Chapter 6: A Tour of the Cell — Endomembrane System, Energy Transformation, Cytoskeleton, ECM, and Cell Connections (Flashcards)

A set of practice flashcards covering the endomembrane system, mitochondria and chloroplasts, peroxisomes, cytoskeleton, extracellular matrix, and cell junctions, with question-and-answer format to review key concepts from the lecture notes.

Describe the structural and functional differences between rough and smooth endoplasmic reticulum (ER).

Rough ER has bound ribosomes and synthesizes secretory and other proteins; smooth ER lacks ribosomes and is involved in lipid synthesis, carbohydrate metabolism, Ca2+ storage, and detoxification.

How do transport vesicles integrate the endomembrane system?

Vesicles bud from one membrane, carry cargo, and fuse with a target membrane to transfer proteins and lipids, thus linking components of the endomembrane system.

What is the path of a protein that functions in the ER but requires Golgi modification before functioning, starting from the mRNA that specifies the protein?

mRNA is translated by ribosomes; the nascent protein with a signal targets the rough ER; the protein enters the ER lumen, is packaged into vesicles to the Golgi, modified there, and sorted into vesicles for final destination (often secretion or plasma membrane).

What is the endosymbiont theory in brief?

An early eukaryotic cell engulfed oxygen-using prokaryotes (mitochondria) and later a photosynthetic prokaryote (chloroplast), which became integrated as organelles.

List three lines of evidence supporting the endosymbiont theory for mitochondria and chloroplasts.

Double membranes; ribosomes and circular DNA inside; autonomous growth/reproduction within the cell.

Which organelles are the primary energy transformers in eukaryotic cells, and what do they do?

Mitochondria generate ATP through cellular respiration; chloroplasts convert light energy into chemical energy via photosynthesis to produce sugars.

Name the two internal compartments of a mitochondrion and what each contains.

Intermembrane space (between outer and inner membranes) and the mitochondrial matrix (contains enzymes, mitochondrial DNA, and ribosomes).

What is the function of the inner mitochondrial membrane's cristae?

Cristae increase surface area, enhancing the capacity for enzymes involved in cellular respiration and ATP production.

What are the three main compartments of a chloroplast and their key features?

Intermembrane space between outer and inner membranes; stroma containing chloroplast DNA and ribosomes; thylakoids (stacked into grana) where light reactions occur.

What pigment is characteristic of chloroplasts and what is its role?

Chlorophyll; it captures light energy to drive photosynthesis.

What are plastids, and name two other types besides chloroplasts with their roles.

Plastids are related organelles; amyloplasts store starch; chromoplasts store pigments in fruits and flowers.

What is a peroxisome and what reaction does it commonly perform?

A single-membrane compartment that removes hydrogen atoms to oxygen, producing hydrogen peroxide (H2O2), which is then detoxified to water.

What is a glyoxysome and where are they found?

A specialized peroxisome in fat-storing tissues of plant seeds that initiates conversion of fatty acids to sugar during germination.

What is the debate about the evolutionary origin of peroxisomes?

Whether peroxisomes originated via endosymbiosis; they may grow by incorporating proteins/lipids from the cytosol and ER and can divide, but this origin is still debated.

What are the three main cytoskeletal components and their primary roles?

Microtubules (shape, organelle transport, chromosome separation); Microfilaments/actin (tension-bearing, movement, muscle contraction, pseudopodia, microvilli); Intermediate filaments (tension-bearing, structural support, nuclear lamina).

From what building block are microtubules made and what is the meaning of the plus end?

Microtubules are built from tubulin dimers (α-tubulin and β-tubulin); the plus end is the end with higher rates of tubulin addition and loss.

Describe centrosomes and centrioles in animal cells and their role in organizing microtubules.

Centrosome is the microtubule-organizing center near the nucleus; contains a pair of centrioles (nine triplets); centrioles replicate before cell division; other eukaryotes may organize microtubules without centrioles.

How do cilia and flagella differ in their beating patterns and structure?

Flagella undulate in a snakelike motion to move the cell; cilia beat with a power stroke and recovery stroke to move the cell or surrounding fluid; both share a 9+2 microtubule arrangement in motile forms.

Describe the 9+2 arrangement found in motile cilia and flagella and the alternative 9+0 arrangement in nonmotile cilia.

Motile cilia/flagella have nine outer doublets around two central single microtubules (9+2); nonmotile primary cilia have 9+0 (no central pair).

What motor protein powers dynein-based bending in flagella and cilia, and how does it operate?

Dynein; ATP-driven motor that 'walks' along adjacent microtubules, causing sliding that is converted to bending due to cross-linking proteins.

What is the role of microfilaments in muscle contraction and cell movement?

Actin filaments interact with myosin to slide past each other, shortening muscle cells; also drive amoeboid movement and cytoplasmic streaming.

What are microvilli and which cytoskeletal component reinforces them?

Microscopic projections that increase surface area for absorption; reinforced by bundles of actin filaments (microfilaments) in the cortex.

What is the nuclear lamina and what cytoskeletal component forms it?

A network of intermediate filaments lining the interior of the nuclear envelope, providing structural support and anchoring the nucleus.

What is the extracellular matrix (ECM) and what are its main components and connections to the cytoskeleton?

A network of glycoproteins and proteoglycans secreted by cells; major components include collagen (fibers) and proteoglycans; fibronectin links ECM to integrins in the plasma membrane, which connect to microfilaments to transmit signals and organize the cytoskeleton.

What are proteoglycans and their role in the ECM?

Core proteins with many carbohydrate chains (glycosaminoglycans) that form a hydrated, gel-like matrix that interacts with collagen and other ECM components.

What are plasmodesmata and what function do they serve in plants?

Plasmodesmata are cytoplasmic channels through plant cell walls that connect adjacent cells, allowing transport of water, small solutes, and sometimes proteins and RNA.

Name the three main types of cell junctions in animals and their functions.

Tight junctions prevent leakage between cells; desmosomes anchor cells together via intermediate filaments; gap junctions create cytoplasmic channels for small molecules to pass between cells.

Compare the plant cell wall and the animal extracellular matrix in terms of composition and function.

Plant cell walls are cellulose microfibrils embedded in a matrix of polysaccharides and proteins, providing structural support and controlling growth; animal ECM is a network of glycoproteins and proteoglycans (eg, collagen, fibronectin) that supports, adheres, and signals between cells and links to the cytoskeleton via integrins.