Membrane Structure and Function

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MEMBRANE

Carbohydrate

Slide 20

Peripheral proteins are bound to the surface of the membrane

Integral proteins penetrate the hydrophobic core

Integral proteins that span the membrane are called transmembrane proteins

The hydrophobic regions of an integral protein consist of one or more stretches of nonpolar amino acids, often coiled into alpha helices

Slide 21

Fig. 7-8

N-terminus

C-terminus

 Helix

CYTOPLASMIC

SIDE

EXTRACELLULAR

SIDE

Slide 22

Six major functions of membrane proteins:

Transport

Enzymatic activity

Signal transduction

Cell-cell recognition

Intercellular joining

Attachment to the cytoskeleton and extracellular matrix (ECM)

Slide 23

Fig. 7-9

(a) Transport

ATP

(b) Enzymatic activity

Enzymes

(c) Signal transduction

Signal transduction

Signaling molecule

Receptor

(d) Cell-cell recognition

Glyco-

protein

(e) Intercellular joining

(f) Attachment to

the cytoskeleton

and extracellular

matrix (ECM)

Slide 24

Fig. 7-9ac

(a) Transport

(b) Enzymatic activity

(c) Signal transduction

ATP

Enzymes

Signal transduction

Signaling molecule

Receptor

Slide 25

Fig. 7-9df

(d) Cell-cell recognition

Glyco-

protein

(e) Intercellular joining

(f) Attachment to

the cytoskeleton

and extracellular

matrix (ECM)

Slide 26

The Role of Membrane Carbohydrates in Cell-Cell Recognition

Cells recognize each other by binding to surface molecules, often carbohydrates, on the plasma membrane

Membrane carbohydrates may be covalently bonded to lipids (forming glycolipids) or more commonly to proteins (forming glycoproteins)

Carbohydrates on the external side of the plasma membrane vary among species, individuals, and even cell types in an individual

Slide 27

Synthesis and Sidedness of Membranes

Membranes have distinct inside and outside faces

The asymmetrical distribution of proteins, lipids, and associated carbohydrates in the plasma membrane is determined when the membrane is built by the ER and Golgi apparatus

Slide 28