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Questions and Answers
What is the primary function of sex pili in bacteria?
What characteristic is true of eukaryotic cells?
In what way do bacteria primarily reproduce?
What does the term 'proteome' refer to in a single organism?
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Which of the following statements is true regarding the shape and organization of cells?
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What is the primary function of the plasma membrane in prokaryotic cells?
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What is peptidoglycan primarily composed of in the prokaryotic cell wall?
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Which of the following statements about the glycocalyx is true?
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How are bacteria classified as gram-positive or gram-negative?
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Which type of bacteria typically lacks a cell wall?
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What is the primary function of the slime layers in bacteria?
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Which statement best describes plasmids in bacteria?
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What is the size of prokaryotic ribosomes compared to eukaryotic ribosomes?
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What defines the nucleoid region in prokaryotic cells?
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What role do inclusion bodies serve in prokaryotic cells?
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Which feature is NOT found in prokaryotic cells?
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Which appendage helps bacteria in locomotion?
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What is a main characteristic of naked DNA in prokaryotic cells?
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What determines a cell's structure and function?
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Which of the following factors can affect a cell's proteome?
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How does the proteome of healthy cells compare to that of cancerous cells?
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What is the primary area where many important metabolic activities take place in eukaryotic cells?
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What are the long, tube-like structures made from alpha and beta tubulin proteins called?
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Which process describes the breakdown of molecules into smaller parts?
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What significant role do microtubules play in a cell?
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What is the structural characteristic of microtubules?
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What function do intermediate filaments primarily serve in cells?
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Which of the following best describes the composition of actin filaments?
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During which phase of cell division do microtubules play a critical role?
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What role do microfilaments play related to the plasma membrane?
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What function do microtubules serve in relation to organelles?
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Study Notes
Prokaryotic Cell Envelope
- Plasma Membrane: Composed of a phospholipid bilayer similar to eukaryotic cells, it regulates what enters and exits the cell.
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Cell Wall: Outer layer made of peptidoglycan—a mix of sugars & peptides, vital for maintaining cell shape (round, rod-shaped, or spiral).
- Some bacteria like mycoplasma lack cell walls, giving them an irregular shape.
- Gram-positive and gram-negative bacteria are classified based on their cell wall structure.
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Glycocalyx: Sticky sugar layer outside the cell wall, providing protection from drying out and the immune system, helping bacteria stick to surfaces.
- Capsule: Tightly attached glycocalyx, common in harmful bacteria as it blocks white blood cells from attacking.
- Slime Layer: Loosely attached glycocalyx, helping bacteria avoid drying out (desiccation).
Prokaryotic Cell Structure
- Nucleoid: Region where DNA floats freely in the cytoplasm, not enclosed by a membrane.
- Chromosome: Single, circular chromosome.
- DNA: Lacking histone proteins, often called “naked DNA.”
Prokaryotic Plasmid
- Plasmids: Smaller circular DNA pieces found in some bacteria.
- Resistance Genes: They carry genes that can be passed to other organisms, conferring resistance to antibiotics.
- Non-essential Genes: Plasmids carry genes not critical for basic survival, but can provide additional advantages.
- Replication: Can replicate independently of the main chromosome.
Prokaryotic Ribosomes
- Size: Smaller than ribosomes in eukaryotic cells (70S ribosomes).
- Structure: Composed of two subunits: 30S and 50S.
- Function: Protein synthesis.
Prokaryotic Cytoplasm
- Semi-Fluid: Contains enzymes for metabolism, the single chromosome within the nucleoid, ribosomes, and inclusion bodies.
- Inclusion Bodies: Storage areas for nutrients, allowing bacteria to utilize them when needed.
Prokaryotic Appendages
- Flagella: Long, tail-like structures for movement, rotating like a motor powered by the plasma membrane.
- Fimbriae: Small, hair-like fibers on the cell surface, used for attachment to surfaces, not movement.
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Sex Pili: Tube-like structures facilitating the transfer of DNA from one bacterium to another.
- This allows for genetic exchange even though bacteria reproduce through binary fission.
Eukaryotic Cells
- DNA: Stored within the nucleus, a membrane-bound organelle.
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Organelles: Specialized compartments with specific functions.
- Animal Cells
- Plant Cells
- Diversity: Shape, size, and organization vary greatly between species and even within different cell types of the same organism.
Proteome: Defining Cell Characteristics
- Shared DNA: All cells within the same organism share the same DNA.
- Unique Proteome: Each cell type produces a unique set of proteins called the proteome.
- Proteome Determination: The proteome defines a cell's structure and function.
- Factors Influencing Proteome: Several factors influence the proteome, including gene regulation, the amount of protein produced, amino acid sequence, and protein modifications.
- Proteome Differences: Healthy and cancerous cells possess distinct proteomes.
Cytosol
- Location: Area between the plasma membrane and organelles, including the cytosol, endomembrane system, and semi-autonomous organelles.
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Metabolite Hub: The site of many important metabolic activities in eukaryotic cells, including
- Catabolism: Breaking down molecules into smaller parts.
- Anabolism: Building up larger molecules and cell components.
Cytoskeleton
- Cellular Support System: Provides internal support, maintains cell shape, strengthens, facilitates movement, and anchors organelles.
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Microtubules: Long, tube-like structures composed of alpha and beta tubulin proteins, forming sheets that fold into cylinders.
- They exhibit dynamic instability, growing & shrinking.
- Functions: Moving organelles, supporting cilia & flagella, assisting in cell division, forming the cell wall in plants.
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Intermediate Filaments: More stable than microtubules and actin filaments, helping to maintain cell shape and rigidity by handling tension.
- Found in cytoplasm, nucleus, and outside the cell to bind cells together.
- Composition: Made of proteins like keratin.
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Actin Filaments (Microfilaments): Two intertwined strands of actin protein, supporting the plasma membrane, providing cell strength and shape.
- They play a role in processes including phagocytosis and provide tensile strength.
- Functions: Maintaining cell shape, cytoplasmic streaming, aiding in chromosome separation during cell division (especially during anaphase), assisting with cytokinesis (especially in animal cells), contributing to the formation of stable tissues.
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Description
Explore the key features of prokaryotic cells, focusing on the plasma membrane, cell wall, and glycocalyx. Understand the differences in structure among various bacteria and how these characteristics contribute to their survival. This quiz will help reinforce your knowledge of prokaryotic cell components.
