There are two types of cell transport mechanisms. These types of transports are passive and active transport. The difference between active and passive is that passive does not require energy and active does require energy.
Passive transport is the movement of molecules across the cell membrane without using energy. This can be accomplished in two ways, diffusion and osmosis. Diffusion is when molecules move from an area of high concentration to an area of low concentration. Osmosis is when water moves across a semipermeable membrane from an area of high concentration to an area of low concentration.
Active transport is the movement of molecules across the cell membrane using energy. This can be accomplished in two ways, facilitated diffusion and active transport. Facilitated diffusion is when molecules move from an area of high concentration to an area of low concentration using a protein carrier. Active transport is when molecules are moved against their concentration gradient from an area of low concentration to an are area of high concentration using a protein pump.
Because it travels down a concentration gradient, passive does not need energy. Molecules on a concentration gradient move naturally from rich to poor concentration. Molecules move from low to high concentration in active transport. Diffusion, osmosis, and facilitated diffusion are the three kinds of passive transports.
The two types of active transports are primary and secondary. Diffusion is the movement of molecules from an area of high concentration to an area of low concentration until both areas reach equilibrium. Equilibrium means that the molecules are equally distributed throughout the space. Osmosis is a type of diffusion that only happens with water molecules.
When there is a difference in solute concentration on either side of a membrane, water will move down its concentration gradient by osmosis until the concentrations on both sides are equal. Facilitated diffusion is when proteins in the cell membrane help small molecules diffuse across the membrane.
Active transport requires energy because it moves molecules against their concentration gradient, from low to high. In primary active transport, ATP is used to directly move molecules across the cell membrane. In secondary active transport, a gradient is first created using primary active transport and then molecules can diffuse down this concentration gradient.
There are two types of cell membranes- eukaryotic and prokaryotic. Eukaryotic cells have a plasma membrane that surrounds the cell. The plasma membrane is made of a lipid bilayer with proteins embedded in it. Prokaryotic cells also have a plasma membrane, but they also have an additional layer called the cell wall. The cell wall is made of peptidoglycan and protects the cell from its environment.
The cell membrane is selectively permeable, which means that it allows some substances to cross it while others are blocked. The cell membrane is made up of a phospholipid bilayer with proteins embedded in it. Phospholipids are amphipathic, meaning that they have a hydrophilic (water-loving) head and a hydrophobic (water-hating) tail. The tails are arranged in the center of the bilayer so that they are not in contact with water. This arrangement creates a semi-permeable barrier that can selective allow certain molecules through.
The proteins in the cell membrane can be divided into two categories – integral and peripheral. Integral proteins are embedded in the lipid bilayer and span the entire width of the membrane. Peripheral proteins are only loosely attached to the surface of the membrane. Some integral proteins are channels that form pores in the membrane. These proteins control which molecules can enter and exit the cell. Other integral proteins are transporters that help move molecules across the cell membrane.
The cell membrane is also involved in cell signaling. Cell signaling is the process by which cells communicate with each other. Cells send and receive signals that tell them what to do. There are four main types of cell signaling – autocrine, paracrine, juxtacrine, and endocrine. Autocrine signaling occurs when a cell secretes a signal that affects itself.
Paracrine signaling occurs when a cell secretes a signal that affects nearby cells. Juxtacrine signaling occurs when two adjacent cells communicate with each other through gap junctions. Endocrine signaling occurs when a cell secretes a hormone that travels through the bloodstream to affect distant cells.
The cell membrane is also involved in cell adhesion. Cell adhesion is the process by which cells attach to each other and to their extracellular matrix. Cells use cell-cell adhesion molecules (CCAMs) to attach to each other. CCAMs are integral proteins that span the cell membrane and bind to complementary proteins on adjacent cells. Cadherins are a type of CCAM that are involved in the development of tissues and organs. Selectins are another type of CCAM that are involved in inflammation and immunity.
The cell membrane is also involved in cell recognition. Cell recognition is the process by which cells identify other cells as being part of their own organism. This allows cells to communicate and cooperate with each other. Cells use cell-surface receptors to recognize other cells. Receptors are integral proteins that span the cell membrane and bind to specific molecules on other cells. These molecules can be hormones, Growth factors, or neurotransmitters.
The cell membrane is a complex and dynamic structure that plays a vital role in the function of the cell. The cell membrane is involved in many important processes, including cell transport, cell signaling, cell adhesion, and cell recognition. Without the cell membrane, these processes would not be possible.
Endocytosis and exocytosis are the two types of active transports. ATP is not required for passive transport since it moves down a concentration gradient. This is due to the fact that molecules move from high to low concentration naturally, without requiring energy. Diffusion is the first form of passive transportation.
Diffusion is when small molecules move from areas of high concentration to low concentration. The second type is called osmosis. Osmosis is when water moves from an area of high concentration to an area of low concentration. The third and final type of passive transport is called facilitated diffusion. Facilitated diffusion is when small molecules are carried through proteins in the cell membrane. These proteins act as channels or pores that the molecules can pass through.
Endocytosis is when a cell takes in materials from its surroundings by engulfing them in its plasma membrane. There are three types of endocytosis: phagocytosis, pinocytosis, and receptor-mediated endocytosis. Phagocytosis is when the cell takes in large particles, such as bacteria. Pinocytosis is when the cell takes in small droplets of fluid. Receptor-mediated endocytosis is when the cell takes in specific molecules by binding to them with receptors on the plasma membrane.
Exocytosis is when a cell expels materials from its interior out into its surroundings. Materials are enclosed in vesicles, which fuse with the plasma membrane and release their contents outside of the cell. Exocytosis can be used to get rid of waste products, or to secrete proteins and other molecules needed by other cells.
Cell transport mechanisms are vital for cells to be able to take in the nutrients they need and expel waste products. Without these mechanisms, cells would not be able to function properly.