Cell Biology: Organelles and Functions

Comprehensive vocabulary flashcards covering eukaryotic cell organelles, their functions, and fundamental biological processes like transcription, translation, and endosymbiosis based on lecture notes.

Cell

The fundamental unit of life, existing as an independent living unit capable of metabolism and reproduction.

Nucleus (Cellkärna)

A membrane-enclosed compartment occupying about $10\%$ of cell volume; it contains genetic information in the form of DNA and is the site for gene regulation and RNA synthesis.

Nucleolus (Nukleol)

The specific region within the cell nucleus where ribosome complexes are assembled.

Rough Endoplasmic Reticulum (Kornigt ER)

A region of the ER covered in ribosomes, responsible for the synthesis and modification of proteins intended for the Golgi apparatus, plasma membrane, or secretion.

Smooth Endoplasmic Reticulum (Slätt ER)

A region of the ER lacking ribosomes; functions include lipid synthesis, storage of calcium ions ($Ca^{2+}$), and detoxification of organic molecules in the liver.

Golgi Apparatus

A system of membrane-enclosed cavities that modifies, sorts, and packages proteins and lipids into vesicles for transport to the cell membrane, lysosomes, or secretion.

Mitochondria

The cell's 'power plant' responsible for $ATP$ synthesis via oxidative phosphorylation; it contains its own circular DNA and originates from bacteria.

Lysosome

The 'stomach of the cell' containing approximately $50$ different enzymes in a sour environment at $pH\,5$; it is responsible for intracellular degradation and recycling.

Peroxisome

An organelle mainly found in the liver and kidneys that breaks down long fatty acids, amino acids, and alcohol, producing hydrogen peroxide ($H_2O_2$) as a byproduct.

Ribosomes

Membrane-free 'organelles' consisting of protein and RNA complexes that synthesize proteins from free amino acids using mRNA as a template.

Cytoskeleton

A network of actin filaments, intermediate filaments, and microtubules that maintains cell shape, holds organelles in place, and facilitates movement and cell division.

Actin Filaments

Cytoskeletal components involved in muscle contraction, cell movement, and maintaining structural support.

Microtubules

Filaments that originate from the centrosome and are essential for intracellular transport and the correct separation of chromosomes during cell division.

Intermediate Filaments

Components of the cytoskeleton that provide structural support to the cell.

Cell Membrane

A double layer of phospholipids and proteins that defines the cell boundary and regulates transport, signaling, and cell communication.

Cytosol

The viscous fluid (more gel-like than liquid) in the cell that excludes membrane-bound organelles.

Cytoplasma

The total contents of the cell, consisting of both the cytosol and the organelles.

Centrosome

An organelle with centrioles that organizes and acts as the starting point for the formation of microtubule filaments.

LUCA

The hypothetical 'Last Universal Common Ancestor' from which all cells (Bacteria, Archaea, and Eukaryotes) are descended.

Endosymbiotic Theory (Endosymbiontteorin)

The theory that chloroplasts and mitochondria originate from bacteria that entered into a symbiotic relationship with early eukaryotic cells.

Chromatin

DNA organized into a complex with proteins called histones.

Heterochromatin

Tightly packed chromatin that is generally not genetically active.

Euchromatin

Loosely packed chromatin that is genetically active.

Transcription

The process occurring in the cell nucleus where RNA-polymerase synthesizes RNA from a DNA template at a rate of approximately $50$ nucleotides per second.

Translation

The process where ribosomes synthesize proteins in the cytosol using mRNA as the information medium.

Replication

The process by which DNA is copied in the nucleus during cell division.

Endocytosis

The process of taking up substances from the outside by the cell membrane budding inward to form vesicles.

Exocytosis

The process of transporting substances out of the cell via vesicles that fuse with the plasma membrane.

Autophagy

The process of breaking down internal cellular particles or damaged organelles within the lysosome.

Vesicles

Small membrane-bound 'bags' used to transport substances or proteins between organelles and the cell membrane via the cytoskeleton.