as a dynamic bilayer primarily made of phospholipids with embedded proteins and carbohydrates. This structure enables selective permeability and cell communication.
Answer: Description of cell membrane structure (b).
Which molecule is a major component of the cell membrane?
Phospholipids form the essential bilayer framework, creating a barrier to water-soluble molecules.
Answer: Phospholipid (c).
| Question | Options | Answer | Explanation |
|---|---|---|---|
| What does ATP stand for? | a) Adenosine triphosphate b) Adenine triphosphate c) Adenosine diphosphate d) Adenine diphosphate | a) Adenosine triphosphate | ATP is the main energy carrier in cells. |
| ATP is primarily used for what? | a) Genetic information b) Energy storage and transfer c) Protein synthesis d) Structural support | b) Energy storage and transfer | ATP supplies energy for processes such as muscle contraction. |
What is the role of the Golgi apparatus?
The Golgi apparatus modifies, sorts, and packages proteins and lipids synthesized in the endoplasmic reticulum for delivery to various cell locations or secretion outside the cell.
Answer: Protein modification and packaging (a).
Which of these is involved in vesicle transport?
Microtubules within the cytoskeleton serve as tracks for the movement of vesicles and organelles, aiding intracellular transport.
Answer: Microtubules (a).
What is the purpose of cellular respiration?
Cellular respiration converts energy stored in nutrients into ATP, which powers various cellular activities.
Answer: To produce ATP (b).
Where in the cell does cellular respiration primarily take place?
Mitochondria are the principal site where cellular respiration occurs, utilizing enzymes to convert glucose into energy.
Answer: Mitochondria (b).
Prokaryotic and eukaryotic cells vary significantly in structure and complexity. First, prokaryotes lack a true nucleus; their DNA resides in the nucleoid region without a membrane, whereas eukaryotes have a membrane-enclosed nucleus. Second, prokaryotes contain a single circular chromosome, while eukaryotes have multiple linear chromosomes. Third, eukaryotic cells possess membrane-bound organelles such as mitochondria and the Golgi apparatus, which prokaryotes do not.
| Feature | Prokaryotic Cells | Eukaryotic Cells |
|---|---|---|
| Nucleus | Absent (nucleoid) | Present (membrane-bound) |
| Chromosomes | Single circular | Multiple linear |
| Organelles | No membrane-bound | Membrane-bound organelles |
The cytoskeleton is an intricate network of protein fibers that provides structural support, preserves cell shape, and enables intracellular transport. It plays a critical role in cell division, motility, and the positioning of organelles. The cytoskeleton is composed of microfilaments, intermediate filaments, and microtubules, each contributing distinct functions.
Eukaryotic flagella exhibit a characteristic “9+2” microtubule pattern, consisting of nine pairs of microtubules arranged in a circle surrounding two central single microtubules. This arrangement is essential for the bending movement that propels cells.
The endomembrane system includes the nuclear envelope, rough and smooth endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles, and the plasma membrane. Together, these organelles coordinate the synthesis, modification, and transport of proteins and lipids inside the cell.
Mitochondria produce ATP through oxidative phosphorylation, fueling cellular activities. They are unique because they contain their own DNA and ribosomes, allowing them to synthesize some proteins independently, supporting the theory that they originated from an ancestral symbiotic relationship.
Which macromolecule is the primary component of the plant cell wall?
Plant cell walls are mostly made of cellulose, a glucose-based polysaccharide that provides rigidity and structural support. Different organisms have varying cell wall components, such as chitin in fungi and peptidoglycan in bacteria.
Answer: Cellulose (a).
What molecule stores genetic information in viruses?
Viruses store genetic material as either DNA or RNA but never both. This genetic material is enclosed within a protein coat and is crucial for viral replication.
Answer: DNA or RNA (a).
What is binary fission?
Binary fission is an asexual reproductive process used by prokaryotes like bacteria, involving the replication of the chromosome and division into two identical daughter cells.
Answer: A form of asexual reproduction in prokaryotes (b).
Which structure helps bacteria stick to surfaces?
Pili are hair-like structures on bacterial surfaces that aid attachment to surfaces and other cells, facilitating colonization and biofilm development.
Answer: Pili (b).
| Question | Options | Answer | Explanation |
|---|---|---|---|
| Which stage of bacterial growth involves rapid cell division? | a) Lag phase b) Log phase c) Stationary phase d) Death phase | b) Log phase | The log phase is marked by exponential growth and rapid division. |
| What is a plasmid? | a) A chromosome b) Small independent DNA molecule c) Ribosome d) Protein | b) Small independent DNA molecule | Plasmids replicate independently and often carry genes for antibiotic resistance. |
What are endospores?
Endospores are dormant, highly resistant bacterial structures formed to survive harsh environmental conditions. They preserve the bacterial genome until conditions improve.
Answer: Dormant, resistant forms of bacteria (b).
Which condition triggers endospore formation?
Endospore formation is a response to environmental stressors such as nutrient scarcity, heat, or desiccation, allowing survival through adverse conditions.
Answer: Environmental stress (b).
What is the function of antibiotics?
Antibiotics are substances that kill or inhibit bacterial growth, making them effective treatments against bacterial infections, but they do not affect viruses.
Answer: Kill or inhibit bacteria (a).
Which bacterial structure is a common antibiotic target?
The bacterial cell wall is a frequent target for antibiotics, which disrupt its synthesis and lead to bacterial death.
Answer: Cell wall (a).
| Question | Options | Answer | Explanation |
|---|---|---|---|
| What is horizontal gene transfer? | a) Parent to offspring b) Between unrelated bacteria c) Mutation d) Gene loss | b) Between unrelated bacteria | It promotes genetic diversity by transferring genes between bacteria. |
| Which process involves uptake of DNA from the environment? | a) Conjugation b) Transformation c) Transduction d) Translation | b) Transformation | Transformation is bacteria taking up free DNA and incorporating it into their genome. |
Binary fission begins with replication of the single circular chromosome. The bacterial cell elongates as the DNA copies separate. A septum then forms, dividing the cell into two genetically identical daughter cells, enabling rapid bacterial population growth under favorable conditions.
Pili are adhesive appendages that allow bacteria to attach to surfaces and host tissues, aiding colonization and biofilm formation. Capsules are protective polysaccharide layers that shield bacteria from desiccation and immune responses, enhancing bacterial virulence and survival in hostile environments.
| Stage | Description |
|---|---|
| Lag phase | Cells metabolically active but not dividing, adapting to new conditions. |
| Log phase | Exponential cell division and rapid population growth. |
| Stationary phase | Growth rate plateaus as nutrients deplete and waste accumulates; division equals death. |
| Death phase | Cells die faster than new cells form due to unfavorable conditions. |
Endospores are dormant, resistant bacterial forms produced in response to environmental stress. They enable bacteria to survive extreme conditions such as heat, radiation, and chemicals, ensuring species survival over time.
Antibiotics exploit differences between bacterial and human cells, targeting structures like the bacterial cell wall or unique ribosomal components. This selective targeting allows antibiotics to kill or inhibit bacteria without damaging human host cells.
Alberts, B., Johnson, A., Lewis, J., Morgan, D., Raff, M., Roberts, K., & Walter, P. (2014). Molecular Biology of the Cell (6th ed.). Garland Science.
Lodish, H., Berk, A., Kaiser, C. A., Krieger, M., Bretscher, A., Ploegh, H., & Matsudaira, P. (2016). Molecular Cell Biology (8th ed.). W. H. Freeman.
Madigan, M. T., Bender, K. S., Buckley, D. H., Sattley, W. M., & Stahl, D. A. (2018). Brock Biology of Microorganisms (15th ed.). Pearson.
Smith, A., & Smith, H. (2020). Cell Biology: A Short Course (4th ed.). Wiley.
