Two fatty acids ( long chains of Hydrogen and carbon) which are attached to a glycerol head , where the glycerol head is attached to a phosphate group
or generally Phospholipids consist of a hydrophilic head and a hydrophobic tail.
Answer:
Kidneys : helps in forming urine
Ureter : They are connected to kidney and by peristaltic action transports urine from kidneys to bladder .
Urinary bladder : It is an hollow sac that holds the urine .
Urethra : transports urine from the bladder to outside of the body .
Explanation:
The human excretory system consists of : Kidney ,ureter ,urinary bladder and urethra .The figure is shown below .
Now , as far as functions are concerned we have :
Kidneys : They have excretory units called nephrons that further consist of :
- Bowman's capsule
- PCT (Proximal convoluted tubule )
- DCT (Distal convoluted tubule)
- CT (collecting tubule )
In nephrons urine is formed and via ureter it is transported to a hollow sac like structure called urinary bladder .
This bladder has muscles that cant remain contracted up to longer period )and then voluntary and involuntary it is excreted through urethra .
The process of passing urine is called Micturition .
In cell signalling, after a signal is sent, signal molecules bind to receptors on target cells and some activity in a target cell changes.
There are three stages in cell signalling :
1. The process of reception occurs when a signalling molecule from the extracellular environment is recognized by a cell. The chemical signal, which is also known as a ligand, is recognized as a signal when it attaches to a receptor protein either on the exterior of the cell or on the interior of the cell.
2. Transduction: This process occurs when the signalling molecule interacts with the receptor, which causes a change in the protein that makes up the receptor. The process of transduction is kicked off by this modification. In most cases, signal transduction occurs through a pathway that consists of numerous stages. The signal transduction route contains relay molecules, each of which influences the subsequent molecule in the pathway.
3. Reaction: In the third and last step, the signal causes a certain cellular response.
Learn more about cell signalling here :
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