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Questions and Answers

What initiates the fusion of the vesicle with the plasma membrane during neurotransmitter release?

  • Acetylcholine is released
  • Calcium binds to synaptotagmin (correct)
  • SNARE proteins coil together
  • Voltage gated sodium channels open

Which mechanism describes the rapid release of neurotransmitters through a small opening in the vesicle?

  • Fusion pore formation
  • Clathrin-mediated endocytosis
  • Kiss and run mechanism (correct)
  • Invagination

What triggers an action potential in muscle cells at the neuromuscular junction?

  • Release of acetylcholine into the synaptic cleft (correct)
  • Binding of dopamine to receptors
  • Calcium influx through the sarcoplasmic reticulum
  • Increased sodium concentration

What is the purpose of the safety factor in muscle action potentials?

<p>To ensure reliable muscle activation (A)</p> Signup and view all the answers

Which type of receptor is involved in the binding of acetylcholine at the neuromuscular junction?

<p>Nicotinic acetylcholine receptor (nAChR) (D)</p> Signup and view all the answers

What is the primary function of ribosomes in a cell?

<p>Translating mRNA to protein (C)</p> Signup and view all the answers

Which structure is closely linked to the Endoplasmic Reticulum?

<p>Golgi Apparatus (D)</p> Signup and view all the answers

What role does the Smooth Endoplasmic Reticulum play in the cell?

<p>Lipid metabolism (C)</p> Signup and view all the answers

Which process occurs within the mitochondria?

<p>Krebs cycle and oxidative phosphorylation (D)</p> Signup and view all the answers

What distinguishing feature do mitochondria have?

<p>They can grow and reproduce within the cell. (B)</p> Signup and view all the answers

What is the primary function of lysosomes?

<p>Breaking down excess or worn-out cell parts (A)</p> Signup and view all the answers

Which molecules can pass through the outer mitochondrial membrane?

<p>Molecules less than 10 kDa (B)</p> Signup and view all the answers

What is the primary role of nuclear receptors?

<p>Regulate gene transcription (A)</p> Signup and view all the answers

Which statement about steroid receptors is true?

<p>They exist as cytoplasmic complexes with Heat Shock Proteins. (A)</p> Signup and view all the answers

How do G-coupled receptors generally transmit signals?

<p>By passing the membrane multiple times (C)</p> Signup and view all the answers

What is the function of enzyme-linked receptors?

<p>To function as enzymes or be closely linked to them (D)</p> Signup and view all the answers

Which type of G-coupled receptor is associated with inhibiting cAMP production?

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

What does the binding of thyroid hormones primarily affect?

<p>Gene regulation in nuclear and mitochondrial DNA (D)</p> Signup and view all the answers

What occurs when TSH binds to its receptor?

<p>It activates both Gs and Gq pathways. (B)</p> Signup and view all the answers

What is phosphorylation in biochemical terms?

<p>The addition of a phosphate group to a molecule (A)</p> Signup and view all the answers

What characterizes GTP binding as a signaling mechanism?

<p>It alters proteins between active and inactive states. (D)</p> Signup and view all the answers

What is the main function of histones in the cell?

<p>Package DNA into nucleosomes (A)</p> Signup and view all the answers

Which phase is characterized by the completion of DNA replication?

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

What significant event occurs during anaphase?

<p>Sister chromatids move to opposite ends of the cell (A)</p> Signup and view all the answers

What is the main purpose of checkpoints in the cell cycle?

<p>To regulate division and ensure proper timing (B)</p> Signup and view all the answers

What is a key feature of metaphase during cell division?

<p>Chromosomes align in the middle of the cell (D)</p> Signup and view all the answers

Which protein complex is crucial for binding chromosomes during cell division?

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

Which phase follows cytokinesis in the cell cycle?

<p>G1 Phase (A)</p> Signup and view all the answers

What is one consequence of apoptosis?

<p>Cell avoids bursting and damaging neighboring cells (D)</p> Signup and view all the answers

What characterizes the G0 phase of a cell?

<p>The cell stops replicating and may undergo apoptosis (A)</p> Signup and view all the answers

What components form a nucleosome?

<p>DNA wrapped around 8 histone proteins (C)</p> Signup and view all the answers

What is the primary buffering system in the body that acts quickly to maintain pH?

<p>Bicarbonate buffering system (D)</p> Signup and view all the answers

Which of the following processes occurs when the body's pH decreases due to increased H+ ions?

<p>Hyperventilation occurs (C)</p> Signup and view all the answers

How does the kidney contribute to the control of plasma bicarbonate?

<p>By secreting H+ ions (C)</p> Signup and view all the answers

What happens to CO2 during gas exchange in the lungs?

<p>It is expired after dissociation from carbonic acid (C)</p> Signup and view all the answers

What is the consequence of pH levels dropping below 6.8?

<p>Decreased enzyme activity (B)</p> Signup and view all the answers

Which statement about buffers is accurate?

<p>Buffers can consist of weak acids and their salts (D)</p> Signup and view all the answers

What defines respiratory acidosis?

<p>Inability to expel CO2 sufficiently (C)</p> Signup and view all the answers

In the oxygen transport process, what role does haemoglobin play?

<p>It binds to oxygen and carries it from the lungs (B)</p> Signup and view all the answers

What is the main issue when the body experiences metabolic acidosis?

<p>Failure to excrete sufficient endogenous acid (B)</p> Signup and view all the answers

What is the consequence of pH fluctuations in the body?

<p>Altered cellular uptake of minerals (C)</p> Signup and view all the answers

Flashcards

What is the basic structural building block of living organisms?

The cell is the fundamental unit of life, responsible for carrying out all the functions necessary for an organism to survive.

What is protoplasm?

Protoplasm is the living material that fills a cell, encompassing both the cytoplasm (fluid portion) and the organelles (functional structures within the cell).

What are ribosomes responsible for?

Ribosomes are responsible for translating genetic information from messenger RNA (mRNA) into proteins. This process is called protein synthesis.

What is the Golgi apparatus involved in?

The Golgi apparatus modifies, sorts, packages, concentrates, and stores secretory products like proteins and lipids. It's essentially the cell's packaging and shipping center.

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What are the roles of the Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER)?

RER is studded with ribosomes and involved in protein synthesis and glycosylation (adding sugar molecules to proteins). SER is involved in lipid metabolism, steroid hormone synthesis, glucose production, and detoxification.

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What is the function of lysosomes?

Lysosomes are responsible for breaking down worn-out cell parts, debris, and other cellular waste.

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What are mitochondria known for?

Mitochondria, often called the powerhouses of the cell, produce energy (ATP) through cellular respiration. They also have their own DNA and can replicate independently.

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Fast Transduction

Rapid alteration of protein function that triggers changes in cytoplasmic machinery and cell behavior within seconds to minutes.

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Nuclear Receptors

Proteins found in the nucleus or cytoplasm that regulate gene transcription. They possess domains for ligand binding, DNA binding, and activation functions.

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Steroid Receptors

Nuclear receptors that regulate transcription and exist as cytoplasmic complexes with Heat Shock Proteins (HSPs). Ligand binding releases HSP, allowing the receptor to bind to specific DNA elements.

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T3 Signaling

Direct regulation of gene transcription by T3 hormone binding to thyroid receptors and coactivators, affecting both nuclear and mitochondrial genes.

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Ion-Channeled Coupled Receptors

Ligand-gated, voltage-gated, or mechanically gated receptors that mediate fast synaptic signaling and electrical communication in the nervous system. Examples include GABAA receptors.

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G-Coupled Receptors

Ligand-activated receptors that span the membrane seven times. They are the largest receptor family and mediate slower, longer-lasting responses. They are linked to cAMP or phosphoinositol signaling pathways.

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Enzyme-Linked Receptors

Receptors that either function as enzymes themselves or are tightly linked to enzymes. They span the membrane once. Examples include receptor tyrosine kinases and cytoplasmic tyrosine kinases.

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Phosphorylation

The addition of a phosphate group to a molecule, often acting as a molecular switch that alters structure and function.

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GTP Binding

A molecular switch where GTP binding and hydrolysis transition a molecule between active and inactive states.

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Cell Cycle

The series of events that a cell goes through from its formation to its division into two daughter cells.

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Mitosis

The process of cell division where the nucleus divides into two nuclei, each containing the same number of chromosomes as the original nucleus.

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G1 Phase

The first phase of the cell cycle, characterized by rapid cell growth and duplication of organelles and cytosolic components.

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S Phase

The second phase of the cell cycle, in which DNA replication occurs, creating two identical copies of the cell's genome.

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G2 Phase

The third phase of the cell cycle, where the cell continues to grow and prepare for cell division. Enzymes and proteins necessary for mitosis are synthesized.

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Interphase

The period between two successive cell divisions, consisting of G1, S, and G2 phases. This is where the cell grows and copies its genetic information.

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Nucleosome

A segment of DNA wrapped around eight histone proteins, acting as a fundamental unit of DNA packaging.

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Chromosome

A thread-like structure of DNA and protein that carries genetic information in the form of genes.

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Chromatid

One of two identical copies of a chromosome that are joined together at the centromere.

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Centromere

The constricted region of a chromosome where the two sister chromatids are held together.

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Synaptic Vesicle Fusion

The process by which a synaptic vesicle, containing neurotransmitters, merges with the presynaptic membrane, releasing its contents into the synaptic cleft.

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SNARE Proteins

Proteins that facilitate the fusion of synaptic vesicles with the presynaptic membrane. They act like molecular 'zippers' to bring membranes together.

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Tetanus Toxin

A toxin that blocks the release of neurotransmitters by interfering with SNARE protein function, leading to muscle spasms.

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Neuromuscular Junction

The specialized synapse between a motor neuron and a skeletal muscle cell, responsible for initiating muscle contraction.

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Acetylcholine Receptor

A receptor protein on the muscle cell membrane that binds to acetylcholine, triggering a chain reaction leading to muscle contraction.

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What is the role of the kidneys in acid-base balance?

Kidneys excrete excess hydrogen ions (H+) through urine, helping to regulate blood pH. This process is essential for maintaining the body's acid-base balance.

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How does the body handle excess CO2?

The lungs are responsible for expelling carbon dioxide (CO2), which is a product of cellular respiration. This prevents CO2 from accumulating in the blood, which could disrupt pH balance.

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What are buffers, and why are they important?

Buffers are solutions that resist changes in pH. They act like sponges for excess H+ ions, preventing drastic pH fluctuations in the body.

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List the major buffering systems in the body.

The main buffering systems are: 1. Bicarbonate buffering system (lungs) - fastest and primary; 2. Phosphate buffering system; 3. Ammonia buffering system (kidneys); and 4. Proteins.

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What happens to respiration rate when H+ concentration increases?

When H+ concentration increases, the body tries to compensate by increasing the respiratory rate (hyperventilation) to expel more CO2 and decrease acidity.

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What is respiratory acidosis?

Respiratory acidosis occurs when the lungs fail to excrete enough CO2, leading to an increase in blood acidity.

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What is metabolic acidosis?

Metabolic acidosis occurs when the kidneys fail to excrete enough acid produced by the body, causing an increase in blood acidity.

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How does the body transport CO2?

Red blood cells (RBCs) play a crucial role in transporting CO2 from tissues to the lungs. They carry CO2 as bicarbonate (HCO3-) and in dissolved form.

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Describe the exchange of gases in the lungs.

In the lungs, oxygen (O2) binds to hemoglobin in red blood cells. Simultaneously, CO2 is released from hemoglobin and converted to CO2 gas, which is exhaled.

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How does gas exchange occur in tissues?

In tissues, oxygen is released from hemoglobin to supply cells. CO2 produced by cells enters the bloodstream and is transported to the lungs.

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Study Notes

Cell Structure & Function

  • The cell is the basic structural unit of living organisms.
  • Protoplasm is the living part of the cell, containing organelles.
  • Approximately 37 trillion cells are in the human body.
  • There are over 200 different cell types.

Parts of the Cell

  • Ribosomes: Composed of a large (60S) and small (40S) subunit containing rRNA. These translate mRNA into proteins.
  • Golgi Apparatus: Modifies, sorts, packages, concentrates, and stores secretory products (proteins and lipids). It works closely with the Endoplasmic Reticulum (ER).
  • Endoplasmic Reticulum (ER): Involved in protein synthesis and processing.
    • Rough ER (RER): aids in protein synthesis and glycosylation.
    • Smooth ER (SER): involved in lipid metabolism, steroid hormone synthesis, and detoxification.
  • Vesicles: Small cellular containers involved in various functions like enzyme storage, molecule transport, and secretion.
  • Vesicle Types:
    • Granules: release molecules outside of the cell via exocytosis
    • Lysosomes: break down excess or worn-out parts of the cell.
    • Peroxisomes: produce hydrogen peroxide and break down fatty acids.

Mitochondria

  • Powerhouse of the cell
  • Membrane-bound organelle
  • Contains its own DNA and some proteins.
  • Involved in energy production (ATP), hormone signals, steroid synthesis, and heat production.

Nucleus

  • Location of DNA replication and transcription.
  • Contains the cell's genome (complete set of DNA instructions).
  • Multiple nuclei are present in some cells.
  • The nuclear membrane has supporting lamins which are protein filaments that regulate the size, shape, and chromatin arrangement of DNA.
  • Nucleolus is where ribosomes are produced.
  • Nuclear pores monitor and regulate the passage of substances.

Cytoskeleton

  • Network of filaments (microtubules, microfilaments, intermediate filaments)
  • Provides support and structure to the cell.
  • Aids in cell movement.
  • Involved in cell division (mitosis).

Microtubules

  • Created from the microtubule organizing center (MTOC).
  • Formed from tubulin heterodimers, with a positive and negative end.
  • Involved in mitosis, organelle deployment, and transport.
  • Cilia are an example of microtubules, including primary cilia for signaling, motile cilia for movement, and nodal cilia for development.

Microfilaments (Actin Filaments)

  • Thin and flexible
  • Formed from actin monomers, forming a double helix.
  • Involved in cell movement, endocytosis/exocytosis, and maintaining cell shape.
  • Types include stress fibers, cell cortex, lamellipodia, and filopodia.

Intermediate Filaments

  • Long, rope-like proteins
  • Stabilize the cell under mechanical stress.
  • Involved in cell adhesion and maintaining shape.
  • Several types based on function (eg, keratins, vimentin, desmin, neurofilaments, and lamins for nuclear stability)

Cell-cell junctions

  • Specialized structures that connect neighboring cells
  • Types: tight junctions, adherens junctions, desmosomes, gap junctions, hemidesmosomes
  • Functions: seal cells together, provide cell adhesion connect cytoskeletal elements and allow passage of small molecules

Cell Membrane

  • Composed of phospholipid bilayer with hydrophilic heads and hydrophobic tails.
  • Relatively impermeable.
  • Contains cholesterol and proteins that maintain shape and regulation.
  • Transports molecules across the membrane (passive and active).

Membrane Trafficking

  • Process of transporting molecules within and outside of a cell
  • Different methods of transport; endocytosis (phagocytosis, pinocytosis, and receptor-mediated), and exocytosis.

Cell Homeostasis

  • Maintaining a stable internal environment within the cell.
  • Fluid membrane due to movements of lipid bilayer (flip-flop, flexion, and rotation)

Action potential

  • A rapid change in membrane voltage across the plasma membrane of a cell, typically neurons or muscle cells, characterized by a rapid depolarization followed by repolarization.
  • Crucial for transmitting signals.

Cell Signaling

  • Communication between cells.
  • Types: juxtacrine, paracrine, synaptic, endocrine.
  • Cell surface receptors and intracellular receptors.
  • Mechanisms: signal transduction pathways.

Principal of Cell Signaling

  • Reception, transduction, response
  • Extracellular signal molecule (ligand) – receptor protein – transduction –response.

Cell Cycle

  • Cell division.
  • Phases: cell growth (G1), DNA replication (S), preparation for division (G2), and division (M).

Apoptosis

  • Programmed cell death.
  • Types: intrinsic and extrinsic pathways.
  • Important for development, maintenance, and health.

Enzyme Kinetics

  • Studying the rates of enzyme-catalyzed reactions.
  • Variables: Vmax, Km, temperature, pH, substrate concentration, enzyme and inhibitor concentration.
  • Models: induced fit and transition state.

Enzyme Inhibition

  • Blocking enzyme activity.
  • Types: competitive and non-competitive inhibition.
  • Impacts on enzyme activity.

Allosteric Regulation

  • Regulation of enzyme activity through allosteric sites.
  • Modification of enzyme activity.
  • Feedback mechanisms

Acids, Bases and Buffering systems

  • Fundamentals of pH.
  • Importance of bicarbonate buffering system in maintaining blood pH.

Oxygen Transport

  • Transport of oxygen from the lungs to tissues.
  • Role of hemoglobin
  • Factors Affecting Oxygen Binding

Neuromuscular Junctions

  • Chemical synapse between motor neurons and muscle fibers (myocytes).
  • Steps of neuromuscular transmission: action potential arrival, neurotransmitter release, binding to receptors, muscle contraction.
  • Recycling of postsynaptic membrane.

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Test your knowledge on key concepts in cell biology and neurobiology. This quiz covers neurotransmitter release, muscle cell function, and the roles of various cellular structures and organelles. Dive into topics such as action potentials, receptors, and the functions of ribosomes and mitochondria.

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