active transport

Definition of active transport

• movement of molecule or ions in and out of cell from a region of lower concentration to a higher concentration using atp and carrier proteins

What is ATP used for?

• directly move molecules

• individually move molecules using a concentration gradient (cotransport)

How does it differ from the passive forms of transport?

• atp

• against concentration gradient

• Selective process

Describe direct active transport of a single molecule

• carrier proteins span the plasma membrane and bind to molecule or ions to transport

• molecule or ion binds to receptor site on carrier protein

• inside the cell, ATP binds to protein and hydrolyses into ADP and Pi. Protein molecule changes shape and opens to release molecule or ion

• the phosphate molecule released causes the protein to revert to original shape.

how can the phosphate molecule revert back into ATP

during respiration

what can sometimes happen? + example

more than one molecule or ions in may be moved in the same direction (Na/K pump)

what happens in the Na/K pump?

Sodium ions removed and potassium ions taken in

what is the Na/K pump process essential to create

nerve impulses

Digestion definition

large insoluble molecules hydrolysed into soluble and smaller molecules to be absorbed into the blood stream

proteins involved in co transport

• Na/K pump

• Glucose uniporter

• Na/glucose symporter

what are the products of digestion

• amino acids glucose and fatty acids

what is the ileum

small intestine

what type of transport does the pump use

Active transport

what type of transport does the glucose uniporter use

Faciliated diffusion

What do epithelial cells lining the ileum possess

microvilli

how does microvilli increase rate of movement

• more surface area for the insertion of carrier proteins through which diffusion, active transport and facilitated diffusion take place.

• maintain concentration gradient and decrease diffusion distance

how are the products of digestion absorbed

cells lining ileum

why is there normally a greater concentration of glucose and amino acids in the ileum than blood

as carbohydrates and proteins are constantly being digested

how can glucose move from ileum to blood

down concentration gradient by faciliated diffusion

what does the removal of glucose by cells maintain and increase

a concentration gradient between inside ileum and blood and increases rate of movement by facilitated diffusion across epithelial cell membrane

how are sodium ions actively transported out of epithelial cells

By Na/K pump, in a protein carrier molecule found in cell membrane of epithelial cells

what does this maintain

a higher concentration of sodium ions in lumen than inside epithelial cells

what happens when sodium ions removed and diffuses into epithelial cells

down concentration gradient through different protein carrier, bring glucose with them

how does the glucose pass into cell

facilitated diffusion

Difference between movement of sodium and glucose

Glucose - against

Sodium - down

What powers the movement of glucose into cell

Sodium ion concentration gradient

What type of form of AT does this make it

indirect

Number of sodium ions lost with potassium ion taken in

3 lost , 2 taken in

What must be ensured to absorb AA and glucose from lumen to gut

Higher concentration in lumen than epithelial cell

Describe the absorption of lipids

• micelles fit in between microvilli

• individual monoglycerides and fatty acids diffuse through cell membrane

• they are turned into triglycerides in SER and packaged with lipoproteins into chylomicrons

• chylomicrons are then shuttled through lacteal