Free response questions

What does the RNA world hypothesis propose?

It proposes that early life was based on RNA, which served as both genetic material and a catalyst for biochemical reactions.

What is one piece of evidence that supports the RNA world hypothesis?

Ribozymes, RNA molecules with catalytic properties, demonstrate that RNA can both store information and facilitate chemical reactions.

What problem does the RNA world hypothesis solve?

It explains a plausible precursor to the DNA-protein system, addressing how life could have originated.

What is the primary structure of proteins?

The linear sequence of amino acids in a protein.

What defines the secondary structure of proteins?

Local folding patterns, such as α-helices and β-sheets, stabilized by hydrogen bonds.

What is the tertiary structure of a protein?

The overall 3D shape of a single polypeptide, determined by various interactions.

What characterizes the quaternary structure of proteins?

The assembly of multiple polypeptide chains into a functional protein complex.

What is a key advantage of using RNAi in C. elegans research?

RNAi enables precise, sequence-specific gene silencing, allowing for effective investigation of gene function.

Why is C. elegans particularly well suited for RNAi techniques?

It effectively takes up RNAi through feeding, injection, or soaking, and has a transparent body for rapid analysis.

What is the rate of lateral diffusion of lipids compared to flip-flop movement?

Lateral diffusion is very fast, occurring on the scale of microseconds, while flip-flop is very slow, taking hours or longer.

What is the role of flippase in lipid movement?

Flippases are enzymes that facilitate the flip-flop of specific lipids by lowering the energy barrier for movement between leaflets.

Outline the steps from an impulse arriving at a presynaptic neuron's terminal knob to action potential initiation in a postsynaptic cell.

Impulse arrival leads to calcium influx, neurotransmitter release, binding to receptors, opening of ion channels, and depolarization that triggers action potential.

How does the conservation of the G domain give Ras-like proteins their identity?

The conserved G domain provides a shared structure and mechanism for binding and hydrolyzing GTP, defining their identity.

How do non-conserved regions in Ras-like proteins create diversity?

Non-conserved regions enable specific interactions with distinct regulators and effectors, contributing to unique signaling pathways.

What similarities exist between mitochondria and chloroplasts?

Both are double-membraned organelles with their own DNA and ribosomes, featuring folded inner membranes to increase surface area.

What is the main difference between mitochondria and chloroplasts?

Mitochondria produce ATP via the electron transport chain, while chloroplasts use thylakoid membranes for photosynthesis.

How do plasmodesmata and gap junctions allow communication between cells?

Both structures permit direct communication and material exchange between adjacent cells.

Can a moderately sized protein pass through a plasmodesma?

Yes, plasmodesmata can transport larger molecules, including proteins, which gap junctions cannot typically accommodate.

Describe the Cisternal Maturation Model of Golgi transport.

This model proposes that Golgi cisternae mature from one type to another, facilitating transport while enzymes are added or removed.

What is the Vesicular Transport Model for Golgi transport?

It suggests that cargo is transported between Golgi cisternae via vesicles that bud from one cisterna and fuse with another.

What distinguishing feature is highlighted in the current model of Golgi transport?

The current model integrates both vesicular transport and the maturation of cisternae as they progress through the stack.

Why is the paper by Reeve et al. on mitochondrial disease considered important?

It established a link between mitochondrial DNA (mtDNA), aging, and neurodegeneration.

What impact does the LARGE- gene have on cell proliferation, according to Akhavan et al.?

LARGE- increases cell proliferation and accelerates the S phase of the cell cycle.

How does sugar release occur in the breakdown of glycogen?

Glycogen breakdown is triggered by glucagon activating adenylate cyclase to produce cAMP, which activates PKA to catalyze glucose release.

What is the role of ATR in response to UV damage?

ATR detects UV-induced DNA lesions and activates Chk1 to inhibit cell cycle progression and allow DNA repair.

What is the organization of intermediate filaments?

Composed of monomers, which form dimers and tetramers, leading to the assembly of protofilaments and the final filament structure.

How does Kinesin-5 contribute to spindle fiber dynamics?

Kinesin-5 has two heads moving towards the plus end of microtubules, facilitating the sliding apart of interpolar microtubules.

How do wee1 and cdc25 control the cell cycle in yeast?

Wee1 inhibits Cdk, delaying transition from G2 to mitosis, while Cdc25 activates Cdk for cell cycle progression.