CH 3-PT 2: Cytoplasm and Organelles

What is cytoplasm?

The cellular material located between the plasma membrane and the nucleus.

What are the main components of cytoplasm?

Cytosol, inclusions, and organelles.

What is cytosol?

A gel-like solution made up of water and soluble molecules such as proteins, salts, and sugars.

What are inclusions in cytoplasm?

Insoluble molecules that vary with cell type, such as glycogen granules, pigments, and lipid droplets.

What are organelles?

Metabolic machinery structures of the cell, each with a specialized function.

What is the function of membranes around organelles?

They allow compartmentalization, which is crucial to cell functioning.

Name a type of membranous organelle.

Mitochondria, endoplasmic reticulum, Golgi apparatus, peroxisomes, lysosomes.

What are nonmembranous organelles?

Organelles that do not have membranes, such as ribosomes, cytoskeleton, and centrioles.

Why are mitochondria called the power plants of cells?

Because they produce most of the cell's energy molecules (ATP) via aerobic cellular respiration.

What is the structure of mitochondria?

Enclosed by double membranes with an inner membrane that has folds called cristae.

What is the role of cristae in mitochondria?

They are embedded with membrane proteins that play a role in cellular respiration.

What unique genetic material do mitochondria contain?

Their own DNA, RNA, and ribosomes.

What is the function of ribosomes?

They are the site of protein synthesis.

What are the two forms of ribosomes found in cells?

Free ribosomes and membrane-bound ribosomes.

What is the difference between free ribosomes and membrane-bound ribosomes?

Free ribosomes synthesize soluble proteins that function in the cytosol, while membrane-bound ribosomes synthesize proteins for membranes or export.

What is the endoplasmic reticulum (ER)?

A series of parallel, interconnected cisterns that enclose fluid-filled interiors and is continuous with the outer nuclear membrane.

What are the two varieties of endoplasmic reticulum?

Rough ER and smooth ER.

What characterizes rough ER?

It appears rough due to attached ribosomes and is the site of protein synthesis for secretion.

What is the function of smooth ER?

It is involved in lipid metabolism, detoxification, and storage and release of calcium.

What is the Golgi apparatus?

A structure consisting of stacked and flattened cisterns that modifies, concentrates, and packages proteins and lipids.

What are the three steps involved in the function of the Golgi apparatus?

1. Transport vesicles from ER fuse to Golgi. 2. Proteins are modified. 3. Proteins are tagged, sorted, and packaged in vesicles.

What happens to proteins destined for secretion in the Golgi apparatus?

They are packaged in secretory vesicles that travel to the plasma membrane and release contents outside the cell via exocytosis.

What are lysosomes?

Vesicles that contain digestive enzymes, which can become lysosomes or fuse with them.

What is the role of the sarcoplasmic reticulum?

It is an elaborate smooth ER in skeletal and cardiac muscle cells involved in calcium storage and release.

How do proteins move from the rough ER to the Golgi apparatus?

Vesicles containing proteins bud off the rough ER, migrate, and fuse with the membranes of the Golgi apparatus.

What modifications occur to proteins inside the Golgi apparatus?

Some sugar groups are trimmed, others are added, and sometimes phosphate groups are added.

What is the function of the Golgi apparatus?

The Golgi apparatus tags, sorts, and packages proteins into vesicles for distribution.

What are the three fates of vesicles budded from the Golgi apparatus?

1. Secretory vesicles for export via exocytosis, 2. Vesicles for membrane incorporation, 3. Vesicles that become lysosomes.

What happens to proteins destined for secretion?

They are packaged into secretory vesicles that migrate to the plasma membrane and release their contents by exocytosis.

What do vesicles containing lipids and transmembrane proteins do?

They fuse with the plasma membrane or other cellular membranes and are incorporated into those membranes.

What is the role of lysosomes in the cell?

They isolate potentially harmful digestion processes and can degrade nonfunctional organelles.

What are peroxisomes?

Peroxisomes are membranous sacs containing detoxifying substances that neutralize toxins and break down fatty acids.

What are the two main detoxifying enzymes found in peroxisomes?

Oxidase converts toxins to hydrogen peroxide, and catalase converts hydrogen peroxide to harmless water.

What is the cytoskeleton?

The cytoskeleton is an elaborate network of rods that provide structural support and facilitate movement within the cell.

What are the three types of cytoskeletal elements?

Microfilaments, intermediate filaments, and microtubules.

What are microfilaments made of?

Microfilaments are made of semi-flexible strands of protein actin.

What is the primary function of microfilaments?

They strengthen the cell surface and help resist compression, as well as assist in cell motility and shape changes.

What are intermediate filaments?

Intermediate filaments are tough, ropelike protein fibers that help cells resist pulling forces.

What are microtubules composed of?

Microtubules are hollow tubes made of tubulin protein subunits.

What is the role of microtubules in the cell?

They determine the overall shape of the cell and the distribution of organelles.

What is the centrosome?

The centrosome is the microtubule organizing center of the cell, consisting of a granular matrix and a pair of centrioles.

What are centrioles?

Centrioles are barrel-shaped organelles that generate microtubules and organize the mitotic spindle during cell division.

What are cilia and flagella?

Cilia and flagella are cellular extensions that aid in the movement of the cell or materials across the cell surface.

What are microvilli?

Microvilli are fingerlike projections that extend from the cell surface to increase surface area.