Eukaryotic microbes — Intro to cell structure, endosymbiosis, protists, fungi, and algae

A comprehensive set of Q&A flashcards covering key concepts from the notes on eukaryotic cell structure, endosymbiosis, protists, fungi, and algae.

What major organelles are found in eukaryotic cells (not necessarily all present in every cell)?

Nucleus, mitochondria, chloroplasts (in photosynthetic organisms), endoplasmic reticulum, Golgi apparatus, peroxisomes, lysosomes, glyoxysomes, microtubules, cilia, and flagella.

What is the function of nuclear pores in the nucleus?

They export mRNA and import proteins such as histones that package DNA.

What is the nucleolus?

A specialised region of the nucleus where rRNA is synthesised and ribosomal proteins are imported for ribosome assembly.

Describe mitochondria and one key metabolic feature.

Double-membrane organelles with inner membrane infoldings containing ETC components and ATP synthase; the matrix houses citric acid cycle (CAC) enzymes.

What structural features define chloroplasts in photosynthetic eukaryotes?

Extensive thylakoid membrane system organized into disc-like thylakoids; stroma contains Rubisco and Calvin cycle enzymes.

What are hydrogenosomes and where are they found?

Organelles in some amitochondriate anaerobic protists (e.g., Trichomonas); convert pyruvate to acetyl-CoA, CO2 and H2, producing ATP via substrate-level phosphorylation.

What is the role of lysosomes?

Vesicles with hydrolytic/digestive enzymes that fuse with phagosomes to digest ingested material and turnover damaged proteins.

Differentiate Rough ER and Smooth ER.

Rough ER has ribosomes and folds/secretes proteins; Smooth ER lacks ribosomes and synthesizes lipids and polysaccharides.

What is the Golgi apparatus known for?

Trafficking and modification of proteins from the ER; exocytosis and directing hydrolytic enzyme-containing vesicles to lysosomes.

Define peroxisomes and glyoxysomes.

Peroxisomes perform fatty acid breakdown and oxidative reactions (producing H2O2); glyoxysomes carry out the glyoxylate bypass.

What is the glyoxylate bypass and its metabolic purpose?

A CAC bypass that preserves carbon skeletons by producing malate from isocitrate via isocitrate lyase, replenishing CAC intermediates for biosynthesis.

What is the main purpose of the citric acid cycle (CAC)?

Oxidize acetyl-CoA to generate energy and provide precursors for biosynthesis; CAC intermediates are finite if not replenished.

Differentiate mitosis and meiosis.

Mitosis: replication and equal segregation of identical chromosomes to two diploid/daughter cells. Meiosis: reductional division producing haploid gametes with recombined alleles.

What is the endosymbiotic hypothesis?

Primitive eukaryotic cells engulfed bacteria that became mitochondria and, in some lineages, cyanobacteria that became chloroplasts.

What evidence supports endosymbiotic origins of mitochondria and chloroplasts?

Mitochondria/chloroplasts have their own DNA, 70S ribosomes (mitochondria) or chloroplasts-like genes, and double membranes with bacterial-like porins; gene transfer to the host nucleus occurs.

What is primary endosymbiosis?

Initial capture of bacteria capable of oxidative phosphorylation or oxygenic photosynthesis, leading to mitochondria and chloroplasts.

What is secondary endosymbiosis?

A eukaryote engulfs another eukaryote that already contains a chloroplast derived from a bacterial endosymbiont, spreading photosynthesis among protists.

What are protists, and what energy strategies do they use?

Eukaryotes excluding fungi, plants, and animals; energy is acquired via organotrophy (organic compounds) or phototrophy (photosynthesis), with aerobic respiration or fermentation in some cases.

Name the six eukaryotic supergroups used to classify protists.

Archaeplastida, Rhizaria, Chromalveolata, Excavata, Amoebozoa, Opisthokonta.

Do protists ever use lithotrophy? Explain.

No lithotrophy in eukaryotes; lithotrophy (using inorganic electron donors) is carried out by prokaryotes.

Why are protists of particular interest scientifically and ecologically?

Some cause serious diseases (e.g., malaria); photosynthetic protists drive ocean phytoplankton and food webs; many have fossilizable hard parts forming limestone or diatomaceous earth.

Giardia lamblia—what group does it belong to and a key feature?

Diplomonad; flagellated parasite with two nuclei and mitosomes; lacks complete mitochondria; causes diarrheal disease.

Trichomonas vaginalis—what group does it belong to and a key feature?

Parabasalid; contains hydrogenosomes; lacks certain CAC enzymes; sexually transmitted parasite.

What are Euglena and the Euglena lineage known for?

Euglenids; motile; can be photosynthetic or organotrophic and can phagocytose bacteria.

What are kinetoplastids and give examples of diseases they cause.

Kinetoplastids—large mass of mitochondrial DNA in a single mitochondrion; examples include Trypanosoma and Leishmania, causing sleeping sickness, Chagas disease, and leishmaniasis.

What are alveolates and their three main groups?

Alveolates possess alveoli under the plasma membrane; include ciliates, dinoflagellates, and apicomplexans.

Ciliates—name a well-known example and a key feature.

Paramecium; motile by cilia and feed on bacteria.

Dinoflagellates—what is a notable ecological phenomenon and a toxin they can produce?

Photosynthetic algae known for red tides; can produce brevetoxin and saxitoxin (neurotoxins).

Apicomplexans—what is the apical complex and what is the apicoplast?

Sporozoans with a complex organelle near the apex for host cell invasion; apicoplast is a degenerate plastid involved in fatty acid and isoprenoid synthesis.

Name examples of apicomplexans.

Cryptosporidium, Plasmodium, Toxoplasma, and Eimeria.

What are stramenopiles and what groups do they include?

Flagellated with distinct hair-like flagella; include diatoms, oomycetes, and golden/brown algae.

Diatoms—why are they ecologically important and what is their cell wall composed of?

Major phytoplankton and primary producers; silica-based cell walls called frustules; produce domoic acid in some species.

Oomycetes—give an example and a key growth feature.

Phytophthora infestans (potato blight) and Pythium; grow as multinucleate hyphae similar to fungi but are not true fungi.

Golden algae and brown algae—what pigment distinguishes them?

Both are photosynthetic; golden algae are unicellular; brown algae are multicellular (kelps); both contain fucoxanthin.

Rhizaria—name three groups and a distinctive feature for each.

Chlorarachniophytes (secondary endosymbiosis with green algae); Foraminiferans (CaCO3 shells; fossilized white cliffs of Dover); Radiolarians (silica shells; buoyant, heterotrophic).

What are Amoebozoa and give two examples of organisms in this group?

Amoeboid organisms with lobe-shaped pseudopodia; examples include gymnamoebas and slime molds like Physarum (plasmodial) and Dictyostelium (cellular).

What role do slime molds play in biology and ecology?

Physarum shows plasmodial slime mold behavior; Dictyostelium exhibits social behavior forming a slug and fruiting body under starvation.

What is a notable feature of fungal cell walls and their basic life cycle?

Cell walls composed of chitin; fungi can be haploid or diploid during life cycle; reproduce via spores; hyphae form mycelium.

Identify the five major fungal groups used in classification.

Chytridiomycetes, Zygomycetes, Glomeromycetes, Ascomycetes, Basidiomycetes.

Chytridiomycetes—an example and a disease they are associated with.

Batrachochytrium dendrobatidis; causes chytridiomycosis in amphibians.

Zygomycetes and Microsporidia—name a characteristic.

Zygomycetes include Rhizopus; Microsporidia are obligate parasites with mitosomes and lack functioning mitochondria.

Glomeromycetes—what is their ecological role?

Obligate symbionts forming endomycorrhizae with plant roots to aid nutrient uptake.

Ascomycetes—what is a key reproductive feature?

Ascus produces haploid ascospores after meiosis and mitosis; includes Saccharomyces, Candida, Aspergillus.

Basidiomycetes—describe their reproductive structure.

Mushrooms and toadstools; dikaryotic mycelium forms basidiocarps; meiosis yields basidiospores.

Red vs green algae—what is a defining pigment difference and a practical use of red algae?

Red algae have phycobiloproteins (phycoerythrin, phycocyanin, allophycocyanin); source of agar and carrageenan. Green algae have chlorophylls a and b and lack phycobiloproteins.

Botryococcus braunii—why is it notable?

Colonial green alga that secretes long-chain hydrocarbons; studied as a potential biofuel source.

What are phycobiloproteins and give two examples?

Pigment-protein complexes (antenna pigments) in red algae; examples include phycoerythrin and phycocyanin (and allophycocyanin).