Chapter 5

What is a glycolipid?

A lipid attached to a carbohydrate

Why do shorter tails make membranes more fluid?

Shorter tails interact less with each other

Select all the processes that are coupled across cell membranes.

The import of K+ ions The export of Na+ ions

What is the basic structure of the plasma membrane?

a phospholipid bilayer

Small, uncharged molecules pass through the membrane via

passive diffusion

A transmembrane protein destined for the plasma membrane will first be inserted into the:

ER membrane

What property of biological membranes describes the ability of individual molecules to move within the membrane?

Fluidity

Which of the following best describes the process of active transport?

Particle moving across a membrane against a concentration gradient

Match each protein with its unique attributes.

Regions inserted into the hydrophobic interior are usually α helices.: Transmembrane protein Not covalently bound to membrane matches: Peripheral membrane protein Lipid tails are inserted into the hydrophobic portion of the membrane.: Lipid-anchored protein

Select all of the following that are functions of membrane proteins.

Cell signaling Energy transduction Cell recognition Transport

Select the true statements comparing simple and facilitated diffusion.

Facilitated diffusion, but not simple diffusion, requires a transport protein Both simple and facilitated diffusion require concentration gradients

Select all of the following that can readily diffuse across the membrane.

Small, uncharged molecules Gases

What separates the internal contents of a cell from the extracellular environment?

The plasma membrane

Match each type of membrane protein with the way it is associated with the plasma membrane.

Transmembrane protein: A segment of amino acids is inserted into the phospholipid bilayer. Lipid-anchored protein: A lipid molecule is covalently attached to an amino acid side chain of the membrane protein Peripheral membrane protein: Noncovalent associations form with phospholipids or other membrane proteins

Active transport is the movement of a solute across the membrane ___ its concentration gradient.

against

The Na+/K+ -ATPase actively transports Na+ and K+ ions ___ their gradients by using the energy from ATP hydrolysis.

against

Glycosylation is the process of covalently attaching a(n) ___ to a protein or a lipid

carbohydrate

What are the three molecular components of cellular membranes?

carbohydrates phospholipids proteins

What type of proteins form an open passageway for facilitated diffusion of ions or molecules across the membrane?

channels

Select the categories of proteins that assist in the movement of molecules and ions across membranes.

channels transporters

Transporter proteins bind their solutes in a hydrophilic pocket and then undergo a(n) ___ change that switches the exposure of the pocket from one side of the membrane to the other.

conformational

Eukaryotic cells can transport large molecules such as proteins and polysaccharides via ___ and ___. Both of these mechanisms involve membrane vesicles or vacuoles.

endocytosis; exocytosis

Most membrane components of a eukaryotic cell are synthesized at the:

endoplasmic reticulum

Isotonic refers to a consequence of osmosis in which the solute on the inside and outside of a cell is

equal

The attachment of a carbohydrate to a lipid creates a(n) ___.

glycolipid

The process of covalently attaching a carbohydrate to a lipid or protein is known as:

glycosylation

Phospholipids have a ___ head region that will interact with aqueous environments.

hydrophilic

Phospholipid bilayers are an effective barrier to many charged or polar solutes because of their ___ interior region.

hydrophobic

A solution whose solute concentration is higher than the concentration of solutes inside a cell is

hypertonic

When the concentration of solutes outside the cell is higher, the solution is said to be ___ relative the inside of the cell.

hypertonic

When the solute concentration is higher inside the cell relative to outside the cell, the outside solution is said to be:

hypotonic

Lipids with shorter tails contribute ___ plasma membrane fluidity.

increased

A membrane protein that has a portion integrated into the hydrophobic region of the membrane is called a(n) ______ membrane protein.

integral

When the solute concentration is equal on both sides of a membrane, the two solutions are said to be

isotonic

The Frye and Edidin experiment showed that

lateral protein movements within the membrane are temperature dependent

Most phospholipids move freely within a semifluid membrane

laterally along the plane of the membrane in two dimensions

In osmosis, water moves from areas of

low solute concentration to areas of high solute concentration

Osmosis describes the movement of water from areas where the solute concentration is ___ to areas in which the solute concentration is ___.

low; high

The black circle in this figure refers to the region of the plasma membrane that is

nonpolar and hydrophobic

Proteins that associate with the plasma membrane through non-covalent interactions with phospholipids or transmembrane proteins are called ___ membrane proteins.

peripheral

The smooth endoplasmic reticulum is where most eukaryotic membrane ___ are synthesized.

phospholipids

The three main types of macromolecules that comprise the plasma membrane are

phospholipids, proteins, and carbohydrates

Movement of ions and large molecules into and out of the cell is mediated by membrane ___.

proteins

Movement of ions and large molecules into and out of the cell is mediated by membrane ______.

proteins

In the 1940s, studies of animal cells suggested that the import of ______ is coupled to the export of ______.

K+; Na+

Select the reasons why it is more appropriate to describe membranes as semifluid.

Molecules move laterally within the membrane leaflet Phospholipids usually move in two dimensions

The Na+/K+-ATPase pump establishes and maintains a gradient such that:

Na+ is higher outside the cell than inside, and K+ is higher inside the cell than outside

Due to the Na+/K+ -ATPase, cells are able to maintain concentration gradients so that the concentration of ___ ions is greater outside the cell than inside, and the concentration of ___ ions is greater inside the cell than outside.

Na+; K+

Where would peripheral (or extrinsic) membrane proteins likely reside with respect to the plasma membrane?

On the outside of the inner leaflet, facing the cytoplasm On the outside of the outer leaflet, facing the outside of the cell

Which of the following are pumped by the Na+/K+ -ATPase? Select all that apply.

three Na+ out of the cell two K+ into the cell

The Na+/K+ -ATPase pumps ______ Na+ ions out of the cell and ______ K+ ions into the cell.

three; two

Select the processes used by eukaryotic cells to transport large molecules such as proteins and polysaccharides.

Endocytosis Exocytosis

The transport of a substance that requires an input of energy is called ___ transport.

active

What is osmosis?

Diffusion of water from an area of low solute concentration to an area of high solute concentration

Select all the regions that are likely binding sites for peripheral membrane proteins.

Hydrophilic regions of integral membrane proteins Polar head groups of phospholipids

A glycoprotein consists of a protein attached to

a carbohydrate

Transporter proteins transport solutes across the membrane via:

a conformational change triggered by solute binding

All cells are surrounded by a ___ permeable plasma membrane, meaning that the membrane allows the passage of some molecules and ions but not others.

semi

Transmembrane proteins are able to span the hydrophobic portion of the bilayer because they have

stretches of nonpolar amino acids

The Frye and Edidin experiment demonstrated that lateral protein movement within the membrane is affected by ___.

temperature

A term that describes a situation in which the concentration of a solute is higher on one side of a membrane than the other is

transmembrane gradient

Membrane proteins that span both leaflets of the lipid bilayer are called

transmembrane proteins

Select all the membrane proteins that are integral membrane proteins.

transmembrane proteins lipid-anchored proteins