Biology and Physiology Quiz

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Questions and Answers

What is the role of the B domain in the process of Diphtheria Toxin?

Helps break disulfide bonds between A and B domains

Fuses with the cell membrane

Binds to EF-2, blocking translation and causing cell death

Binds to a receptor for cell entry (correct)

How does the pH change in the lysosomes contribute to the activation of Diphtheria Toxin?

It stimulates the A domain to bind to EF-2

It activates the GEF protein

It causes the T domain to flip inside out and fuse with the cell membrane

It breaks disulfide bonds between A and B domains (correct)

What is the role of GAP in regulating Ras activity?

It binds to EF-2, blocking translation and causing cell death

It regulates the localization of Ras

It stimulates Ras to take up GTP, leading to its activation

It stimulates Ras to hydrolyze GTP, causing it to be inactive (correct)

What is the role of GEF in regulating Ras activity?

It stimulates Ras to take up GTP, leading to its activation Signup and view all the answers

How does the A domain of Diphtheria Toxin enter the cytoplasm?

It is released from the lysosomes after pH change Signup and view all the answers

What is the consequence of Diphtheria Toxin binding to EF-2?

It blocks translation and causes cell death Signup and view all the answers

What is the role of EF-Tu in bacterial translation?

It stimulates protein synthesis Signup and view all the answers

What is the role of the T domain in Diphtheria Toxin?

It fuses with the cell membrane Signup and view all the answers

What is the primary function of the eukaryotic ABC transporter?

To control the movement of molecules in and out of the cell Signup and view all the answers

What is the primary mechanism by which HBO therapy reduces the half-life of CO-haemoglobin?

Facilitating CO dissociation from haemoglobin Signup and view all the answers

How does the binding of ATP to the CFTR receptor affect its function?

It further opens the channel, allowing chloride to exit the cell Signup and view all the answers

What is the characteristic of a protein domain?

A region of a protein's polypeptide chain that is self-stabilizing and folds independently Signup and view all the answers

What is the role of GEF in protein function regulation?

It facilitates the exchange of guanine nucleotides, activating GTP-binding proteins Signup and view all the answers

How do cells control protein function by localization?

By specific sequences guiding proteins to certain cellular regions, post-translational modifications, and binding to scaffold proteins Signup and view all the answers

What is the optimal pH for cathepsin activity?

pH 5.5 Signup and view all the answers

What is the result of GTP -> GDP hydrolysis during translation?

The release of tRNA from the ribosome Signup and view all the answers

How do myosin filaments regulate protein movement during muscle contraction?

Through the binding of ATP, which induces a conformational change Signup and view all the answers

What is the effect of pH change on cathepsin conformation?

pH change alters the protein's conformation, freeing the active site for normal function Signup and view all the answers

What is the consequence of cystic fibrosis on the CFTR receptor?

The receptor becomes inactive, leading to impaired chloride transport Signup and view all the answers

How is time control achieved in protein regulation?

By regulating transcription and degradation Signup and view all the answers

What is the role of scaffold proteins in protein regulation by localization?

They bring proteins together, relaying signals and facilitating interactions Signup and view all the answers

What is the primary function of GAP in protein function regulation?

It activates GTPase, promoting protein degradation Signup and view all the answers

What is the role of phosphorylation in regulating the CFTR receptor?

It opens the channel, allowing chloride to exit the cell Signup and view all the answers

What is the effect of HBO therapy on tissue oxygenation?

It maintains tissue oxygenation while circulation recovers Signup and view all the answers

Study Notes

Oxygen Transport

HBO (hyperbaric oxygen) reduces the half-life of CO-haemoglobin (CO-Hb) and facilitates CO dissociation from haemoglobin.
HBO allows oxygen (O2) to directly diffuse to tissues, bypassing the normal circulation, and maintains tissue oxygenation while circulation recovers.

Protein Domains

A protein domain is a region of a protein's polypeptide chain that is self-stabilizing and folds independently from the rest.

Protein Regulation by Localization

Cells control protein expression and activity but not protein location.
Proteins can be specific or non-specific in their actions.
Control of protein function involves managing when and where it operates.
Time control is achieved by regulating transcription and degradation.
There are three ways of protein localization:
- Specific sequences guiding proteins to certain cellular regions.
- Post-translational modifications triggered by signal pathways.
- Binding to scaffold proteins that relay signals, bringing proteins together.

Protein Regulation by pH

Cathepsins are lysosomal proteases that require pH 5.5 to be active and are inactive at pH 7.4.
An alpha helix initially blocks their active site, and a pH change alters the protein's conformation due to increased hydrogen ions, freeing the active site for normal function.
Diphtheria toxin comprises A (catalytic) and B (regulatory) domains.
The B domain binds to a receptor for cell entry.
Lysosomes, with their acidic environment, help break disulfide bonds between A and B domains.
A pH change causes the T domain to flip inside out and fuse with the cell membrane.
The A domain enters the cytoplasm and binds to EF-2, blocking translation and causing cell death.

GTP Binding Proteins

Rho kinase is an example of GTP Binding Proteins.
Regulation by GAP (GTPase activating protein) and GEF (guanine nucleotide exchange factors):
- Ras activity is regulated by two proteins: a GEF (guanine nucleotide exchange factor) and a GAP (GTPase-activating protein).
- GEF stimulates Ras to take up GTP, leading to its activation, initiating a signaling pathway.
- GAP stimulates Ras to hydrolyze GTP, causing it to be inactive.

EF-Tu - A Bacterial Translation Elongation Factor

Works in elongation during translation.
Carries tRNA to the ribosome’s A site, can regulate translation by inhibiting or promoting the transport to the ribosome.
Can only bind to tRNA when it is bound to GTP.
GTP -> GDP hydrolysis results in release of tRNA.

Protein Movement (Myosin and Actin)

Myosin filaments have a head that is regulated by ATP activity.
Binding of ATP and subsequent hydrolysis of ATP to ADP results in the pushing of the myosin head along the actin.

Membrane Bound Transporters - Eukaryotic ABC Transporter

Control movement of molecules in and out of the cell.
Molecules bind to receptors, can't escape.
ATP binding induces a conformational change, pushing molecules out of the cell.

CFTR Receptors

Normally closed; chloride can't move out.
Phosphorylation of the regulatory domain at a specific site opens the channel.
ATP binding to secondary domains further opens the channel.
In cystic fibrosis, if the CFTR channel can't open, chloride and water can't exit, leading to thick mucus, bacterial growth, lung infections, and potential death.

Comparison between Phosphorylated and GTP-binding Protein

GEF (guanine nucleotide exchange factor).
GAP (GTPase-activating protein).

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Description

This quiz covers various biology and physiology topics such as oxygen transport, protein domains, and protein regulation by localization.