secondary active transport

Examples of secondary active transport in the following topics:

• Secondary Active Transport

  • In secondary active transport, a molecule is moved down its electrochemical gradient as another is moved up its concentration gradient.
  • Unlike in primary active transport, in secondary active transport, ATP is not directly coupled to the molecule of interest.
  • Both antiporters and symporters are used in secondary active transport.
  • Secondary active transport brings sodium ions, and possibly other compounds, into the cell.
  • An electrochemical gradient, created by primary active transport, can move other substances against their concentration gradients, a process called co-transport or secondary active transport.

• Primary Active Transport

  • The primary active transport that functions with the active transport of sodium and potassium allows secondary active transport to occur .
  • The secondary transport method is still considered active because it depends on the use of energy as does primary transport.
  • This difference in charge is important in creating the conditions necessary for the secondary process.
  • Primary active transport moves ions across a membrane, creating an electrochemical gradient (electrogenic transport).

• Importance of Glycolysis

  • One method is through secondary active transport in which the transport takes place against the glucose concentration gradient.
  • The other mechanism uses a group of integral proteins called GLUT proteins, also known as glucose transporter proteins.
  • These transporters assist in the facilitated diffusion of glucose.

• Electrochemical Gradient

  • To move substances against the membrane's electrochemical gradient, the cell utilizes active transport, which requires energy from ATP.
  • Because active transport mechanisms depend on a cell's metabolism for energy, they are sensitive to many metabolic poisons that interfere with the supply of ATP.
  • Primary active transport moves ions across a membrane and creates a difference in charge across that membrane, which is directly dependent on ATP.
  • Secondary active transport describes the movement of material that is due to the electrochemical gradient established by primary active transport that does not directly require ATP.
  • An important membrane adaption for active transport is the presence of specific carrier proteins or pumps to facilitate movement.

• Vascular Tissue: Xylem and Phloem

  • Tracheids have thick secondary cell walls and are tapered at the ends.
  • Despite the fact that their cytoplasm is actively involved in the conduction of food materials, sieve-tube members do not have nuclei at maturity.
  • The activity of the sieve tubes is controlled by companion cells through plasmadesmata.
  • Xylem and phloem tissue make up the transport cells of stems.
  • The direction of water and sugar transportation through each tissue is shown by the arrows.

• Transport of Electrolytes across Cell Membranes

  • Ions cannot diffuse passively through membranes; instead, their concentrations are regulated by facilitated diffusion and active transport.
  • For this reason, athletes are encouraged to replace electrolytes and fluids during periods of increased activity and perspiration.
  • The mechanisms that transport ions across membranes are facilitated diffusion and active transport.
  • All movement can be classified as passive or active.
  • Active transport requires additional energy as particles move against their gradient.

• Primary and Secondary Growth in Stems

  • Plants undergo primary growth to increase length and secondary growth to increase thickness.
  • The increase in stem thickness that results from secondary growth is due to the activity of the lateral meristems, which are lacking in herbaceous plants.
  • The thickening of the stem that occurs in secondary growth is due to the formation of secondary phloem and secondary xylem by the vascular cambium, plus the action of cork cambium, which forms the tough outermost layer of the stem.
  • This supplies oxygen to the living- and metabolically-active cells of the cortex, xylem, and phloem.
  • The activity of the vascular cambium gives rise to annual growth rings.

• Plant Defenses Against Pathogens

  • Plants defend against pathogens with barriers, secondary metabolites, and antimicrobial compounds.
  • Secondary metabolites are compounds that are not directly derived from photosynthesis and are not necessary for respiration or plant growth and development.
  • In addition to secondary metabolites, plants produce antimicrobial chemicals, antimicrobial proteins, and antimicrobial enzymes that are able to fight the pathogens.
  • Mechanical wounding and predator attacks activate defense and protective mechanisms in the damaged tissue and elicit long-distancing signaling or activation of defense and protective mechanisms at sites farther from the injury location.

• Components of Plasma Membranes

  • The movement of a substance across the selectively permeable plasma membrane can be either "passive"—i.e., occurring without the input of cellular energy—or "active"—i.e., its transport requires the cell to expend energy.
  • The cell employs a number of transport mechanisms that involve biological membranes:
  • Transmembrane protein channels and transporters: transports small organic molecules such as sugars or amino acids
  • Endocytosis: transports large molecules (or even whole cells) by engulfing them
  • These proteins can be receptors, which work as receivers of extracellular inputs and as activators of intracellular processes, or markers, which allow cells to recognize each other.

• Electron Transport Chain

  • The most vital part of this process is the electron transport chain, which produces more ATP than any other part of cellular respiration.
  • Electron transport is a series of redox reactions that resemble a relay race.
  • A prosthetic group is a non-protein molecule required for the activity of a protein.
  • Once it is reduced to QH2, ubiquinone delivers its electrons to the next complex in the electron transport chain.
  • The electron transport chain is a series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen.