Bio essay - ions Flashcards
(12 cards)
What role do hydrogen ions play in aerobic respiration?
Hydrogen ions are crucial in oxidative phosphorylation, which occurs in the cristae of the mitochondria, generating 28 out of 32 ATP molecules.
Reduced NAD (NADH) and FAD (FADH₂) from the Krebs cycle donate hydrogen atoms that split into H⁺ ions and electrons.
How is ATP produced during oxidative phosphorylation?
High-energy electrons pass through the electron transfer chain, releasing energy to pump H⁺ ions into the intermembrane space, creating a concentration gradient.
These ions return to the matrix via facilitated diffusion through ATP synthase, providing energy for ATP synthesis.
What is the final electron acceptor in aerobic respiration?
Oxygen serves as the final electron acceptor, combining with H⁺ ions and electrons to form water.
How does ATP power the sodium-potassium pump?
ATP powers the sodium-potassium pump by actively transporting Na⁺ out of epithelial cells, maintaining a Na⁺ gradient.
What is the role of light energy in photosynthesis?
Light energy is absorbed by pigments in the thylakoid membrane, exciting electrons and creating a H⁺ ion gradient across the thylakoid membrane.
This results in the production of ATP and reduced NADP, which is important for the light-independent stage.
What happens in the light-independent stage of photosynthesis?
Carbon dioxide reacts with ribulose bisphosphate to form two molecules of glycerate 3-phosphate, which is then reduced to triose phosphate using energy from ATP and H from reduced NADP.
What initiates muscle contractions?
An action potential arrives at the motor neurone, causing Acetylcholine (ACh) to be released into the neuromuscular junction.
How do myosin heads contribute to muscle contraction?
Myosin heads bind to exposed binding sites on actin filaments, change angle, and pull the actin filament along during the power stroke, requiring energy from ATP hydrolysis.
What is the role of reflexes in muscle contractions?
Muscle contractions in response to stimuli are rapid involuntary actions essential for survival, such as moving away from a heat source.
What is the resting potential of a neuron?
At rest, the neuron is at -60mV, maintained by voltage-gated Na⁺ and K⁺ channels and the Na⁺/K⁺ pump.
What occurs during an action potential?
A stimulus opens Na⁺ channels, causing Na⁺ influx and depolarization. If the threshold is exceeded, an action potential fires, followed by K⁺ exit and repolarization.
How do action potentials regulate heart rate?
Baroreceptors detect blood pressure changes; low pressure increases heart rate via sympathetic neurons, while high pressure decreases it via parasympathetic neurons.
