transport (+ATP) (topic 3)

Question 1

simple diffusion

Answer 1

passive, net movement of molecules from a region of higher concentration to a region of lower concentration until evenly distributed

Question 2

facilitated diffusion

Answer 2

passive, net movement of molecules from a region of higher concentration to a region of lower concentration with the AID of a PROTEIN CARRIER or protein channel

Question 3

osmosis def

Answer 3

the net movement of water from an area of high water potential to an area of low water potential across a partially permeable membrane
(passive)

Question 4

water potential

Answer 4

represented by psi ψ
measured in units of pressure, kPa
wp = pressure created by water molecules

zero is the highest water potential (pure water at 25°C and 100kPa)

Question 5

haemolysis

Answer 5

due to low WP, red blood cells osmosis continues until cell bursts

Question 6

plant cells in solutions with lower water potential than its own

Answer 6

water leaves by osmosis. volume of cell decreases. cytoplasm (call it protoplast) no longer presses on the cellulose cell wall (said to be at incipient plasmolysis)
further loss of water causes the vacuole to shrink further and cytoplasm pull away from cell wall (said to be plasmolysed)

Question 7

active transport def

Answer 7

movement of a substance from a region of lower concentration to a region of higher concentration. requires protein carriers and metabolic energy in the form of ATP

Question 8

how active transport works

Answer 8

a molecule binds to a complementary binding site on a protein carrier
ATP binds to the protein carrier on the INSIDE of the cell
ATP is HYDROLYSED to ADP and Pi (inorganic phosphate) by the enzyme ATP hydrolase, releasing energy.
this causes a conformational change in the protein which allows the molecule to be transported to the other side of the membrane, where it is released
the Pi molecule is released from a protein carrier and recombines with the ADP to form ATP in a condensation reaction catalysed by ATP synthase
this causes the protein to return to its original shape to repeat the process

Question 9

the breaking down of ATP

Answer 9

hydrolysis reaction
ATP -> ADP + Pi

Question 10

building of ATP

Answer 10

condensation reaction
ADP + Pi -> ATP

Question 11

structure of ATP

Answer 11

adenine |
ribose —P—P—P

Question 12

why/how is energy released from ATP

Answer 12

bonds between the phosphate groups in ATP are unstable and have a low activation energy, sp they are easily broken, releasing lots of energy in the process

Question 13

why is ATP a good immediate energy source

Answer 13

each ATP molecule releases less energy than glucose molecules, this is more manageable for cell reactions
quicker to release than glucose

Question 14

transport from the lumen of the small intestine to the blood capillary

Answer 14

lumen of small intestine -> epithelial cell -> capillary

SODIUM IONS
- ATP is hydrolysed to release energy that causes a conformational change and allows Na+ ions to be pumped out of the epithelial cell into the capillary by active transport
- as Na+ conc decreases, more Na+ ions from the lumen moves into the cell. Na+ takes glucose with it (against its conc gradient) and cell glucose conc increases. they travel through a co-transport protein

GLUCOSE:
- moves via facilitated diffusion from the cell into the capillary

Question 15

how do cells allow for rapid transport

Answer 15

increase surface area
increase in number
of protein channels and carrier molecules in their membranes

Question 16

phosphorylation

Answer 16

inorganic phosphate can be used to phosphorylate compounds making them more reactive

Question 17

ATP uses in energy requiring processes in cells

Answer 17

movement: contraction of muscles, cilia or flagella movement
active transport: movement of ions against a conc gradient eg NaK pump
synthesis: protein, DNA
nuclear/cell division: mitosis, meiosis
homeostasis: maintenance of body temp in endotherms

phosphorylation