EBio 1 Test 2

Which of the following statements is TRUE with regard to this animation?

Both sodium and potassium ions are transported against their concentration gradients. Both ions are transported from where their concentration is low to where their concentration is high, and the cell expends energy in the form of ATP to do it.

The formula of the amino acid glycine is C2O2NH5. Deduce the formula of the molecule made from two monomers of glycine.

C4O3N2H8 The formula of the amino acid glycine is C2O2NH5. Deduce the formula of the molecule made from two monomers of glycine.

Which statement below is correct about the passage of substances directly through the phospholipid bilayer of a biological membrane?

CH4 or O2 can pass through the bilayer, whereas Na+ or H2O cannot.

Which transport proteins are fueled by ATP?

Ca2+ transporters that move Ca2+ from the cytosol to the SR pouch during muscle relaxation ATP fuels transport proteins that build gradients. Facilitated diffusion utilizes a gradient but does not build a gradient. Both Na+and K+channels open up like floodgates and utilize Na+or K+gradients to facilitate diffusion. Muscle contraction involves a Ca2+channel that opens like a floodgate and lets Ca2+rush out of the SR pouch into the cytosol by facilitated diffusion utilizing the Ca2+gradient built by the Ca2+pump on the SR membrane that actively pumps Ca2+from the cytosol into the SR pouch.

What makes a motor protein move along a cytoskeletal track?

Energy is provided by ATP.

Cells that produce protein hormones move vesicles from the rough endoplasmic reticulum to the ______, and from there to the outer cell membrane. Vesicles are moved along ________ and their movement is energized by ______.

Golgi apparatus; cytoskeletal tracks; ATP

Which of the following statements is FALSE?

Many of the amino acids on the outside of whale myoglobin have hydrophobic side chains. Whales are able to dive for longer time periods than humans because whales have higher concentrations of myoglobin in their muscles. Whale myoglobin has a large number of same charges on its surface which causes myoglobin molecules to repel each other and prevents clumping of the myoglobin molecules. Electrically charged amino acids are hydrophilic and not hydrophobic.

Which movement across a membrane does not require a protein? First exclude all movements that do require a protein.

O2 moving from high to low concentration

Which statement about protein hormone synthesis is FALSE. First exclude the four statements that are true.

Protein hormones are synthesized on free ribosomes.

Find the correct statement. First exclude the four incorrect statements.

Some amino acids have hydrophilic side chains and others have hydrophobic side chains

Test your understanding by predicting how the sodium-potassium pump becomes integrated into the outer cell membrane. Find the statement that is FALSE.

The mRNA coding for the sodium potassium pump is translated into the pump on free ribosomes.

Find the feature not shared by lipids, nucleic acids, and proteins. First exclude the four features that are shared by all three classes of large molecules

They can all form strings of hundreds of repeating monomer units.

What is needed to move a hydrophilic sugar across a membrane from high to low concentration?

a membrane protein, but no ATP

Which of the following is most similar in structure to ATP?

a nucleotide

What powers transport proteins that build gradients across a membrane?

addition of a phosphate group to the transport protein

What do all transport proteins found in the cell membrane have in common? They

allow only specific types of molecule to pass through.

What do all transport proteins found in the outer cell membrane have in common? They

allow only specific types of molecule to pass through.

A cow that eats grass will break down grass proteins into their ____________ building blocks (monomers) and could use these monomers to assemble cow _____________.

amino acid; protein

A protein's function is determined by the properties of its amino acids. Which replacement of one amino acid with another is least likely to affect the protein's function?

an amino acid with a C=O group is replaced by an amino acid with an O-H group.

Which statement correctly completes the following statement? Exclude the four incorrect options. Omega-3 polyunsaturated fatty acids

are necessary to allow shape changes in the sodium-potassium pump. Omega-3 polyunsaturated fatty acids are very fluid (squiggly) and thereby support the shape changes of the sodium-potassium pump. Double-check the other options. Since omega-3 fatty acids cannot be synthesized in the human body without an omega-3 fatty acid, they have to be consumed with the diet. Omega-3 fatty acids are polyunsaturated and contain more C=C bonds and fewer C-H bonds than either monounsaturated fatty acids or saturated fatty acids with the same number of carbon atoms. The additional kinks in polyunsaturated fatty acids cause membranes to be less stable at higher temperatures.

Which is correct? Estrogen ____________________________.

binds to a receptor inside the target cell Estrogen is a steroid hormone. Steroids are lipids, are hydrophobic (not water soluble), and can therefore move across the inner hydrophobic core of the cell membrane's bilayer. In contrast to steroid hormones, protein hormones do not enter their target cells, but instead bind to a receptor on the outer cell membrane and use a signal transduction system to transfer their message to the nucleus. Steroid hormones don't do any of this. Steroid hormones make it all the way into the target cell's nucleus. After entering the target cell, the steroid is bound by a cytosolic receptor that shuttles the steroid into the nucleus, where the receptor-steroid complex binds to DNA and activates a gene.

Which cell structure is correctly matched with its function?

cell membrane: selective passage of substances

Diving mammals are able to accumulate high levels of oxygen-storing proteins in their muscles because they have _________ on the surface of their myoglobin.

electrical charges that repel each other

If the concentration of a negatively charged particle outside of a cell is high and its concentration within the cell is low, the particle moves into the cell by ____________ and out of the cell by _____________.

facilitated diffusion through a channel; active transport by a pump

Predict what will be seen in large quantities in a cell producing a lot of proteins that function in the cytosol of this same cell.

free ribosomes Proteins for export are synthesized on bound ribosomes (rough ER), while proteins that function in the cytosol of the same cell in which they are made are synthesized on free ribosomes. Smooth ER does not function in protein synthesis. Protein hormones are secreted from the cell that made them. Transport vesicles fuse with the cell membrane to secrete protein hormones to the outside of the cell.

What reaction breaks the bonds that join the phosphate groups in an ATP molecule?

hydrolysis Hydrolysis involves breaking bonds with the addition of water.

Compare the sodium/potassium pump with the barrel-shaped protein (LDL) that carries cholesterol through the blood stream. The pump is _________ on the inside; LDL is ________ on the outside.

hydrophilic, hydrophilic The sodium/potassium pump's inner channel must be hydrophilic to be able to allow the charged substances Na+and K+ to move through it. The LDL protein must be hydrophilic on the outside to be able to interact with water molecules with their partial electrical charges and dissolve in the water-based blood fluid.

For proteins that transport substances across membranes, the exterior middle portions in contact with membrane fatty acid tails must be _________. The exterior of proteins that transport substances through the blood stream must be _________.

hydrophobic; hydrophilic

Defensive proteins are manufactured by the _____ system.

immune

A steroid hormone reaches a target cell and triggers a response. Where in the cell will the hormone be located when it triggers the response?

in the nucleus of the target cell

Predict where hydrophobic amino acids are found in the sodium-potassium pump:

in the outer middle regions of the protein in contact with the membrane's fatty acid tails

Endocytosis moves materials _____ a cell via _____.

into ... membranous vesicles

Complete the sentence: The phosphorylation of ADP to ATP

is powered by an outside energy source.

Which correctly describes the differences between DNA and mRNA?

mRNA nucleotides contain a different sugar than DNA nucleotides, and DNA stays in the nucleus while mRNA moves out of the nucleus.

An example of mechanical work is ________; an example of transport work is _______.

movement of a vesicle by a motor protein; building a K+ gradient across a membrane

Which type of membrane phospholipid is most helpful in supporting any type of membrane pump that needs to change its shape to function? Phospholipids containing

omega-3 polyunsaturated fatty acids.

Which of these does NOT contain a structural protein?

ovalbumin

A nucleotide is composed of a(n) _____.

phosphate group, a nitrogen-containing base, and a five-carbon sugar

A squirrel eating nuts breaks down nut __________ into their three components: fatty acids, glycerol, and phosphate monomers. Some or all of these building blocks could contribute to the formation of __________ by the squirrel.

phospholipids; fats, phospholipids, and ATP The three components listed in the question prompt are the components of phospholipids. These components (fatty acids, glycerol, and phosphate monomers) can contribute to the formation of several substances: fats (using fatty acids and glycerol), phospholipids (using all three components listed), and ATP (using only the phosphate monomers).

What specific membrane structures serve to build gradients?

proteins that span the membrane

The conversion of ADP + P to ATP _______ energy; the conversion of ATP to ADP + P _______ energy.

requires; releases

Protein hormones are synthesized by

ribosomes bound to the endoplasmic reticulum.

Which correctly describes the sequence of steps for synthesis and export of proteins by the endomembrane system?

rough ER → vesicle → Golgi apparatus → vesicle → cell membrane

Because it is a protein hormone, leptin must be synthesized by which?

rough endoplasmic reticulum

Movement across membranes of a small molecule consisting of only bonds where electrons are shared evenly between partner atoms occurs

simple diffusion

Which will be attracted to a negatively charged region of a protein?

the H atom in the water molecule Opposite charges attract each other by electrical attraction between positive and negative charges. All negative poles or charges are attracted to positive poles or positive charges, but repelled by negative poles or charges: (1) Oxygen as the negative pole of the water molecule, (2) a negatively charged phosphate group, and (3) Cl-. The C-H bond has no partial electrical charges and its H is neither attracted nor repelled. Hydrogen as the positive pole of the water molecule is attracted to negative charges.

A hydrophilic amino acid on the surface of a protein hormone could NOT interact with which? First exclude the four options with which this amino acid could interact.

the center of a biological membrane

Predict which change in a protein's amino acid sequence is LEAST likely to interfere with a protein's function: Replacement of an amino acid _________ with another amino acid that ___________.

with a hydrophobic side chain; has a hydrophobic side chain