Bio Chapter 5

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

Molecules move laterally within the membrane leaflet and phospholipids usually move in two dimensions.

What is a glycolipid?

A lipid attached to a carbohydrate

Cholesterol in a membrane has which of the following effects?

At a high temperature, it makes the membrane less fluid; at a low temperature, it makes the membrane more fluid.

Where does lipid synthesis occur?

At the cytsolic leaflet of the smooth ER

Select the true statements comparing simple and facilitated diffusion.

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

In the embryonic development of animals, the proper migration of cells relies on the recognition of cell types via the ______ on each cell's surface.

Carbohydrates

_______ proteins provide an open passageway all the way across the plasma membrane

Channel

What is the short, rigid molecule produced by animal cells that is involved in membrane fluidity?

Cholesterol

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

ER membrane

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

Endocytosis and exocytosis

Select the types of transport that require a transport protein.

Facilitated diffusion and active transport

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

Fluidity

What is the significance of being able to gate a channel protein?

Gating a channel protein allows the cell to regulate the movement of solutes.

Which of the following statements is correct about a biological membrane that is fluid?

Individual molecules can move within the membrane

How does cholesterol affect the plasma membrane at low temperatures?

It makes the membrane more fluid and prevents freezing.

The double bonds in unsaturated lipids create ______ in the acyl tails, making it more difficult for neighboring lipids to interact.

Kinks

What are ways in which lipids can be transferred from the ER to other membranes in the cell?

Lateral diffusion, lipid exchange proteins, vesicular transport

Lipid tails are inserted into the hydrophobic portion of the membrane.

Lipid-anchored protein

Select all of the following statements that are consistent with the fluid-mosaic model.

Many membrane proteins move within the plane of the membrane, Phospholipids can move within the plane of the membrane, Membranes are mainly composed of proteins and phospholipids.

Not covalently bound to membrane.

Peripheral membrane protein

Which of the following types of transport involves pumping ions against a gradient using ATP as a source of energy?

Primary active transport

Why do shorter tails make membranes more fluid?

Shorter tails interact less with each other

______ proteins do not flip flop across bilayer leaflets because hydrophilic protein regions would pass through the hydrophobic bilayer interior.

Transmembrane

Regions inserted into the hydrophobic interior are usually α helices.

Transmembrane proteins

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

Transporters and channels

How do transporters differ from channel proteins?

Transporters must change conformation to allow solutes to cross the membrane.

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

active

The difference between passive transport and active transport is that

active transport requires an input of energy

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

against

The plasma membrane consists of a(n) phospholipid

bilayer

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

The presence of a ________ bond in a phospholipid tail makes the membrane more fluid because it prevents phospholipids from packing tightly.

double

A gradient that includes both electrical and chemical components is called a(n) ________ gradient

electrochemical

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

endoplasmic reticulum

When they are synthesized, transmembrane proteins are first inserted into the ____ ____ membrane before being transferred via vesicles to other regions of the cell.

endoplasmic reticulum

Glycolipids and glycoproteins that participate in cell surface recognition have carbohydrates that lie within the:

extracellular region

Cellular membranes are described as ______ because their lipids and proteins can move relative to each other.

fluid

Some molecules are known to move laterally in the plane of the membrane. As such, we can say the membrane is

fluid

When channel proteins are _______, it means they can open and close to regulate the movement of ions and molecules across the cell membrane.

gated

A protein with a covalently attached carbohydrate is referred to as a(n)

glycoprotein

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

glycosylation

A solution in which the solute concentration on both sides of the membrane is equal is classified as

isotonic

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

lipids

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

low; high

The plasma _______ separates the internal contents of a cell from the extracellular environment.

membrane

Lipids with shorter tails contribute to ______ plasma membrane fluidity

more

Because the plasma membrane contains lipids, proteins, and carbohydrates, it is often described as a(n)

mosaic

The selective ______ of the plasma membrane allows the cell to maintain a favorable internal environment.

permeability

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

phospholipids, carbohydrates, and proteins

Select functions of the selectively permeable plasma membrane.

remove waste products from within the cell, maintain a proper balance of ions within the cell, maintain a proper supply of essential molecules such as glucose and amino acids

Transporters are classified by the number of ______ they bind, as well as the ________ of transport.

solutes; direction

The primary difference between endocytosis and exocytosis is

the direction of transport

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 _______ gradient

transmembrane

Most phospholipids move freely within a semifluid membrane laterally along the plane of the membrane in _____.

two dimensions

Transmembrane protein flip-flop does not occur spontaneously because it would be energetically _______.

unfavorable

An _____ lipid contains double bonds

unsaturated

When a double bond is present in the fatty acid tail of a phospholipid, the lipid is said to be _______.

unsaturated

Endocytosis and exocytosis involve packaging substances into a membrane-enclosed ______.

vesicle