Cell Biology Exam 2

Which of the following processes is a form of primary active transport?

Sodium-potassium pump orientation

Your doctor has scheduled to have a mole removed from your arm as he is concerned it might become cancerous. You arrive to get the minor surgery, but there is a new intern helping. This intern accidentally swaps the Lidocaine for snake venom (dendrotoxin). Instantly you feel a persistent pain coming from the site of injection. Why is the pain not subsiding?

The snake venom is blocking the K+ voltage-gated ion channels from pumping out K+ ions from the neuron.

What is the net gain of ATP in glycolysis?

2

What is oxygen’s role in the electron transport chain?

Oxygen acts as a final electron acceptor, combining with electrons and protons to form water.

Insulin is a hormone that plays a key role in the regulation of glycolysis in vertebrates. Which of the following best describes how insulin works within the body in response to blood glucose levels?

When blood glucose levels are high, insulin is released to signal liver cells to store glucose as glycogen.

The mechanism of insulin regulation is directly mediated by:

Phosphorylation or dephosphorylation of enzymes

This kind of transport is exemplified by glucose, as it binds to the GLUT1 transporter in the intestine and the choline transporter within the acetylcholine synapse. These transporters have kinetics similar to that of an enzyme, and the process does not require ATP.

Facilitated Transport

When we exercise (perform work), we catabolize glucose and lose mass. Why does this happen?

Our cells convert glucose into CO2 and water, which are eliminated from our bodies when we exercise through our breath and sweat.

Which statements regarding mitochondria is false?

Mitochondria morphology and numbers are the same across all cell types.

You are performing an experiment that observes metabolic rate in rat liver. You observe high levels of ATP. What might you hypothesize about the rate of glycolysis in these cells?

Due to a negative feedback loop, glycolysis will be slowed.

The O confirmation of ATP synthase’s active site performs which function?

Releases ATP from the active site

Cytoplasmic generated NADH Cannot be processed by the cell during aerobic respiration. How does the cell regenerate the NAD in the cytoplasm during aerobic respiration if only matrix NADH can be processed by the electron transport chain?

The cell uses reactions that process metabolites associated with glycolysis and Krebs cycle to process NADH into NAD in the cytoplasm, these metabolites are then actively transported through antiporters into the mitochondria where these reactions are reversed regenerating either NADH or FADH2

You are doing interval training (short periods of high intensity exercise followed by a short low intensity exercise) at the gym. You are in your last low circuit, and are walking comfortably around the track. You reach the last interval of the day, and decide to sprint until you are exhausted. As you are running, you start to feel a little light headed and your calf muscles exhausted. You can barely think because you are trying to breathe but your chest is aching and you are not getting enough air. Contrast what is happening in the calf muscle cells during low intensity walk versus the end of your high intensity sprint.

During the walk, Pyruvate enters the TCA, and oxygen binds to complex IV. At the end of the high intensity sprint, oxygen deprivation of the muscles begin, and pyruvate remains in the cytoplasm. It is converted to lactic acid to maintain glycolysis, but the ETC is shut off as there are not electron acceptors present.

You have started working at a health company, and they have developed a kombucha-style fermented sports drink (KomBoom) that has about 10% ethanol and probiotics that promote gut health. Marketing would like to promote its use during strenuous anaerobic exercise. They have asked you to design an experiment that looks at it impact on basic metabolism. Your team brainstorms several ideas. As the lead investigator, you evaluate the idea and determine a set of experiments you would like to run. Below questions that your team generated.

1. Can KomBoom impact the rate of glycolysis?

2. What is the impact of KomBoom on lactic acid production?

3. What is the rate of ethanol metabolism during an anaerobic bout of exercise?
   What is the most likely theory behind these sets of questions?

They are focusing on the impact that ethanol and lactate metabolism will have on NAD/NADH levels.

Following your initial tests of KomBoom, you find that the rate of glycolysis is decreased and the subsequent production of Lactic Acid is down in KaBoom drinkers following anaerobic exercise. You have several concerns regarding whether KaBoom is beneficial for the athlete's use at this point. Which of the following is not an impact of reduced Lactic Acid Level?

The acidification of the muscle would lead to more soreness directly associated with Lactic Acid build up over the subsequent 48 hours reducing the likelihood of the athlete returning to the gym.

You perform a little more research on the ingredients of Kaboom, and realize that it is abnormally high in antioxidants. Therefore, to soften the blow of your results for the marketing, your team suggests KomBoom should not be marketed as a sports drink, but rather potentially as an anti-aging drink. Why do you, as a metabolism specialist, suggest this?

Anti-oxidants are important for reducing the effects of reactive oxygen species that are formed from inefficiencies in the electron transport chain that develop as a person ages.

A new bacterial pathogen has been discovered. It lives within the cytoplasm of the cell, and releases of a toxin that alters the permeability of the mitochondrial membranes of the host cell leading to a release of matrix proteins into the cytoplasm. What is the most probable impact on the host cell?

The matrix proteins will induce mitochondrial mediated cell death releasing the bacteria to infect other cells.

Osmosis is the movement of ______ from a region of ______ concentration to a region of ______ solute concentration.

Water; low; high

Which of the following is not a function of cholesterol?

Interacts with the cytoskeleton to initiate Integral protein clustering.

Patients with Cystic Fibrosis use a saline inhaler which functions to increase what? *hint this decreases the viscosity of mucus.

Osmosis

The primary cause on cystic fibrosis is the deletion of a phenylalanine at amino acid location 508 within the CFTR protein. This protein is important because it is a chloride ion channel. The result is that Cl- ions are trapped inside the cell.

Researcher have identified that in addition to respiratory tract cells, the CFTR protein is also expressed in very specific subset of neurons. You decide to look at how this mutation alters the action potentials of these neurons. How would you hypothesize the neurons ability to form an action potential might be affected.

The mutants would have a neural membrane potential more negative than wild type making it harder to fire an action potential.

The structure found at number 7 (the Node of Ranvier) in the picture is defined by very specific integral membrane proteins that localize sodium channels between areas of myelin sheath coverage. It is important for what process that speeds up propagation in myelinated neurons?

Saltatory Conduction

The Axon Initial Segment (AIS) is located at #4. This location is critical for integrating the signals from the receiving end of the neuron (the input) and passing them on to the axon terminal (the output). One might hypothesize the presence of this cellular structure at the AlS maintaining membrane composition asymmetry?

A Protein Picket Fence

You place a stimulating electrode at #1. This delivers a voltage shock to the neuron. Place these events below in the most likely order with regard to the action potential.

1. Voltage gated Potassium channels open hyperpolarizing the cell

2. The Stimulus is received (Voltage shock from the stimulating electrode)

3. Voltage Gated Sodium channels open, depolarizing the cell.

4. The Sodium/Potassium pump and leak channels set the membrane potential

5. The Sodium influx causes an electrochemical gradient and propagation.

4-2-3-5-1-4

An acetylcholine neuron has been stimulated and the first synaptic vesicle fuses with the plasma membrane. Acetylcholine is most likely to move to and bind receptors on the postsynaptic cell via the following process.

The high concentration of the secreted acetylcholine causes the protein to move away from the presynaptic cells in any unimpeded direction.

Loss of myelin in peripheral demyelinating disorder can lead to neuronal dysfunction and death. Which of the following might you hypothesize due to a loss of myelin on the propagation of the action potential down the neuron?

The rate of axon potential propagation down the neuron will slow.

The process of acetylcholine signaling from one cell to another is initiated by a voltage gated ______ Channel that causes fusion of the synaptic vesicles and is terminated by a collagen bound _______ which catabolizes acetylcholine into acetate and choline.

Ca2+, Acetylcholine Esterase

In the image, the #1 arrow is pointing at:

The outer leaflet

If you wanted to measure the flow of ions through the ion channel in the membrane at arrow #4 membrane, what technique would you use? Hint: It involves a pipette, and won a Nobel prize.

Patch Clamping

Which of the following features is not going to affect membrane fluidity?

1. Phospholipid structure (saturation vs. non-saturation)

2. The actin-spectrin cytoskeletal network and associated integral membrane proteins.

3. The Presence of cholesterol and other single chain fatty acids.

4. The presence of Lipid Rafts

5. all of these will affect membrane fluidity.

You are working on an experiment in the very well funded lab, and asked to assess membrane fluidity of #3. What experiment would you perform?

I would attach a fluorescent dye to my protein, and then use a laser to bleach out the color from a region of the membrane. I would record the time that it took for the fluorescence to return.

You are a genetic counselor, a person who consults with families regarding genetic disorders, and you find out that the male in the couple you are counseling came into the clinic due to quick tiring and rare seizures. He was diagnosed with a mitochondrial disorder in which 50% of his mitochondria are defective (Heteroplasmic). He and his wife are looking to have a child. The wife is completely healthy. How might you counsel this couple with regards to the chances that their child would be born with his disorder?

The child has a near 0% chance of having the disorder.

In some diseases, there can be mutations in collagen. For example Osteogenesis imperfecta (lethal disorder where bones are extremely fragile), Ehlers-Danlos Syndrome (a disorder where tissues have less cohesion, exemplified by the guy who could pull his skin away from his body), and Alport Syndrome a disorder that impacts the filtering function of the body). Why can mutations in DNA sequence of collagen have such diverse impacts?

Collagen represents a diverse gene family with many different genes. This means that each disorder could be caused by a mutation in a different collagen gene.

This extracellular protein family is one of the most stable and abundant in multicellular organisms. It is characterized by its triple helix quaternary structure. It is so stable that it was isolated from Tyrannosaurus rex leg bones, and suggests chicken (birds) are the closest living relative of the dinosaurs.

Collagens

One of the hottest fields in biology is optogenetics. It has fundamentally changed how we can approach experiments looking at the activity of cells. What does this field entail?

The use fluorescent molecules to visualize the mobility of ion channels within the membrane.