KA 4 Flashcards
(27 cards)
How do multicellular organisms signal between cells?
Multicellular organisms signal between cells using extracellular signaling molecules like steroid hormones, peptide hormones, and neurotransmitters.
What are receptor molecules?
Receptor molecules are proteins on target cells with a binding site for specific signaling molecules. Binding changes the receptor’s conformation, triggering a cellular response.
Why do different cell types have specific receptors?
Different cell types produce specific signals that can only be detected and responded to by cells with the specific receptor for that signal.
Can the same signaling molecule have different effects on different cell types?
Yes, signaling molecules can have different effects on different cell types due to variations in intracellular signaling molecules and pathways.
How do hydrophobic signaling molecules function?
Hydrophobic signaling molecules can diffuse through the phospholipid bilayer and bind to intracellular receptors, typically transcription factors.
What is the role of transcription factors in hydrophobic signaling?
Transcription factors, when bound to DNA, can stimulate or inhibit transcription, affecting gene expression.
Give an example of hydrophobic signaling molecules.
Steroid hormones like oestrogen and testosterone are examples of hydrophobic signaling molecules.
How do steroid hormones affect gene expression?
Steroid hormones bind to specific receptors, move to the nucleus, and bind to hormone response elements (HREs) on DNA, influencing transcription.
How do hydrophilic signaling molecules function?
Hydrophilic signaling molecules bind to transmembrane receptors on the cell surface, triggering a response without entering the cytosol.
What happens when a ligand binds to a transmembrane receptor?
The receptor undergoes a conformational change, transducing the signal across the membrane, leading to intracellular signaling.
What is the role of G-proteins in signal transduction?
G-proteins relay signals from activated receptors to target proteins like enzymes and ion channels.
What are phosphorylation cascades?
Phosphorylation cascades involve a series of kinase activations, amplifying the signal and activating multiple intracellular pathways.
How does insulin signaling work?
Insulin binds to its receptor, triggering a phosphorylation cascade that leads to the movement of GLUT4 transporters to the cell membrane for glucose uptake.
What is diabetes mellitus?
Diabetes can be caused by insulin production failure (type 1) or receptor malfunction (type 2), with type 2 often linked to obesity.
How does exercise help people with type 2 diabetes?
Exercise triggers GLUT4 recruitment, improving glucose uptake in muscle and fat cells even in individuals with type 2 diabetes.
What is the resting membrane potential?
The resting membrane potential is the state where there is no net ion flow across the membrane, with the inside of the cell being more negative than the outside.
What is an action potential?
An action potential is a wave of electrical excitation along the neuron’s membrane, caused by changes in the membrane potential.
How does neurotransmitter binding trigger an action potential?
Binding of a neurotransmitter to its receptor opens ligand-gated ion channels, causing depolarization. If the threshold is reached, voltage-gated sodium channels open, generating an action potential.
How is the resting membrane potential restored?
After depolarization, voltage-gated potassium channels open to restore the resting membrane potential, and the sodium-potassium pump restores ion gradients.
What is the role of the sodium-potassium pump after an action potential?
The sodium-potassium pump restores sodium and potassium ions to their resting concentrations after an action potential, maintaining the electrochemical gradients.
What is the function of the retina in the eye?
The retina detects light and contains photoreceptor cells, rods for dim light and cones for color vision.
How do rods and cones differ?
Rods function in dim light but cannot detect color, while cones are responsible for color vision and function in bright light.
What is rhodopsin?
Rhodopsin is the retinal-opsin complex in rod cells that absorbs light and initiates a signal transduction cascade.
How does photoexcited rhodopsin activate G-proteins?
Photoexcited rhodopsin activates transducin, a G-protein that then activates phosphodiesterase (PDE), leading to a reduction in cGMP and ion channel closure.
