CD4 and CD 8 are molecules present on the surface of T cells where they interact with major histocompatibility (MHC) Molecules.
CD4 and CD8 improve T cell signalling by attaching to MHC class II (CD4) or MHC class I (CD8) molecules on APCs.
- The association of CD4 with MHC class II significantly decreases the number of antigenic peptides necessary for T cell activation (5) and significantly boosts cytokine output by helper T cells.
The MHC molecules' wide polymorphism is their distinguishing trait.
- This polymorphism is crucial for T cell antigen recognition.
- A T cell detects antigen as a peptide bound by a specific allelic variation of an MHC molecule and will not identify the identical peptide bound by other MHC molecules.
- This type of T cell activity is known as MHC limitation.
Hence, the correct answer is option C
Learn more about MHC here,
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# SPJ4
The “powerhouses” of the cell, mitochondria are oval-shaped organelles found in most eukaryotic cells. As the site of cellular respiration, mitochondria serve to transform molecules such as glucose into an energy molecule known as ATP (adenosine triphosphate).
Species is defined as a group of organisms that consist of similar individuals capable of interbreeding or exchanging genes among themselves.
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Answer:
B
Explanation:
Gas exchange provides oxygen that is required for aerobic cellular respiration. Aerobic respiration produces more ATP molecules than anaerobic respiration. This is because oxygen acts as the ultimate proton acceptor (in the Krebs/Citric cycle) in the matrix of the mitochondria to form water as the waste product. This allows a proton motive force to be created in the mitochondria that is harnessed by ATP synthase to produce ATP molecules.
Answer:
CAT ATG TAC
Explanation:
Adenine (A) pairs with Thymine (T)
Cytosine (C) pairs with Guanine (G)
And vice-versa