Lifesci 7C Midterm 1 Review

These flashcards cover key vocabulary and concepts related to cell signaling, membrane potentials, action potentials, and homeostasis.

Signal Molecules

Chemical substances that trigger a response in cells by binding to specific receptors.

Receptor Tyrosine Kinase

A type of cell surface receptor involved in signaling pathways that regulate cellular processes like growth and differentiation.

Signal Cascade

A sequence of events in which a signal molecule activates a series of proteins, leading to a large amplification of the initial signal.

Pluripotent Cells

Stem cells that have the potential to differentiate into any cell type in the body.

Resting Membrane Potential

The electrical potential difference across the plasma membrane of a cell, typically around -70 mV in neurons.

Depolarization

A change in membrane potential that makes the inside of the cell more positive compared to the resting potential.

Graded Potentials

Changes in membrane potential that vary in size and can occur over short distances.

Action Potentials

Rapid, large changes in membrane potential that are transmitted along the axon over long distances.

EPSP (Excitatory Postsynaptic Potential)

A temporary increase in postsynaptic membrane potential, generally caused by the influx of Na+.

IPSP (Inhibitory Postsynaptic Potential)

A temporary decrease in postsynaptic membrane potential, often due to the influx of Cl-.

Feedback Loops

Processes that help maintain homeostasis by regulating internal conditions based on sensed stimuli.

Thyroid Hormones (T3 and T4)

Hormones produced by the thyroid gland that regulate metabolism and affect physical development.

Cyclic AMP (cAMP)

A second messenger involved in signal transduction pathways, often resulting from the activation of GPCRs.

Phosphatase

An enzyme that removes phosphate groups from proteins, which can either activate or inactivate the proteins.

Kinesin and Dynein

Motor proteins that transport cellular materials along microtubules; kinesin moves towards the plus end and dynein towards the minus end.

Describe the role of signal molecules in cellular responses.

Signal molecules, such as PDGF, bind to cellsurface receptors, leading to various cellular responses including increased collagen synthesis, cytoskeletal remodeling, changes in lipid composition, and enhanced expression of cell cycle regulatory genes.

Explain the difference between nonpolar small molecules and larger molecules in terms of cell membrane crossing.

Nonpolar small molecules, like estradiol and cortisone, can cross the cell membrane directly and require intracellular receptors, while larger molecules such as PDGF, adrenaline, glucagon, and acetylcholine cannot cross the membrane and need cell-surface receptors.

Define signal cascade and its significance in cellular signaling.

A signal cascade is a process where one signal molecule activates multiple proteins, amplifying the signal. For example, one Ras protein can lead to the activation of 10,000 target proteins.

How does signal-receptor binding occur and what is its nature?

Signal-receptor binding is a reversible process where the signal molecule binds to the receptor and can later dissociate, allowing for dynamic regulation of cellular responses.

Do all signal molecules require cell-surface receptors to elicit a response?

No, only larger or polar signal molecules like PDGF, adrenaline, glucagon, and acetylcholine require cell-surface receptors, while nonpolar small molecules can use intracellular receptors.

Explain the significance of Ras proteins in signal transduction.

Ras proteins are crucial in signal transduction as they initiate the signal cascade, amplifying the response from a single signal molecule to activate thousands of target proteins.

What happens to the expression of cell cycle regulatory genes in response to signal molecules?

The expression of cell cycle regulatory genes increases in response to signal molecules, contributing to the regulation of the cell cycle.

Describe the changes that occur in a cell upon binding of a signal molecule.

Upon binding of a signal molecule, a cell may experience increased collagen synthesis, cytoskeletal remodeling, changes in lipid composition, and enhanced expression of cell cycle regulatory genes.

Describe the role of binding affinity in cell signaling.

Binding affinity refers to how attractive two molecules are to each other and how long they will remain bound, influencing the duration of the signal in cell signaling.

Explain the function of phosphatases in protein regulation.

Phosphatases are enzymes that remove phosphate groups from proteins, which can lead to the inactivation of proteins or, in some cases, their activation.

Define the hierarchy of stem cells.

The hierarchy of stem cells includes totipotent cells, which can become an entire organism (like a zygote), pluripotent cells, which can become any cell in the body (like embryonic stem cells), and multipotent cells, which can differentiate into specific cell types such as blood, muscle, nerve, and bone stem cells.

How do kinases function in cellular processes?

Kinases are enzymes that phosphorylate proteins using ATP, which can activate or modify the function of those proteins.

Explain the significance of cell adhesion in tissue structure.

Cell adhesion is crucial for maintaining the shape of tissues, as it allows cells to anchor to each other and to the extracellular matrix, facilitating the formation of stable structures

Describe the relationship between cytoskeletal components and cell adhesion.

Cytoskeletal components interact with cell adhesion molecules, helping to maintain the integrity and shape of cells and tissues.

What are desmosomes and their function in cells?

Desmosomes are structures that attach to intermediate filaments in cells, keeping adjacent cells together while allowing the passage of food and waste.

How does the size of a surface area affect diffusion rates in cells?

A larger surface area increases the rate of diffusion, allowing for more efficient exchange of materials between cells and their environment.

Define the apical and basal sides of epithelial cells.

The apical side of epithelial cells is where secretion and absorption occur, while the basal side connects to the extracellular matrix.

Explain the role of actin in cell shape changes

Actin filaments are important for changing the shape of a cell, allowing for movement and structural adjustments.

Describe the smallest to largest components of the cytoskeleton.

The components of the cytoskeleton, from smallest to largest, are actin filaments (microfilaments), intermediate filaments, and microtubules.

What is the impact of inhibition and disinhibition on cellular pathways?

Inhibition and disinhibition can regulate whether a cellular pathway is active or inactive, influencing cellular responses.

How do cells build tissues and organs?

Cells build tissues and organs through the expression of cytoskeletal components and cell adhesion properties, which facilitate organization and structure.

Explain the diversity of epithelial cells.

Epithelial cells are considered the most diverse cells in the body, performing various functions related to protection, absorption, and secretion.

Describe the role of fibroblasts in connective tissue.

Fibroblasts secrete the extracellular matrix (ECM) which is a major component of connective tissue.

Explain how ECM disorders affect tissues.

ECM disorders can change the strength of tissues, potentially leading to structural weaknesses.

Define the primary component of the extracellular matrix.

Collagen is the primary component of the extracellular matrix.

How do motor proteins function on microtubules?

Motor proteins, such as kinesin and dynein, walk along microtubules to transport cellular materials.

Differentiate between the movement directions of kinesin and dynein.

Kinesin moves from the minus end to the plus end of microtubules, while dynein moves in the opposite direction.

Explain the dependence of cell structure on cytoskeletal components.

The structure and shape of a cell are determined by its cytoskeletal components.

Describe the characteristics of signals in neuron cells

signals in neuron cells are fast, travel in one direction, and move along the axon.

Define potential difference in the context of cellular membranes

Potential difference is calculated as the voltage inside the cell minus the voltage outside the cell.

What is the function of the sodium-potassium pump?

The sodium-potassium pump moves 3 Na+ ions out of the cell and 2 K+ ions into the cell, against their concentration gradients, using ATP.

State the resting membrane potential in neurons.

The resting membrane potential in neurons is approximately -70 mV.

Explain how resting membrane potential varies among different cells.

Different types of cells have different resting membrane potentials (RMP), which can affect their function.

Describe the direction of movement for ions in relation to the chemical gradient.

Ions move down the chemical gradient, which means they move from areas of higher concentration to areas of lower concentration.

What happens to positive charges in relation to the electrical gradient?

Positive charges move towards negative areas when going down the electrical gradient and towards positive areas when going up the electrical gradient.

Explain the concept of the electrochemical gradient.

The electrochemical gradient determines the direction and extent to which an ion will move across a membrane.

What occurs when positive charge enters a cell?

When positive charge enters a cell, the inside becomes more positive than the outside.

Define depolarization in the context of membrane potential.

Depolarization occurs when the membrane potential becomes more positive than the resting potential.

What is hyperpolarization in relation to resting potential?

Hyperpolarization occurs when the membrane potential becomes more negative than the resting potential.

Describe where graded potentials occur in a neuron.

Graded potentials occur on dendrites and the cell body of a neuron.

Explain the role of ligand-gated ion channels in graded potentials.

Graded potentials depend on ligand-gated ion channels to initiate changes in membrane potential.

How does the variability of graded potentials compare to action potentials?

Graded potentials allow for more variability in the signal compared to action potentials, which have less variability.

Define the distance traveled by graded potentials.

Graded potentials travel short distances within the neuron.

Identify where graded potentials are initiated.

Graded potentials are initiated at synapses.

Explain the dependence of action potentials on ion channels.

Action potentials depend on voltage-gated ion channels to propagate the signal.

Describe the distance traveled by action potentials.

Action potentials travel long distances along the axon.

Where do action potentials occur in a neuron?

Action potentials occur at the axon hillock

What does EPSP stand for and what does it indicate?

EPSP stands for Excitatory PostSynaptic Potential, indicating depolarization.

What ions are involved in causing EPSP?

EPSP is caused by the influx of Na+ ions.

Define IPSP and its effect on the neuron.

IPSP stands for Inhibitory PostSynaptic Potential, indicating hyperpolarization.

What ions contribute to IPSP?

IPSP is caused by the influx of Cl- ions and the efflux of K+ ions.

Explain the concentration gradient of ions in a neuron.

Everything is higher in concentration outside the cell, except for potassium, which is higher inside the cell.

How does a neuron decide how much signal to send?

The neuron decides how much signal to send based on time and space considerations.

What analogy is used to describe the function of the axon hillock?

The axon hillock is described as an accountant that assesses whether the threshold potential has been reached.

What is the threshold potential in the context of action potentials?

The threshold potential is the level of depolarization that must be reached for an action potential to be initiated.

Describe the refractory period in relation to voltage-gated sodium channels.

The refractory period is a phase during which voltage-gated sodium channels on the axon are temporarily inactivated, preventing further action potentials from occurring immediately after one has been initiated.

Explain the significance of reaching the threshold in action potential generation.

Reaching the threshold is crucial as it triggers the action potential, allowing the rapid depolarization and repolarization of the neuron.

Define temporal summation in the context of excitatory postsynaptic potentials (EPSPs).

Temporal summation occurs when multiple EPSPs are summed over time, leading to a greater likelihood of reaching the threshold for an action potential.

How does spatial summation differ from temporal summation?

Spatial summation involves the simultaneous arrival of EPSPs at different synapses, while temporal summation involves the accumulation of EPSPs over time at the same synapse.

Identify the role of different ions in the phases of an action potential.

Different ions, such as sodium and potassium, play distinct roles in the various phases of an action potential, including depolarization and repolarization.

Do all axons have the same structure?

No, some axons are myelinated, which increases the speed of action potentials, while others are not myelinated.

Explain the concept of a homeostatically regulated system.

A homeostatically regulated system maintains internal stability by responding to stimuli and adjusting physiological processes to keep conditions within a narrow range.