The cAMP receptor protein (CRP) is said to be responsible for positive regulation of the lac operon because (D) CRP bound to the CRP-binding site stimulates the transcription of the lac operon.
CRP is a regulatory protein. It binds to the cAMP and causes a conformational change. This allows the CRP to bind to a specific site at the promoter region of the DNA. This then activates the transcription process.
Lac operon is a group of genes that allow the uptake of glucose in bacteria. There are four components of lac operon: regulator gene, promoter gene, operator gene and structural genes. The machinery of operon is turned on the lactose itself.
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Explanation:
adj. Moving or operating in one direction only: a unidirectional microphone.
Answer:
Answered below
Explanation:
Cell membranes are barriers which protect and regulate the movement of substances in and out of the cells. It is a semi-permeable and selective structure.
In the passive transport system, substances move along a concentration gradient and it doesn't require energy. The examples of passive transports include; simple diffusion which transports carbon dioxide and oxygen, osmosis and facilitated diffusion which transports charged molecules like ions, sucrose etc.
In active transport, substances move against the concentration gradient. This requires energy. The two main types are: primary active transport, which uses direct metabolic energy e.g Na+/K+ pump, and the secondary active transport system which couples the transported molecules with another molecule moving along the gradient, example the Na+/glucose transporter.
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Explanation:
A polar orbit is one in which a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth, but possibly another body such as the Moon or Sun) on each revolution. It therefore has an inclination of (or very close to) 90 degrees to the body's equator.
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C. Platelet adhesion
Explanation:
Platelet adhesion comes first in the process of hemostasis.
The process of hemostasis has got three phases:
- Vascular spasm
- Platelet plug formation
- Blood coagulation
The process occurs in the body in the event of a bleeding injury.
In the first phase, damaged blood vessels constrict to prevent more bleeding.
In the second phase, platelets adhere to damaged endothelium to form platelet plug.
In the third phase, fibrinogen is converted to fibrin to form a clot.
