Chapter 4 Evolutionary origin of cells and their general features

Origin of living cells on Earth

The process hypothesized to consist of 4 overlapping stages leading to the first living cells.

The 4 overlapping stages of cell origin

1. Organic molecules formed; 2. Formation of polymers; 3. Enclosure of polymers in membranes; 4. Properties of living cells acquired.

Reducing atmosphere hypothesis

A theory proposing that organic molecules formed through redox reactions in the early Earth's atmosphere.

Miller-Urey experiment

A landmark experiment that demonstrated organic molecules can form from simple precursors under early Earth conditions.

Extraterrestrial hypothesis

The theory suggesting that organic molecules were delivered to Earth by meteorites.

Deep-sea vent hypothesis

A hypothesis proposing that organic molecules originated at deep-sea vents mixing superheated water with cold seawater.

Protobiont

An aggregate of prebiotically produced molecules contained within a boundary, considered a precursor to living cells.

RNA world

A hypothetical stage of early life where RNA was the primary molecule for both information storage and catalysis.

Cytosol

The fluid portion of the cytoplasm where various metabolic processes occur, excluding organelles.

Cytoskeleton

A network of protein filaments in the cytosol that provides structural support, shape, and movement to the cell.

Microtubules

Hollow cylinders made of tubulin that are part of the cytoskeleton, important for maintaining cell shape and organization.

Cilia and flagella

Cell appendages that allow for cell movement; cilia are shorter, while flagella are longer.

Endoplasmic reticulum (ER)

A network of membranes involved in the sorting, synthesis, and modification of proteins.

Golgi apparatus

A stack of membranes that processes, sorts, and directs the secretion of cellular molecules.

Lysosomes

Organelles that degrade macromolecules using acid hydrolases, functioning best at an acidic pH.

Mitochondria

Semiautonomous organelles that produce ATP by converting chemical energy stored in nutrients.

Chloroplasts

Organelles in plants that carry out photosynthesis, converting light energy into chemical energy.

Endosymbiosis theory

The theory that mitochondria and chloroplasts originated from ancient symbiotic relationships with bacteria.

Extracellular matrix (ECM)

A network of proteins and polysaccharides outside the cell membrane that provides structural support and regulates cell behavior.

Plant cell wall

A rigid structure that surrounds plant cells, providing strength and resistance to compression.

Protein sorting

The process by which proteins are directed to their appropriate cellular location based on sorting signals.

Systems Biology

The study of a eukaryotic cell as a system of interacting components: nucleus, cytosol, endomembrane system, and semiautonomous organelles.

Cell membrane

A phospholipid bilayer that surrounds the cell, providing protection and regulating the movement of substances in and out.

Chromatin

The material of which the chromosomes of organisms are composed, consisting of protein, RNA, and DNA.

Nucleus

The membrane-bound organelle that contains the cell's genetic material and controls its growth and reproduction.

Ribosomes

The molecular machines responsible for protein synthesis, found in both prokaryotic and eukaryotic cells.

Vesicles

Small membrane-bound sacs that transport materials within the cell.

Peroxisomes

Organelles that detoxify harmful substances and metabolize fatty acids.

Centrioles

Cylindrical structures involved in cell division and organization of microtubules.

Plasma membrane

Another term for the cell membrane, highlighting its role in maintaining the integrity and functionality of the cell.

Hydrophobic interaction

The tendency of nonpolar substances to aggregate in aqueous solutions to minimize their exposure to water.

Apoptosis

Programmed cell death that occurs in multicellular organisms, which is essential for development and homeostasis.