Cell Transport Mechanisms Quiz
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Questions and Answers

What type of transport mechanism does Pump2 represent?

  • Symport
  • Antiport (correct)
  • Facilitated diffusion
  • Passive diffusion

Moving Mg2+ ions out of the vesicle creates a charge difference across the membrane after one minute.

False (B)

What will be the concentration of K+ inside the vesicle after 1 minute?

Higher than 100 µM

In Experiment 1, after 1 minute, the concentration of _______ will be higher outside the vesicle.

<p>Mg2+</p> Signup and view all the answers

Which channel is responsible for the passive movement of K+ ions in Experiment 2?

<p>Pot3 (D)</p> Signup and view all the answers

ATP is required for the function of the potassium leak channel, Pot3.

<p>False (B)</p> Signup and view all the answers

Which ion will be at a higher concentration outside of the vesicle after 1 minute?

<p>Mg2+ (A)</p> Signup and view all the answers

Will the vesicle in Experiment 2 contain K+ after two minutes? Explain your answer.

<p>Yes, due to the electrochemical gradient of K+ that will allow it to enter the vesicle through Pot3.</p> Signup and view all the answers

The membrane is permeable to both K+ and Mg2+.

<p>False (B)</p> Signup and view all the answers

What ions are initially present inside and outside the vesicle?

<p>Mg2+, K+, and ATP, each at 100 µM.</p> Signup and view all the answers

Match the ions with their expected location after the experiments:

<p>Mg2+ = Higher outside in Experiment 1 K+ = Enter through Pot3 in Experiment 2 ATP = Present both inside and outside in Experiment 1</p> Signup and view all the answers

After 1 minute, K+ will flow down its ______ gradient due to the presence of channels.

<p>electrochemical</p> Signup and view all the answers

Match the ions with their respective characteristics in the experiment:

<p>K+ = Flows down its electrochemical gradient Mg2+ = Remains at a constant concentration ATP = Provides energy for Pump2 activity Pump2 = Transports ions across the membrane</p> Signup and view all the answers

What is the main component that your friend wants to express using the lac operon promoter?

<p>GFP (C)</p> Signup and view all the answers

EcoRV is one of the restriction enzymes used to cut the plasmid.

<p>True (A)</p> Signup and view all the answers

What is the role of Pump2 in this experiment?

<p>To move ions against their concentration gradient (C)</p> Signup and view all the answers

K+ will be closest to its equilibrium potential after 1 minute.

<p>True (A)</p> Signup and view all the answers

How many linear pieces will be created when the plasmid is cut with XbaI and EcoRV?

<p>2</p> Signup and view all the answers

Explain why K+ will be at a higher concentration inside the vesicle after one minute.

<p>K+ moves down its electrochemical gradient, and since the membrane is permeable to K+, it will leave the vesicle.</p> Signup and view all the answers

The CAP activator binds to the ______ binding site in the lac operon.

<p>CAP</p> Signup and view all the answers

Match the restriction enzymes with their role:

<p>XbaI = Cuts DNA at specific sites EcoRV = Cuts DNA at specific sites CAP = Activates transcription Lac repressor = Inhibits transcription</p> Signup and view all the answers

The lac repressor binds to the CAP binding site.

<p>False (B)</p> Signup and view all the answers

Can an XbaI-EcoRV fragment from the lac operon be found in a cDNA library? Provide a brief explanation.

<p>No, cDNA libraries contain complementary DNA synthesized from mRNA and do not contain genomic DNA sequences.</p> Signup and view all the answers

What is the purpose of cutting the plasmid with XbaI and EcoRV in this context?

<p>To create sticky ends for ligation (A)</p> Signup and view all the answers

What do cDNA libraries contain?

<p>mRNA derived sequences (A)</p> Signup and view all the answers

The operator sequence that binds to the lac repressor is included in the Xba1-EcoRV fragment.

<p>False (B)</p> Signup and view all the answers

What enzyme is used to join the nicks in the sugar phosphate backbone when creating a new plasmid?

<p>DNA ligase</p> Signup and view all the answers

When glucose is absent, cAMP levels will be ______, leading to CAP binding and transcription of the GFP gene.

<p>high</p> Signup and view all the answers

Match the genes to their associated functions:

<p>LacZ = Encodes β-galactosidase GFP = Fluorescent protein CAP = Regulatory protein lac operon = Regulates lactose metabolism</p> Signup and view all the answers

In the absence of glucose and lactose, will the GFP gene be transcribed?

<p>Yes, it will be transcribed (A)</p> Signup and view all the answers

Write the amino acid sequence encoded by the peptide SCRKML.

<p>Serine-Cysteine-Arginine-Lysine-Methionine-Leucine</p> Signup and view all the answers

The function of the lac operon is to regulate ______ metabolism.

<p>lactose</p> Signup and view all the answers

In which year was the sequence of the human genome first published?

<p>2001 (D)</p> Signup and view all the answers

Humans have approximately 20 million protein-coding genes.

<p>False (B)</p> Signup and view all the answers

What type of molecules would cause a stop in DNA replication when added to the process?

<p>dideoxy nucleotide</p> Signup and view all the answers

The majority of the human genome is made up of ___________ percent coding regions.

<p>1</p> Signup and view all the answers

Match the scientific concepts with their descriptions:

<p>Ribosome = Site of protein synthesis Vacuole = Storage organelle in cells Nucleus = Contains the genetic material Endosome = Involved in material transport</p> Signup and view all the answers

Which enzyme's function was crucial for sequencing the human genome?

<p>DNA polymerase (A)</p> Signup and view all the answers

The human genome contains more exons than introns.

<p>False (B)</p> Signup and view all the answers

The genome of eukaryotic organisms can be primarily found in the _____________.

<p>nucleus</p> Signup and view all the answers

Human cells add cholesterol to their membranes to make them stiffer.

<p>True (A)</p> Signup and view all the answers

What is the primary function of the citric acid cycle?

<p>Creation of NADH molecules (C)</p> Signup and view all the answers

When there is not enough oxygen, pyruvate is converted to __________.

<p>lactic acid</p> Signup and view all the answers

What type of molecules are detergents considered to be in relation to studying membrane proteins?

<p>amphipathic</p> Signup and view all the answers

The citric acid cycle is a linear pathway that occurs within the mitochondria.

<p>False (B)</p> Signup and view all the answers

What is required for cloning vectors to successfully replicate DNA in a cell?

<p>An origin of replication (B)</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Cholesterol = Makes cell membranes stiffer Citric acid cycle = Energy-producing metabolic pathway Lactic acid = Product of anaerobic respiration Detergents = Molecules that can interact with lipids</p> Signup and view all the answers

Detergents are __________ molecules that can interact with charged and non-polar parts of lipids.

<p>amphipathic</p> Signup and view all the answers

Flashcards

Antiporter

A type of transporter protein that moves two different molecules across the membrane in opposite directions. One molecule moves into the cell, while the other moves out of the cell.

Pump2

A pump protein that transports one magnesium ion (Mg2+) out of the cell and two potassium ions (K+) into the cell. The movement requires energy from ATP.

Concentration

The concentration of an ion or molecule inside or outside a cell.

Concentration gradient

A difference in the concentration of a substance between two areas. This difference creates a force driving the substance to move from the area of high concentration to the area of low concentration.

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Passive Transport

The movement of ions or molecules across a cell membrane without the input of energy.

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Electrochemical gradient

The combined effects of the concentration gradient and the electrical potential across a membrane.

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Potassium leak channel (Pot3)

A protein channel that allows potassium ions (K+) to move across the cell membrane.

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Artificial membrane vesicles

Small compartments that mimic the environment inside a cell. They are used to study the function of individual proteins in isolation.

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Promoter

A sequence of DNA that controls the expression of a gene by binding to specific proteins, like repressors or activators.

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Activator

A type of protein that binds to a promoter and increases the rate of gene expression.

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Repressor

A type of protein that binds to a promoter and prevents the expression of a gene.

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Operator

A specific DNA sequence that is recognized by a repressor protein.

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CAP binding site

A specific DNA sequence that is recognized by an activator protein.

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cDNA library

A collection of DNA fragments that represent all of the mRNA molecules being transcribed in a cell.

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Restriction enzyme digestion

The process of cutting or removing DNA at specific sequences.

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Linear fragment

A linear piece of DNA that has been cut by a restriction enzyme.

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Leak Channel

A transmembrane protein that allows specific ions to move passively down their concentration gradient.

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Equilibrium Potential

The point at which the electrical and chemical gradients for an ion are balanced, resulting in no net movement of the ion across the membrane.

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Vesicle Experiment

A type of experiment that uses artificial membrane vesicles to study the transport of ions across the membrane.

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Ion Concentration Outside Vesicle

The relative concentration of an ion outside of a vesicle after a specific time period.

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Ion Closest to Equilibrium Potential

The ion that is closest to its equilibrium potential after a specific time period, indicating its movement towards a balanced state.

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What is the composition of cDNA libraries?

cDNA libraries are created from mRNA, which excludes sequences like regulatory elements from genes. This means they lack sections that are not transcribed, like the LacZ gene's regulatory region.

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Which enzyme joins DNA fragments?

DNA ligase is the enzyme responsible for sealing nicks in the sugar-phosphate backbone of DNA, creating a continuous, unbroken strand.

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Will GFP be expressed in the absence of glucose and lactose?

GFP will be produced because the absence of glucose leads to high cAMP levels, which activate CAP. CAP binds to its site and recruits RNA polymerase, initiating transcription of the GFP gene. The lack of the LacZ operator means the lac repressor has no effect.

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What is the DNA sequence encoding the peptide SCRKML?

The amino acid sequence SCRKML is encoded by the DNA sequence 5'-AGCTGTAGCAAAATGG-3'.

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What is the RNA sequence for the SCRKML peptide?

The RNA sequence for the SCRKML peptide is 5'-AGCU GUA GCA AAA UGG-3'.

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What is the genetic code?

The genetic code is a set of rules that translate a sequence of three DNA bases (a codon) into a specific amino acid. This process is necessary for protein synthesis.

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What is a promoter?

A promoter is a DNA sequence that initiates transcription. It acts as the starting point for RNA polymerase to bind and begin making mRNA.

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What is an operator?

The operator is a DNA sequence that functions as a regulatory element for gene expression. The lac repressor binds to the operator, blocking RNA polymerase from transcribing the gene.

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What role does cholesterol play in cell membranes?

Cholesterol is a lipid that makes cell membranes more rigid and less permeable to water. It assists in maintaining the structural integrity of the membrane.

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What is the citric acid cycle?

The citric acid cycle, also known as the Krebs cycle, is a series of chemical reactions that occur in the mitochondria of cells. It is a cyclic pathway that generates ATP (energy currency) and NADH (an electron carrier molecule) for cellular processes.

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What happens to pyruvate during anaerobic conditions?

When oxygen is scarce, pyruvate (a product of glycolysis) is converted to lactic acid instead of entering the mitochondria. This process is called fermentation.

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How are detergents useful in membrane protein research?

Detergents are amphipathic molecules, possessing both hydrophilic (water-loving) and hydrophobic (water-fearing) properties. They are used in membrane protein research because they disrupt cell membranes, making it easier to isolate and study proteins.

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What is the role of an origin of replication in cloning vectors?

Cloning vectors are essential tools in molecular biology. It is a DNA molecule that serves as a carrier for foreign DNA fragments into a host cell. They typically contain an origin of replication (ori) that allows them to replicate independently inside the host cell, ensuring the replication of the inserted gene.

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When was the human genome first published?

The year 2001 marks the date when the complete sequence of the human genome was first published. This achievement, a culmination of years of research, was a landmark in the field of genetics and opened doors to understanding the intricate blueprint of our species.

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What is the role of dideoxy-nucleotides in DNA sequencing?

DNA polymerase plays a crucial role in DNA replication. Dideoxynucleotides are modified nucleotides that lack a hydroxyl group at the 3' position. This modification makes them unable to form a phosphodiester bond with the next nucleotide, effectively halting DNA synthesis.

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How many protein-coding genes does the human genome have?

The human genome contains approximately 20,000 protein-coding genes, which dictate the production of proteins essential for various biological functions.

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What percentage of the human genome codes for proteins?

Only about 1% of the human genome directly encodes for proteins. The remaining 99% includes non-coding regions, regulatory elements, and other components that contribute to the complex regulation of gene expression.

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Where can the human genome be found in a eukaryotic cell?

In eukaryotic cells, the nucleus houses the cell’s genetic material, or genome, organized into chromosomes. DNA replication and transcription occur within the nucleus, ensuring the integrity and proper functioning of the genetic information.

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What does 'sequencing the genome' mean?

The process of sequencing refers to determining the order of nucleotides (adenine, guanine, cytosine, and thymine) in a DNA molecule. This information provides a detailed blueprint of the genetic instructions within a genome.

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What is the role of DNA polymerase in genome sequencing?

Replication is the process by which DNA is copied to create two identical DNA molecules. DNA polymerase is an enzyme that plays a crucial role in this process, adding nucleotides to the growing DNA strand.

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What is a protein?

A protein is a chain of amino acids linked together by peptide bonds. Each amino acid has a unique chemical structure, contributing to the overall shape and function of the protein.

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Study Notes

Exam 2 – Biology 210/212 – November 4, 2024

  • Instructions:
    • Two points for correctly filling in exam information.
    • 100 points total.
    • 50 minutes to complete exam.
    • Answer easier questions first, and return to more difficult ones.

Question 1: Glycolysis (Step 1)

  • Phosphorylation of Glucose:
    • Hexokinase phosphorylates glucose -> glucose-6-phosphate.
    • ∆G° for this reaction = +12.8 kJ/mol (unfavorable).
  • Coupling with ATP Hydrolysis:
    • ATP hydrolysis (ATP → ADP + Pi) has ∆G° = -30.6 kJ/mol (favorable).
    • The coupling of the two reactions makes the overall reaction favorable (∆G° = -17.8 kJ/mol).

Question 2: Drosophila Hexokinase Gene

  • Hexokinase Gene:
    • The gene sequence in Drosophila is known to show the locations and sequences.
  • Primers for Amplification:
    • Specific primers are needed. The correct primers sequences are:
      • 5'-GTATCCGGACATGAT-3'
      • 5'-AGTCCATCTACGCAT-3'
  • Taq Polymerase Extension:
    • Next seven bases for the top strand primer:
      • 5'-CTTTCAT-3'

Question 3: Antiport Pump2

  • Pump2 Function:
    • Pump2 moves Mg2+ out of, and K+ into the vesicle.
  • Experiment 1:
    • Initial concentrations of Mg2+, K+, and ATP are 100 µM inside and outside the vesicle.
    • K+ will be at higher concentration inside the vesicle.
    • Mg2+ will be at higher concentration outside the vesicle.
    • No charge difference will be created.
  • Experiment 2:
    • Potassium leak channel (Pot3) is present and Mg2+, K+, and ATP are at 100 µM outside, and 100µM ATP inside.
    • Vesicle will contain K+.
  • Experiment 3:
    • Pump2 and Pot3 proteins are both present.
    • Mg2+ will be at higher concentration outside the vesicle.
  • Equilibrium Potential:
    • K+ is closest to its equilibrium potential.
    • It flows down electrochemical gradient, leading to more K+ inside

Question 4: GFP Expression from Lac Operon

  • Creating the Plasmid:
    • XbaI and EcoRV sites are used to cut the DNA fragment for the lac operon promoter before transcription.
    • The fragment is added to a plasmid cut using the same enzymes.
  • DNA Library and Enzyme:
    • A cDNA library is made from mRNA but does not include non-transcribed regions.
    • DNA ligase is needed to rejoin the DNA fragments in the plasmid.
  • Lac Operon and Glucose:
    • No lactose is present; cAMP levels will be high, CAP will bind, and GFP will be transcribed.
  • RNA Sequence:
    • 5'-GAGCTGCCGTAAGATGCTTAG-3'
      • 3'-CTCGACGGCATTCTACGAATC-5'

Question 5: Enzyme Glp2 and Fat Cells

  • Glp2 Function:
    • Enzyme that affects fat cell function
  • Glp2 and GFP Expression:
    • Glp2 regulatory region is placed upstream of the GFP gene.
    • GFP expression is seen in fat cells, not blood cells (as expected) in experiment 1.
  • DBP1 and DBP2 - Activator/Repressor:
    • DBP1 (binds to site A) acts as a repressor
    • DBP2 (binds to site B) acts as an activator

Question 6: Amino Acid Preferences

  • Amino Acid for α-helix:
    • Alanine and valine are favored for use in an alpha-helix that spans a membrane bilayer.

Question 7: Fill-in-the-blanks

  • Fill-in-the-blank: These contain information on various scientific terms, dates, numbers, etc.

Question 8: True/False Statements

  • True/False Statements: These consist of various statements that students need to evaluate as true or false based on biological principles.

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F24 Biology 210/212 Exam 2 Key PDF

Description

Test your understanding of the transport mechanisms in cellular biology. This quiz covers ion concentrations, channel functions, and vesicle integrity based on different experimental setups. Explore the concepts of active and passive transport as well as the role of ATP.

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