Essay - ATP

Question 1

Glycolysis in respiration

Answer 1

• Glucose phosphorylated from ATP hydrolysis of phosphate.
• Phosphorylation provides energy.
• Glucose split using molecule of water to make two molecules of triose phosphate.
• Oxidised using energy released from hydrolysis of four ATP molecules = 2 pyruvate.
• NAD –> Reduced NAD. Pyruvate enters link reaction.
• ATP important as glycolysis occurs in cytoplasm of all living cells to produce energy for metabolic processes.

Question 2

Reabsorption of glucose and water by proximal convoluted tubule to produce urine.

Answer 2

• Sodium ions actively transported using ATP out of epithelial cells lining PCT into blood capillaries where they are taken away.
• Sodium ions diffuse down concentration gradient via carrier proteins via facilitated diffusion.
• The molecules that have been co-transported into cells of the PCT diffuse into blood. All valuable molecules are reabsorbed.
• In descending limb of Loop of Henle, walla are very permeable to water, so it passes out filtrate via osmosis into the interstitial space.
• Sodium ions diffuse out of filtrate and move up ascending limbs before being actively transported out using ATP, filtrate WP increases.
• More sodium ions actively transported out distal convoluted tubule.
• Collecting duct permeable to water, water passes out it via osmosis, lowering filtrate water potential. u r i n e.
• ATP needed to produce the urine!

Question 3

Resynthesis of acetylcholine.

Answer 3

• Action potential arrives at presynaptic neurone, calcium channels open.
• Calcium ions enter presynaptic neurone.
• Vesicles fuse to presynaptic membrane, releasing acetylcholine into synaptic cleft.
• Acetylcholine binds to receptor sites on sodium protein channels in postsynaptic neurone, opening sodium channels, sodium ions diffuse in.
• Generates an action potential in postsynaptic neurone.
• Acetylcholinesterase hydrolyses ester bonds in acetylcholine, diffuses back across synoptic cleft into presynaptic membrane, ready to be put back in vesicles for next action potential. This uses ATP.
• Enzyme stops acetylcholine from continuously binding to postsynaptic membrane which would prevent transfer of information across synapses.

Question 4

ATP needed for sodium potassium pump for cotransport of glucose

Answer 4

1) Active transport of sodium ions out from epithelial cells, into the blood.
2) Lowers the conc. of Na+ in cell, sets up a conc. gradient.
3) Na+ diffuse down their conc. gradient through co-transport proteins in epithelial cell membrane.
4) Carrier proteins transport glucose molecules and Na+ together into the cell.
5) Raises the conc. of glucose molecules inside epithelial cell, which then diffuse down conc. gradient into blood capillaries through channel proteins, via facilitated diffusion.
6) Moves glucose molecules against their conc. gradient from the lumen of the small intestine into the cell, and down their conc. gradient out of the cell into blood.

Question 5

Actions of glucagon

Answer 5

Binds to complementary receptor, activates adenylate cyclase, hydrolyses ATP to cAMP, which activates protein kinase. Glycogen hydrolysed into glucose.

No ATP = no cAMP = no protein kinase = no glycogenolysis = low blood glucose levels = water moves into cells from blood = low blood pressure = dizziness, fainting.