Cell: Structure and Function - Cell Organelles (Mitochondria, Ribosomes, Golgi, ER, Lysosomes, Vacuoles)
Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Mitochondria: Known as the 'Powerhouse of the cell', it is a double-membrane bound organelle where aerobic respiration occurs to produce (Adenosine Triphosphate). The inner membrane forms folds called cristae to increase surface area.
Ribosomes: These are non-membrane bound granular structures composed of ribonucleic acid () and proteins. In eukaryotes, they are (subunits and ), while in prokaryotes and within mitochondria/chloroplasts, they are (subunits and ).
Endoplasmic Reticulum (ER): A network of tiny tubular structures. Rough ER () has ribosomes attached and is involved in protein synthesis. Smooth ER () lacks ribosomes and is the site for lipid synthesis and detoxification of drugs.
Golgi Apparatus: Consists of flattened, disc-shaped sacs or cisternae. It functions as the packaging and dispatching unit of the cell, modifying proteins and lipids (e.g., glycosylation to form glycoproteins and glycolipids).
Lysosomes: Membrane-bound vesicular structures formed by the Golgi apparatus. They contain hydrolytic enzymes (hydrolases like lipases, proteases, carbohydrases) active at acidic (approx. ). They are termed 'suicidal bags'.
Vacuoles: Membrane-bound space found in the cytoplasm. In plant cells, the vacuole is bound by a single membrane called the and can occupy up to of the cell volume, maintaining turgor pressure.
📐Formulae
💡Examples
Problem 1:
Calculate the total sedimentation coefficient of a eukaryotic cytoplasmic ribosome and name its subunits.
Solution:
The eukaryotic cytoplasmic ribosome is . Its subunits are (large) and (small).
Explanation:
The 'S' stands for Svedberg unit, a measure of sedimentation rate. Note that does not equal mathematically because 'S' values are based on surface area and density, not just additive mass.
Problem 2:
Explain how the is maintained within a lysosome for enzyme activation.
Solution:
The internal of lysosomes is maintained at approximately .
Explanation:
Lysosomes possess proton pumps in their membrane that actively transport ions from the cytosol into the lysosomal lumen using hydrolysis, ensuring the acidic environment necessary for hydrolytic enzyme activity.