active transport , cotransport

Question 1

what is active transport

Answer 1

-The movement of molecules and ions through a cell membrane against the concentration gradient using energy from respiration.
-Requires ATP and carrier proteins

Question 2

What is active transport used for

Answer 2

-Uptake of glucose and amino acids in the small intestine
-Absorption of mineral ions by plant roots
-Excretion of hydrogen ions and urea by kidneys
-Exchange of sodium and potassium ions in neurons and muscle cells.

Question 3

when is bulk transport used

Answer 3

-When extremely large substances need to be moved across a cell membrane

Question 4

What is endocytosis

Answer 4

-Endocytosis is the bulk transport of material INTO the cell, and can be split into three processes: phagocytosis, pinocytosis and receptor-mediated endocytosis.

Question 5

What is exocytosis

Answer 5

-Exocytosis is the bulk transport of material OUT of the cell – essentially the reverse of endocytosis.

Question 6

Details of active transport

Answer 6

1. Transport is through carrier proteins spanning the cell membrane.
2. Molecule binds to the receptor complementary in shape of protein.
3. ATP binds to the carrier protein from inside the cell and it is hydrolysed into ADP + Pi
4. This causes the carrier proteins to change shape and release the molecule to other side
5. The phosphate ion is then released and the protein returns to its original shape.

Question 7

What is co-transport

Answer 7

-Co-transporters use concentration gradient of one molecule (Na+) to move another molecule against its concentration gradient (glucose)

Question 8

What are the 2 section of small intestine

Answer 8

-duodenum = most digestion

-ileum = absorption of nutrients & water

Question 9

Factors which affect the rate if absorption

Answer 9

-Folded membrane/microvilli s o large surface area (for absorption)
-Large number of carrier proteins so fast rate (of absorption)
-Large number of mitochondria so make more ATP by respiration

Question 10

Transport of sodium ions and glucose

Answer 10

-Na+ ions leave epithelial cell and enter blood by active transport via carrier proteins using (the hydrolysed ) ATP
-So Na+ concentration in cell is lower than in lumen which maintains a gradient
-Sodium/Na ions enter by facilitated diffusion;
-Glucose absorbed with Na ions against their concentration gradient