Chapter 4: Eukaryotic Cells and Microorganisms

These vocabulary flashcards identify the key biological structures, evolutionary history, and characteristic microorganisms discussed in the Chapter 4 lecture notes.

Last Common Ancestor (LCA)

A precursor organism existing between $3\text{ and }4\text{ billion}$ years ago from which bacteria, archaea, and eukarya all evolved.

Endosymbiosis

The process occurring approximately $2.5\text{ billion}$ years ago where pre-eukaryotic cells engulfed bacteria, which then evolved into mitochondria and chloroplasts.

Eukaryotic Flagella

Long, sheathed cylinders containing microtubules that are $10\text{ times}$ thicker and more structurally complex than bacterial flagella.

Cilia

Short, numerous hair-like structures found in certain protozoa and animal cells that are used for locomotion and filtering.

Glycocalyx

An outermost layer made of polysaccharides that serves in protection, adherence, and signal reception.

Chitin

A polysaccharide found in the thick inner layer of fungal cell walls that provides structural support.

Eukaryotic Cell Membrane

A phospholipid bilayer containing sterols, which provide rigidity and stability to cells, especially those lacking a cell wall.

Nucleolus

The site within the nucleus where ribosomal RNA synthesis occurs and ribosomal subunits are collected.

Chromatin

The genetic material of the eukaryotic cell, composed of linear DNA and histone proteins.

Rough Endoplasmic Reticulum (RER)

A network of membrane tunnels with attached ribosomes involved in protein transport to the cytoplasm or outside the cell.

Smooth Endoplasmic Reticulum (SER)

A tubular network without ribosomes that functions in lipid synthesis and nutrient processing.

Golgi Apparatus

An organelle consisting of flattened sacs called cisternae where proteins are modified and packaged into vesicles.

Lysosomes

Vesicles containing a variety of enzymes used for intracellular digestion of food and protection against invading microorganisms.

Mitochondria

Unique organelles that generate ATP, contain circular DNA, and possess $70S$ ribosomes.

Cristae

Folds on the inner membrane of mitochondria that hold the enzymes and electron carriers for aerobic respiration.

Chloroplasts

Organelles in algae and plant cells that convert sunlight into chemical energy through photosynthesis, releasing oxygen as a by-product.

Eukaryotic Ribosome

The $80S$ ribosome, which is composed of $60S$ and $40S$ subunits.

Actin Filaments

Long, thin protein strands in the cytoskeleton responsible for movement and shape changes.

Microtubules

Long, hollow tubes in the cytoskeleton that anchor organelles and move RNA and vesicles.

Yeasts

Fungal cells with a round to oval shape that reproduce asexually through budding.

Hyphae

Long, threadlike cells that make up the bodies of filamentous fungi or molds.

Dimorphic

The ability of some fungal cells to exist as either yeast or hyphae depending on growth conditions.

Saprobe

A fungus that obtains nutrients from the organic remnants of dead plants and animals.

Mycelium

The woven, intertwining mass of hyphae that constitutes the body or colony of a mold.

Septa

Cross walls found in fungal hyphae that permit the flow of nutrients and organelles between adjacent compartments.

Sporangiospores

Asexual fungal spores formed by cleavages within a saclike head known as a sporangium.

Conidiospores

Free asexual fungal spores, also called conidia, that are not enclosed by a sac.

Trophozoite

The active, motile, and feeding stage of a protozoan's life cycle.

Cyst

The dormant, resistant, and resting stage of a protozoan that protects it from unfavorable environmental conditions.

Pseudopods

Flexible protrusions also known as "false feet" that allow certain protozoans to move and feed.

Nematodes

A phylum of helminths characterized by elongated, cylindrical, and unsegmented bodies, commonly known as roundworms.

Cestodes

A type of flatworm with a thin and segmented body plan, commonly referred to as tapeworms.

Trematodes

A group of flatworms, also known as flukes, characterized by thin, unsegmented bodies.

Intermediate Host

The host in the helminth life cycle where larval development occurs.

Definitive Host

The host in which adult helminths mate and reproduce sexually.

Enterobius vermicularis

The common pinworm that infests the large intestine and measures between $2\text{ and }12\text{ mm}$ long.