1. What is the function of each of the three biomolecules in the CELL MEMBRANE?
2. What are the two types of cell transport and what’s the difference between them?
1. The three biomolecules found in the cell membrane are lipids, proteins, and carbohydrates.
- Lipids, specifically phospholipids, are the main component of the cell membrane. They form a double layer called the lipid bilayer, which provides a barrier and allows for the selective permeability of the membrane. Phospholipids have a hydrophilic (water-loving) head and hydrophobic (water-fearing) tails, which helps maintain the integrity of the membrane.
- Proteins embedded in the cell membrane serve various functions. Some proteins act as transport channels, allowing specific molecules and ions to enter or exit the cell. Other proteins serve as receptors, which can bind to signaling molecules and initiate cellular responses. Additionally, proteins are involved in cell communication, adhesion, and enzymatic reactions.
- Carbohydrates are found on the outer surface of the cell membrane attached to lipids or proteins in the form of glycolipids or glycoproteins. These carbohydrate molecules act as identification tags, allowing cells to recognize each other and participate in cell-cell recognition and cell signaling processes.
2. The two types of cell transport are passive transport and active transport. The main difference between them lies in the requirement of energy expenditure by the cell.
- Passive transport: This type of transport does not require energy expenditure by the cell. It occurs spontaneously and relies on the concentration gradient of substances. Passive transport includes diffusion, osmosis, and facilitated diffusion.
- Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration until equilibrium is reached.
- Osmosis is the diffusion of water molecules through a selectively permeable membrane from an area of lower solute concentration to an area of higher solute concentration.
- Facilitated diffusion involves the movement of molecules across the membrane with the assistance of transport proteins.
- Active transport: This type of transport requires energy in the form of ATP (adenosine triphosphate). It is used to move molecules or ions against their concentration gradient, from an area of lower concentration to an area of higher concentration. Active transport includes processes like primary active transport and secondary active transport.
- Primary active transport involves the direct use of ATP to pump molecules against their concentration gradient, such as the sodium-potassium pump.
- Secondary active transport utilizes the energy stored in an electrochemical gradient, established by primary active transport, to transport molecules across the membrane.
In summary, passive transport occurs without energy expenditure, while active transport requires the use of energy by the cell.