carrier

Examples of carrier in the following topics:

• Facilitated transport

  • Another type of protein embedded in the plasma membrane is a carrier protein.
  • Carrier proteins are typically specific for a single substance.
  • Channel and carrier proteins transport material at different rates.
  • Channel proteins transport much more quickly than do carrier proteins.
  • Carrier proteins change shape as they move molecules across the membrane.

• Primary Active Transport

  • With the enzyme oriented towards the interior of the cell, the carrier has a high affinity for sodium ions.
  • ATP is hydrolyzed by the protein carrier, and a low-energy phosphate group attaches to it.
  • As a result, the carrier changes shape and re-orients itself towards the exterior of the membrane.
  • The protein's affinity for sodium decreases, and the three sodium ions leave the carrier.
  • Subsequently, the low-energy phosphate group detaches from the carrier.

• The Two Parts of Photosynthesis

  • In the light-dependent reactions, energy from sunlight is absorbed by chlorophyll and converted into stored chemical energy, in the form of the electron carrier molecule NADPH (nicotinamide adenine dinucleotide phosphate) and the energy currency molecule ATP (adenosine triphosphate).
  • These energized electrons are transported by "energy carrier" molecules, which power the light-independent reactions.
  • The light-independent molecules depend on the energy carrier molecules, ATP and NADPH, to drive the construction of new carbohydrate molecules.
  • After the energy is transferred, the energy carrier molecules return to the light-dependent reactions to obtain more energized electrons.

• Electrons and Energy

  • The principal electron carriers we will consider are derived from the vitamin B group, which are derivatives of nucleotides.
  • It is noteworthy that NAD+must accept two electrons at once; it cannot serve as a one-electron carrier .
  • The oxidized form of the electron carrier (NAD+) is shown on the left and the reduced form (NADH) is shown on the right.

• Sex-Linked Traits

  • When they inherit one recessive X-linked mutant allele and one dominant X-linked wild-type allele, they are carriers of the trait and are typically unaffected.
  • Carrier females can manifest mild forms of the trait due to the inactivation of the dominant allele located on one of the X chromosomes.
  • However, female carriers can contribute the trait to their sons, resulting in the son exhibiting the trait, or they can contribute the recessive allele to their daughters, resulting in the daughters being carriers of the trait.
  • The son of a woman who is a carrier of a recessive X-linked disorder will have a 50 percent chance of being affected.
  • A daughter will not be affected, but she will have a 50 percent chance of being a carrier like her mother.

• Electrochemical Gradient

  • An important membrane adaption for active transport is the presence of specific carrier proteins or pumps to facilitate movement.
  • These three types of carrier proteins are also found in facilitated diffusion, but they do not require ATP to work in that process.
  • Both of these are antiporter carrier proteins.
  • Two other carrier protein pumps are Ca2+ ATPase and H+ ATPase, which carry only calcium and only hydrogen ions, respectively.

• The Energy-Releasing Steps of Glycolysis

  • The sixth step in glycolysis oxidizes the sugar (glyceraldehyde-3-phosphate), extracting high-energy electrons, which are picked up by the electron carrier NAD+, producing NADH.
  • The continuation of the reaction depends upon the availability of the oxidized form of the electron carrier NAD+.

• Electron Transport Chain

  • The electron transport chain uses the electrons from electron carriers to create a chemical gradient that can be used to power oxidative phosphorylation.
  • The electron transport chain is an aggregation of four of these complexes (labeled I through IV), together with associated mobile electron carriers.

• Control of Catabolic Pathways

  • Catabolic pathways are controlled by enzymes, proteins, electron carriers, and pumps that ensure that the remaining reactions can proceed.
  • Enzymes, proteins, electron carriers, and pumps that play roles in glycolysis, the citric acid cycle, and the electron transport chain tend to catalyze non-reversible reactions.

• Transport of Electrolytes across Cell Membranes

  • Active transport requires energy in the form of ATP conversion, carrier proteins, or pumps in order to move ions against the concentration gradient.