LB

Chapter 4 (Campbell's Biology in Focus)

Internal Membranes and Functions

  • ==Cytosol== is the semifluid, jellylike substance inside cells

  • In eukaryotic cells, most of the DNA is found in the ==nucleus==

  • In prokaryotic cells, DNA is focused in a region called the ==nucleoid== which is not membrane enclosed

  • The interior of either type of these cells is called cytoplasm

  • At the boundary of every cell the ==plasma membrane== functions as a selective border that allows oxygen, nutrients, and wastes to service the entire cell

    • the plasma membrane consists of a double layer of phospholipids

  • ==Microvilli== increase the surface area of an object due to the crevices

  • The nucleus contains most of the genes in a eukaryotic cell

  • The ==nuclear envelope== encloses the nucleus separating its contents from the cytoplasm

    • the two membranes are each a lipid bilayer associated with proteins

  • The nuclear side of the envelope is lined by the ==nuclear lamina==

  • DNA is organized into discrete components called ==genes==

  • The complex of DNA and proteins making up chromosomes is called ==chromatin==

  • A prominent structure in the nondividing nucleus is the ==nucleolus== (plural of nucleoli) which is a mass of densely stained granules and fibers adjoining part of the chromatin

  • ==Ribosomes== are complexes made of ribosomal (RNA) proteins

    • They carry out protein synthesis

Endomembrane System

  • Many of the different membrane-bounded organelles of the eukaryotic cell are part of the ==endomembrane system,==

    • the endomembrane system includes the
    • nuclear envelope
    • endoplasmic reticulum
    • Golgi apparatus
    • lysosomes
    • various kinds of vesicles and vacuoles
    • plasma membrane.

  • The ==endoplasmic reticulum== is a large network of membranes that accounts for more than half of the plasmic membranes in eukaryotic cells

    • ==Smooth ER== lacks ribosomes
    • ==Rough ER== is studded with ribosomes on the outer surface of the membrane

Functions of Rough ER

  • Most secretory proteins are ==glycoproteins==
  • ==Transport Vesicles== are vesicles in transit from one part of the cell to another

The Golgi Apparatus: the shipping and receiving center

  • After leaving the endoplasmic reticulum in transport vesicles, they head to the Golgi Apparatus

    • The ==Golgi Apparatus== is like a warehouse for receiving, sorting, shipping, and some manufacturing.

  • A ==lysosome== is a membranous sac of hydrolytic enzymes that many eukaryotic cells use to digest macromolecules

  • ==Phagocytosis== is the process of engulfing smaller organisms or food particles

    • The food vacuole formed through this then fuses with a lysosome

  • ==Vacuoles== are large vesicles formed by the endoplasmic reticulum and Golgi Apparatus

  • ==Food Vacuoles== are formed by phagocytosis

  • Many unicellular protists living in freshwater have ==contractile vacuoles== that pump excess water out of the cell, thereby maintaining a suitable concentration of ions and molecules inside the cell.

  • Mature plants generally contain a ==central vacuole==, which develops by the coalescence of smaller vacuoles

  • The ==endosymbiont theory== states that an early ancestor of eukaryotic cells engulfed an oxygen-using non-photosynthetic prokaryotic cell. Eventually, the engulfed cell formed a relationship with the host cell in which it was enclosed, becoming an endosymbiont.

  • The inner folds of a phospholipid bilayer are called a ==cristae==

  • The ==cytoskeleton== is a network of fibers extending throughout the cytoplasm

  • Eukarya have ==microtubules==, hollow rods constructed from a globular protein called tubulin

  • In animal cells, microtubules grow out of a ==centrosome==, a region that is often located near the nucleus and is a “microtubule organizing center”

  • Within the centrosome is a pair of ==centrioles==, each composed of nine sets of triplet microtubules arranged in a ring

    • In eukaryotes, a special arrangement of microtubules results in the beating of the flagella and cilia

  • The microtubule assembly of a cilium or flagellum is anchored in the cell by the basal body

  • Bending involves large motor proteins called dynein

  • ==Microfilaments== are thin, solid rods. They are also called actin filaments because they are built from molecules of actin.

  • Thousand of actin filaments and thicker filaments of a motor protein called ==myosin== interact to cause a contraction in a muscle cell

  • ==Intermediate filaments== are named for their diameter, which is larger than the diameter of microfilaments but smaller than that of microtubules