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General Biology II > Exam 2 - Chapters 5, 6 & 7 > Flashcards

Exam 2 - Chapters 5, 6 & 7 Flashcards

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1
Q

The phospholipid bilayer is composed of what type of polar/non-polar parts?

A

Nonpolar hydrophobic tails and polar hydrophilic heads.

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2
Q

Cellular membranes have four components. What are they?

A
  1. Phospholipid bilayer (flexible matrix, barrier to permeability)
  2. Transmembrane proteins (integral membrane proteins)
  3. Interior protein network (peripheral membrane proteins)
  4. Cell surface markers (gylcoproteins and glycolipids)
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3
Q

What do TEM and SEM stand for?

A

TEM = transmission electron microscope

SEM = scanning electron microscope

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4
Q

What is the structure of a phospholipid?

A
  1. Glycerol (a 3-carbon polyalcohol)
  2. 2 fatty acids attached to the glycerol (these are hydroPHOBIC and NON-POLAR)
  3. Phosphate group attached to the glycerol (POLAR and hydroPHILIC)
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5
Q

How do phospholipid bilayers form?

A

Spontaneously forms a bilayer with fatty acids on the inside and phosphate groups on both surfaces.

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6
Q

Polar hydrophilic heads are on which side(s) of the phospholipid bilayer?

A

The polar hydrophilic heads are on the outside of the phospholipid bilayer (facing the extracellular fluid on one side, and the intracellular fluid [e.g., cytosol] on the other side). The non-polar hydrophobic tails are on the inside.

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7
Q

How are the two layers held together in a phospholipid bilayer?

A

Hydrogen bonding holds the two layers together.

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8
Q

How do saturated fatty acids affect a cellular membrane? Unsaturated fatty acids?

A

SATURATED fatty acids make the membrane less fluid; UNSATURATED fatty acids make the membrane more fluid (at least comparatively).

“kinks” introduced by the double bonds keep [saturated? un-? both?] fatty acids from packing tightly.

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9
Q

What effects to sterols have on membrane fluidity?

A

Most membranes contain sterols, such as CHOLESTEROL, which can either increase or decrease fluidity, depending on the TEMPERATURE.

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10
Q

What are the 6 functions of membrane proteins?

A
  1. TRANSPORTERS
  2. ENZYMES
  3. cell-surface RECEPTORS
  4. cell-surface IDENTITY MARKERS
  5. cell-to-cell ADHESION PROTEINS
  6. ATTACHMENTS TO THE CYTOSKELETON
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11
Q

What are anchoring molecules?

A

Anchoring molecules are modified lipids with:

  1. non-polar regions that insert into the internal portion of the lipid bilayer.
  2. chemical bonding domains that link directly to proteins.
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12
Q

What are integral membrane proteins?

A

Integral membrane proteins:

Span the lipid bilayer (i.e., they are transmembrane proteins)

- non-polar regions are embedded in the interior of the bilayer
- polar regions protrude from both sides of the bilayer

The transmembrane domain

- spans the lipid bilayer
- hydrophobic amino acids are arranged in alpha helices
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13
Q

How many transmembrane domains do proteins need to be anchored in the membrane?

A

Proteins NEED ONLY ONE transmembrane domain to be anchored in the membrane, but they OFTEN HAVE MORE THAN ONE such domain.

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14
Q

BACTERIORHODOPSIN…

A

Has 7 transmembrane domains, forming a structure within the membrane through which protons pass during the light-driven pumping of protons.

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15
Q

Describe the PORES in MEMBRANE PROTEINS.

A

PORES…

- EXTENSIVE NON-POLAR REGIONS within a transmembrane protein can create a pore through the membrane
- Cylinder of β sheets in the protein secondary structure are called a β-barrel
	- int. is POLAR and ALLOWS WATER and SMALL POLAR MOLECULES to PASS THROUGH
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16
Q

What is Passive Transport?

A

Passive transport is the movement of molecules through the membrane in which:

- NO ENERGY IS REQUIRED
- molecules move IN RESPONSE TO A CONC. GRADIENT
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17
Q

How do molecules diffuse during passive transport?

A

Diffusion is movement of molecules FROM HIGH CONCENTRATION to LOW CONCENTRATION.

This will continue until the concentration is the same in all regions.

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18
Q

The fl uid mosaic model shows proteins embedded

in a fluid lipid bilayer.

A

Membranes are sheets of phospholipid bilayers with associated
proteins (fi gure 5.2). Hydrophobic regions of a membrane are
oriented inward and hydrophilic regions oriented outward. In the
fl uid mosaic model, proteins fl oat on or in the lipid bilayer.

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19
Q

Cellular membranes consist of four component groups.

A

In eukaryotic cells, membranes have four components: a phosopholipid
bilayer, transmembrane proteins (integral membrane proteins), an
interior protein network, and cell-surface markers. The interior
protein network is composed of cytoskeletal fi laments and peripheral
membrane proteins, which are associated with the membrane but are
not an integral part. Membranes contain glycoproteins and glycolipids
on the surface that act as cell identity markers.

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20
Q

Membrane fluidity can change.

A

Membrane fl uidity depends on the fatty acid composition of the
membrane. Unsaturated fats tend to make the membrane more
fl uid because of the “kinks” of double bonds in the fatty acid tails.
Temperature also affects fl uidity. Some bacteria have enzymes
that alter the fatty acids of the membrane to compensate for
temperature changes.

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21
Q

The fluid mosaic model of the membrane describes the

membrane as:

A

a. containing a significant quantity of water in the interior.
b. composed of fluid phospholipids on the outside and protein
on the inside.
c. composed of protein on the outside and fluid phospholipids
on the inside.
<b>d. made of proteins and lipids that can freely move.</b>

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22
Q

What chemical property characterizes the interior

of the phospholipid bilayer?

A

<b>a. It is hydrophobic.</b> c. It is polar.

b. It is hydrophilic. d. It is saturated.

23
Q

The transmembrane domain of an integral membrane protein

A

a. is composed of hydrophobic amino acids.
b. often forms an α-helical structure.
c. can cross the membrane multiple times.
<b>d. is all of the above.</b>

24
Q

The specifi c function of a membrane within a cell is determined
by the:

A

a. degree of saturation of the fatty acids within
the phospholipid bilayer.
b. location of the membrane within the cell.
c. presence of lipid rafts and cholesterol.
<b>d. type and number of membrane proteins.</b>

25
Q

The movement of water across a membrane is dependent on

A

a. the solvent concentration.
<b>b. the solute concentration.</b>
c. the presence of carrier proteins.
d. membrane potential.

26
Q

If a cell is in an isotonic environment, then…

A

a. the cell will gain water and burst.
b. no water will move across the membrane.
c. the cell will lose water and shrink.
<b>d. osmosis still occurs, but there is no net gain or loss of cell volume.</b>

27
Q

Which of the following is NOT a mechanism for bringing

material into a cell?

A

<b>a. Exocytosis</b> c. Pinocytosis

b. Endocytosis d. Phagocytosis

28
Q

A bacterial cell that can alter the composition of saturated and
unsaturated fatty acids in its membrane lipids is adapted to a
cold environment. If this cell is shifted to a warmer
environment, it will react by…

A

a. increasing the amount of cholesterol in its membrane.
b. altering the amount of protein present in the membrane.
<b>c. increasing the degree of saturated fatty acids in its membrane.</b>
d. increasing the percentage of unsaturated fatty acids in its
membrane.

29
Q 
What variable(s) infl uence(s) whether a nonpolar molecule
can move across a membrane by passive diffusion?
A

a. The structure of the phospholipids bilayer
<b>b. The difference in concentration of the molecule across the membrane</b>
c. The presence of transport proteins in the membrane
d. All of the above

30
Q

Which of the following does NOT contribute to the selective

permeability of a biological membrane?

A

a. Specifi city of the carrier proteins in the membrane
b. Selectivity of channel proteins in the membrane
c. Hydrophobic barrier of the phospholipid bilayer
<b>d. Hydrogen bond formation between water and phosphate groups</b>

31
Q

How are active transport and coupled transport related?

A

a. They both use ATP to move molecules.
b. Active transport establishes a concentration gradient,
but coupled transport doesn’t.
<b>c. Coupled transport uses the concentration gradient established by active transport.</b>
d. Active transport moves one molecule, but coupled transport moves two.

32
Q

A cell can use the process of facilitated diffusion to

A

a. concentrate a molecule such as glucose inside a cell.
b. remove all of a toxic molecule from a cell.
c. move ions or large polar molecules across the membrane
regardless of concentration.
<b>d. move ions or large polar molecules from a region of high concentration to a region of low concentration.</b>

33
Q

Energy can take many forms.

A

Energy is the capacity to do work. Potential energy is stored energy,
and kinetic energy is the energy of motion. Energy can take many
forms: mechanical, heat, sound, electric current, light, or radioactive
radiation. Energy is measured in units of heat known as kilocalories.

34
Q

The Sun provides energy for living systems.

A

Photosynthesis stores light energy from the Sun as potential energy
in the covalent bonds of sugar molecules. Breaking these bonds in
living cells releases energy for use in other reactions.

35
Q

Oxidation–reduction reactions transfer electrons while bonds are
made or broken.

A

Oxidation is a reaction involving the loss of electrons. Reduction is
the gain of electrons (see fi gure 6.2). These two reactions take place
together and are therefore termed redox reactions.

36
Q

The First Law states that energy cannot be created or destroyed.

A

Virtually all activities of living organisms require energy. Energy
changes form as it moves through organisms and their biochemical
systems, but it is not created or destroyed.

37
Q

The Second Law states that some energy is lost as disorder increases.

A

The disorder, or entropy, of the universe is continuously increasing. In
an open system like the Earth, which is receiving energy from the Sun,
this may not be the case. To increase order however, energy must be
expended. In energy conversions, some energy is always lost as heat.

38
Q

Chemical reactions can be predicted based on changes in free energy.

A

Free energy (G) is the energy available to do work in any system.
Changes in free energy (ΔG) predict the direction of reactions.
Reactions with a <b>negative ΔG are spontaneous (exergonic)</b> reactions,
and reactions with a <b>positive ΔG are not spontaneous (endergonic)</b>.

Endergonic chemical reactions absorb energy from the surroundings, whereas exergonic reactions release energy to the surroundings.

39
Q

Spontaneous chemical reactions require activation energy.

A

Activation energy is the energy required to destabilize chemical
bonds and initiate chemical reactions (see fi gure 6.5). Even exergonic
reactions require this activation energy. Catalysts speed up chemical
reactions by lowering the activation energy.

40
Q

Cells store and release energy in the bonds of ATP.

A

The energy of ATP is stored in the bonds between its terminal
phosphate groups. These groups repel each other due to their
negative charge and therefore the covalent bonds joining these
phosphates are unstable.

41
Q

ATP hydrolysis drives endergonic reactions.

A

Enzymes hydrolyze the terminal phosphate group of ATP to release
energy for reactions. If ATP hydrolysis is coupled to an endergonic
reaction with a positive ΔG with magnitude less than that for ATP
hydrolysis, the two reactions together will be exergonic.

42
Q

An enzyme alters the activation energy of a reaction.

A

Enzymes lower the activation energy needed to initiate a

chemical reaction.

43
Q

Active sites of enzymes conform to fi t the shape of substrates.

A

Substrates bind to the active site of an enzyme. Enzymes adjust their
shape to the substrate so there is a better fi t (see figure 6.8).

44
Q

Enzymes occur in many forms.

A

Enzymes can be free in the cytosol or exist as components bound
to membranes and organelles. Enzymes involved in a biochemical
pathway can form multienzyme complexes. While most enzymes are
proteins, some are actually RNA molecules, called ribozymes.

45
Q

Environmental and other factors aff ect enzyme function.

A

An enzyme’s functionality depends on its ability to maintain its
three-dimensional shape, which can be affected by temperature
and pH. The activity of enzymes can be affected by inhibitors.
Competitive inhibitors compete for the enzyme’s active site, which
leads to decreased enzyme activity (see fi gure 6.13 ) . Enzyme activity
can be controlled by effectors. Allosteric enzymes have a second site,
located away from the active site, that binds effectors to activate or
inhibit the enzyme. Noncompetitive inhibitors and activators bind
to the allosteric site, changing the structure of the enzyme to inhibit
or activate it. Cofactors are nonorganic metals necessary for enzyme
function. Coenzymes are nonprotein organic molecules, such as
certain vitamins, needed for enzyme function. Often coenzymes serve
as electron acceptors.

46
Q

A covalent bond between two atoms represents what kind of energy?

A

a. Kinetic energy
<b>b. Potential energy</b>
c. Mechanical energy
d. Solar energy

47
Q

During a redox reaction the molecule that gains an electron

has been

A

<b>a. reduced and now has a higher energy level.</b>

b. oxidized and now has a lower energy level.
c. reduced and now has a lower energy level.
d. oxidized and now has a higher energy level.

48
Q

An endergonic reaction has the following properties

A

a. +ΔG and the reaction is spontaneous.
<b>b. +ΔG and the reaction is not spontaneous.</b>
c. –ΔG and the reaction is spontaneous.
d. –ΔG and the reaction is not spontaneous.

49
Q

A spontaneous reaction is one in which

A

<b>a. the reactants have a higher free energy than the products.</b>

b. the products have a higher free energy than the reactants.
c. an input of energy is required.
d. entropy is decreased.

50
Q

What is activation energy?

A

a. The thermal energy associated with random movements
of molecules
b. The energy released through breaking chemical bonds
c. The difference in free energy between reactants and products
<b>d. The energy required to initiate a chemical reaction</b>

51
Q

Which of the following is NOT a property of a catalyst?

A

a. A catalyst reduces the activation energy of a reaction.
<b>b. A catalyst lowers the free energy of the reactants.</b>
c. A catalyst does not change as a result of the reaction.
d. A catalyst works in both the forward and reverse directions
of a reaction.

52
Q

Where is the energy stored in a molecule of ATP?

A

a. Within the bonds between nitrogen and carbon
b. In the carbon-to-carbon bonds found in the ribose
c. In the phosphorus-to-oxygen double bond
<b>d. In the bonds connecting the two terminal phosphate groups</b>

53
Q

Cells use ATP to drive endergonic reactions because

A

a. ATP is the universal catalyst.
b. energy released by ATP hydrolysis makes ΔG for coupled
reactions more negative.
c. energy released by ATP hydrolysis makes ΔG for coupled
reactions more positive.
d. the conversion of ATP to ADP is also endergonic.

54
Q

Which of the following statements is NOT true about enzymes?

A

Which of the following statements is NOT true about enzymes?

General Biology II (2 decks)

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