Biology 111 Exam 2

The compounds of biological membranes that form a barrier to the movement of hydrophilic materials across the membrane are?


Which of the following statements about cholesterol molecules is true?

They alter the fluidity of the membrane

The hydrophilic regions of a membrane protein are most likely to be found?

Exposed on the surface of the membrane

Competitive inhibitors of enzymes work by?

Fitting into the active site

this functions as a recognition signal for interactions between the cells?


The difference between tight junctions, desmosomes, and gap junctions is that?

Tight junctions desmosomes have mechanical roles, where as gap junctions facilitate communication between cells

Which of the following is an example of passive transport?

Facilitated diffusion

Which of the following molecules is the most likely simply to diffuse across a cell membrane?

A steroid

The difference between osmosis and diffusion?

Osmosis refers specifically to the movement of water across a membrane, whereas diffusion is the movement of molecules.

Osmosis moves water from a region of ___ to a region of ___?

Low concentration of dissolved material; High concentration of dissolved material

Osmosis helps plant cells maintain..

turgor pressure

When a severely dehydrated patient is brought to the hospital, an IV of normal saline is started immediately. Distilled water is not used because?

It would cause the patients blood cells to swell and eventually burst

The speed and direction of ions as they move into and out of the cell are determined by the?

Concentration gradient and electrochemical imbalances

In facilitated diffusion, the diffusion rate of a specific molecule across a membrane does not continue to increase as the concentration difference of the molecule across the membrane increases. This is the case because?

The carrier proteins are saturated.

Plant cells transport sucrose across the vacuole membrane against its concentration gradient by a process known as?

Active transport

How does the second law of thermodynamics apply to organisms?

To maintain order, life requires a constant input of energy

Which of the following represents potential energy?

- Chemical bonds
- Concentration gradient
- Electric charge imbalance

The sum total of all the chemical reactions in a living structure is called its?


When ADP gains a phosphate to form ATP?

Energy is consumed

Large molecules that contain carbon and are held together by covalent bonds are categorized as?


How do competitive and non-competitive enzyme inhibitors differ?

Competitive inhibitors bind to the active site, whereas non-competitive inhibitors change the shape of the active site

Molecules containing a large number of hydroxyl groups are?

Highly soluble in water

An essential functional group involved in cellular energy transfer is the ___ group?


In condensation (AKA: dehydration synthesis) reactions, the atoms that make up a water molecule are derived from?

Both of the reactants

Which of the following is responsible for making every amino acid unique?

R" group

Starch and glycogin which are both polysaccharides differ in their functions in that starch is ____ whereas glycogin ____?

The principle energy storage compound of plants; Is the main energy storage of animals

The amino acids of protein keratin are arranged in a helix. This secondary structure is stabilized by?

Hydrogen bonds

Quaternary structure is found in proteins?

Composed of two or more polypeptides subunits

A ____ protein is a protein that has become nonfunctional due to the loss of it's three dimensional structure?


A molecule with the formula C16 H30 O15 is a?


The main function of cellulose, the most abundant organic compound on earth is?

To provide mechanical strength to plant cell walls

The side chain of leucine is a hydrocarbon. In a folded protein, where would you expect to find the leucine?

Both A and B"
- In the interior of a cytoplasmic enzyme
- On the exterior of a protein embedded in a membrane

A fat contains fatty acids and?


Negative feedback in a sequence of chemical reactions involves a chemical that appears ___ in the sequence and ____ reaction?

Late; Inhibits an earlier

The basis of nucleic acids are purines or pyrimidines. Purines and pyrimidines are distinguished by the fact that?

Purines are double-ringed structures, whereas pyrimidines are single-ringed structures

Which of the following is not a difference between DNA and RNA?

DNA is polymer whereas RNA in monomer

Unsaturated fatty acids do not pack together due to?

Kinks in the hydrocarbon chains ribozymes

When placed in a hypertonic solution, animal cells


metabolism is

the total of all chemical reactions in an organism

activation energy is

the minimum amount of energy needed to start a chemical reaction

transition state is

an unstable grouping of atoms that exists momentarily in the course of a reaction, when a system is highest in energy.

3 important properties of catalysts

speed up reaction rates by lowering the activation energy of a reaction
-are not consumed by the reaction- no change
- are present in very small amounts compared to the other reactants

conformational change

a slight change in the three dimensional structure of a protein that may result in a change in activity. often involved in regulation of enzyme activity.

induced fit

the change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by entry of the substrate. like shaking hands


the substance acted upon by an enzyme


a process in which a protein unravels and loses its native conformation, thereby becoming biologically inactive. denaturation occurs under extreme conditions of ph, salt concentration, and temperature.

competitive inhibitor

a substance that reduces the activity of an enzyme by entering the active site in place of the substrate whose structure it mimics.

non-competitive inhibitor

a substance that reduces the activity of an enzyme by binding to a location remote from the active site, changing its conformation so that it no longer binds to the substrate.

allosteric regulation

the binding of a regulatory molecule to a protein at one site that affects the function of the protein at a different site.

feedback inhibition

a method of metabolic control in which the end product of a metabolic pathway acts as an inhibitor of an enzyme within that pathway. (negative feedback) --> switching off a metabolic pathway by the form of its end product


are larger than their substrates
changes shape when it binds to a substrate.
lower the activation energy.
are highly specific.
may orient substrates, induce strain, or temporarily add chemical groups.

a transition state is

The state at which the bonds of reactants are unstable

an active site is

the part of the enzyme that binds with a substrate.

in some cases, a substrate-enzyme complex is stabilized by

hydrogen bonds.
covalent bonds.
ionic attractions.
hydrophobic interactions.

Binding of substrate to the active site of an enzyme is


The ability of an enzyme to change shape when it binds to its substrate is called

induced fit

competetive inhibitors work by

fitting into the active site.

how do competitive and noncompetitive inhibitors differ?

Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site.

Which type of inhibitor can be overcome completely by the addition of more substrate?


an allosteric inhibitor

changes the shape of an enzyme

the process that involves an end product acting as an inhibitor of an earlier step in a metabolic pathway is called

feedback inhibition

The regulation of biochemical pathways in cells often occurs by _______ mechanisms, with the end product of the pathway acting as a(n) _______ of the enzyme that catalyzes the first step of the pathway.

allosteric; noncompetitive inhibitor

Metabolism is organized into pathways that are linked in which of the following ways?

The product of one step in the pathway functions as the substrate in the next step

the tertiary structure of a protein is determined by it's

interactions among R groups

Quaternary structure is found in proteins

composed of subunits

A(n) _______ protein is a protein that has become nonfunctional due to the loss of its three-dimensional structure.


starch is energy storage in ____; glycogen is energy storage in ___

plants; humans

in animals, glucose is stored in the form of


The main function of cellulose, the most abundant organic compound on Earth, is

to provide mechanical strength to plant cell walls