Chapter 5 - Biomembranes and Cell Architecture

lateral diffusion rate

The ________ of a mobile protein in a pure phospholipid bilayer or isolated plasma membrane is similar to that of lipids.

smallest cells

Prokaryotes, which represent the simplest and ________, are about 1- 2 m in length.

peroxisomal oxidation

The energy released during ________ is converted into heat, and the acetyl groups are transported into the cytosol.

Glycophorin A

________: the major protein in the erythrocyte plasma membrane, is a representative single- pass transmembrane protein, which contains only one membrane- spanning B helix.

porin monomer

In a(n) ________, the outward- facing side groups on each of the B strands are hydrophobic and form a nonpolar ribbonlike band that encircles the outside of the barrel Covalently Attached Hydrocarbon Chains Anchor Some Proteins to Membranes.

plasma membranes

Lipids may be organized within the leaflets was the discovery that the residues remaining after the extraction of ________ with detergents contain two lipids: cholesterol and sphingomyelin.

Cholesterol

________ and its derivatives constitute the third important class of membrane lipids, the steroids.

Protein Components

Biochemical and microscopic evidence supports the existence of lipid rafts in natural membranes 5.2- Biomembranes: ________ and Basic Functions.

lateral movements

The ________ of specific plasma membrane proteins and lipids can be quantified by a technique called fluorescence recovery after photobleaching (FRAP)

pure bilayers

In ________, phospholipids do not spontaneously migrate, or flip- flop, from one leaflet to the other.

transport proteins

Specific membrane ________ in the plasma membrane permit the passage of nutrients into the cell and metabolic wastes out of it.

E coli

Several types of porin are found in the outer membrane of gram- negative bacteria such as ________ and in the outer membranes of mitochondria and chloroplasts.

hydrocarbon chains

The ________ of the phospholipids in each layer, or leaflet, form a hydrophobic core that is 3- 4 nm thick in most biomembranes.

cytosolic leaflet

Some proteins are buried within the lipid- rich bilayer; other proteins are associated with the exoplasmic or ________ of the bilayer.

ribosome

A(n) ________ that fabricates such a protein is bound to the rough ER by the nascent polypeptide chain of the protein.

two dimensional plane

In the ________ of a bilayer, thermal motion permits lipid molecules to rotate freely around their long axes and to diffuse laterally within each leaflet.

PLAP

Although ________ and other GPI- anchored proteins lie in the opposite membrane leaflet from acyl- anchored proteins, both types of membrane proteins are concentrated in lipid rafts All Transmembrane Proteins and Glycolipids Are Asymmetrically Oriented in the Bilayer.

cytoplasm

The ________ is the part of the cell outside the largest organelle, the nucleus.

plasma membrane

The ________ is intimately engaged in the assembly of cell walls, which in plants are built primarily of cellulose.

derivative inositol

In other phosphoglycerides, an OH- containing molecule such as ethanolamine, serine, and the sugar ________ is linked to the phosphate group.

eukaryotic cells

All ________ contain a discernible amount of rough ER because it is needed for the synthesis of plasma- membrane proteins and proteins of the extracellular matrix The Golgi Complex Processes and Sorts Secreted and Membrane Proteins.

initial stages of platelet

In the ________ stimulation by serum, phosphatidylserine is briefly translocated to the exoplasmic face.

Peroxisomes

________ contain several oxidases- enzymes that use molecular oxygen to oxidize organic substances.

Lysosomes

________ are a great example of the ability of intracellular membranes to form closed compartments in with the composition of the lumen differs substantially from that t= of the surrounding cytosol.

small conformational change

Binding induces a(n) ________ in phospholipase A2 that fixes the protein to the phospholipid heads and opens the hydrophobic channel.

Phosphatidylserine

________ also is normally most abundant in the cytosolic leaflet of the plasma membrane.

Endoplasmic Reticulum

In most eukaryotic cells, the peroxisome is the principal organelle in which fatty acids are oxidized, thereby generating precursors for important biosynthetic pathways The ________ Is a Network of Interconnected Internal Membranes.

hydrophobic core

First, the ________ is an impermeable barrier that prevents the diffusion of water- soluble (hydrophilic) solutes across the membrane.

05 m

All the phospholipids are freely mobile over distances of about ________, but most can not diffuse over much longer distances Lipid Composition Influences the Physical Properties of Membranes.

distinctive proteins

The cytosol, the aqueous part of the cytoplasm outside all of the organelles, also contains its own ________.

lipid bilayer

The ________ has two important properties.

acid pH

The ________ helps to denature proteins, making them accessible to the action of the lysosomal hydrolases, which themselves are resistant to acid denaturation.

fatty acyl chain

The plasmalogens are a group of phosphoglycerides that contain one ________, attached to glycerol by an ester linkage, and one long hydrocarbon chain, attached to glycerol by an ether linkage (C- O- C)

animal cells

All ________ (except erythrocytes) and many plant cells contain peroxisomes.

usual physiologic temperatures

At ________, the hydrophobic interior of natural membranes generally has a low viscosity and a fluidlike, rather than gel- like, consistency.

Natural membranes

________ from different cell types exhibit a variety of shapes, which complement a cells function.

lipid composition

Differences in ________ may also correspond to the specialization of membrane function.

relative abundance

The ________ of a particular phospholipid in the two leaflets of a plasma membrane can be determined on the basis of its susceptibility to hydrolysis by phospholipases.

hydrophobic residues

Polar and ________ lining the center of the bundle form a channel in the membrane, but as with bacteriorhodopsin virtually all of the amino acids on the exterior of the membrane- spanning domain are hydrophobic Multiple B Strands in Porins Form Membrane- Spanning "Barrels.

fatty acyl

A group of cytosolic proteins is anchored to the cytosolic face of a membrane by a(n) ________ group (e.g., myristate or palmitate) attached to the N- terminal glycine residue.

derivatives of glycerol

Phosphoglycerides, the most abundant class of lipids in most membranes, are ________ 3- phosphat.

phospholipid molecule

As a(n) ________ diffuses from the bilayer into the channel, the enzyme- bound Ca2+ binds to the phosphate in the head group, thereby positioning the ester bond to be cleaved next to the catalytic site The Plasma Membrane Has Many Common Functions in All Cells.

Ion channels

________ compose a second large and important family of multipass transmembrane proteins.

Primary lysosomes

________ are roughly spherical and do not contain obvious particulate or membrane debris.

transmembrane proteins

In all ________ examined to date, the membrane- spanning domains consist of one or more helices or of multiple B strands.

Rough Endoplasmic Reticulum

The ________: Ribosomes bound to the rough ER synthesize certain membrane and organelle proteins and virtually all proteins to be secreted from the cell.

sheetlike phospholipid bilayers

Phospholipids of the composition present in cells spontaneously form ________, which are two molecules thick.

GPI

Treatment of cells with phospholipase C releases ________- anchored proteins such as Thy- 1 and placental alkaline phosphatase (PLAP) from the cell surface.

Transport vesicles

________ from the rough ER fuse with the cis region of the Golgi complex, where they deposit their protein contents.

cellular membranes

All ________ enclose an entire cell or an internal compartment, they have an internal face (the surface oriented toward the interior of the compartment) and an external face (the surface presented to the environment)