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