What are the two fundamental types of cells, and what is a key distinction between them?
Prokaryotic cells and eukaryotic cells. Prokaryotic cells lack a true nucleus and other membrane-enclosed organelles, while eukaryotic cells possess a nucleus and other membrane-enclosed organelles.
Who first observed cell walls and living cells, and in what years?
Robert Hooke in 1665 (cell walls) and Antoni van Leeuwenhoek in 1674 (living cells).
Differentiate between magnification, resolution, and contrast in microscopy.
Magnification: Ratio of image size to real size.
Resolution: Clarity of the image, minimum distance two points can be separated.
Contrast: Difference in brightness between light and dark areas.
What are the main types of electron microscopes (EMs) and what are they used for?
Scanning Electron Microscope (SEM): Studies surface texture, producing a 3D image.
Transmission Electron Microscope (TEM): Studies internal structure of cells.
What is the primary function of cell fractionation and how does it relate to microscopy?
Separates cellular components by centrifuging disrupted cells, allowing analysis of specific cell components and correlating them with observed structures.
Describe the structure and function of the plasma membrane.
Composed of a double layer of phospholipids with embedded proteins. Functions include enclosing the cell and facilitating selective permeability.
Why are cells generally small?
Upper limits set by metabolic requirements and surface area-to-volume ratio; lower limits determined by minimum cellular components needed for life.
What are the key components of the nucleus in a eukaryotic cell?
Nuclear envelope, chromosomes, chromatin, nucleolus.
Describe the structure and function of ribosomes.
Complexes of rRNA and protein that carry out protein synthesis. They exist as free or bound ribosomes.
List the components of the endomembrane system and its general functions.
Nuclear envelope, endoplasmic reticulum, Golgi apparatus, lysosomes, vesicles/vacuoles, plasma membrane. Functions: protein synthesis, transport, lipid metabolism, detoxification.
Compare and contrast the functions of the smooth ER and rough ER.
Smooth ER: Lipid synthesis, detoxification, calcium storage.
Rough ER: Protein synthesis, particularly secretory and membrane proteins.
What is the function of the Golgi apparatus?
Modifies, stores, and ships products synthesized in the ER.
What are lysosomes and what roles do they play?
Membranous sacs of hydrolytic enzymes used for digestion of macromolecules, involved in phagocytosis and autophagy.
Describe the function of the central vacuole in plant cells.
Stores organic compounds, inorganic ions, helps cell growth, stores defensive compounds, contains pigments.
What is the endosymbiont theory and what evidence supports it?
Proposes mitochondria and chloroplasts originated as prokaryotic cells engulfed by eukaryotic cells. Evidence: double membranes, own ribosomes, circular DNA.
Describe the structure and primary function of mitochondria.
Sites of cellular respiration with a smooth outer membrane and inner membrane folded into cristae. Function: ATP production.
Describe the structure and primary function of chloroplasts.
Sites of photosynthesis, containing chlorophyll and thylakoids. Function: Convert light energy into chemical energy.
What is the cytoskeleton and what are its three main components?
A network of fibers for structural support, motility, and signal transmission. Components: microtubules, microfilaments, intermediate filaments.
What are cilia and flagella, and how do they move?
Motile appendages containing microtubules, moving via motor proteins called dyneins.
How do plant cell walls and the animal extracellular matrix (ECM) differ in composition and function?
Plant cell walls: Made of cellulose, protect and maintain shape. Animal ECM: Composed of glycoproteins, provides support and regulates activities.
Name and briefly describe three types of cell junctions found in animal cells.
Tight junctions: Prevent leakage.
Desmosomes: Fasten cells into sheets.
Gap junctions: Provide cytoplasmic channels for communication.
Why is a cell considered ‘greater than the sum of its parts’?
Cellular functions arise from coordinated activities of components, integrating to perform complex life functions.
What is the fluid mosaic model of cell membranes?
Describes the cell membrane as a mosaic of proteins embedded in a fluid bilayer of phospholipids.
How do unsaturated hydrocarbon tails and cholesterol influence membrane fluidity?
Unsaturated tails increase fluidity; cholesterol acts as a fluidity buffer, reducing fluidity at warm temperatures and hindering solidification at cold temperatures.
