1. Eucaryotic cells have membrane-delimited nuclei
2. In addition to the nucleus, eucaryotic cells have other membrane-bound organelles that perform specific functions within the cells; this allows simultaneous independent control
3. The large membrane surface area of eucaryotic cells allows greater respiratory and photosynthetic activity

1. The cytoplasmic matrix, although superficially featureless, provides the complex environment required for many cellular activities
2. Microfilaments (4 to 7 nm) may be scattered throughout the matrix or organized into networks and parallel arrays; they play a major role in cell motion and cell shape changes
3. Microtubules are hollow cylinders (25 nm) that help maintain cell shape, are involved (with microfilaments) in cellular movement, participate in intracellular transport of substances, and participate in organelle movements; they also form the mitotic spindle during cell division and are present in cilia and flagella
4. Intermediate filaments (8 to 10 nm), along with microfilaments and microtubules, are major components of the cytoskeleton, an intricate network of interconnected filaments that help maintain cell shape and contributes to cellular movement

1. The endoplasmic reticulum (ER) is a complex set of internal membranes that may have ribosomes attached (rough or granular endoplasmic reticulum; RER or GET) or may be devoid of ribosomes (smooth or agranular endoplasmic reticulum; SER or AER)
2. The ER has many important functions:
1. It transports proteins, lipids, and other materials within the cell
2. It is a major site of cell membrane synthesis
3. ER-associated enzymes and ribosomes synthesize lipids and many proteins

New ER is produced through expansion of old ER

1. The Golgi Apparatus is a set of membrane sacs (cisternae) that is involved in the modification, packaging, and secretion of materials; they exist in stacks called dictyosomes
2. The Golgi Apparatus is present in many eucaryotic cells, but many fungi and ciliated protozoa lack it

1. Lysosomes are membrane-bound vesicles that contain enzymes needed for intracellular digestion of all types of macromolecules
2. Endocytosis is the process in which the cell takes up solutes or particles by enclosing them in vesicles (endosomes) pinched off from the plasma membrane
1. Phagocytosis-endocytosis of large particles by engulfing them into a phagocytic vacuole (phagosome)
2. Pinocytosis-endocytosis of small amounts of liquid with its solute molecules
3. Material in endosomes is digested with the aid of lysosomes, which fuse with the endosomes
4. Lysosomes join with phagosomes for defensive purposes such as to destroy invading bacteria
5. Autophagic vacuoles are lysosomes that selectively digest portions of the cellís own cytoplasm as part of the normal turnover of cellular components
6. Proteasomes are a nonlysosomal protein degradation system that has been recently discovered in eucaryotic cells, a few bacteria, and many archaea

1. Eucaryotic ribosomes are generally larger than procaryotic ribosomes,
2. Eucaryotic ribosomes, like their procaryotic counterparts, are responsible for synthesis of cellular proteins; they can either be attached to the ER or free in the cytoplasm
1. ER-associated ribosomes synthesize integral membrane proteins or proteins that are secreted out of the cell
2. Free ribosomes synthesize nonsecretory, nonmembrane proteins
3. Several ribosomes can attach to a single mRNA; these compexes are called polyribosomes or polysomes

1. Mitochondria are the site of tricarboxylic acid (TCA) cycle activity and the generation of ATP by electron transport and oxidative phosphorylation
2. Mitochondria have both an inner membrane and an outer membrane enclosing a fluid matrix
1. The inner and outer membranes have different lipids and enzymes
2. The enzymes of the TCA cycle and the b-oxidation pathway for fatty acids are located within the matrix
3. Electron transport and oxidative phosphorylation occur only on the inner mitochondrial membrane
3. Mitochondria use their own DNA and their own ribosomes to synthesize some of their proteins; mitochondrial DNA and mitochondrial ribosomes are similar to bacterial DNA and ribosomes in terms of size and structure; mitochondria reproduce by binary fission

1. Chloroplasts are the site of photosynthesis
2. Chloroplasts have an outer membrane and an inner membrane system of flattened sacs called thylakoids that often form stacks known as grana; the fluid matrix compartment is called the stroma
1. The formation of carbohydrate from carbon dioxide and water (dark reaction) occurs in the stroma
2. The trapping of light energy to generate ATP, NADPH, and oxygen (light reaction) occurs in the thylakoid membranes of the grana

1. Nuclei are membrane-bound structures that house most of the genetic material of the cell
2. Nuclear Structure
1. Chromatin is the dense fibrous material seen within the nucleoplasm of the nucleus; this is the DNA containing part of the nucleus; when the cell is dividing, chromatin condenses into visible chromosomes
2. The nuclear envelope is a double-membrane structure penetrated by nuclear pores that allow materials to be transported into or out of the nucleus
3. The nuclear lamina, a network of intermediate filaments, lies against the inner surface of the nuclear envelope and supports it
4. Nuclear pores penetrate the nuclear envelope and allow materials to be transported into or out of the nucleus
3. The nucleolus is involved in the synthesis of ribosomes
4. Mitosis is a process of nuclear division in which the (duplicated) genetic material is distributed equally to two daughter nuclei so that each has a full set of chromosomes and genes
5. Meiosis is a complex, two-stage process of nuclear division in which the number of chromosomes in the resulting daughter cells is reduced from the normal (diploid) number to one-half of that number (haploid)
6. Cytokinesis is the process by which the cytoplasm and its components are distributed to the new daughter cells; it usually occurs following mitosis and meiosis

1. Some cells have a rigid cell wall but many do not; cell walls of eucaryotic microbes vary in composition, but are generally chemically simpler than peptidoglycan
2. Other cells, such as some protozoa, have a pellicle, which is a rigid layer of components just within the plasma membrane

1. Cilia and flagella are locomotor structures that differ in length and how they propel the cell
2. Cilia and flagella are structurally very similar; both are membrane-bound cylinders composed of microtubules, in a 9+2 arrangement, embedded in a matrix

1. Eucaryotes have a membrane-delimited nucleus and many complex membrane-bound organelles, each of which perform a separate function for the cell
2. Procaryotes lack a membrane-delimited nucleus and internal membrane-bound organelles; they are functionally simpler and do not undergo mitosis, meiosis, endocytosis, and other complex activities performed by many eucaryotes
3. Despite the significant differences between procaryotes and eucaryotes, they have remarkable biochemical similarities: the same basic chemical composition, the same genetic code, and the same basic metabolic processes