Week 6

Match the organelle with its description. Responses may be used multiple times or not at all. B. Golgi apparatus 1. involved in the sorting of lipids and proteins 2. composed of two membranes 3. composed of multiple cisternae 4. involved in the synthesis of lipids and proteins 5. connected to the endoplasmic reticulum

1. involved in the sorting of lipids and proteins 3. composed of multiple cisternae

Imagine you are following a particular tRNA, called tRNAQ, through the process of translation in a eukaryote. In what order does tRNAQ go through the steps listed below? (Note that some steps may be used more than once.) 1. The polypeptide is transferred to tRNAQ. 2. tRNAQ binds the A site of the ribosome. 3. tRNAQ binds the P site of the ribosome. 4. The ribosome shifts, with tRNAQ still bound. 5. tRNAQ binds the E site of the ribosome.

2, 1, 4, 3, 4, 5

Match the organelle with its description. Responses may be used multiple times or not at all. C. nuclear envelope 1. involved in the sorting of lipids and proteins 2. composed of two membranes 3. composed of multiple cisternae 4. involved in the synthesis of lipids and proteins 5. connected to the endoplasmic reticulum

2. composed of two membranes 5. connected to the endoplasmic reticulum

Match the organelle with its description. Responses may be used multiple times or not at all. A. endoplasmic reticulum 1. involved in the sorting of lipids and proteins 2. composed of two membranes 3. composed of multiple cisternae 4. involved in the synthesis of lipids and proteins 5. connected to the endoplasmic reticulum

4. involved in the synthesis of lipids and proteins

Which of the following sequences of events correctly describes the progress of a protein that will be secreted from the cell? 1. SRP binds to the growing polypeptide chain and to the ribosome. 2. Translation resumes. 3. SRP binds to its receptor. 4. The signal sequence is cleaved. 5. Protein synthesis begins in the cytosol. 6. Translation pauses.

5 → 1 → 6 → 3 → 2 → 4

How is the amino acid held on the charged tRNA? A., covalent bond B., hydrogen bonds C., It can be a combination of all bond types.

A. covalent bond

The ribosome ______ subunit has _______ binding sites for tRNA molecules. A., large; two B., small; two C., large; three D., small; three E., large; four

C., large; three E(xit) P(ass) A(ccess)

Enzymatic catalysis of the peptide bond between the growing polypeptide and the next incoming amino acid takes place in which binding site? Choice A., A site Choice B., P site Choice C., E site Choice D., combined A and P sites

Choice A., A site

Consider a protein that is targeted to be an integral membrane protein on the surface of a cell. It has a specific functional domain (domain X) facing the external environment of the cell. How will this protein be oriented in the E.R.? Choice A., It will be embedded in the E.R. membrane with domain X facing the lumen of the E.R. Choice B., It will be embedded in the E.R. membrane with domain X facing the cytoplasm of the cell. Choice C., It will be outside the E.R. as a peripheral membrane protein. Choice D., It will be completely within the E.R. lumen, not embedded in the membrane.

Choice A., It will be embedded in the E.R. membrane with domain X facing the lumen of the E.R.

Consider a protein that is targeted to be excreted to the outside of the plasma membrane. Where would this protein be located in the endoplasmic reticulum? Choice A., in the lumen (inside) of the E.R. Choice B., embedded as an integral membrane protein in the E.R. membrane Choice C., outside the E.R. as a peripheral membrane protein

Choice A., in the lumen (inside) of the E.R.

Consider a protein that is targeted to be excreted to the outside of the plasma membrane. Where would this protein be located in the Golgi? Choice A., in the lumen (inside) of the Golgi Choice B., embedded as an integral membrane protein in the Golgi membrane Choice C., outside the Golgi as a peripheral membrane protein

Choice A., in the lumen (inside) of the Golgi

Consider a protein that is targeted to be an integral membrane protein on the surface of a cell. It has a specific functional domain (domain Y) facing the cytoplasm of the cell. How will this protein be oriented in the Golgi? Choice A., It will be embedded in the Golgi membrane with domain Y facing the lumen of the E.R. Choice B., It will be embedded in the Golgi membrane with domain Y facing the cytoplasm of the cell. Choice C., It will be outside the Golgi as a peripheral membrane protein. Choice D., It will be completely within the Golgi lumen, not embedded in the membrane.

Choice B., It will be embedded in the Golgi membrane with domain Y facing the cytoplasm of the cell.

Which of the following is not considered to be a part of the endomembrane system? Choice A., endoplasmic reticulum Choice B., mitochondria Choice C., Golgi Choice D., lysosome Choice E., plasma membrane

Choice B., mitochondria

How many aminoacyl-tRNA synthetase enzymes must be present in cells to properly synthesize proteins? Choice A., 3, one for each base in a codon Choice B., 4, one for each base in the mRNA Choice C., 20, one for each amino acid Choice D., 64, one for each possible codon

Choice C., 20, one for each amino acid

Many cell functions involve communication between cells via molecular signals that must be sent from one cell to be received by a target cell. Suppose the signal to be sent is a small protein. Where would you expect to find the protein in the Golgi? Choice A., It would be an integral membrane protein with its functional domain on the lumen side of the membrane. Choice B., It would be an integral membrane protein with its functional domain on the cytoplasmic side of the membrane. Choice C., It would be in the lumen of the Golgi. Choice D., It would be on the exterior of the Golgi.

Choice C., It would be in the lumen of the Golgi.

Most elements of the endomembrane system are connected by: Choice A., continuous membranes. Choice B., cytoskeleton. Choice C., vesicular trafficking.

Choice C., vesicular trafficking.

Which of the following is the actual event that translates the language of nucleic acids (the sequence of bases, A, T (U), C, and G) to the language of proteins (determining which amino acid will be added to the polypeptide)? A., binding of charged tRNA to the ribosome A site B., catalysis of a new peptide bond from the growing polypeptide to the next amino acid C., release of the finished polypeptide at the stop codon D., attachment of the appropriate amino acid to the tRNA by aminoacyl tRNA synthetase E., establishing the correct reading frame by the ribosome

D., attachment of the appropriate amino acid to the tRNA by aminoacyl tRNA synthetase

Most proteins retain metabolic activity when denatured. False True

False

The start codon is translated True False

False

Hemoglobin would be synthesized by a ribosome on the rough ER: a) True b) False

False Hemoglobin is in the cytosol, therefore is synthesized in the cytosol

Individual alpha-helices found in hemoglobin are stabilized by ionic bonds: True False

False they are stabilized by hydrogen bonds

What kind of interaction holds beta strands together?

Hydrogen bonds

What is the bond that links amino acids together?

Peptide bond

SRP (signal-recognition particle)

SRP binds to the signal peptide for proteins that are meant to be translated on the ER *all proteins start developing in the cytosol, the SRP binds and stops protein development and sends it to the ER

The start codon is translated True False

True

How do vesicles know where to go?

V-snares on the vesicles match to their corresponding T-snares

determine which of the following is an anticodon found on a tRNA that carries a tyrosine (Tyr or Y) amino acid? Tyr = UAU, UAC (mRNA) a) 3'-AUG-5' b) 3'-UAC-5' c) 5'-AUG-3' d) 5'-UAC-3'

a) 3'AUG-5' *3'-AUA-5' also works

Which of the following occurs in the E site of the ribosome during translation? a) An uncharged tRNA is ejected from this site as the ribosome slides to the next codon. b) None of the other answer options is correct. c) An incoming charged tRNA binds to this site. d) The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon.

a) An uncharged tRNA is ejected from this site as the ribosome slides to the next codon.

which molecules are associated with which end of the mRNA? a) NH2 - 5' b) NH2 - 3' c) COOH - 5' d) COOH - 3'

a) NH2 - 5' d) COOH - 3'

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 that was carrying the polypeptide will be ejected from the ribosome. b) The tRNA that is shown in the A site in the figure above will be ejected from the ribosome. c) The sites of the ribosomes will be relabeled (from left to right) P, A, E. d) A new tRNA will bind to the ribosome. e) The tRNA carrying the polypeptide will be in the P site.

a) The tRNA that was carrying the polypeptide will be ejected from the ribosome. d) A new tRNA will bind to the ribosome. e) The tRNA carrying the polypeptide will be in the P site.

which secondary structure is more stable? a) alpha helix b) beta pleated sheets

a) alpha helix

insulin is a secreted protein. what would you expect to see in cells treated with a compound that prevents the recognition of signal sequence by SRP?

a) an accumulation of insulin in the cytosol (probably unfinished too)

Which of the following are processed in the Golgi apparatus? (Select all that apply.) a) proteins that will be broken down by lysosomes b) integral membrane proteins of the plasma membrane c) proteins that are secreted from the cell d) enzymes required for the synthesis of phospholipids e) mRNA molecules for the removal of introns

a) proteins that will be broken down by lysosomes b) integral membrane proteins of the plasma membrane c) proteins that are secreted from the cell

mutation where base pair changes but no change is made in amino acid sequence a) silent mutation b) missense mutation c) nonsense mutation d) frameshift mutation

a) silent mutation

In a protein-coding region, a mutation that replaces a single nucleotide for another always changes the resulting amino acid. a) True b) False

b) False

Protein families contain proteins with identical primary, secondary, and tertiary structures. a) True b) False

b) False

insulin is a secreted protein. what would you expect to see in cells that have been treated with a drug that prevents transport vesicles from forming? a) an accumulation of insulin in the cytosol b) an accumulation of insulin in the ER c) an accumulation of insulin in the golgi d) an accumulation of insulin in the plasma membrane

b) an accumulation of insulin in the ER

Insulin is a secreted protein. Based on this information, where do you expect insulin to be synthesized? a) in the cytosol b) at the rough ER c) depends on the ribosome d) no way to know

b) at the rough ER

Which of the following accurately describes the path traveled by a new protein as it is synthesized and released from the cell? a) cytosol → Golgi → ER → vesicle → plasma membrane → external environment b) cytosol → ER → Golgi → vesicle → plasma membrane → external environment c) plasma membrane → ER → vesicle → Golgi → cytosol → external environment d) nucleus → ER → Golgi → vesicle → plasma membrane → external environment e) nuclear envelope → ER → vesicle → Golgi → plasma membrane → external environment

b) cytosol → ER → Golgi → vesicle → plasma membrane → external environment

To initiate translation of a eukaryotic mRNA into protein, a ribosome must first locate and bind to an mRNA transcript. Where in the cell does this initial ribosome-mRNA binding take place? a) in the nucleus b) in the cytosol c) in the rough ER d) in the smooth ER e) it depends on the protein being translated

b) in the cytosol

mutation where base pair changes and a single amino acid is changed a) silent mutation b) missense mutation c) nonsense mutation d) frameshift mutation

b) missense mutation

Ribosomes in prokaryotes and eukaryotes are: a) similar in structure and translate using different genetic codes. b) similar in structure and translate using the same genetic code. c) identical in structure and translate using the same genetic code. d) identical in structure but translate using different genetic codes.

b) similar in structure and translate using the same genetic code.

Which of the following brings amino acids to the ribosome for use in translation? a) mRNA b) tRNA c) rRNA

b) tRNA

The fully folded structure of a functional protein composed of a single polypeptide chain is referred to as the _____ structure. a) primary b) tertiary c) secondary d) quaternary

b) tertiary

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) endoplasmic reticulum b) the Golgi apparatus c) nucleus d) plasmids e) plasma membrane

b) the Golgi apparatus

Binding sites for tRNA are located in: a) both ribosomal subunits. b) the large ribosomal subunit. c) the small ribosomal subunit. d) neither ribosomal subunit.

b) the large ribosomal subunit.

which of the following statements is true about protein synthesis in prokaryotes? a) extensive RNA processing is required before the prokaryotic transcripts can be translated b) translation can begin while transcription is still in progress c) translation does not require ribosomes d) more than one of the above is true

b) translation can begin while transcription is still in progress

After translation has been initiated, for how long does elongation go on? a) until the ribosome reaches an AUG codon b) until the ribosome reaches a UAA, UAG, or UGA codon c) until the ribosome reaches the end of the mRNA d) until the ribosome reaches the poly(A)tail of the mRNA e) until the cell runs out of tRNAs

b) until the ribosome reaches a UAA, UAG, or UGA codon

Two major types of protein secondary structures are referred to as: a) amino and carboxyl. b) α helix and β sheet. c) residual and permanent. d) ionic and covalent. e) elementary and primary.

b) α helix and β sheet.

A double-stranded DNA molecule is being transcribed, only part of which is shown below. If the molecule is translated 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 of the following 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' *translated from left to right = transcribed from left to right = transcription starts from 3' to 5'

Assuming A-U and G-C pairing between the anticodon and the codon, what anticodon in tRNAMet would pair with the codon 5'-AUG-3'? a) 5'-AUG-3' b) 5'-GUA-3' c) 5'-CAU-3' d) 5'-UAC-3' e) 5'-ATG-3'

c) 5'-CAU-3'

If a mutation rendered the signal recognition particle receptor nonfunctional such that it is no longer able to dissociate from the SRP, what would be the most obvious effect on the cell? a) All proteins normally secreted by the cell would remain in the cytosol. b) Translation of most proteins would be incomplete. c) All proteins normally secreted by the cell would remain partially formed and attached to the endoplasmic reticulum. d) Proteins destined for the nucleus would remain in the cytosol. e) No proteins would arrive at their proper destinations within the cell.

c) All proteins normally secreted by the cell would remain partially formed and attached to the endoplasmic reticulum.

Which of the following occurs in the A site of the ribosome during translation? a) An uncharged tRNA is ejected from this site as the ribosome slides to the next codon. b) None of the other answer options is correct. c) An incoming charged tRNA binds to this site. d) The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon.

c) An incoming charged tRNA binds to this site.

The unfolding of a protein by heat or chemical treatment is referred to as: a) uncoupling. b) hydrolysis. c) denaturation. d) disaggregation. e) depolymerization.

c) denaturation.

A region of a polypeptide that folds in a particular way, relatively independently of the rest of the molecule, is a folding: a) region. b) segment. c) domain. d) exon. e) lariat.

c) domain.

The process of a vesicle fusing with the plasma membrane and depositing its contents into the extracellular space is referred to as: a) budding. b) bridging. c) exocytosis. d) endocytosis. e) active transport.

c) exocytosis.

When a charged tRNA is about to bind to the vacant A site of a ribosome, where is the growing polypeptide? a) The polypeptide is equally likely to be in any of the three sites. b) in the E site c) in the P site d) in the A site

c) in the P site

mutation where base pair changes and premature stop codon is made a) silent mutation b) missense mutation c) nonsense mutation d) frameshift mutation

c) nonsense mutation

Where will translation of the mRNA start? a) At the 5' end of the mRNA b) adjacent to the 5' cap on the mRNA c) the AUG nearest the 5' cap on the mRNA d) None of the above

c) the AUG nearest the 5' cap on the mRNA

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

c) the nucleus.

The interactions between amino acids are major factors in determining the shape of a protein. These interactions can be affected by the environment surrounding a protein. Which of the following would have an effect on the shape of a protein? a) the temperature of the environment b) the pH of the environment c)All of the other answer options are correct. d) whether the other molecules in the environment are predominantly hydrophilic or hydrophobic e) the concentrations of ions present in the environment

c)All of the other answer options are correct.

Which of the following occurs in the A site of the ribosome during translation? a) None of the other answer options is correct. b) An uncharged tRNA is ejected from this site as the ribosome slides to the next codon. c) The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon. d) An incoming charged tRNA binds to this site.

d) An incoming charged tRNA binds to this site.

Which of the following occurs in the P site of the ribosome during translation? a) An uncharged tRNA is ejected from this site as the ribosome slides to the next codon. b) None of the other answer options is correct. c) An incoming charged tRNA binds to this site. d) The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon.

d) The tRNA carrying the growing polypeptide moves to this site as the ribosome slides to the next codon.

Where are ribosomes found inside a cell? a) in the cytosol b) attached to the Golgi apparatus c) attached to the rough endoplasmic reticulum d) both in the cytosol and attached to the rough endoplasmic reticulum

d) both in the cytosol and attached to the rough endoplasmic reticulum *proteins synthesized in the cytosol are destined for the cytosol, mitochondria, chloroplast, or nucleus *proteins synthesized in the rough ER are destined for the lumen, used as transmembrane proteins, or secreted out of the cell (passes through golgi apparatus)

Which of the following actions would affect the secondary, but not primary, structure of a protein? a) break the ionic bonds between amino acids b) disrupt the interactions between two different polypeptide chains c) change the sequence of amino acids d) break the hydrogen bonds between amino acids

d) break the hydrogen bonds between amino acids

Proteins that prevent inappropriate folding of newly synthesized proteins are called: a) synthetases. b) enzymes. c) ribosomes. d) chaperones. e) polymerases.

d) chaperones.

Insulin is a secreted protein. This means that insulin is ________ the cell through the process of ________. a) entering; endocytosis b) exiting; endocytosis c) entering; exocytosis d) exiting; exocytosis

d) exiting; exocytosis

mutation where open reading frame is shifted a) silent mutation b) missense mutation c) nonsense mutation d) frameshift mutation

d) frameshift mutation *usually due to single or double base pair insertion/deletion

Which of the following organelles could be considered recycling centers of eukaryotic cells? a) Golgi apparatus b) the nucleus c) mitochondria d) lysosomes e) smooth endoplasmic reticulum

d) lysosomes

In a population of organisms, beneficial and harmful random mutations are retained or eliminated through the process of: a) conservation. b) translation. c) expression. d) selection. e) folding.

d) selection.

Which one of the following can contribute to a protein's tertiary structure? a) ionic bonding b) hydrogen bonding c) van der Waal's forces d) covalent bonding e) All of the other answer options are correct.

e) All of the other answer options are correct.

Secondary structure is characterized by which one of the following types of interactions? a) ionic bonding between an acidic R group and a basic R group b) hydrogen bonding between R groups of amino acids c) a covalent bond between two cysteines d) the covalent bond between an amino nitrogen and a carboxyl carbon e) hydrogen bonding within the peptide backbone

e) hydrogen bonding within the peptide backbone