BI108 Quiz 5

What are the four primary steps in the cell signaling sequence?

1. Signaling molecule release, 2. Messenger travel to target, 3. Signal binding to receptor, 4. Protein shape change/trigger.

What is a ligand in the context of cell signaling?

Any molecule that binds to a specific receptor.

How are animal signaling molecules categorized?

Amines (derived from amino acids), peptides (small proteins), and steroids (lipid-based).

Which type of signaling molecule can cross the cell membrane directly?

Small, hydrophobic molecules like steroids.

How do large, hydrophilic signaling molecules interact with target cells?

They bind to external receptors on the cell membrane because they cannot cross the lipid bilayer.

What is signal transduction?

The process of converting an extracellular signal into a specific cellular response.

What is the function of a kinase enzyme?

It catalyzes phosphorylation, which turns proteins on or off.

What is signal amplification?

A process where a small amount of signal molecule triggers a much larger cellular response, often through a phosphorylation cascade.

What are second messengers?

Small molecules or ions released inside the cell upon receptor activation that help amplify the signal.

Define homeostasis.

The process by which biological systems maintain stability while adjusting to changing external conditions.

What is the role of an effector in a homeostatic control system?

It is a tissue or organ that alters the internal environment to correct a deviation from the set point.

What is the difference between negative and positive feedback?

Negative feedback returns a system to its set point (balance), while positive feedback amplifies a response and increases deviation from the set point.

Provide an example of negative feedback in the human body.

The regulation of blood glucose levels by the pancreas and liver.

Provide an example of positive feedback in the human body.

Childbirth, where uterine contractions increase in response to the stretching of the cervix.

What is juxtacrine signaling?

Cell signaling that requires direct physical contact between cells.

How does endocrine signaling differ from paracrine signaling?

Endocrine signaling involves hormones traveling long distances to distant cells, while paracrine signaling occurs on a local level.

What happens to a receptor protein when it binds to its specific ligand?

It undergoes a conformational (shape) change that initiates subsequent events within the cell.

What are the three main steps of signaling pathways?

1. Reception, 2. Transduction, 3. Cellular response.

What are two ways cells terminate signaling?

Degradation/removal of signaling molecules and the use of phosphatases to remove phosphates from proteins.

What is the role of an activated receptor in the cortisol pathway?

It acts as a transcription factor to regulate the expression of target genes.

What is the primary cellular response in the mitogen pathway?

The transcription of Cyclin D, which stimulates mitosis.

What is the function of adenylyl cyclase in the epinephrine pathway?

It produces cAMP from ATP, which then activates protein kinase A.

What is the final result of the epinephrine pathway in liver cells?

The breakdown of glycogen into glucose, which is then released into the blood.

Why is signal amplification important for hormone signaling?

Because hormones are often present at extremely low levels, amplification ensures a robust cellular response.

What is diffusion in a biological context?

The passive and spontaneous movement of ions or molecules from an area of high concentration to an area of low concentration.

How do electrical gradients influence ion movement?

Ions move toward areas of opposite charge, driven by the electrical potential difference across a membrane.

What is the primary function of transport proteins in cell membranes?

They facilitate the movement of ions or molecules that are unable to pass through the membrane on their own.

What is the key difference between ion channels and carrier proteins?

Channels provide an open pore for specific ions to pass through passively, while carriers require the molecule to bind to an active site to trigger transport.

How do pumps differ from channels and carriers?

Pumps use ATP to move ions or molecules against their concentration gradient, which is an active transport process.

What creates the membrane potential in a cell?

The separation of charge across the cell membrane, resulting in a voltage difference between the inside and outside of the cell.

What is an electrochemical gradient?

The combined effect of both a concentration gradient and an electrical potential gradient acting on an ion simultaneously.

What is co-transport?

A process where the electrochemical gradient established by one ion is used to transport other molecules or ions across the membrane.

What are the primary components of the central nervous system (CNS)?

The brain and the spinal cord.

What is the function of the peripheral nervous system (PNS)?

It carries information to and from the central nervous system.

What is an action potential?

A rapid, temporary, and all-or-nothing swing in membrane voltage used for electrical signaling.

What are the three main parts of a neuron and their functions?

Dendrites (receive communication), cell body (processes information), and axon (sends signals to other neurons).

How does the sodium-potassium pump maintain the resting potential?

It uses ATP to pump 3 Na+ ions out of the cell and 2 K+ ions into the cell, moving both against their concentration gradients.

What role do K+ leak channels play in resting potential?

They allow K+ to move out of the cell along its concentration gradient until the inside of the membrane becomes negative enough to oppose further movement.

What is the difference between the sympathetic and parasympathetic nervous systems?

The sympathetic system controls 'fight or flight' responses, while the parasympathetic system controls 'rest and digest' functions.

What is the role of sensory (afferent) neurons?

They carry signals from sensors to the central nervous system.

What is the role of interneurons?

They are located only in the CNS and integrate or coordinate signals between the CNS and PNS.

What is the role of efferent neurons?

They convey signals from the CNS to effectors (muscles or tissues).

What is the function of glial cells?

They do not transmit electrical signals but provide essential support for neurons.

What defines a hyperpolarized membrane?

A membrane potential that has become more negative than the resting potential.

What defines a depolarized membrane?

A membrane potential that has become more positive than the resting potential.

What is the refractory period?

A phase following an action potential during which another action potential cannot be generated until the membrane returns to its normal state.

How do voltage-gated Na+ channels contribute to an action potential?

When the membrane depolarizes, these channels open, allowing Na+ to rush into the cell, which further depolarizes the membrane.

What is the significance of reductionism in studying the nervous system?

It is the practice of analyzing complex phenomena by breaking them down into smaller, manageable parts.

What triggers an action potential to travel down an axon?

Depolarization to threshold, where enough positive charges enter the membrane to trigger the influx of sodium ions.

What is the function of myelin in neurons?

Myelin, formed by Schwann cells, prevents ion movement in/out of the cell, forcing the charge to spread efficiently down the axon.

What is saltatory conduction?

The process where the signal 'jumps' from node to node along a myelinated axon, significantly increasing speed.

What is a synapse?

The area where the cell membranes of a presynaptic neuron and a postsynaptic cell meet, separated by a small gap called the synaptic cleft.

What happens when an action potential reaches the axon terminus?

Voltage-gated calcium channels open, calcium rushes in, and synaptic vesicles fuse with the membrane to release neurotransmitters into the cleft.

How do neurotransmitters affect the postsynaptic neuron?

They bind to ligand-gated channels, causing them to open and change the membrane potential of the postsynaptic cell.

What is the difference between a chemical and an electrical gradient?

A chemical gradient is a difference in concentration of a substance, while an electrical gradient is a difference in electric charge (voltage) across a membrane.

What is the typical resting membrane potential of a neuron?

A negative value between -60 and -70 mV, meaning the inside of the cell is negative compared to the outside.

What is the role of the Na+/K+ pump?

It uses energy to move sodium and potassium against their concentration gradients to maintain the electrochemical gradient.

How do potassium leak channels contribute to resting potential?

They are always open, allowing potassium to flow down its concentration gradient out of the cell, making the interior more negative.

What defines the peak of an action potential?

The point where sodium voltage-gated channels close and potassium voltage-gated channels open.

What occurs during the falling phase of an action potential?

Potassium leaves the cell down its concentration and electrical gradients, repolarizing the membrane potential.

What is the refractory period in an action potential?

A phase where the membrane hyperpolarizes below resting potential and voltage-gated channels are temporarily unable to reopen.

What three factors influence the efficiency of diffusion in circulatory systems?

The steepness of the electrochemical gradient, the available surface area, and the distance of movement.

What is the primary difference between open and closed circulatory systems?

In open systems, fluid (hemolymph) leaves vessels to circulate; in closed systems, blood is contained within vessels at all times.

What is the function of an atrium versus a ventricle?

An atrium receives blood from the body, while a ventricle pumps blood into the body.

What is the role of capillaries in the circulatory system?

They are the site where nutrients and oxygen diffuse into tissues, and wastes and carbon dioxide diffuse into the blood.

What is the path of blood flow through the human heart?

Right atrium to right ventricle, to lungs, to left atrium, to left ventricle, and then out to the body.

Why is oxygen considered the final electron acceptor in respiration?

It is required in the oxidation of glucose to CO2, a process that releases energy to synthesize ATP.

What is partial pressure?

The pressure exerted by a particular gas within a mixture of gases.

How do gases move during respiratory exchange?

They diffuse from areas of high partial pressure to areas of low partial pressure.

Which environmental factors increase the amount of oxygen available in water?

Freshwater holds more oxygen than saltwater, and cold water holds more oxygen than warm water.

What are spiracles in tracheal respiratory systems?

Body openings that allow air to enter a network of tracheae or air sacs.

Why are capillaries efficient for gas exchange?

They possess a high surface area-to-volume ratio.

How do CO2 and O2 move across cell membranes?

They move via diffusion.

What is the relationship between surface area and diffusion?

A higher surface area allows for more diffusion.

What is the primary function of the alveoli in the respiratory system?

They provide a large surface area for gas exchange between the lungs and capillaries.

How do red blood cells travel through capillary beds?

They flow single-file through highly branched capillaries, which maximizes surface area for diffusion.

What is the main role of hemoglobin?

It binds to O2 molecules that have diffused into red blood cells and transports them to oxygen-depleted areas.

What is cooperative binding in the context of hemoglobin?

It is the phenomenon where the binding of one oxygen molecule changes the hemoglobin structure to make it easier for additional oxygen molecules to bind.

What is the function of axon terminals?

They carry information as action potentials away from the presynaptic cell to the postsynaptic cell.

What neurotransmitter is involved in neuromuscular junctions?

Acetylcholine (ACh).

What is the difference between an open and a closed circulatory system?

In an open system, hemolymph is pumped into an open body cavity to bathe tissues directly; in a closed system, blood remains contained within tubes/vessels.

What is hemolymph?

A fluid consisting of blood and other fluids found in organisms like arthropods and mollusks.

What are the three main components of a closed circulatory system?

A muscular pump (heart), tubes (passageways), and blood (the fluid).

What is the difference between oxygenation and deoxygenation of a respiratory pigment?

Oxygenation is the loading of O2 onto the pigment, while deoxygenation is the release of O2.

What are the two circuits of blood flow in humans?

The pulmonary circuit (to the lungs) and the systemic circuit (to the rest of the body).

What is the function of arteries versus veins?

Arteries carry blood away from the heart, while veins return blood to the heart.

Which heart chambers receive blood and which pump blood out?

Atria receive blood, and ventricles pump blood out.

What are the two primary ways gases move in animal respiratory systems?

Bulk flow (mass movement of fluids/gases) and diffusion (across membranes).

What does the x-axis of the Oxygen-Hemoglobin Dissociation curve represent?

The partial pressure of oxygen in the blood or tissues.

What does the y-axis of the Oxygen-Hemoglobin Dissociation curve represent?

The percent saturation of hemoglobin (the percentage of heme sites occupied by oxygen).

In what three formats is CO2 transported from tissues to the lungs?

Dissolved in plasma (~5%), bound to hemoglobin (~20%), and as bicarbonate ions (the remainder).

What happens to blood pH when CO2 levels increase?

The blood becomes more acidic, resulting in a lower pH.

How does the body respond when CO2 production increases due to high cellular respiration?

Chemosensory cells in the medulla oblongata detect the change in PCO2 and H+ concentration, stimulating an increased breathing rate.

What is the difference between innate and acquired immunity?

Innate immunity is present at birth, while acquired (adaptive) immunity develops over time.

What is the primary function of macrophages in the innate immune response?

They alert nearby cells to danger and engulf/destroy pathogens.

What role do mast cells play during an inflammatory response?

They secrete histamines to make nearby blood vessels expand and become more permeable, while also constricting vessels at the wound site to reduce blood loss.

What is the function of neutrophils?

They move out of nearby blood vessels to engulf and destroy bacteria and pathogens in a wound.

Define antigens.

Non-self molecules that elicit a specific response from the immune system.

What are antibodies and what do they do?

Proteins produced by B cells that bind to specific antigens to tag them for destruction.

What are epitopes?

Specific locations on an antigen where antibodies bind.