Chapter 05: Eukaryotic Cell Structure

What are the groups of eukaryotes and how do they compare to Bacteria and Archaea cells?

Two groups: Protists and Fungi

Eukarya are typically larger than bacterial and archaeal cells and are morphologically diverse to adapt to environments.

What is the cytoplasm of eukaryotes made of?

• Cytosol — the liquid component where organelles are located

• Cytoskeleton — helps organize the cytoplasm

  • Microfilaments (actin)

  • Intermediate filaments

  • Microtubules

  • Plays a role in cell shape and motor proteins associated with filaments guide cell movement.

What is the Endoplasmic Reticulum?

Irregular network of tubules and cisternae. It is split into the Rough & Smooth ER.

Rough ER — Ribosomes are attached to outer surface and proteins are synthesized by it.

Smooth ER — No ribosomes and used to synthesize lipids.

Acts as a hub for molecular synthesis & transport and cell membrane synthesis

What is the Golgi Apparatus?

Organelle made of flattened cisternae stacked on top of each other.

• Cis is the forming face closest to ER

• Trans is the maturing face farthest from ER

Function: Package materials and prepare for secretion.

What are lysosomes?

A roughly spherical organelle involved in the digestion of nutrients.

• Contains digestion enzymes like hydrolases

• Maintains an acidic environment by pumping protons into their interior.

How are materials moved in and out of the cells"?

Via membranous organelles and vesicles.

Endoyctic pathway — movement into the cell from outside

Secretory pathway — movement out of and within the cell

How does the eukaryotic cell do endocytosis?

Via the lysosomes.

Clathrin-coated and caveolin-coated vesicles deliver its contents to early endosomes, which develop into late endosomes that fuse with lysosomes. Phagosomes fuse directly with lysosomes.

What is the nucleus?

The organelle that acts as DNA storage and is the biggest difference between eukaryotes compared to bacterial and archaeal cells.

The nucleus houses chromosomes which contain chromatin, which is a complex of DNA and proteins (histones).

What is the nuclear envelope?

A two lipid bilayer membrane that surrounds the nucleus and is continuous with the ER (so outer membrane is covered with ribosomes).

Nucelar pore complex are the proteins that makes pores that penetrate the envelop, with the pores allowing materials to transported in or out of the nucleus.

What are eukaryotic ribosomes?

• 80S in size with 60S + 40S subunits (making them larger than bacterial or archaeal ribosomes).

• Either bound to ER or free in the cytoplasm

What are mitochondria?

The powerhouse of the cell.

What are hydrogenosomes?

Organelles that generate some energy in anaerobic protists. There is a double membrane, no cristae, and usually no DNA.

The ATP generated by hydrogenosomes is typically from fermentation, rather than respiration.

What are chloroplasts?

Pigment-containing organelles in plants and algae that do photosynthesis. Thylakoids are the site of light reactions of photosynthesis.

What is the structure of eukaryotic flagella and cilia and how are they different from prokaryotic flagella and cilia?

They are membrane-bound cylinders that have axoneme inside (which is a set of microtubules in a 9+2 arrangement.

Eukaryotic flagella move via whip-like movements while the cilia beat in two phases like oars, while prokaryotic is more like a propeller.