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Questions and Answers
K+ ions are highly concentrated in the extracellular side of the cell.
K+ ions are highly concentrated in the extracellular side of the cell.
False
Anaerobic reactions produce a larger amount of energy compared to oxidative reactions.
Anaerobic reactions produce a larger amount of energy compared to oxidative reactions.
False
Neurons are able to receive and transmit signals due to their excitable nature.
Neurons are able to receive and transmit signals due to their excitable nature.
True
The lipid bilayer of the cell membrane is hydrophilic on both sides.
The lipid bilayer of the cell membrane is hydrophilic on both sides.
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Cells can change their intracellular and extracellular conditions to recover homeostasis.
Cells can change their intracellular and extracellular conditions to recover homeostasis.
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Muscle cells have the ability to slide filaments to enable contraction.
Muscle cells have the ability to slide filaments to enable contraction.
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The transport mechanism in cells is crucial for maintaining the membrane potential.
The transport mechanism in cells is crucial for maintaining the membrane potential.
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Fatty acid portions of phospholipids are soluble in water.
Fatty acid portions of phospholipids are soluble in water.
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The G protein complex is a dimeric protein formed by two subunits: α and β.
The G protein complex is a dimeric protein formed by two subunits: α and β.
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CAMP is formed as a result of the activation of adenylate cyclase.
CAMP is formed as a result of the activation of adenylate cyclase.
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Aquaporins are responsible for the passage of ions through the cell membrane.
Aquaporins are responsible for the passage of ions through the cell membrane.
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The Gq protein activates the enzyme adenylate cyclase directly.
The Gq protein activates the enzyme adenylate cyclase directly.
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Calcium ions play a role as intracellular messengers when released into the cytoplasm.
Calcium ions play a role as intracellular messengers when released into the cytoplasm.
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The hydrophilic phosphate portions of the cell membrane are found in the center of the membrane.
The hydrophilic phosphate portions of the cell membrane are found in the center of the membrane.
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IP3 and diacylglycerol are both active molecules produced by the breakdown of phospholipids.
IP3 and diacylglycerol are both active molecules produced by the breakdown of phospholipids.
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Integral proteins do not span across the cell membrane.
Integral proteins do not span across the cell membrane.
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Osmotic pressure is created when water molecules move from a more concentrated solution to a less concentrated one.
Osmotic pressure is created when water molecules move from a more concentrated solution to a less concentrated one.
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The activation of the specific membrane receptor is the first step in the signaling pathway involving G proteins.
The activation of the specific membrane receptor is the first step in the signaling pathway involving G proteins.
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Carrier proteins serve as transporters in the cell membrane.
Carrier proteins serve as transporters in the cell membrane.
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G protein coupled receptors span the membrane three times.
G protein coupled receptors span the membrane three times.
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Receptors on the cell membrane have a role in cellular communication.
Receptors on the cell membrane have a role in cellular communication.
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Permissive proteins assist in the formation of ion channels in the cell membrane.
Permissive proteins assist in the formation of ion channels in the cell membrane.
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The cell membrane allows all substances to pass without any regulation.
The cell membrane allows all substances to pass without any regulation.
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Peripheral proteins span the entire membrane.
Peripheral proteins span the entire membrane.
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Passive channels are only found in excitable cells.
Passive channels are only found in excitable cells.
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Active channels are always open and have no gating regulation.
Active channels are always open and have no gating regulation.
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Ligand-gated ion channels can be activated by neurotransmitters.
Ligand-gated ion channels can be activated by neurotransmitters.
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Conductivity in ion channels refers to their ability to let ions flow through them.
Conductivity in ion channels refers to their ability to let ions flow through them.
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Some ion channels can be opened by intracellular messengers such as cAMP.
Some ion channels can be opened by intracellular messengers such as cAMP.
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Ion channels gated by physical stimuli can be activated through membrane stretching.
Ion channels gated by physical stimuli can be activated through membrane stretching.
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Only passive channels can contribute to large ion currents.
Only passive channels can contribute to large ion currents.
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Excitable cells express both passive and active channels.
Excitable cells express both passive and active channels.
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Increasing K+ concentration in the blood will have no effect on membrane potential.
Increasing K+ concentration in the blood will have no effect on membrane potential.
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If the membrane potential is at -60 mV, potassium ions will move inside the cell.
If the membrane potential is at -60 mV, potassium ions will move inside the cell.
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Hyperpolarization of the membrane potential to -100 mV causes potassium ions to enter the cell.
Hyperpolarization of the membrane potential to -100 mV causes potassium ions to enter the cell.
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The passive properties of a neuron do not influence its ability to sum up different stimuli.
The passive properties of a neuron do not influence its ability to sum up different stimuli.
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Cell membranes act as insulators, keeping charges separated between two conducting solutions.
Cell membranes act as insulators, keeping charges separated between two conducting solutions.
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The presence of certain potassium channels helps neurons return to resting membrane potential after strong hyperpolarization.
The presence of certain potassium channels helps neurons return to resting membrane potential after strong hyperpolarization.
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Applying a solution with high potassium concentration during electrophysiology measurements depolarizes the neuron.
Applying a solution with high potassium concentration during electrophysiology measurements depolarizes the neuron.
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Capacitance in electrical circuits is unrelated to the passive properties of cell membranes.
Capacitance in electrical circuits is unrelated to the passive properties of cell membranes.
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The membrane potential can become hyperpolarized, reaching values around -90 mV.
The membrane potential can become hyperpolarized, reaching values around -90 mV.
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Voltage-gated Na+ channels are involved primarily in the repolarization of membrane potential.
Voltage-gated Na+ channels are involved primarily in the repolarization of membrane potential.
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A mutation in genes coding for ion channels can potentially impact channel inactivation rates.
A mutation in genes coding for ion channels can potentially impact channel inactivation rates.
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The inactivation of voltage-gated K+ channels happens more quickly than that of voltage-gated Na+ channels.
The inactivation of voltage-gated K+ channels happens more quickly than that of voltage-gated Na+ channels.
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Channelopathies can lead to serious alterations in neuronal and muscle excitability.
Channelopathies can lead to serious alterations in neuronal and muscle excitability.
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Voltage-gated K+ channels increase the membrane's permeability to potassium ions during repolarization.
Voltage-gated K+ channels increase the membrane's permeability to potassium ions during repolarization.
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Resting membrane potential is usually around -90 mV.
Resting membrane potential is usually around -90 mV.
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Increased inactivation rate of ion channels will shorten the duration of ion current.
Increased inactivation rate of ion channels will shorten the duration of ion current.
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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.
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Neurotransmitters bind to receptors on the postsynaptic cell
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This binding causes changes in postsynaptic cell's membrane potential.
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Post-synaptic potentials
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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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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.
