Bios256 Week 5

1.Discuss the structure of the plasma membrane and explain the process of active and passive transport through the membrane.

What two parameters are responsible for creating the movement (filtration and reabsorption) of fluid across the capillary wall?

The carrier then returns to its original shape, releasing the two K+ions and the remnant of the ATP molecule to the inside of the cell. The carrier is now ready for another pumping cycle” (McCance & Huether pg. 29)

By a form of passive transport called diffusion, across a concentration gradient. Water soluble substances such as sugars and inorganic ions diffuse very slowly, with no energy expenditure. It is a uniport mechanism and demonstrates saturation kinetics where the glucose specific receptors are all occupied and operating at max capacity.

Consequently, the efferent arteriole, which filters blood away from the glomerulus, is tinier in diameter than the afferent arteriole, which carries blood into each glomerulus. This puts blood under high pressure in the glomerulus; thus it forces tiny molecules and liquid out of the capillary and into the Bowman’s capsule. Soon afterwards, the tiny and liquid molecules cross the epithelium of the Bowman’s capsule, the basement membrane and capillary wall in order to get into the Bowman’s capsule and to arrive in the nephron tubules. The consequence of this is that the filtrate (the tiny and liquid molecules) pass along the remainder of the nephron and helpful substances are reabsorbed along the route. Last of all, “the filtrate flows through the collecting duct and passes out of the kidney along the ureter” as mentioned by (Parson’s, R: p128).

Sometimes one substance is transported in one direction at the same time as another substance is transported in the other direction. This is called Co- transport. In Co-tansport one of the two substances are transported in the direction of their concentration gradient utilizing the energy derived from the transport of the second substance (mostly Na+, K+ or H+) down its concentration gradient. Active transport often takes place in the

the kidney nephron. What other substances must be transported from the tubular fluid into the PCT cell

The hydrostatic pressure (or blood pressure) and osmotic pressure (water pressure) are responsible for balancing and creating the movement of fluid across the capillary wall.

1. In passive transport, what determines the direction of movement of small particles? The direction of movement of particles in passive transport is determined by the concentration gradient (diffusion) between the cytoplasm and the extracellular fluid. 2. Why do the molecules in facilitated diffusion need help moving across the plasma membrane? Likely, the molecules are too large to pass unaided through the plasma membrane with the concentration gradient; they need to pass through special transport proteins.

9. The movement of electrons form the proton gradient, the electron transport chain pumps Hydrogen plus from the matrix to the intermembrane space. This causes more protons outside than inside. The first and third complexes of the electron transport chain move the protons through the membrane. The first complex in the electron transport chain pumps

*Purpose-How do different solutions and water potentials affect the movement of water across a cell membrane?

There are four main types of transport mechanisms across the cellular membrane these mechanisms are: bulk, active, passive, and osmosis. Bulk transport is the movement of polysaccharides or proteins in or out of the cell, there are two types of bulk transport endocytosis and exocytosis. During endocytosis materials are transported into the cell, while in exocytosis materials are transported out of the cell, both of these also require the use of ATP making them examples of active transport. Active transport means it requires the use of energy to move materials across the membrane it is used for larger non-polar macromolecules. Many times active transport occurs to move molecules against

The proximal convoluted tubule is a small tubular structure contained within the nephron of the kidney. It’s involved in the reabsorption of water and solutes from the filtrate located within the nephron. The lining of the proximal convoluted tubule contains numerous protein channels, which use both active and passive transport are used to move substances such as glucose across the tubule's lining and into the interstitial fluid for reabsorption. The epithelium of the proximal convoluted tubule also prevents waste products from being reabsorbed into the bloodstream safeguarding from diseases.

Active transport uses energy to move substances up a concentration gradient or across a partially permeable membrane. In active transport a special transport protein in the cell membrane picks up the useful particle on one side of the membrane. The transport protein then rotates through the membrane and releases the particle on the other side of the membrane. This uses energy from cel-lular respiration. Cells which carry out a lot of active transport often have lots of mitochondria to give them the energy they need. Active transport is important in the kidney for hanging on to the substances needed by the body such as glucose and some sodium ions.

Because it does not require energy to force the molecules in or out, it is considered a passive transport, moving along with the concentration gradient. The concentration gradient is a process where molecules move from a higher concentration to a low concentration.