Cell Biology Concepts Quiz
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Questions and Answers

K+ ions are highly concentrated in the extracellular side of the cell.

False (B)

Anaerobic reactions produce a larger amount of energy compared to oxidative reactions.

False (B)

Neurons are able to receive and transmit signals due to their excitable nature.

True (A)

The lipid bilayer of the cell membrane is hydrophilic on both sides.

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

Cells can change their intracellular and extracellular conditions to recover homeostasis.

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

Muscle cells have the ability to slide filaments to enable contraction.

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

The transport mechanism in cells is crucial for maintaining the membrane potential.

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

Fatty acid portions of phospholipids are soluble in water.

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

The G protein complex is a dimeric protein formed by two subunits: α and β.

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

CAMP is formed as a result of the activation of adenylate cyclase.

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

Aquaporins are responsible for the passage of ions through the cell membrane.

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

The Gq protein activates the enzyme adenylate cyclase directly.

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

Calcium ions play a role as intracellular messengers when released into the cytoplasm.

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

The hydrophilic phosphate portions of the cell membrane are found in the center of the membrane.

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

IP3 and diacylglycerol are both active molecules produced by the breakdown of phospholipids.

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

Integral proteins do not span across the cell membrane.

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

Osmotic pressure is created when water molecules move from a more concentrated solution to a less concentrated one.

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

The activation of the specific membrane receptor is the first step in the signaling pathway involving G proteins.

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

Carrier proteins serve as transporters in the cell membrane.

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

G protein coupled receptors span the membrane three times.

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

Receptors on the cell membrane have a role in cellular communication.

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

Permissive proteins assist in the formation of ion channels in the cell membrane.

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

The cell membrane allows all substances to pass without any regulation.

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

Peripheral proteins span the entire membrane.

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

Passive channels are only found in excitable cells.

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

Active channels are always open and have no gating regulation.

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

Ligand-gated ion channels can be activated by neurotransmitters.

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

Conductivity in ion channels refers to their ability to let ions flow through them.

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

Some ion channels can be opened by intracellular messengers such as cAMP.

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

Ion channels gated by physical stimuli can be activated through membrane stretching.

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

Only passive channels can contribute to large ion currents.

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

Excitable cells express both passive and active channels.

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

Increasing K+ concentration in the blood will have no effect on membrane potential.

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

If the membrane potential is at -60 mV, potassium ions will move inside the cell.

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

Hyperpolarization of the membrane potential to -100 mV causes potassium ions to enter the cell.

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

The passive properties of a neuron do not influence its ability to sum up different stimuli.

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

Cell membranes act as insulators, keeping charges separated between two conducting solutions.

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

The presence of certain potassium channels helps neurons return to resting membrane potential after strong hyperpolarization.

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

Applying a solution with high potassium concentration during electrophysiology measurements depolarizes the neuron.

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

Capacitance in electrical circuits is unrelated to the passive properties of cell membranes.

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

The membrane potential can become hyperpolarized, reaching values around -90 mV.

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

Voltage-gated Na+ channels are involved primarily in the repolarization of membrane potential.

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

A mutation in genes coding for ion channels can potentially impact channel inactivation rates.

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

The inactivation of voltage-gated K+ channels happens more quickly than that of voltage-gated Na+ channels.

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

Channelopathies can lead to serious alterations in neuronal and muscle excitability.

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

Voltage-gated K+ channels increase the membrane's permeability to potassium ions during repolarization.

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

Resting membrane potential is usually around -90 mV.

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

Increased inactivation rate of ion channels will shorten the duration of ion current.

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

Flashcards

Cell Ions

K+ ions are concentrated inside cells, while Na+ ions are concentrated outside. This difference is crucial for cell function and survival.

Homeostasis

The body's ability to maintain a stable internal environment despite external changes.

Cellular Energy Production

Cells obtain energy from nutrients (e.g., glucose) through catabolic reactions.

Catabolic Reaction

A series of reactions where large molecules are broken down, ultimately producing energy through the oxidation (adding oxygen) of molecules.

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Glucose Oxidation (in mitochondria)

A key energy-producing process that occurs in mitochondria. It involves glucose being oxidized for more energy.

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Lipid Bilayer

A double layer of lipids (fats) that forms the cell membrane.

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Hydrophilic Head

The water-loving part of a phospholipid.

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Hydrophobic Tails

The water-fearing part of a phospholipid that faces inward in the membrane.

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Cell membrane structure

The cell membrane is composed of a phospholipid bilayer with embedded proteins.

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Integral proteins

Proteins that span the cell membrane, extending from one side to the other.

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Peripheral proteins

Proteins that are associated with one side of the membrane, but do not span it.

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Ion channels

Integral proteins with a pore that allows ions to pass through the membrane.

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Carrier proteins

Integral proteins that transport specific molecules across the membrane.

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Receptor proteins

Proteins that bind to specific molecules (ligands) triggering intracellular responses.

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Cell membrane function (separation)

Maintains different environments inside and outside the cell.

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Cell membrane function (exchange)

Controls what molecules enter and leave the cell.

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G protein activation

A G protein, a protein complex, is activated when a signaling molecule binds to a membrane receptor. This activates a specific subunit, causing it to swap GDP for GTP.

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Adenylate Cyclase

An enzyme activated by a G protein that catalyzes the formation of cAMP (cyclic AMP). cAMP is a secondary messenger.

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cAMP

A secondary messenger molecule produced by adenylate cyclase, triggering a cellular response.

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Phospholipase C

An enzyme activated by a specific G protein that breaks down phospholipids, creating DAG and IP3 as secondary messengers, triggering a cellular response.

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IP3

A secondary messenger molecule produced by Phospholipase C, triggering calcium release from the endoplasmic reticulum.

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Aquaporins

Channel proteins in cell membranes that facilitate the passage of water molecules.

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Osmotic Pressure

The pressure generated by the unequal concentration of water molecules across a semi-permeable membrane, driving water movement.

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Secondary Messenger

A small molecule that relays a signal from a membrane receptor to target molecules inside a cell, amplifying the initial signal.

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Ion Channel Selectivity

Each ion channel is designed to allow specific ions to pass through, based on its unique amino acid structure.

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Ion Channel Conduction

The ability of an ion channel to allow ions to flow through it. Some channels can handle a lot of ion flow, while others are less efficient.

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Ion Channel Gating

The process of opening or closing an ion channel in response to a specific stimulus, like a chemical signal or a change in voltage.

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Passive Ion Channel

An ion channel that is always open, allowing ions to flow freely across the membrane.

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Active Ion Channel

An ion channel that can be opened or closed in response to a specific stimulus, controlling ion flow.

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Ligand-Gated Ion Channel

An ion channel that is activated by a neurotransmitter, which binds to it like a key to a lock.

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Ion Channels Gated by Intracellular Messengers

These channels are opened or closed by chemical signals inside the cell, like cAMP or phosphorylation.

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Ion Channels Gated by Physical Stimuli

These channels are opened or closed by physical changes such as membrane stretching, allowing for the flow of ions and depolarization.

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Depolarization

The process of becoming less negative (more positive); a shift in membrane potential towards zero.

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Potassium Disequilibrium

An imbalance in potassium concentration, particularly outside the cell, leading to changes in membrane potential and potentially involuntary muscle contractions.

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Equilibrium Potential

The electrical potential across a cell membrane when the net flow of a specific ion is zero, meaning the forces driving the ion in and out of the cell are balanced.

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Hyperpolarization

The process of becoming more negative; a shift in membrane potential further away from zero.

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Protection Mechanisms

Cellular mechanisms that help to maintain normal membrane potential and ensure proper functioning, such as specific potassium channels.

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Summation of Inputs

The ability of a neuron to integrate multiple signals by adding the effects of different inputs together to generate a response.

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Capacitance

The ability of a membrane to store electrical charge, due to the separation of charges across its lipid insulation layer.

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Voltage-gated K+ Channel Inactivation

After a period of being open, voltage-gated potassium channels close, reducing potassium ion permeability and allowing the membrane potential to return to its resting state.

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Channelopathies

Diseases caused by mutations affecting ion channels, leading to changes in ion current amplitude or inactivation rate.

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Reduced Inactivation Rate

A mutation that prolongs the open time of an ion channel, leading to increased ion flow and potential consequences.

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Neuronal Excitability

The tendency of a nerve cell to generate an electrical signal (action potential). Channelopathies can affect this, leading to conditions like epilepsy.

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Muscle Excitability

The ability of muscle cells to contract. Channelopathies can affect this, causing problems like cardiac or back issues.

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How do therapies target ion channels?

Many medications and treatments work by targeting ion channels, either enhancing or blocking their activity.

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Study Notes

General Principles of Cell Physiology

  • All physiological processes can be described by equations.
  • A general and simple equation is v = F/R, where:
  • v = speed
  • F = driving force (stimulates the process)
  • R = resistance (opposes the process)
  • Speed of a process is directly proportional to the driving force and inversely proportional to the resistance.

Regulation of Physiological Functions

  • Feedforward regulation: the final product reinforces its own production.
  • Feedback regulation:
  • Negative feedback: the product inhibits the process, to prevent excess, in hormone production.
  • Positive feedback: the product further stimulates the process (less common).

The Cell

  • Cells continuously interact with the environment and maintain homeostasis.
  • Homeostasis is a dynamic state, continuously adjusting to internal and external conditions
  • Cells are not in equilibrium, but are in a state of disequilibrium
  • This state of disequilibrium is essential for cell life (e.g., different intracellular and extracellular ion concentrations)
  • Cells obtain energy from molecules in the diet, particularly glucose (this involves catabolic reactions).
  • Glucose is initially broken down through anaerobic reactions followed by further oxidation in mitochondria.

Cell Membrane

  • The cell membrane consists of a lipid bilayer
  • Hydrophilic head group, soluble in water.
  • Hydrophobic tail, soluble in fats.
  • Proteins are embedded in the membrane and play various roles.
  • Integral proteins: span the membrane
  • Ion channels (p.e., Na+ channels, K+ channels)
  • Carrier proteins (transporters)
  • Receptors (bind ligands, triggering intracellular messages)
  • Peripheral proteins: are associated with one side of the membrane

Water Transport

  • Water crosses the membrane through aquaporins (channels).
  • Osmotic pressure is the driving force for water movement.
  • Water moves from a region of lower solute concentration to a region of higher solute concentration.

Ion Concentrations in the Cell

  • Sodium (Na+) is highly concentrated outside cells, relatively low inside.
  • Potassium (K+) is highly concentrated inside cells, relatively low outside.
  • Calcium (Ca2+) is maintained at low levels inside most cells.
  • Chloride (Cl-) is highly concentrated outside cells, relatively low inside.

Passive Transport

  • Passive transport doesn't require energy.
  • Diffusion involves the movement of molecules from higher to lower concentration gradients.
  • Simple diffusion: movement of molecules directly across the membrane lipid bilayer.
  • Facilitated diffusion: uses protein channels/carriers for molecules that are not readily soluble in the lipid bilayer
  • Gated diffusion: channel opening can be regulated by various factors.

Active Transport

  • Active transport requires energy (e.g., ATP).
  • It moves molecules against the concentration gradient.
  • Primary active transport directly uses ATP.
  • Secondary active transport uses a gradient established by primary active transport.
  • Co-transport: transported substances move in the same direction.
  • Counter-transport: transported substances move in opposite directions.

Ion Channels and Membrane Potential

  • Ion channels are integral membrane proteins that control ion movement.
  • Passive channels: always open
  • Active channels: opening and closing are regulated (e.g., voltage-gated, ligand-gated, mechanically gated).
  • Membrane potential: difference in electrical charge across the membrane due to different ion concentrations.
  • The resting membrane potential is primarily maintained by the unequal distribution of ions.

Synaptic Transmission (Electrical Synapses)

  • Electrical synapses:
  • Direct connection between cells facilitated by gap junctions.
  • Allows ions and small molecules to flow from one cell to another in both directions.

Synaptic Transmission (Chemical Synapses)

  • Chemical synapses employ neurotransmitters

  • Vesicles release neurotransmitters into the synaptic cleft.

  • Neurotransmitters bind to receptors on the postsynaptic cell

  • This binding causes changes in postsynaptic cell's membrane potential.

  • Post-synaptic potentials

  • GRADED: magnitude depends on the amount of neurotransmitters released and receptor activation.

Different types of Neurotransmitters

  • Small-molecule neurotransmitters (e.g., glutamate, GABA, acetylcholine)
  • Synthesized in the terminal
  • Rapid transmission
  • Neuropeptides (e.g., endorphins, enkephalins)
  • Synthesized in the cell body
  • Slower transmission

Synaptic Vesicle Cycling

  • Recycling of synaptic vesicles is essential for neurotransmitter release.
  • The process includes docking, priming, fusion, and endocytosis.
  • Different proteins are involved to maintain the efficiency.

Synaptic Plasticity

  • Short-term plasticity: involves temporary changes in synaptic strength or efficiency without structural changes.
  • Long-term plasticity: involves lasting changes in synaptic strength and has a prominent role in learning and memory.
  • LTD and LTP: represent opposite processes (long-term potentiation and long term depression)

Neurotransmitters: Different types, and how they work

  • These neurotransmitter classes also play a regulatory role in controlling different physiological functions. e.g. Dopamine, Serotonin

Fluid compartments

  • Total body water is about 60% of body weight (but variable with age and sex)
  • Intracellular fluid (ICF) contains water and important solutes like proteins.
  • Extracellular fluid (ECF) comprises interstitial fluid (ISF) which surrounds cells and plasma, which is the fluid portion of blood.
  • Transcellular fluids: CSF, intracellular and intraocular fluids.

Water and Salts

  • Water moves to balance osmolarity.
  • Substances like sodium are not readily moved.
  • Measuring fluids involves using markers that are not immediately metabolized or lost. (e.g., mannitol or inulin)

The Capillaries

  • Filtration and reabsorption occur due to the differences in hydrostatic and oncotic pressures between blood and interstitial fluids within capillaries.

Edema

  • Edema: abnormal fluid buildup, caused by variations in the balance of pressure gradients and lymphatic drainage which leads to fluid accumulation in tissues.
  • Dependent edema: due to gravity force.
  • Insufficient lymphatic drainage: poor lymphatic system.
  • Increase in hydrostatic pressure

The Gas Laws

  • Boyle's Law: the relationship between pressure and volume at constant temperature.
  • Charles's Law: the relationship between volume and temperature at constant pressure.
  • Gay-Lussac's Law: the relationship between pressure and temperature at constant volume.

Nervous Transmission and Neuronal Signal

  • Electrical synapse vs Chemical synapse
  • Afferent, Efferent, and Interneurons

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Cell Physiology PDF Notes

Description

Test your knowledge on essential cell biology concepts including ion concentration, energy production, and membrane dynamics. This quiz covers the critical roles of different cellular components and their functions. Challenge yourself with these key topics in cell physiology.

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