Ch 15 Textbook Material Pt 1 (membrane-enclosed organelles)

What encloses the cytosol of an animal cell?

the plasma membrane

What is generally the most prominent organelle in eukaryotic cells?

the nucleus

What surrounds the nucleus?

a double membrane called the nuclear envelope

How does the nucleus communicate with the cytosol?

through nuclear pores in the nuclear envelope

What is the outer nuclear membrane continuous with?

the membrane of the ER

What is the major site of new membrane synthesis in the cell?

the ER

Why is rough ER called “rough”?

it has ribosomes attached to its cytosolic surface

What do ribosomes on the rough ER do?

synthesize proteins that are inserted into the ER membrane or delivered to the ER lumen

What is the ER lumen?

the interior space of the ER where some proteins are delivered

What is the main difference between rough ER and smooth ER?

the smooth ER doesnt have ribosomes

How does the smooth ER participate in calcium regulation?

it sequesters Ca2+ from the cytosol and releases it during processes like muscle contraction

What is the function of the Golgi apparatus?

it recieves proteins and lipids from the ER, modifies them, and dispatches them to other destinations

What are lysosomes?

membrane sacs containing digestive enzymes that degrade worn-out organelles, macromolecules, and ingested particles

What are endosomes?

sorting compartments that process materials taken in by endocytosis before they reach lysosomes

What are peroxisomes?

organelles containing enzymes that break down lipids and toxic molecules, producing hydrogen peroxide

Mitochondria perform

oxidative phosphorylation

Chloroplasts perform

photosynthesis

What do mitochondria and chloroplasts have in common structurally?

both are surrounded by double membranes and contain internal membranes specialized for ATP production

How are organelles positioned and moved within a cell?

they attach to cytoskeletal filaments, especially microtubules

• serve as tracks for movement

What drives organelle and vesicle movement along cytoskeletal filaments?

motor proteins that use ATP hydrolysis for energy

What type of organisms are thought to be the precursors of the first eukaryotic cells?

simple microorganisms resembling present-day archaea

What did the earliest archaeal cells lack?

internal membranes

What structure performed all membrane-dependent functions in early cells?

the plasma membrane

What are two key functions carried out by the plasma membrane in prokaryotes?

ATP synthesis & lipid synthesis

Why can archaea and bacteria survive with only a plasma membrane?

their small size gives them a high surface area-to-volume ratio

• allows sufficient membrane surface for metabolism

How did internal membranes likely begin to form?

through plasma membrane protrusions and invaginations that increased surface area

What may have formed when membrane invaginations surrounded genetic material?

the double-layered nuclear envelope

Which organelles formed from membrane infoldings that split off and fused together?

the endomembrane system

• ER

• golgi apparatus

• lysosomes

• endosomes

• peroxisomes

How do the interiors of endomembrane organelles communicate?

by vesicles that bud off from one organelle and fuse with another

From what did mitochondria and chloroplasts evolve?

bacteria that were engulfed by ancestral archaeal cells

• endosymbiosis

What evidence supports the bacterial origin of mitochondria and chloroplasts?

they have small genomes and proteins similar to bacterial proteins

What happened to the engulfed bacteria over time?

they lost their outer host membrane and evolved into permanent organelles

Why are mitochondria and chloroplasts isolated from vesicular traffic in the cell?

because they evolved separately from the endomembrane system

Which process explains the origin of mitochondria and chloroplasts?

the endosymbiotic theory

How do the interiors of the ER, golgi apparatus, endosomes, and lysosomes exchange contents with each other?

by small vesicles that bud off of one organelle and fuse with another