communication across membranes Flashcards
(20 cards)
What is the primary function of cell membranes?
To provide a permeability barrier for the cell.
What are the two main classes of membrane transport proteins?
- Transporters
- Channels
How do transporters function?
They alternate between two conformations, making the solute-binding site sequentially accessible on either side of the bilayer.
What is the difference between simple diffusion and transporter-mediated diffusion?
Transporter-mediated diffusion reaches a maximum rate (Vmax) when saturated, while simple diffusion does not.
True or False: Channel proteins allow specific solutes to passively diffuse across the bilayer.
True
What is the effect of cholesterol on membrane fluidity?
Cholesterol decreases the flexibility of fatty acid side chains.
Fill in the blank: The _______ model describes the structure of cell membranes.
fluid mosaic
What are the four transport mechanisms across cell membranes?
- Simple diffusion
- Channel-mediated
- Transporter-mediated
- Active transport
What drives active transport?
An energy source, such as ion-concentration gradients.
What is the role of Na+ in glucose transport across intestinal epithelial cells?
It powers the glucose symport, allowing glucose to be transported against its gradient.
What is the biological function of adrenaline?
Stress response.
How does cyclic AMP function in signal transduction?
It activates protein kinase A (PKA) signaling cascade.
What are the two second messengers produced from the hydrolysis of PI(4,5)P2?
- Diacylglycerol (DAG)
- Inositol 1,4,5-trisphosphate (IP3)
What happens to IP3 in the cell?
It diffuses through the cytosol and releases Ca2+ from the ER.
What is the role of protein kinase C (PKC) in signal transduction?
It phosphorylates various targets, including enzymes, through covalent modification.
True or False: G-protein-coupled receptors (GPCRs) are involved in signal transduction.
True
What is the significance of the alpha subunit in G-proteins?
It changes conformation and releases GDP when activated.
Fill in the blank: The binding of a ligand to its GPCR changes the GPCR’s _______.
conformation
What is the function of Ca2+ in intracellular signaling?
It acts as a ubiquitous intracellular mediator.
What is the role of CREB in cells?
It transforms short-lived signals into long-term changes, influencing learning and memory.
