bio exam 2

Refer to Animation: Translation Elongation. Referring to the figure, what is the anticodon of the next tRNA to enter the A site? a. 3'CUU5' b. 5'CUU3' c. 3'UGG5' d. 5'GAA3' e. 3'GAA5'

a. 3'CUU5'

How many different mRNA sequences could encode the amino acid sequence Met-Leu-Val-His? a. 48 b. 24 c. 12 d. 84

a. 48

A proton pump is needed in the lysosomal membrane because: a. All of these choices are correct. b. the interior of the lysosome needs to be acidic. c. protons cannot move across a membrane on their own. d. protons are being moved from low to high concentration.

a. All of these choices are correct.

Examine the figure shown, which depicts one stage in the process of translation in a eukaryote. What will happen when the ribosome shifts one codon further on the mRNA, assuming the next codon is not a stop codon? Select all that apply. a. The tRNA carrying the polypeptide will be in the P site. b. A new tRNA will bind to the ribosome. c. The sites of the ribosomes will be relabeled (from left to right) P, A, E. d. The tRNA that is no longer carrying the polypeptide will be ejected from the ribosome. e. The tRNA that is in the A site in the figure shown will be ejected from the ribosome.

a. The tRNA carrying the polypeptide will be in the P site. b. A new tRNA will bind to the ribosome. d. The tRNA that is no longer carrying the polypeptide will be ejected from the ribosome.

In response to seasonal changes in temperature, many organisms must alter the composition of their plasma membranes to maintain the proper degree of fluidity. Which change in the fatty acids of phospholipids would be most effective in maintaining membrane fluidity in a colder environment? a. a decrease in phospholipid fatty acid side chain length and a decrease in side chain saturation b. an increase in phospholipid fatty acid side chain length and an increase in side chain saturation c. a decrease in phospholipid fatty acid side chain length and an increase in side chain saturation d. an increase in phospholipid fatty acid side chain length and a decrease in side chain saturation

a. a decrease in phospholipid fatty acid side chain length and a decrease in side chain saturation

All 64 possible codons have corresponding anticodons in tRNAs. a. false b. true

a. false

Purified phospholipids mixed in water will only form membranes if the appropriate enzyme is present. a. false b. true

a. false

Which particles are pumped across the lysosomal membrane by a transport protein to create a special internal environment in the lysosome? a. protons b. broken-down macromolecules c. phospholipids and cholesterol d. enzymes capable of breaking down macromolecules being delivered from the Golgi apparatus

a. protons

All polypeptides have tertiary structure. a. true b. false

a. true

The sequence of amino acids in a protein is referred to as its primary structure. a. true b. false

a. true

Referring to the following mRNA sequence, 5′—AUGAGACUUACCGAA—3′, what would the anticodon look like if the second nucleotide of the fourth codon was mutated to U? a. 3′--AUG--5′ b. 3′--UAG--5′ c. 3′--TAG--5′ d. 3′--AAC--5′

b. 3′--UAG--5′

Which factors are used during translation? a. elongation factors b. All of these choices are correct. c. release factors d. initiation factors

b. All of these choices are correct.

The beaker in the illustration contains two solutions of salt with different concentrations (measured by molarity, M). The two solutions are separated by a membrane that is permeable to water but not to salt. What will occur in this container? a. diffusion of salt from B to A, but not of water b. diffusion of water from A to B but no diffusion of salt c. diffusion of water from B to A and of salt from A to B d. diffusion of both water and salt from B to A

b. diffusion of water from A to B but no diffusion of salt

All β sheets are comprised of protein strands running antiparallel to each other. a. true b. false

b. false

Mitochondria and chloroplasts are integral parts of the endomembrane system and are specifically connected to the endoplasmic reticulum. a. true b. false

b. false

Most proteins retain metabolic activity when denatured a. true b. false

b. false

Where are lysosomal enzymes synthesized? a. in the cytosol b. on the rough endoplasmic reticulum c. on the Golgi apparatus d. in a vesicle

b. on the rough endoplasmic reticulum

Which is more likely to form a micelle rather than a liposome if mixed in an aqueous environment? Refer to the figure. a. phospholipids with two fatty acid tails b. phospholipids with a single fatty acid tail c. Phospholipids with one or two fatty acid tails are equally likely to form a micelle rather than a liposome. d. Neither type of phospholipid could form a micelle.

b. phospholipids with a single fatty acid tail

According to the codon table, which amino acid sequence results from a synthetic "poly-A" mRNA terminating with a single C at the 3' end (i.e., 5'-|AAA|AAA| . . . |AAA|AAC|-3') when translated in the reading frame indicated by the vertical lines? a. polylysine terminated by a His b. polylysine terminated by a Thr. c. polylysine terminated by a Ser d. polylysine terminated by a Lys e. polylysine terminated by an Asn

b. polylysine terminated by a Thr.

A protein with an internal signal sequence is most likely to be located in: a. the extracellular space. b. the nucleus. c. a mitochondrion. d. the cytoplasm. e. a chloroplast.

b. the nucleus.

What would be synthesized on the rough endoplasmic reticulum? a. cytoskeletal proteins b. transmembrane protein receptors c. mRNAs d. nuclear proteins

b. transmembrane protein receptors

The codons in mRNA specify the amino acids that are used to make a protein. Is the statement true or false? a. false b. true

b. true

A double-stranded DNA molecule, only part of which is shown, is being transcribed. If the molecule is transcribed from left to right, one of the nucleotides shown in bold would be the first transcribed in this small molecule. 5′—ATGATCGGATCGATCCAT—3′ 3′—TACTAGCCTAGCTAGGTA—5′ Which sequence is the correct mRNA produced from the transcription of this DNA molecule? a. 3′-AUGAUCGGAUCGAUCCAU-5′ b. 3′-UACUAGCCUAGCUAGGUA-5′ c. 5′-AUGAUCGGAUCGAUCCAU-3′ d. 5′-UACUAGCCUAGCUAGGUA-3′

c. 5′-AUGAUCGGAUCGAUCCAU-3′

If a mutation blocked the function of the signal recognition particle, making it unable to bind signal sequence, what would result? a. All proteins would end up in the nucleus. b. All proteins would be secreted from the cell. c. All proteins would be translated on free ribosomes in the cytoplasm. d. All proteins would end up in the mitochondria or chloroplast.

c. All proteins would be translated on free ribosomes in the cytoplasm.

A researcher has devised a technique that allows her to label all the integral membrane proteins with a fluorescent tag. She uses a laser to bleach the fluorescence in a specific area of the cell membrane. After 24 hours, she notices that fluorescence has returned to the bleached area. What can she deduce from this experiment? a. Integral membrane proteins may not be permanently associated with the cell membrane. b. Integral membrane proteins are stationary in the membrane and cannot undergo lateral movement. c. Integral membrane proteins are able to move laterally within the cell membrane. d. Integral membrane proteins are not located within the cell membrane.

c. Integral membrane proteins are able to move laterally within the cell membrane.

During the translation of mRNA molecules, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal peptides. What would you expect to find in the polypeptide that will eventually fold to become a histone protein? a. an amino-terminal signal peptide b. no signal peptide c. a nuclear localization signal d. a signal anchor peptide

c. a nuclear localization signal

Where are the ribosomes that translate proteins to be secreted from the cell? a. in the nucleolus b. in the cytosol c. attached to the rough endoplasmic reticulum d. attached to the Golgi apparatus

c. attached to the rough endoplasmic reticulum

Enzymes present in the lumen of the Golgi apparatus are responsible for modifying proteins and lipids. Where must these proteins have been before they entered the Golgi apparatus? a. in the nucleus Before proteins get into the lumen of the Golgi apparatus, they must be translated on the rough ER. b. floating in the cytosol c. in the rough endoplasmic reticulum d. translated on free ribosomes

c. in the rough endoplasmic reticulum

Individuals with a condition known as exercise intolerance lack sufficient ATP and suffer extreme fatigue from minimal exertion. Defects in which structures are most likely responsible for this condition? a. Golgi apparatus b. ribosomes c. mitochondria d. lysosome e. endoplasmic reticulum

c. mitochondria

Disorders of which organelle are often associated with defects in transport from compartment to compartment, resulting in poor sorting of protein components within the cell? a. nucleus b. plasmids c. the Golgi apparatus d. plasma membrane e. endoplasmic reticulum

c. the Golgi apparatus

Which part of a cholesterol molecule is polar? a. both the four interconnected planar rings and the hydrocarbon tail b. the four interconnected planar rings c. the OH group d. the hydrocarbon tail

c. the OH group

Which of the environmental factors affect the interactions between amino acids that in turn determine the shape of a protein? a. pH b. ion concentration c. temperature d. All of these choices are correct. e. hydrophilic or hydrophobic properties of the environment f. temperature and ion concentration

d. All of these choices are correct.

Which of the statements is true regarding glycine? a. Glycine is an asymmetric amino acid. b. Glycine is special because it contains a -SH group important in protein folding. c. Glycine is similar to tyrosine in terms of structure and chemical properties. d. Glycine increases the flexibility of the peptide backbone. e. Glycine is a large, polar amino acid.

d. Glycine increases the flexibility of the peptide backbone.

. Assuming that transcription and translation both proceed from left to right, which is the correct orientation of the DNA template, the RNA transcript, and the protein product? DNA template 3′- ......... -5′ a. RNA transcript 5′- ......... -3′ Protein product HOOC-......... -NH2 DNA template 5′- ......... -3′ b. RNA transcript 3′- ......... -5′ Protein product HOOC-......... -NH2 DNA template 5′- ......... -3′ c. RNA transcript 5′- ......... -3′ Protein product H2N-......... -COOH DNA template 3′- ......... -5′ d. RNA transcript 5′- ......... -3′ Protein product H2N- ......... -COOH

d. RNA transcript 5′- ......... -3′ Protein product H2N- ......... -COOH

While many proteins move freely in the plane of the membrane, there are some proteins that are confined to specific places or regions of the membrane. If a membrane protein that is confined to a specific membrane region were labeled in a FRAP experiment, what result would you predict? a. The bleached spot will slowly recover fluorescence over time. b. The entire cell will become fluorescent over time. c. The entire cell will become bleached over time. d. The bleached spot will not recover fluorescence over time. e. It is impossible to predict the results of this experiment.

d. The bleached spot will not recover fluorescence over time.

During the translation of mRNA molecules, the new polypeptides are often directed to specific parts of the cell by the presence or absence of short sequences of amino acids called signal peptides. What would you expect to find in the polypeptide that will eventually fold to become RNA polymerase? a. no signal peptide b. an amino-terminal signal peptide c. a signal anchor peptide d. a nuclear localization signal

d. a nuclear localization signal

Which one is responsible for the addition of amino acids after translation initiation has begun? a. tRNA b. small ribosomal subunits c. mRNA d. elongation factors

d. elongation factors

In which of the ribosomal sites does the anticodon of a tRNA pair completely with the mRNA codon? a. the P site only b. the A site, the P site, and the E site c. the P site and the E site d. the A site and the P site e. the A site only

d. the A site and the P site