cell : the unit of life Flashcards
What is the fundamental structural and functional unit of life?
The cell.
Who first saw and described a living cell?
Anton Von Leeuwenhoek.
What did Matthias Schleiden and Theodor Schwann contribute to cell theory?
Schleiden stated that all plants are composed of cells, and Schwann stated that animal cells have a plasma membrane and plant cells have a cell wall. Together, they formulated the initial cell theory.
What is the main structure responsible for cellular activities in both plant and animal cells?
The cytoplasm.
What are ribosomes and where are they found?
Ribosomes are non-membrane-bound organelles found in the cytoplasm, mitochondria, chloroplasts, and on the rough ER in both eukaryotic and prokaryotic cells.
What is the most accepted model for the structure of the cell membrane?
The fluid mosaic model given by Singer and Nicolson (1972).
How does passive transport differ from active transport?
Passive transport moves molecules across the membrane without energy, while active transport requires energy/ATP (e.g., Na+/K+ pump).
What is the main difference between prokaryotic and eukaryotic cells?
Prokaryotic cells lack membrane-bound nuclei, while eukaryotic cells have them.
What are mesosomes, and what is their role in prokaryotic cells?
Mesosomes are extensions of the plasma membrane that help in cell wall formation, DNA replication, distribution of daughter cells, and respiration.
What types of ribosomes are found in prokaryotes and eukaryotes?
Prokaryotes have 70S ribosomes (50S + 30S subunits), while eukaryotes have 80S ribosomes (60S + 40S subunits).
What is the cell envelope in prokaryotic cells?
It is a three-layered structure composed of the glycocalyx, cell wall, and plasma membrane, acting as a protective unit.
What is a plasmid, and why is it significant?
A plasmid is a small circular DNA molecule in bacteria that can confer unique traits like antibiotic resistance.
What is the composition of the cell membrane in human RBCs?
52% proteins and 40% lipids, primarily phospholipids.
What are inclusion bodies in prokaryotic cells?
They are stored reserves, e.g., phosphate granules and glycogen granules.
What are chromatophores, and where are they found?
Chromatophores contain pigments and are found in cyanobacteria.
What is the function of gas vacuoles?
Gas vacuoles help maintain buoyancy and are found in some photosynthetic bacteria.
What is the difference between Gram-positive and Gram-negative bacteria?
Gram-positive bacteria have a thicker peptidoglycan layer, while Gram-negative bacteria have a thinner one with an outer membrane.
What is the function of the cell wall in young plant cells?
It is capable of growth, made up of cellulose, hemicellulose, and pectin, and contains the middle lamella of calcium pectate.
What are thylakoids and grana?
Thylakoids are membrane sacs in chloroplasts that form grana stacks, essential for photosynthesis.
What pigments are present in chloroplasts?
Chlorophyll and carotenoid pigments.
What are the three types of plastids, and their functions?
Chloroplasts (photosynthesis), chromoplasts (pigments for color), and leucoplasts (storage of starch, oils, or proteins).
What did Robert Brown discover?
He first described the nucleus in 1831.
What is the nucleolus, and its function?
The nucleolus is a non-membrane-bound structure responsible for synthesizing rRNA.
What are centrioles, and what is their role?
Centrioles are cylindrical structures involved in the organization of microtubules and formation of the spindle during cell division.
What is the 9+2 arrangement?
The arrangement of microtubules in the axoneme of cilia and flagella, with nine doublets surrounding two singlets.
What is the cytoskeleton made of, and its function?
A network of filamentous protein structures providing mechanical support, motility, and cell shape maintenance.
What is the Svedberg unit (S), and how does it relate to ribosomes?
It measures the sedimentation rate; prokaryotic ribosomes are 70S, and eukaryotic ribosomes are 80S.
What is the role of the Golgi apparatus?
Modifies, packages, and transports proteins and lipids, and forms lysosomes and vesicles.
What is the structure of mitochondria?
A double membrane with an inner membrane forming cristae and a matrix containing enzymes, DNA, and 70S ribosomes.
What is the role of ribosomes in protein synthesis?
Ribosomes translate mRNA into proteins by facilitating the linkage of amino acids.
What are polysomes?
Polysomes are clusters of ribosomes attached to a single mRNA strand, translating it simultaneously.
What is the function of the plasma membrane?
It acts as a selectively permeable barrier, regulating the movement of substances in and out of the cell.
What is the cell wall’s main function in plant cells?
It provides structural support and protection to the cell.
What are the main components of the primary cell wall in plants?
Cellulose, hemicellulose, and pectin.
What is the difference between the primary and secondary cell walls?
The primary cell wall is capable of growth, while the secondary cell wall is thicker, more rigid, and forms after the cell matures.
What is the middle lamella’s function?
It acts as a cementing layer between adjacent plant cells.
What is the glycocalyx, and what is its significance?
The glycocalyx is an outer covering of prokaryotic cells that helps in protection and adherence to surfaces.
What are the two types of glycocalyx?
Slime layer (loose) and capsule (thick and tough).
What are mesosomes, and where are they found?
Mesosomes are infoldings of the plasma membrane found in prokaryotes that help in cellular processes.
What is the role of flagella in prokaryotic cells?
Flagella provide motility to prokaryotic cells.
What is the structural arrangement of prokaryotic flagella?
It consists of three parts: the filament, hook, and basal body.
What are pili and fimbriae, and what is their function?
Pili and fimbriae are hair-like structures on the surface of bacteria that help in attachment and conjugation but do not assist in motility.
What are chromatophores, and their role in cyanobacteria?
Chromatophores contain pigments necessary for photosynthesis.
What are inclusion bodies in prokaryotic cells?
Non-membrane-bound structures that store reserve materials like glycogen and phosphate granules.
What is the function of the prokaryotic cell envelope?
It acts as a protective unit consisting of the glycocalyx, cell wall, and plasma membrane.
What is the role of the nuclear envelope in eukaryotic cells?
It encloses the nucleus and separates it from the cytoplasm.
What are nuclear pores?
Openings in the nuclear envelope that allow the exchange of materials between the nucleus and the cytoplasm.
What is the nucleoplasm?
The semi-fluid substance inside the nucleus that contains chromatin and the nucleolus.
What is the function of chromatin?
Chromatin contains genetic material (DNA) and condenses to form chromosomes during cell division.
What is the nucleolus, and why is it important?
The nucleolus is a non-membrane-bound structure responsible for synthesizing rRNA and assembling ribosomes.
What is the centrosome, and what does it contain?
The centrosome is an organelle near the nucleus that contains centrioles and organizes microtubules for cell division.
What are centrioles, and how are they structured?
Centrioles are cylindrical structures made of microtubule triplets arranged in a 9+0 pattern.
What is the function of the cytoskeleton?
Provides structural support, helps in cell movement, and maintains cell shape.
What are the three main types of cytoskeletal elements?
Microtubules, microfilaments, and intermediate filaments.
What is the function of microtubules?
Microtubules help in cell shape, organelle movement, and cell division.
What are microfilaments made of, and what is their role?
Made of actin, they help in cell movement and muscle contraction.
What are intermediate filaments, and what is their function?
Intermediate filaments provide mechanical strength to cells.
What is the axoneme structure in cilia and flagella?
The axoneme has a 9+2 microtubule arrangement, with nine doublets surrounding two singlets.
What is the basal body?
A structure similar to a centriole that anchors cilia and flagella to the cell body.
What is the role of mitochondria in cells?
They are the sites of aerobic respiration and energy production in the form of ATP.
What is unique about mitochondrial DNA?
Mitochondria contain their own circular DNA, similar to prokaryotic DNA.
What is the matrix of mitochondria?
The inner compartment of mitochondria containing enzymes, DNA, and ribosomes.
What are cristae, and what is their function?
Cristae are folds in the inner mitochondrial membrane that increase surface area for ATP production.
What are plastids, and where are they found?
Plastids are double-membrane-bound organelles found in plant cells and euglenoids.
What are the three types of plastids?
Chloroplasts, chromoplasts, and leucoplasts.
What is the function of chloroplasts?
They contain chlorophyll for photosynthesis.
What are thylakoids, and where are they found?
Membranous sacs in chloroplasts that contain chlorophyll and are the sites of light-dependent reactions of photosynthesis.
What is stroma, and what does it contain?
The fluid matrix in chloroplasts containing enzymes for carbohydrate and protein synthesis, DNA, and ribosomes.
What are grana?
Stacks of thylakoids within chloroplasts.
What is a vacuole, and what is its function?
A membrane-bound space in the cytoplasm that stores water, ions, and waste products and helps maintain cell turgor pressure.
What is the tonoplast?
The membrane that surrounds the vacuole.
What are lysosomes, and what do they contain?
Lysosomes are vesicles containing hydrolytic enzymes that digest cellular waste and foreign particles.
What is the function of the Golgi apparatus?
Modifies, sorts, and packages proteins and lipids for storage or transport out of the cell.
What are cisternae in the Golgi apparatus?
Flattened, membrane-bound sacs that make up the Golgi apparatus.
What is the role of the rough ER?
Involved in protein synthesis and modification.
What is the role of the smooth ER?
Involved in lipid and steroid synthesis and detoxification processes.
What is the perinuclear space?
The space between the inner and outer membranes of the nuclear envelope.
What is the function of the nuclear matrix?
Provides structural support and organizes chromatin within the nucleus.
What are kinetochores?
Structures on chromosomes where spindle fibers attach during cell division.
What is osmosis?
Osmosis is the movement of water molecules through a selectively permeable membrane from a region of lower solute concentration to a higher solute concentration.
What is the fluid nature of the plasma membrane important for?
It allows for cell growth, formation of intercellular junctions, secretion, endocytosis, and cell division.
What are integral proteins in the cell membrane?
Proteins that are embedded within the lipid bilayer and play roles in transport and signaling.
What are peripheral proteins?
Proteins attached to the surface of the cell membrane, aiding in cell signaling and structural support.
What is active transport?
The movement of molecules across a cell membrane requiring energy/ATP, such as the Na+/K+ pump.
What are cell junctions?
Specialized structures that connect cells together and facilitate communication and adhesion.
What is the role of ribosomes in the cytoplasm?
Ribosomes synthesize proteins by translating mRNA.
What are polyribosomes?
Chains of ribosomes translating the same mRNA strand simultaneously for efficient protein synthesis.
What is the significance of ribosomal RNA (rRNA)?
rRNA is a key component of ribosomes and plays a crucial role in protein synthesis.
What are food vacuoles, and where are they found?
Vacuoles formed by engulfing food particles, typically found in protists.
What is the role of contractile vacuoles in protists?
Contractile vacuoles expel excess water to maintain osmotic balance.
What is the structure of the endoplasmic reticulum (ER)?
A network of membranous tubules and sacs that extends from the nuclear envelope.
What are chromatophores in cyanobacteria?
Structures containing pigments that aid in photosynthesis.
What is the structure of chloroplasts?
Double-membrane organelles with an inner system of thylakoids stacked as grana and a stroma containing enzymes, DNA, and ribosomes.
What is the composition of the primary cell wall in plants?
Cellulose, hemicellulose, and pectin.
What is the structure of the secondary cell wall?
A thicker, more rigid structure that provides additional support.
What is the structure of the secondary cell wall?
A thicker, more rigid structure that provides additional strength and is laid down after cell growth stops.
What are gas vacuoles?
Structures found in some bacteria that help maintain buoyancy.
What are reserve materials stored as in prokaryotic cells?
Inclusion bodies such as phosphate granules, cyanophycean granules, and glycogen granules.
What is the function of mesosomes in prokaryotes?
They help in cell wall formation, DNA replication, and distribution of daughter cells.
What is the role of the cytoskeleton in cell movement?
Microfilaments and microtubules facilitate cell motility and organelle transport.
What are the functions of intermediate filaments?
Providing mechanical strength and maintaining cell integrity.
What is the function of cilia in eukaryotic cells?
Cilia move fluid over cell surfaces or propel single-celled organisms through a fluid.
What is the difference between cilia and flagella?
Cilia are shorter and more numerous, while flagella are longer and fewer, used primarily for cell movement.
What are primary and secondary constrictions on chromosomes?
The primary constriction is the centromere, while secondary constrictions can appear as non-staining regions.
What are satellite chromosomes?
Chromosomes with secondary constrictions giving rise to a segment known as the satellite.
What is the basal body of cilia and flagella?
The structure at the base that anchors cilia and flagella to the cell.
What is the arrangement of microtubules in cilia and flagella?
A 9+2 arrangement of microtubules, with nine doublets surrounding two central singlets.
What is a centromere, and what is its function?
The region of a chromosome where spindle fibers attach during cell division.
What are kinetochores?
Protein complexes on either side of the centromere that bind spindle fibers during mitosis.
What is a plasmid, and its function in prokaryotic cells?
Small, circular DNA molecules that provide additional genetic traits like antibiotic resistance.
What is the structure of a chromosome?
Chromosomes consist of DNA wrapped around histone proteins forming chromatin, condensed during cell division.
What are nucleosomes?
Structural units of chromatin, consisting of DNA wrapped around histone proteins.
What is the function of the Golgi apparatus in protein modification?
It modifies proteins by adding carbohydrates (glycosylation) and packages them for transport.
What is a cis face in the Golgi apparatus?
The side of the Golgi apparatus facing the endoplasmic reticulum where vesicles enter.
What is the trans face of the Golgi apparatus?
The side where vesicles exit, moving toward the plasma membrane.
What are glycoproteins and glycolipids, and where are they formed?
Molecules formed in the Golgi apparatus by adding carbohydrates to proteins and lipids.
What are ribosomes composed of?
rRNA and proteins.
What are polysomes, and what is their significance?
Multiple ribosomes translating a single mRNA strand simultaneously, increasing the efficiency of protein synthesis.
What are the types of ribosomes found in mitochondria and chloroplasts?
70S ribosomes, similar to those found in prokaryotes.
What is the role of the perinuclear space?
It separates the inner and outer membranes of the nuclear envelope and facilitates molecular transport.
What are the components of chromatin?
DNA, histone proteins, non-histone proteins, and RNA.
What is the function of histone proteins?
To package and organize DNA into structural units called nucleosomes.
What is the main function of the nucleolus?
It synthesizes rRNA and assembles ribosomal subunits.
What is the matrix of mitochondria, and what does it contain?
The matrix is the inner compartment containing enzymes for the Krebs cycle, mitochondrial DNA, and ribosomes.
What is a centrosome, and what is its function?
A structure that organizes microtubules and regulates cell division by forming the mitotic spindle.
