Explanation:
Cyanobacteria, including Nostoc, are photosynthetic organisms that utilize water as a source of electrons and protons in the process of photosynthesis. During this process, they split water molecules (H2O) to release oxygen (O2) as a byproduct. This oxygenic photosynthesis is similar to that of plants and algae.
Explanation:
(a) There are 20 types of amino acids that are used to form proteins.
- This statement is correct. Proteins are composed of 20 different amino acids, each with unique chemical properties that contribute to protein structure and function.
(c) Some proteins are made up of multiple polypeptide chains aggregated together.
- This statement is also correct. Proteins can have a quaternary structure, which involves multiple polypeptide chains coming together to form a functional protein complex.
Explanation:
Learned behaviors are those that an animal acquires through experience or interaction with the environment. In this case, the sea hare initially responds reflexively to the tactile stimulus by retracting its gill. However, with repeated exposure to the same stimulus, the sea hare learns not to retract its gill, indicating an adaptive change in behavior based on experience.
Explanation:
(a) Aqueous sodium hydroxide (NaOH) is added to aluminum (Al).
- This reaction produces hydrogen gas
(d) Dilute sulfuric acid is added to iron (II) sulfide (FeS).
- This reaction produces hydrogen sulfide gas
Explanation:
When body temperature decreases (hypothermia), the body initiates several responses to maintain warmth and normal physiological function:
*Heartbeat is accelerated by the action of the sympathetic nervous system: This helps circulate blood faster to distribute heat.
*Adrenaline secretion is stimulated: Adrenaline (epinephrine) increases metabolic rate to generate heat.
*Arrector pili muscles contract: This causes goosebumps, which can help trap heat.
*Blood vessels in the skin constrict (vasoconstriction): This reduces blood flow to the skin, minimizing heat loss.
Explanation:
(a) If the temperature of this reaction is raised, the equilibrium constant will become smaller.
- This is correct for exothermic reactions. Increasing temperature shifts the equilibrium to favor the reactants, decreasing the equilibrium constant.
(d) It is impossible to derive an equation explaining the relation between the rate of reaction and the concentration of reactants directly from the chemical equation.
- This is correct. The rate law is determined experimentally and cannot be derived directly from the stoichiometric coefficients of the chemical equation.
Explanation:
A reflex arc is the neural pathway that allows a reflex action to occur in response to a stimulus. It involves sensory neurons detecting the stimulus, transmitting signals to the spinal cord or brainstem (not the cerebrum), and then motor neurons sending signals to produce the reflexive response. This process bypasses conscious control to enable rapid reactions.
Explanation:
Green sulfur bacteria use bacteriochlorophyll as their primary photosynthetic pigment, rather than chlorophyll found in plants. This pigment enables them to perform photosynthesis using light energy to produce organic compounds.
Explanation:
Given:
*Water: 100 g at 10°C
*Container heat capacity: 150 J/K
*Ice formed: 5 g
*Specific heat of water: 4.2 J/(g·K)
*Heat of fusion of ice: 330 J/g
Steps:
1. Heat lost by water cooling to 0°C: 100 × 4.2 × 10 = 4200J
2. Heat to freeze 5 g of water: 5 × 330 = 1650J
3. Total heat lost: 4200 + 1650 = 5850J
4. Heat gained by container: 150 × (0 − t) = −150t
5. Solve for 𝑡:
−150t = 5850
t = −39
Explanation:
Ribosomes are responsible for translating mRNA into proteins, making them essential for protein synthesis in both prokaryotic and eukaryotic cells.
Explanation:
(c) Hydrogen sulfide, hydrogen, ammonia, methane, etc.: These are simple inorganic molecules that were likely present in the early Earth's atmosphere or hydrothermal vents.
(b) Amino acids, sugars, phospholipids, etc.: These are organic molecules that could have formed through prebiotic chemistry, such as the Miller-Urey experiment, which simulated conditions believed to be present on early Earth.
(a) Proteins, nucleic acids, etc.: These are complex biomolecules that are essential for life and likely formed later, possibly through the polymerization of simpler organic molecules.
This sequence reflects a plausible progression from simple inorganic molecules to more complex organic molecules during the early stages of chemical evolution on Earth.
