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Questions and Answers
What is the genetic material that makes up the genes of the chromosomes?
Which category of cells includes bacteria and archaea?
What is the 'command center' of a cell called?
Where are genes located within a eukaryotic cell?
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What makes up an organism's complete collection of genes?
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What is the main difference between flagella and cilia based on the text?
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How do cilia aid in movement according to the text?
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Where can cilia be found based on the information provided?
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What is a distinguishing feature of prokaryotic cells compared to eukaryotic cells?
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Which external structures surround the cytoplasm of prokaryotic cells?
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What is the main function of the bacterial cell wall?
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What is a common characteristic of prokaryotic ribosomes compared to eukaryotic ribosomes?
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What is the primary component of most bacterial cell walls?
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Where are many enzymes attached in a prokaryotic cell?
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What differentiates Gram-positive bacteria from Gram-negative bacteria in terms of their cell walls?
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What are plasmids in a prokaryotic cell?
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What is the main function of the cell membrane?
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Which type of cells lack a true nucleus and other membrane-bound organelles?
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Where do most metabolic reactions occur within a cell?
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Which organelle is known as the 'powerhouse' of the cell?
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What is the main function of plastids within a cell?
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Which organelle completes the transformation of newly synthesized proteins and packages them for storage or export?
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Which structure provides shape, protection, and rigidity to some eukaryotic cells?
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What is the main function of lysosomes within eukaryotic cells?
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Which type of fibers are essential for strengthening, supporting, and stiffening the cell, giving it its shape?
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What is the primary function of flagella in eukaryotic cells?
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What is the purpose of the Widal test?
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Who are Ziehl and Neelsen, after whom the acid-fast stain method is named?
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What is the purpose of the Venereal Disease Research Laboratory (VDRL) Test?
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How is a fixed smear prepared for staining according to the text?
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What is the differential staining method named after two German doctors?
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Which test is used to identify the causative agents of infections?
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Study Notes
Cell Structure
- Cell: the fundamental unit of any living organism
- Metabolism: all of the chemical reactions that occur within a cell
- DNA (Deoxyribonucleic acid): genetic material that makes up the genes of the chromosomes
Cell Categories
- Eukaryotic cells: contain a true nucleus and a complex system of membrane-bound organelles (algae, protozoa, fungi, plants, animals, humans)
- Prokaryotic cells: lack a true nucleus and other membrane-bound organelles (bacteria and archaea)
Eukaryotic Cell Structure
- Nucleus:
- The “command center” of the cell
- Composed of nucleoplasm, chromosomes, and a nuclear membrane
- Cell membrane:
- Encloses the cell
- Composed of large molecules of proteins and phospholipids
- Regulates the passage of nutrients, waste products, and secretions into and out of the cell
- Has selective permeability
- Cytoplasm:
- A semifluid, gelatinous, nutrient matrix
- Contains storage granules and a variety of organelles
- Where most metabolic reactions occur
- Endoplasmic reticulum (ER):
- A highly convoluted system of membranes arranged to form a transport network in the cytoplasm
- Rough ER has ribosomes attached to it, whereas smooth ER does not
- Rough ER – involved in secretion and membrane protein synthesis; site of glycosylation of proteins
- Smooth ER – synthesizes lipids, phospholipids, and steroids
- Ribosomes:
- Consist of ribosomal RNA and protein
- Sites of protein synthesis
- Golgi complex:
- Connects or communicates with ER
- Completes the transformation of newly synthesized proteins and packages them for storage or export
- A stack of flattened, membranous sacs
- Lysosomes and peroxisomes:
- Originate in the Golgi complex
- Lysosomes contain lysozyme and other digestive enzymes
- Found in ALL eukaryotic cells
- Break down worn-out parts of the cell or the whole cell
- Peroxisomes are membrane-bound vesicles where H2O2 is generated and broken down
- Found in MOST eukaryotic cells
- Break down long chain fatty acids so they can be utilized by the mitochondria
- Mitochondria:
- The “powerhouses” of the cell
- ATP molecules are produced within mitochondria by cellular respiration
- Energy is released from glucose and other nutrients
- Number of mitochondria varies depending on the activities of the cell
- Plastids:
- Membrane-bound structures containing photosynthetic pigments
- Sites of photosynthesis
- Light energy → chemical energy
- Chloroplasts are a type of plastid; they contain chlorophyll
- Cytoskeleton:
- A system of fibers throughout the cytoplasm
- Three types of fibers: microtubules, microfilaments, and intermediate filaments
- Microtubules and microfilaments are essential for a variety of activities
- Strengthen, support, and stiffen the cell; gives the cells its shape; cell division, contraction, and motility
- Cell wall:
- Some eukaryotic cells contain cell walls – an external structure to provide shape, protection, and rigidity
- Simpler in structure than prokaryotic cell walls
- Chitin found in cell walls of fungi; cellulose in cell walls of algae and plants
- Flagella and cilia:
- Some eukaryotic cells (e.g., spermatozoa and certain protozoa) possess long, thin, whiplike organelles of locomotion called flagella
- Flagellated cells may possess one or more flagella
- Some cells move by means of cilia, which are shorter, thinner, and more numerous than flagella, and described as being “hair-like”
- Movement occurs by cilia beating with a coordinated, rhythmic movement
- Cilia can be found on some species of protozoa and certain types of cells in our bodies (e.g., ciliated epithelial cells in the respiratory tract)
Prokaryotic Cells
- About 10 times smaller than eukaryotic cells
- Simple compared to eukaryotic cells
- Reproduce by binary fission
- Bacteria and archaea
- The cytoplasm is not filled with internal membranes
- The cytoplasm of prokaryotic cells is surrounded by a cell membrane, a cell wall (usually), and sometimes a capsule or slime layer
- LACK membrane-bound organelles
- Cell membrane:
- Similar in structure and function to the eukaryotic cell membrane
- Selectively permeable
- Flexible and thin, cannot be seen with a compound microscope
- Many enzymes are attached to the cell membrane where metabolic reactions take place
- Chromosome:
- Prokaryotic chromosome usually consists of a single, long, supercoiled, circular DNA molecule and serves as the control center of the cell
- Suspended in the cytoplasm
- Plasmids are small, circular molecules of DNA that are not part of the chromosome (extra-chromosomal)
- Capable of self-replication
- Can give the cell an advantage
- Cytoplasm:
- A semifluid that consists of water, enzymes, waste products, nutrients, proteins, carbohydrates, and lipids – materials required for metabolic functions
- Cytoplasmic particles:
- Most are ribosomes, some of which occur in clusters
- Prokaryotic ribosomes are smaller than eukaryotic ribosomes
- Granules present in some bacteria
- Consist of starch, lipids, sulfur, iron, or other stored substances
- Bacterial cell wall:
- A rigid exterior that defines the shape of bacterial cells and gives protection
- Chemically complex
- Not present in all bacteria
- Main constituent of most bacterial cell walls is peptidoglycan (found only in bacteria)
- Gram-positive bacteria have a thick layer of peptidoglycan; Gram-negative bacteria have a much thinner layer
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Description
Explore the movement mechanisms of flagellated and ciliated cells, including their structures and functions. Learn how flagella and cilia contribute to cellular locomotion and transportation in various organisms and tissues.
