Exam 3 Missed Questions

Question 1

Three phospholipids, X, Y, and Z are distributed in the plasma membrane as indicated in the figure below. For which of these phospholipids does a flippase probably exist?

• X only
• Z only
• X and Y
• Y and Z

Answer 1

X and Y

Question 2

Each of the following is typical characteristics of a single pass integral membrane protein transmembrane segment except…

• alpha helical structure
• 20-30 amino acids long
• composed primarily of hydrophobic amino acids
• amphipathic
• all are characteristics of a typical transmembrane segment

Answer 2

Amphipathic

Question 3

Which of the following statements best describes some aspect of the function of a protein that co-transports glucose and sodium ions into the intestinal cells of an animal?

• Sodium and glucose compete for the same binding site in the cotransporter
• A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose
• Glucose entering the cell down its concentration gradient provides energy for uptake of sodium ions against the electrochemical gradient
• Sodium ions can move down their electrochemical gradient through the cotransporter whether or not glucose is present outside the cell

Answer 3

A substance that blocks sodium ions from binding to the cotransport protein will also block the transport of glucose

Question 4

Which of the following best describes the behavior of a gated channel?

• It stays open continuously when stimulated
• It opens more frequently in response to a given stimulus
• It opens more widely as the stimulus becomes stronger
• It requires a stimulus to change from closed to open

Answer 4

It opens more frequently in response to a given stimulus

Question 5

Energy released from the electron transport chain is used to pump H+ ions into which location in eukaryotic cells?

• mitochondrial intermembrane space
• cytoplasm adjacent to the mitochondrial outer membrane
• mitochondrial inner membrane
• mitochondrial matrix

Answer 5

Mitochondrial intermembrane space

Question 6

Which of the following metabolic processes normally occurs in most cells regardless of oxygen (O2) availability?

• citric acid cycle
• glycolysis
• lactate fermentation
• oxidative phosphorylation

Answer 6

glycolysis

Question 7

Which of the following statements describes a primary function of both alcohol fermentation and lactic acid fermentation?

• reduction of NAD+ to NADH
• reduction of FAD to FADH2
• oxidation of NADH to NAD+
• hydrolysis of ATP to ADP + Pi

Answer 7

oxidation of NADH to NAD+

Question 8

The enzyme phosphofructokinase (PFK) catalyzes a key step in glycolysis and is inhibited by high levels of which of the following molecules?

• glucose and NAD+
• AMP and ATP
• ATP and citrate
• citrate and CO2

Answer 8

ATP and citrate

Question 9

In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins?

• the nucleus
• on the rough ER
• in the cytosol
• in the lumen of the ER

Answer 9

in the cytosol

Question 10

N-linked oligosaccharides on secreted glycoproteins are attached to…

• nitrogen atoms in the polypeptide backbone
• the serine or threonine in the sequence Asn-X-Ser/Thr
• the N-terminus of the protein
• the asparagine in the sequence Asn-X-Ser/Thr

Answer 10

the asparagine in the sequence Asn-X-Ser/Thr