BioExam2

What do cilia contribute to during embryonic development?

Cilia contribute to left-right asymmetry and organ patterning.

How do cilia assist in maintaining fluid balance?

Cilia in kidney tubules regulate blood pressure by facilitating fluid movement.

What functions do cilia serve in unicellular organisms?

Cilia aid in locomotion, feeding, sensory perception, defense, and reproduction.

What are some sensory cues detected by cilia in unicellular organisms?

Cilia detect light, chemicals, and temperature changes.

What is the role of cilia in facilitating movement of gametes in some unicellular organisms?

Cilia aid in the movement of sex cells for reproduction.

What are the basic steps in transporting proteins across organelle membranes?

Recognition of signals, complex formation, translocation, and release.

How do GEFs contribute to GTPase activity control?

GEFs promote the exchange of GDP for GTP on GTPase proteins.

What happens to actin filaments at the 'minus' end?

They depolymerize.

What nucleotide does G-actin bind initially?

ATP.

What happens to ATP once incorporated into the actin filament?

It is hydrolyzed to ADP.

How does the Arp2/3 complex initiate filament growth?

By binding and activating actin monomers.

In the dendritic nucleation model, what is the first step?

Activation of Arp2/3 complex and NPFs.

What structure is involved in cell migration according to the dendritic nucleation model?

Lamellipodia.

Describe the core structural component of cilia responsible for motility.

Axoneme with a '9+2' arrangement of microtubules, radial spokes, nexin links, and dynein arms.

How are proteins imported into the ER lumen?

Proteins are imported co-translationally or post-translationally.

Describe the effect of splice site mutations on mRNA transcripts.

Splice site mutations disrupt normal splicing, leading to abnormal mRNA isoforms.

Discuss the gene dosage effect resulting from gene duplication.

Gene duplication can increase protein dosage, altering phenotypic traits.

How do protein import and RNA export mechanisms differ?

Protein import recognizes NLS, MTS; RNA export recognizes specific RNA sequences.

Explain how repressors inhibit transcription.

Repressors block RNA polymerase binding, other activator binding, or induce chromatin remodeling.

Explain the process of viral maturation in a retrovirus lifecycle.

Viral proteases cleave precursor proteins into functional forms.

Why is cell movement essential?

For migration, chemotaxis, cellular interactions, intracellular transport, and extracellular matrix remodeling.

What are the reasons for cell movement?

Migration, chemotaxis, cellular interactions, intracellular transport, extracellular matrix remodeling.

What are the factors contributing to bleb formation?

Factors include actomyosin contractility, cytoskeletal disassembly, membrane properties, and cellular signaling.

Why is understanding cell movement in 3D important?

It is crucial for processes like metastasis where cells spread to distant sites.

How do microRNAs regulate gene expression?

MicroRNAs bind to mRNA, affecting translation or degrading the mRNA to control protein levels.

Why are microRNAs considered efficient regulators of gene expression?

MicroRNAs are efficient due to multiple targets, robustness, flexibility, and fine-tuning ability.

Differentiate between somatic and germ line mutations.

Somatic mutations occur in non-reproductive cells, while germ line mutations affect cells that give rise to eggs or sperm.

Explain the role of mutations in evolution.

Mutations in genes introduce genetic variation, crucial for natural selection and driving evolution.

What is the role of exocytosis in cytotoxic T cells and NK cells?

Exocytosis releases cytotoxic granules to induce apoptosis in infected or transformed cells.

How do cilia regulate processes in tissue and organ development?

Cilia-mediated signaling pathways regulate cell differentiation and morphogenesis.

What is the role of primary cilia in cell signaling?

Primary cilia detect and transduce extracellular signals to regulate cell functions.

What is the role of the Arp2/3 complex in actin filament nucleation?

It promotes nucleation and branching.

What role do Nucleation Promoting Factors (NPFs) play?

They stimulate the nucleation activity of the Arp2/3 complex.

What do actin filaments undergo in terms of turnover during cell movement?

Continuous assembly and disassembly.

What does the Dendritic Nucleation Model propose?

Actin filaments are nucleated and branched by the Arp2/3 complex.

Explain the Convergent Elongation Model in brief.

Actin filaments elongate and converge towards the leading edge.

According to the Polarity Sorting Model, what pushes against the membrane?

Elongating barbed ends of actin filaments.

What does the Membrane Flow Model describe?

Actin filaments generate forces that push against and cause membrane flow.

How does Listeria monocytogenes move within host cells?

By hijacking the host actin cytoskeleton.

What do Listeria monocytogenes secrete to hijack the actin cytoskeleton?

Proteins that mimic host cell signaling molecules.

What is the main function of motile cilia?

Generate movement or flow across the cell surface.

Where are motile cilia primarily found?

Specialized epithelial cells in tissues like the respiratory tract and reproductive system.

What differentiates primary cilia from motile cilia in structure?

Primary cilia lack the central pair of singlet microtubules.

What is the primary role of primary cilia in mammalian cells?

Serve as sensory organelles for detecting and transducing signals.

How is cilia assembly facilitated in cells?

Through active transport of building materials using molecular motors like kinesins and dyneins.

Explain the importance of active transport in cilia assembly.

Ensures precise regulation, proper structure, and function of cilia.

What are ciliopathies, and how are they characterized?

Genetic disorders with abnormal cilia structure and function.

Name two functions of cilia in multicellular organisms.

Movement of fluids and sensory reception.

Give examples of cilia functions in the human body.

Helping in breathing, egg transport, and sound detection in the inner ear.

What determines the destination of protein synthesis in ribosomes?

The presence of a signal sequence at the N-terminus of a protein.

Describe the two populations of ribosomes in a cell.

There are free ribosomes and membrane-bound ribosomes (attached to the ER).

What are the two main pathways of the endomembrane system?

The secretory pathway and the endocytic pathway.

How is organelle identity maintained within the endomembrane system?

By specific composition and function of membrane proteins and lipids.

Explain the stages of clathrin-mediated vesicle assembly.

Nucleation, Cargo Selection, and Vesicle Budding.

What is the relationship between the ER, nuclear envelope, and nuclear pore complexes?

The ER is continuous with the nuclear envelope, and NPCs facilitate transport.

What types of proteins are imported into the ER?

Secretory proteins, membrane proteins, and proteins for other organelles.

What is the role of mutations in evolutionary change?

Mutations provide genetic variation that can lead to differences among individuals.

Explain the impact of missense mutations on proteins.

Missense mutations change a single amino acid in the protein sequence, affecting protein function.

What is the consequence of nonsense mutations?

Nonsense mutations introduce a premature stop codon, resulting in non-functional proteins.

Define frameshift mutations.

Frameshift mutations insert or delete nucleotides, causing a shift in the reading frame.

How does gene duplication contribute to genetic diversity?

Gene duplication creates raw material for new genes and evolutionary innovation.

Explain the concept of subfunctionalization after gene duplication.

Subfunctionalization leads to partitioning of ancestral gene function between duplicates.

What is neofunctionalization in the context of gene duplication?

Neofunctionalization involves acquiring new functions not present in the ancestral gene.

Define pseudogenization and its outcome in duplicated genes.

Pseudogenization occurs when duplicated genes become non-functional over time.

What is the role of GEFs in GTPase activation?

GEFs stimulate the dissociation of GDP, allowing GTP to bind.

How do GAPs contribute to GTPase inactivation?

GAPs enhance GTPase activity, accelerating GTP hydrolysis.

Explain how GEFs and GAPs influence nuclear transport.

They regulate Ran activity, controlling nucleocytoplasmic transport directionality.

What are the similarities between protein and RNA transport mechanisms?

Both involve signal recognition, complex formation, and membrane translocation.

What evidence supports the endosymbiotic origin of mitochondria and chloroplasts?

Structural similarities, endosymbiotic gene transfer, phylogenetic evidence, and horizontal gene transfer.

How is membrane potential established and maintained in mitochondria?

Primarily by the electron transport chain and proton pumping.

Explain the Brownian Ratchet Model for mtHsp70-driven protein translocation into the mitochondrial matrix.

mtHsp70 acts as a molecular motor pulling proteins into the matrix.

Describe the Power Stroke Model for mtHsp70-driven protein translocation into the mitochondrial matrix.

mtHsp70 pushes proteins into the matrix using energy from ATP hydrolysis.

What additional signals are required for inner mitochondrial membrane protein localization?

Proteins require hydrophobic stop-transfer sequences in addition to MTS.

Define transcription factors.

Proteins that bind to specific DNA sequences and regulate nearby gene transcription.

What are the two general types of transcription factors?

Activators and repressors.

How do activators enhance transcription?

By promoting the binding of RNA polymerase and transcriptional machinery to gene promoters.

What are extrinsic factors in gene expression?

External stimuli or environmental cues that influence gene expression.

How can extrinsic factors influence gene expression?

Through signaling pathways, chromatin remodeling, post-translational modifications, and competitive binding.

What are epigenetic modifications?

Heritable changes in gene expression that do not involve alterations in the DNA sequence.

How does DNA methylation impact gene expression?

It typically leads to gene silencing by inhibiting transcription factor binding or inducing chromatin condensation.

Explain the role of histone modifications in gene expression.

Histone modifications alter chromatin structure and accessibility, influencing transcriptional activity.

What is the stability feature of epigenetic modifications?

Epigenetic marks are faithfully transmitted to daughter cells, maintaining cell identity.

List the control points in gene expression.

Transcriptional initiation, RNA processing, and mRNA stability.

Explain the lifecycle of a retrovirus.

Attachment and Entry, Reverse Transcription, Integration, Transcription and Translation, Assembly and Budding, Maturation, Release.

How does a retrovirus enter a host cell?

Through membrane fusion or endocytosis.

What is reverse transcription in the context of a retrovirus?

The process where the RNA genome is converted into DNA by reverse transcriptase.

What is the role of integrase in the lifecycle of a retrovirus?

Integration of viral DNA into the host cell genome.

How do retroviruses contribute to novel cellular functions?

Through insertional mutagenesis, horizontal gene transfer, co-option of viral elements, and viral mimicry.

Explain actin filament dynamics.

Actin filaments grow and shrink through treadmilling by adding ATP-bound monomers to grow and hydrolyzing to shrink.

What is the role of ActA in Listeria infection?

ActA recruits and activates Arp2/3 complex for actin polymerization.

How does Listeria move within host cells?

Listeria propels forward by forming actin filament tail-like structure.

What are the levels of molecular organization in microtubules?

Levels include tubulin dimers, protofilaments, microtubule lattice, dynamic instability, and MAPs.

How do microtubules grow and shrink?

They grow by adding GTP-bound tubulin dimers and shrink when GTP is hydrolyzed.

What is the role of the centrosome in microtubule nucleation?

The centrosome serves as the primary microtubule-organizing center (MTOC).

Define Translation Initiation.

Translation Initiation is the assembly of the translation machinery at the start codon of mRNA.

Explain Post-translational Modifications.

Post-translational Modifications are changes to proteins after translation, like phosphorylation and glycosylation.

What is Protein Degradation?

Protein Degradation is the breakdown of proteins by proteasomes or lysosomes.

What is Small Subunit Ribosome Sequencing used for?

Small Subunit Ribosome Sequencing is used for phylogenetic analysis to determine evolutionary relatedness.

What is the role of clathrin in vesicle formation?

Clathrin promotes membrane deformation by self-assembling into a lattice structure.

How does SNARE complex formation facilitate membrane fusion?

SNARE complex formation brings vesicle and target membranes into close proximity.