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.

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.

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.

pure bilayers

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

impermeable barrier

First, the** hydrophobic** core is a(n) ________ that prevents the diffusion of water- soluble** (hydrophilic**) solutes across the membrane.

Cholesterol

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

transport proteins

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

small molecules

The plasma membrane is highly permeable to water but poorly permeable to salts and ________ such as sugars and amino acids.

extraction of plasma membranes

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

ribosome

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

Domains

________ resemble other water- soluble proteins in their amino acid composition and structure.

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.

E coli

The porins in the outer membrane of a(n) ________ cell provide channels for the passage of disaccharides and other small molecules as well as phosphate.

typical animal cell

Lysosomes vary in size and shape, and several hundred may be present in a(n) ________.

plasma membrane

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

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.

cytoplasm

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

initial stages of platelet

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

OH containing

In other phosphoglycerides, a(n) ________ molecule such as ethanolamine, serine, and the sugar derivative inositol is linked to the phosphate group.

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.

Lipid

________- anchored proteins are just one example of membrane proteins that are asymmetrically located with respect to the faces of cellular membranes.

Biochemical

________ and microscopic evidence supports the existence of lipid rafts in natural membranes.

Peroxisomes

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

Acidic Organelles

# # Lysosomes Are ________ That Contain a Battery of Degradatuve Enzymes.

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.

own distinctive proteins

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

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.

Endoplasmic Reticulum

# # The ________ Is a Network of Interconnected Internal Membranes.

cytosolic leaflet

Phosphatidylserine** also is normally most abundant in the ________ of the plasma membrane.

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)

Natural membranes

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

usual physiologic temperatures

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

animal cells

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

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.

terminal glycine

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

artificial membranes

In both natural and ________, a typical lipid molecule exchanges place with its neighbors in a leaflet about 107 times per second and diffuse several micrometers per second at 37oC.

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.

phospholipid bilayer

Membrane proteins** are defined by their location within or at the surface of a(n) ________.

Secondary lysosomes

________, which are larger and irregularly shaped, appear to result from the fusion of primary lysosomes with other membrane- bounded organelles and vesicles.

Ion channels

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

Soluble proteins

________ exhibit hundreds of distinct localized folded structures or motifs.

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.

GPI

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