Lecture 8: Cell Organelles and Cytoskeleton

Vocabulary flashcards covering eukaryotic cell organelles, endomembrane system, energy transformations, endosymbiosis, cytoskeletal filaments, and cell membrane properties based on Lecture 8.

Vesicles

Membrane-bound sacs separated from the cytosol that serve as basic cellular tools to store and transport substances.

Central Vacuole

A major plant cell organelle responsible for regulating the cell's water concentration under changing environmental conditions.

Lysosomes

Organelles existing only in animal cells that contain digestive enzymes to break down macromolecules, recycle broken down organelles, and act as the cell's clean up crew.

Peroxisomes

Digestive enzyme sacs in plant and animal cells that detoxify poisons such as alcohol, convert fatty acids to sugars, and produce hydrogen peroxide ($\text{H}_2\text{O}_2$) that is broken down into water ($\text{H}_2\text{O}$) and oxygen.

Rough Endoplasmic Reticulum

Region of the endoplasmic reticulum continuous with the nuclear envelope that is studded with ribosomes and functions in protein synthesis.

Smooth Endoplasmic Reticulum

Region of the endoplasmic reticulum that lacks ribosomes and functions in lipid synthesis.

Golgi Apparatus

Organelle that receives proteins at its cis end, modifies and packages them, and pinches off vesicles from its trans end for secretion or membrane insertion.

Mitochondria

Double-membrane energy organelles containing their own DNA and ribosomes that generate ATP through cellular respiration and catabolism of fuels in the presence of oxygen.

Cristae

The folded structures of the inner mitochondrial membrane that increase total surface area for chemical reactions during energy generation.

Matrix

The interior fluid compartment enclosed by the inner membrane of a mitochondrion.

Chloroplasts

Double-membrane energy-transforming organelles in plants and algae containing chlorophyll that perform photosynthesis to synthesize glucose.

Chlorophyll

A green pigment contained within chloroplasts essential for capturing light energy during photosynthesis.

Photosynthesis

The metabolic process in plant cells that converts light energy, carbon dioxide ($\text{CO}_2$), and water into glucose and oxygen ($\text{O}_2$).

Endosymbiotic Theory

The theory proposing that eukaryotic organelles like mitochondria and chloroplasts originated when host cells ingested independent prokaryotic microbes that persisted in a symbiotic relationship.

Heterotroph

An organism that obtains energy and nutrients by consuming other organisms such as plants or animals.

Cytoskeleton

A network of protein fibers that maintains cell shape, anchors organelles, enables cytoplasmic and vesicle transport, and allows cellular movement.

Microfilaments

Cytoskeletal protein filaments composed of actin ($7\text{--}9\text{ nm}$ diameter) that provide cell rigidity, facilitate shape changes, and interact with myosin for cell motility.

G-actin and F-actin

Globular actin monomers (G-actin) that undergo polymerization to assemble into filamentous actin strands (F-actin).

Intermediate Filaments

Cytoskeletal fibers approximately $10\text{ nm}$ in diameter (such as keratin and vimentin) that bear tension, anchor the nucleus and organelles, and form desmosomes.

Microtubules

Hollow cytoskeletal tubes approximately $25\text{ nm}$ in diameter made of polymerized $\alpha\text{-tubulin}$ and $\beta\text{-tubulin}$ dimers that resist compression, direct vesicle transport, and separate chromosomes during cell division.

$$\gamma\text{-tubulin}$$

A specific tubulin protein localized to the centrosome that initiates microtubule assembly.

Motor Proteins

ATP-powered transport molecules such as myosin and dynein that move along cytoskeletal tracks to carry organelles and vesicles to targeted destinations.

Amphipathic

Describing molecules (such as phospholipids) that possess both a hydrophilic (polar, water-loving) region and a hydrophobic (non-polar, water-fearing) region.

Nucleolus

An organelle inside the nucleus responsible for producing ribosomes from ribosomal RNA (rRNA) and protein.

Catabolism

The chemical breakdown of larger molecules into smaller ones to liberate energy.