{"id":284,"date":"2016-09-20T17:55:14","date_gmt":"2016-09-20T17:55:14","guid":{"rendered":"https:\/\/pressbooks.hcfl.edu\/bio1\/chapter\/membrane-and-cytoplasm-2\/"},"modified":"2025-08-29T17:45:08","modified_gmt":"2025-08-29T17:45:08","slug":"membrane-and-cytoplasm-2","status":"publish","type":"chapter","link":"https:\/\/pressbooks.hcfl.edu\/bio1\/chapter\/membrane-and-cytoplasm-2\/","title":{"raw":"The Plasma Membrane and The Cytoplasm","rendered":"The Plasma Membrane and The Cytoplasm"},"content":{"raw":"At this point, it should be clear that eukaryotic cells have a more complex structure than do prokaryotic cells. Organelles allow for various functions to occur in the cell at the same time. Before discussing the functions of organelles within a eukaryotic cell, let us first examine two important components of all\u00a0cells (prokaryotic and eukaryotic): the\u00a0plasma membrane and the cytoplasm.\n\n[caption id=\"attachment_56\" align=\"alignnone\" width=\"300\"]\"figure_03_05\" Figure 1<\/strong>\u00a0A prokaryotic cell. The cytoplasm is not labeled, but is the light blue area inside the cell membrane. The ribosome label is pointing to one of the small brown dots representing the ribosome.[\/caption]\n\n \n\n[caption id=\"attachment_58\" align=\"alignnone\" width=\"251\"]\"figure_03_07a\" Figure 2<\/strong>\u00a0This figure shows a typical animal cell[\/caption]\n\n \n\n[caption id=\"attachment_59\" align=\"alignnone\" width=\"300\"]\"figure_03_07b Figure 3<\/strong>\u00a0This figure shows a typical plant cell.[\/caption]\n

The Plasma Membrane<\/h1>\nLike prokaryotes, eukaryotic cells have a plasma membrane <\/strong>(Figure 4<\/strong>) made up of a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment. A phospholipid is a lipid molecule composed of two fatty acid chains, a glycerol backbone, and a phosphate group. The plasma membrane regulates the passage of some substances, such as organic molecules, ions, and water, preventing the passage of some to maintain internal conditions, while actively bringing in or removing others. Other compounds move passively across the membrane.\n\n[caption id=\"attachment_60\" align=\"alignnone\" width=\"300\"]\"figure_03_08 Figure 4 The plasma membrane is a phospholipid bilayer with embedded proteins. There are other components, such as cholesterol and carbohydrates, which can be found in the membrane in addition to phospholipids and protein.[\/caption]\n\nThe plasma membranes of cells that specialize in absorption are folded into fingerlike projections called microvilli<\/strong> (singular = microvillus). This folding increases the surface area of the plasma membrane. Such cells are typically found lining the small intestine, the organ that absorbs nutrients from digested food. This is an excellent example of form matching the function of a structure.\n

The Cytoplasm<\/h1>\nThe cytoplasm <\/strong>comprises the contents of a cell between the plasma membrane and the nuclear envelope (a structure to be discussed shortly). It is made up of organelles suspended in the gel-like cytosol<\/strong>, the cytoskeleton, and various chemicals (Figures 2 and 3)<\/strong>. Even though the cytoplasm consists of 70 to 80 percent water, it has a semi-solid consistency, which comes from the proteins within it. However, proteins are not the only organic molecules found in the cytoplasm. Glucose and other simple sugars, polysaccharides, amino acids, nucleic acids, fatty acids, and derivatives of glycerol are found there too. Ions of sodium, potassium, calcium, and many other elements are also dissolved in the cytoplasm. Many metabolic reactions, including protein synthesis, take place in the cytoplasm.\n

References<\/h1>\nUnless otherwise noted, images on this page are licensed under CC-BY 4.0<\/a>\u00a0by\u00a0OpenStax<\/a>.\n\nText adapted from: OpenStax<\/span>, Concepts of Biology. OpenStax CNX. May 18, 2016 http:\/\/cnx.org\/contents\/b3c1e1d2-839c-42b0-a314-e119a8aafbdd@9.10","rendered":"

At this point, it should be clear that eukaryotic cells have a more complex structure than do prokaryotic cells. Organelles allow for various functions to occur in the cell at the same time. Before discussing the functions of organelles within a eukaryotic cell, let us first examine two important components of all\u00a0cells (prokaryotic and eukaryotic): the\u00a0plasma membrane and the cytoplasm.<\/p>\n

\"figure_03_05\"
Figure 1<\/strong>\u00a0A prokaryotic cell. The cytoplasm is not labeled, but is the light blue area inside the cell membrane. The ribosome label is pointing to one of the small brown dots representing the ribosome.<\/figcaption><\/figure>\n

 <\/p>\n

\"figure_03_07a\"
Figure 2<\/strong>\u00a0This figure shows a typical animal cell<\/figcaption><\/figure>\n

 <\/p>\n

\"figure_03_07b
Figure 3<\/strong>\u00a0This figure shows a typical plant cell.<\/figcaption><\/figure>\n

The Plasma Membrane<\/h1>\n

Like prokaryotes, eukaryotic cells have a plasma membrane <\/strong>(Figure 4<\/strong>) made up of a phospholipid bilayer with embedded proteins that separates the internal contents of the cell from its surrounding environment. A phospholipid is a lipid molecule composed of two fatty acid chains, a glycerol backbone, and a phosphate group. The plasma membrane regulates the passage of some substances, such as organic molecules, ions, and water, preventing the passage of some to maintain internal conditions, while actively bringing in or removing others. Other compounds move passively across the membrane.<\/p>\n

\"figure_03_08
Figure 4 The plasma membrane is a phospholipid bilayer with embedded proteins. There are other components, such as cholesterol and carbohydrates, which can be found in the membrane in addition to phospholipids and protein.<\/figcaption><\/figure>\n

The plasma membranes of cells that specialize in absorption are folded into fingerlike projections called microvilli<\/strong> (singular = microvillus). This folding increases the surface area of the plasma membrane. Such cells are typically found lining the small intestine, the organ that absorbs nutrients from digested food. This is an excellent example of form matching the function of a structure.<\/p>\n

The Cytoplasm<\/h1>\n

The cytoplasm <\/strong>comprises the contents of a cell between the plasma membrane and the nuclear envelope (a structure to be discussed shortly). It is made up of organelles suspended in the gel-like cytosol<\/strong>, the cytoskeleton, and various chemicals (Figures 2 and 3)<\/strong>. Even though the cytoplasm consists of 70 to 80 percent water, it has a semi-solid consistency, which comes from the proteins within it. However, proteins are not the only organic molecules found in the cytoplasm. Glucose and other simple sugars, polysaccharides, amino acids, nucleic acids, fatty acids, and derivatives of glycerol are found there too. Ions of sodium, potassium, calcium, and many other elements are also dissolved in the cytoplasm. Many metabolic reactions, including protein synthesis, take place in the cytoplasm.<\/p>\n

References<\/h1>\n

Unless otherwise noted, images on this page are licensed under CC-BY 4.0<\/a>\u00a0by\u00a0OpenStax<\/a>.<\/p>\n

Text adapted from: OpenStax<\/span>, Concepts of Biology. OpenStax CNX. May 18, 2016 http:\/\/cnx.org\/contents\/b3c1e1d2-839c-42b0-a314-e119a8aafbdd@9.10<\/p>\n","protected":false},"author":130,"menu_order":3,"template":"","meta":{"pb_show_title":"on","pb_short_title":"","pb_subtitle":"","pb_authors":["lisa-bartee-do7vbnbexe","christine-anderson-t15c7lrfew"],"pb_section_license":"cc-by"},"chapter-type":[],"contributor":[67,66],"license":[53],"class_list":["post-284","chapter","type-chapter","status-publish","hentry","contributor-christine-anderson-t15c7lrfew","contributor-lisa-bartee-do7vbnbexe","license-cc-by"],"part":223,"_links":{"self":[{"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/284","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters"}],"about":[{"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/wp\/v2\/types\/chapter"}],"author":[{"embeddable":true,"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/wp\/v2\/users\/130"}],"version-history":[{"count":1,"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/284\/revisions"}],"predecessor-version":[{"id":286,"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/284\/revisions\/286"}],"part":[{"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/parts\/223"}],"metadata":[{"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapters\/284\/metadata\/"}],"wp:attachment":[{"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/wp\/v2\/media?parent=284"}],"wp:term":[{"taxonomy":"chapter-type","embeddable":true,"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/pressbooks\/v2\/chapter-type?post=284"},{"taxonomy":"contributor","embeddable":true,"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/wp\/v2\/contributor?post=284"},{"taxonomy":"license","embeddable":true,"href":"https:\/\/pressbooks.hcfl.edu\/bio1\/wp-json\/wp\/v2\/license?post=284"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}