Practise essay Flashcards
Title
Phosphorus-containing substances and their importance in biological systems.
4 topics to cover this title
ATP
Cyclic AMP
Phospholipids and membranes
Triose phosphate in LIR
RNA
4 ways each topic shows importance
Production of glucose following LIR used for
ATP AO1
-Nucleotide derivative consists
-Adenine, ribose, 3 phosphorous containing inorganic phosphate groups
-Energy release by breaking bond in a hydrolysis reaction catalysed by ATP hydrolase eliminates water = ADP + Pi
-Then resynthesized catalysed by ATP synthase in a condensation reaction from ADP + Pi
Cyclic AMP formation - AO1
-Phosphorous is present in Cyclic AMP as an inorganic phosphate group
-First messenger such as glucagon arrives at complementary receptor on target cell and binds
-Tertiary structure of receptor changes, transmitted to enzyme adenylate cyclase to expose its active site
-Catalyses conversion of ATP to cyclic AMP
Cyclic AMP use - AO1
-Cyclic AMP Binds to enzyme in cytoplasm called protein kinase, changes tertiary structure and exposes active site
-Protein kinase can activate enzymes for hydrolysis of glycogen to glucose
Why is AMP important - AO2?
This shows the importance because without cyclic AMP, this glucose produced could not be released from liver cells.
Because the enzymes for hydrolysis of glycogen are not activated by second messenger
So, following a decrease in blood glucose concentration, the water potential of the blood would increase causing osmosis of water into body cells which would burst.
Formation of NADPH AO1
-Phosphorous is present in NADP, a co enzyme used in photosynthesis
-NADP acts as final electron acceptor of electron transfer chain in the thylakoid membrane to gain H+ and electron = reduced NADP (NADPH)
Use of NADPH AO1
NADPH is used in the chloroplast stroma during Calvin cycle to reduce 2 molecules of GP to 2 Triose phosphate
NADPH is therefore oxidised back to NADP to be reused for light dependent reaction
Importance of NADPH AO2
Without the help of NADP to form triose phosphate, then the later stages of the Calvin cycle could not occur to either reform RuBP and glucose
Hence, useful organic substances needed to construct cellulose are not produced
Cell surface membranes AO1
Cell surface membranes and organelles membranes are composed of a phospholipid bilayer in a fluid mosaic model
(Phospholipid contains phosphate group attached to glycerol and 2 fatty acid tails)
The non polar fatty acid region of the bilayer is centred on the inside with polar inorganic phosphate heads sticking out
Cell surface membranes for transport AO1
This means simple diffusion can occur over the cell surface membrane, since the fatty acid region id non polar, then only small non polar molecules can move directly over down their concentration gradient over membranes
Importance of phospholipid bilayer AO2
The importance of the cell membrane is shown in the biological system of digestion
IN absorption of fatty acids, monoglycerides in the ileum cell
Where micelles carry these products of lipid digestion to epithelial cell membrane and due to their non polar properties, they directly diffuse over the cell surface membrane
AO1 - RNA
RNA is a polymer formed in condensation reaction between RNA nucleotides (eliminates water) to contain phosphodiester bonds between monomers
Each nucleotide has a phosphate group containing phosphorous bonded to ribose sugar, bonded to a nitrogenous base
This base could either be adenine, cytosine, guanine or uracil
AO2 - RNA
The importance of RNA is shown by its ability to control translation.
Small interfering RNA’s single strand combines with an enzyme, by complementary base pairs, is able to bind to a specific mRNA and enzyme can hydrolyse mRNA and destroy it
The control of translation of specific polypeptides means a cell can undergo differentiation and be specialised to form tissue and thus organs in biological systems
AO2 ATP
ATP’s energy release (by hydrolysis into ADP and Pi) is coupled with active transport of substances against their electrochemical gradient
For example, in plants, sucrose is actively transported from a source into the sieve vessel
And actively transported from sieve into sink. This shows the importance, because this establishes a water potential gradient in a sieve tube so organic substances can be transported around a plant down a hydrostatic pressure gradient
