Cell Boundaries & Support
Which structure encloses the cell and controls the passage of materials in and out?
The cell membrane (composed of a phospholipid bilayer with embedded proteins) regulates selective permeability.
What organelle houses most of the cell’s DNA?
The nucleus, double-membrane envelope that separates contents from cytoplasm.
Which ER type has ribosomes attached and appears rough?
Rough ER (synthesizes secretory and membrane proteins).
What organelle contains hydrolytic enzymes for digestion?
Lysosome - works best in acidic pH to digest macromolecules.
What is the main function of mitochondria?
Cellular respiration - converts energy from sugars/fats into ATP.
What is the main structural difference between the cell wall and the cell membrane?
The cell wall is rigid, made of cellulose (plant cells) and provides protection and shape. The cell membrane is flexible and regulates material exchange.
What is the difference between chromatin and chromosomes?
Chromatin: loosely packed DNA + proteins (non-dividing cell). Chromosomes: condensed DNA (dividing cell) for efficient segregation.
List at least two main functions of the smooth ER.
Lipid synthesis, detoxification of drugs/poisons, calcium storage, metabolism of carbohydrates.
Describe the process of autophagy.
Damaged organelle or cytosol is surrounded by a double membrane → fuses with lysosome → enzymes digest material → monomers returned to cytosol.
What structure in mitochondria increases surface area for ATP production?
Cristae - folds of inner membrane house enzymes for respiration.
What is cytoplasm and what is its function?
The cytoplasm is the aqueous environment (cytosol) inside the cell that surrounds organelles. It supports organelles and is a site of chemical reactions.
Describe the nucleolus and its function.
Dense structure inside nucleus, synthesizes ribosomal RNA and assembles ribosomal subunits.
How does the Golgi apparatus modify ER products?
Glycoproteins have sugars modified (some removed, some added). Phospholipids may also be altered, sorts and packages proteins into vesicles.
What is the main function of the plant cell central vacuole?
Stores ions, pigments, toxins, absorbs water to enlarge cell, maintains turgor pressure.
List the three main compartments of a chloroplast.
Intermembrane space, stroma, thylakoid space (grana in stacks).
Describe the cytoskeleton’s components and their specific roles.
Microfilaments: support shape, cell movement. Intermediate filaments: maintain structural integrity. Microtubules: guide organelle movement and cell division.
Compare free and bound ribosomes in terms of structure, location, and function.
Free ribosomes: float in cytosol, make proteins for cytosol. Bound ribosomes: attached to rough ER/nuclear envelope, make secretory or membrane proteins. Structurally identical.
Explain the cisternal maturation model of the Golgi.
Cisternae themselves move from cis to trans, carrying cargo and modifying it along the way. Enzymes may recycle backward to less mature cisternae.
Compare lysosomes, vacuoles, and vesicles in terms of structure and function.
Lysosome: digestive, hydrolytic enzymes. Vacuole: storage, enzymatic hydrolysis (plants/fungi). Vesicle: transport between organelles and membrane.
Explain how chloroplast structure supports photosynthesis.
Thylakoids → light reactions, stroma → Calvin cycle, double membrane separates chloroplast from cytosol, compartmentalization optimizes energy conversion.
Explain how the cell membrane and cytoskeleton work together to maintain the cell’s structure while allowing flexibility.
The cell membrane provides a flexible boundary, while the cytoskeleton reinforces shape and anchors organelles. Together, they enable movement, intracellular transport, and maintain strength under stress.
Explain how nuclear pores, nuclear envelope, and ribosomes coordinate protein synthesis.
Nuclear pores allow messenger RNA to exit the nucleus. Ribosomes translate mRNA in cytosol (free) or ER (bound). The nuclear envelope separates genetic material while providing continuity with rough ER for protein synthesis.
Describe how rough ER, smooth ER, and Golgi work together to produce and ship a secretory protein.
Ribosomes on rough ER synthesize protein → protein enters ER lumen, folds, may be glycosylated → vesicles carry protein to Golgi → Golgi modifies, sorts, packages → vesicle targets plasma membrane for secretion.
Explain how vacuoles, vesicles, and lysosomes coordinate to maintain cellular homeostasis.
Vesicles transport materials → lysosomes digest macromolecules or recycle organelles → vacuoles store ions, toxins, or pigments → combined action maintains nutrient balance, growth, and protection.
Compare and contrast mitochondria and chloroplasts in terms of structure, function, and evolutionary origin.
Both have double membranes, own DNA + ribosomes, grow/reproduce independently. Mitochondria: cellular respiration. Chloroplasts: photosynthesis. Both likely evolved via endosymbiosis from prokaryotes.