McGraw-Hill Education Thesis
Because learning changes everything.®
Chapter 5
Lecture Outline
See separate PowerPoint slides for all
figures and tables pre-inserted into
PowerPoint without notes and animations.
© 2020 McGraw-Hill Education. All rights reserved. Authorized only for instructor use in the classroom.
No reproduction or further distribution is permitted without the prior written consent of McGraw-Hill Education.
© McGraw-Hill Education 2
Chapter 5
Membrane Structure, Synthesis and Transport
Key Concepts:
• Membrane Structure
• Fluidity of Membranes
• Synthesis of Membrane Components in Eukaryotic Cells
• Overview of Membrane Transport
• Transport Proteins
• Exocytosis and Endocytosis
© McGraw-Hill Education 3
Membrane Structure
• The framework of the membrane is the phospholipid bilayer
• Phospholipids are amphipathic molecules Hydrophobic (water-fearing) region faces in
Hydrophilic (water-loving) region faces out
• Membranes also contain proteins and carbohydrates
• The two leaflets (halves of bilayer) are asymmetrical, with different amounts of each component
© McGraw-Hill Education 4
Fluid-mosaic model
• Membrane is considered a mosaic of lipid, protein, and carbohydrate molecules
• Membrane resembles a fluid because lipids and proteins can move relative to each other within the membrane
© McGraw-Hill Education 5
Figure 5.1
© McGraw-Hill Education 6
Proteins bound to membranes
Integral or intrinsic membrane proteins
Transmembrane proteins
• Region(s) are physically embedded in the hydrophobic portion of the phospholipid bilayer
Lipid-anchored proteins
• An amino acid of the protein is covalently attached to a lipid
Peripheral or extrinsic membrane proteins
Noncovalently bound either to integral membrane proteins that project out from the membrane, or to polar head groups of phospholipids
© McGraw-Hill Education 7
Figure 5.2
© McGraw-Hill Education 8
Approximately 20 to 30% of All Genes Encode Transmembrane Proteins
• Membranes are important medically as well as biologically
• Computer programs can be used to predict the number of transmembrane proteins
• Estimated percentage of membrane proteins is substantial: 20 to 30% of all genes may encode transmembrane proteins
• This trend is found throughout all domains of life including archaea, bacteria, and eukaryotes
• Function of many genes is unknown – study may provide better understanding and better treatments for disease
© McGraw-Hill Education 9
Copyright © McGraw-Hill Education. All rights reserved. No reproduction or distribution without the prior written consent of McGraw-Hill Education.
Table 5.2
Table 5.2 Estimated Percentage of Genes That Encode Transmembrane Proteins*
Organism Percentage of protein-encoding genes that encode transmembrane proteins
Archaea
Archaeoglobus fulgidus 24.2
Methanococcus jannaschii 20.4
Pyrococcus horikoshii 29.9
