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Hormones attach to plasma membrane proteins called receptors. These receptors can trigger signaling pathways within the cell when activated by the hormone binding.
Steroid hormones bind to specific receptors within the target cells to regulate gene expression and control various physiological functions. Thyroid hormones regulate metabolism by influencing the activity of enzymes and affecting the consumption of oxygen by cells.
Well Wiki say "A hormone (from Greek ὁρμή - "impetus") is a chemical released by a cell in one part of the body that sends out messages that affect cells in other parts of the organism." So a hormone knows where to go because that's where the signal is coming from.
HIV's surface protein, gp120, can attach to CD4 receptors on healthy human cells. This interaction allows HIV to enter and infect the cell by binding to the CCR5 or CXCR4 co-receptors on the cell surface.
Egg cells have receptors on their surface that can bind to chemicals like sperm. These receptors help facilitate the process of fertilization by allowing the sperm to attach to the egg cell.
Hormones attach to plasma membrane proteins called receptors. These receptors can trigger signaling pathways within the cell when activated by the hormone binding.
Neurotransmitters attach to specific proteins called receptors on the cell membrane. These receptors are typically ligand-gated ion channels or G protein-coupled receptors that initiate cellular responses when neurotransmitters bind to them.
Steroid hormones bind to specific receptors within the target cells to regulate gene expression and control various physiological functions. Thyroid hormones regulate metabolism by influencing the activity of enzymes and affecting the consumption of oxygen by cells.
Viruses have to attach them selves by way of a protein called a recognition factor. They bind to receptors on the host cell and then lose their capsid (coat).
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Well Wiki say "A hormone (from Greek ὁρμή - "impetus") is a chemical released by a cell in one part of the body that sends out messages that affect cells in other parts of the organism." So a hormone knows where to go because that's where the signal is coming from.
receptor molecules in the cell membrane
HIV's surface protein, gp120, can attach to CD4 receptors on healthy human cells. This interaction allows HIV to enter and infect the cell by binding to the CCR5 or CXCR4 co-receptors on the cell surface.
receptor molecules in the cell membrane
Tendons attach muscles to bones.
Egg cells have receptors on their surface that can bind to chemicals like sperm. These receptors help facilitate the process of fertilization by allowing the sperm to attach to the egg cell.
A virus attaches to a specific cell because it has proteins on its surface that can only bind to receptors on that specific cell. This binding is necessary for the virus to enter the cell and replicate. This specificity is determined by the structure of the virus and the receptors on the cell surface.