Biology 120 Notes (Part 8) Vacuoles, Mitochondria, Chloroplasts, the Cytoskeleton, and the Three Fibers

Vacuoles

  • ==Vacuoles== are membranous sacs that are larger than vesicles.
  • Plant cells typically have a larger central vacuole which helps with storage and some functions are performed by lysosomes in other eukaryotes.

Energy-Related Organelles

Mitochondria and Chloroplasts

  • The ==mitochondria== and ==chloroplasts== are involved in producing energy and have double membranes.
  • They are also involved in the ==Endosymbiosis Theory==, which means that they both may have once been free-living bacteria.

Chloroplasts

  • ==Chloroplasts== are the site of photosynthesis.
  • They convert solar energy into carbohydrates.
  • They contain ==chlorophyl==, which is a green pigment. They also contain thylakoids and grana which are suspended in semi-fluid stroma.

Mitochondria

  • The ==mitochondria== are involved in cellular respiration.
  • They break down carbohydrates to form ATP and CO2.
  • Mitochondria also produce most of the ATP utilized by the cell.

More About ==Endosymbiosis Theory==

  • Evidence suggests that mitochondria and chloroplasts were once free-living bacteria. Some evidence for this theory is that both mitochondria and chloroplast produce/process their own energy, have their own DNA outside of the nucleus, have their own ribosomes, and can produce independently of the rest of the cell.

Plant Cell Walls

  • The ==cell wall== is a rigid protective structure external to the plasma membrane.
  • The plant cell wall is different from prokaryotic cell walls.

The Cytoskeleton

  • The ==cytoskeleton== maintains the cell’s shape.
  • It also assists in the movements of cells and organelles.

Three Types of Fibers

  • ==There are three types of fibers: intermediate filaments, microfilaments, and microtubules.==
  • Intermediate filaments are defined by size rather than composition, provides structural support for the cell, and are not involved in movement.
  • ==Microfilaments== are also called actin filaments. They help define the cell’s shape, are usually found inside the plasma membrane, and cause movements like muscle contractions and hypokinesis.
  • ==Microtubules== are the largest in diameter of all cytoskeleton filaments. They have hollow cylinders made of two globular proteins and they originate from the microtubule organizing center.
  • In animal cells, this center is called the ==centrosome==. It contains two bundles of microtubules called ==centrioles==.
  • Microtubules serve as tracks for vesicle support.
  • They provide stability, a structural framework for organelles, involving the movement of a cell (specifically chromosome separation.)