Biology Ch 5-8 Fifth edition Brooker BRCC
1033
Describe the chemical composition of biological membranes? - ANS Biological membranes are
bilayers of phospholipids with associated proteins and carbohydrates.
What can never be energetically favorable in a biological membrane and therefore will not occur
spontaneously? - ANS the flip-flop of phospholipids to the opposite leaflet
Let's suppose an insect, which doesn't maintain a constant body temperature, was exposed to a
shift in temperature from 60°F to 80°F. Which of the following types of membrane changes
would be the most beneficial in helping the insect cope with the temperature shift? - ANS
increase the length of the lipid tails of phospholipids
Carbohydrates of the plasma membrane - ANS are bonded to a protein or lipid, are located on
the outer surface of the plasma membrane, and can function as cell markers for recognition by
other cells.
A transmembrane protein in the plasma membrane is glycosylated at two sites in the
polypeptide sequence. Where in this protein would you expect these two sites to be? - ANS in
hydrophilic regions that project into the extracellular environment
The tendency for Na+ to move into the cell can be due to - ANS The higher numbers of Na+
outside the cell, resulting in a chemical concentration gradient. And the net negative charge
inside the cell attracting the positively charged Na+
Let's suppose the solute concentration inside the cells of a plant is 0.3 M and the concentration
outside is 0.2 M. If we assume that the solute does not readily cross the membrane, which of
the following statements best describes what will happen? - ANS The plant cells will take up a
little water, and the plasma membrane will push against the cell wall.
What features of a biological membrane are major contributors to its selective permeability? -
ANS phospholipid bilayer, transport proteins
What is the name given to the process in which solutes are moved across a membrane against
their concentration gradient? - ANS active transport
Large particles or large volumes of fluid can be brought into the cell by - ANS endocytosis.
, How are phospholipids transferred to the leaflet of the ER membrane that faces the ER lumen?
- ANS Figure 5.6 Phospholipids are transferred to the other leaflet of the ER membrane via
enzymes called flippases.
What structural feature of a polypeptide causes a region of it to form a transmembrane
segment? - ANS Figure 5.7 The most common feature causing a transmembrane segment to
form is a stretch (about 20) of amino acids that mostly have hydrophobic (nonpolar) side chains.
Let's suppose the inside of a cell has a solute concentration of 0.3 M and the outside has a
concentration of 0.2 M. If the membrane is impermeable to solutes, in which direction will water
move? - ANS Figure 5.13 Water will move from outside to inside, from the lower to the higher
concentration.
What is the purpose of gating? - ANS Figure 5.15 The purpose of gating is to regulate the
function of channels, allowing them to be open or closed.
What is the function of the protein coat? - ANS Figure 5.21 The protein coat allows the budding
process at the surface of the Golgi membrane to form a vesicle.
Discuss how transmembrane proteins are important in the binding of cells to each other and the
binding of cells to the extracellular matrix. - ANS Figure 5.5 Transmembrane proteins called cell
adhesion molecules bind to each other to promote cell-to-cell adhesion. In addition, they can
bind to filaments in the extracellular matrix, such as collagen fibers, thereby causing a cell to
adhere to the extracellular matrix.
Which amino acid, described in Chapter 3 (see Figure 3.13), would you expect to be more likely
to cross an artificial phospholipid bilayer, leucine or lysine? - ANS Figure 5.10 Leucine would be
more likely to cross an artificial phospholipid bilayer because it is more hydrophobic than lysine.
What types of ion gradients are important for the conduction of action potentials across the
plasma membrane of a neuron? - ANS Figure 5.11 Gradients of sodium and potassium ions are
important for the conduction of action potentials.
Reactions that release free energy are - ANS exergonic and spontaneous.
Enzymes speed up reactions by - ANS lowering the activation energy necessary to initiate a
reaction.
For the idealized reaction aA + bB ⇌ cC + dD, suppose that the equilibrium constant, Keq, is
0.01. If the starting concentrations for A, B, C, and D are 1 M each, what would you predict
based on the value of Keq? - ANS The reverse reaction is favored.
Researchers analyzed a cell extract—a mixture of molecules isolated from a certain type of
cell—and studied a chemical reaction in which a carbohydrate was broken down into smaller
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller KINGJAY. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $11.49. You're not tied to anything after your purchase.
