Co-transport

Why can diffusion not be used in the small intestine?

• this would result in the same concentration of nutrients inside the intestine and inside the bloodstream.

• this means not all of the available glucose and amino acids are absorbed, so some may be lost and pass out the body

what process is used in the small intestine?

active transport- it ensures all glucose and amino acid ends up in the bloodstream. it uses co-transport

what are co-transporters?

a type of carrier proteins

what do co-transporters move?

2 types of molecules/ions at the same time

how do co-transporters move 2 types of molecules/ions at the same time?

they can use the concentration gradient of one molecule to move the other against its concentration gradient

what are co-transporters needed for?

the absorption of glucose and amino acids

How is glucose absorbed into the blood?

• sodium ions actively transported out of epithelia cells into blood stream using Na+/K+ pump

• creating concentration gradient

• sodium ions diffuse down concentration gradient from  lumen into epithelia via Na-glucose co-transporter protein

• glucose also transported across into the epithelial cell

• high concentrations of glucose in epithelial cell so will move into blood stream by facilitated diffusion using a glucose transporter

why is the concentration of glucose in the blood lower than in the epithelial cells?

the blood flows and carries away absorbed glucose

what else increases the surface area for co-transporter proteins?

microvilli

what is exocytosis?

transport of macromolecules and large particles outside the cell

what happens to materials inside the cell during exocytosis?

packed in a vesicle, which fuses to the plasma membrane

what is endocytosis?

used to move macro molecules, or larger objects, such as cell fragments into the cell

give 2 types of endocytosis?

• phagocytosis- pathogens and large particles

• pinocytosis- water and solutes in the water