Option C - Human biochemistry (HL) -- written by Cristina Porro
C.7 Enzymes
C.7.1 Characteristics:
-most of the proteins in the organism are enzymes. They act as catalysts for biochemical reactions in the body.
-an enzyme's activity depends on its tertiary and quaternary structure- different enzymes catalyse different reactions depending on their structure because substrates bind to the enzyme's active site during the reaction. this active site is only present in tertiary and quaternary structures. The properties and positions of the R-groups exposed at the active site determine which substrates will bind to the enzyme.
-some enzymes do not bind to substrates unless their active sites don't contain additional ions or molecules.
-CO-FACTOR: a substance held to the protein by other bonds eg ions Ca2+
-CO-ENZYMES: non protein organic molecules eg vitamins
C.7.2 SUBSTRATE CONCENTRATION:
-a single enzyme can process only a limited amount of substrate in a given time, when substrate concentration increases, reaction rate increases. When all the enzymes are bound to substrates, the rate depends on the enzymes' rate of processing the substrates. The reaction rate eventually reaches a maximum limit.
C.7.3 Vmax and Michelis Constant (Kmax):
-the rate is expressed as the number of reactions catalyzed by a given enzyme molecule per unit time.
-in a graph of substrate concentration vs rate of reaction, the graph rises in a curved fashion, with a decreasing slope. Vmax is recognized as being the point in which the graph continues in a horizontal line, parallel to the x-axis.
-the Kmax is the substrate concentration at which the reaction rate is 1/2 Vmax. this is a measure of how readily the enzyme-substrate binding occurs. when Kmax is low, the reaction proceeds at a rapid rate even at low substrate concentrations
-Kma is recognized on a graph by finding the 1/2 Vmax rate on the y-axis and drawing a perpendicular down to the x-axis. The perpendicular will reveal the concentration at Kmax.
C.7.4 I guess this is part of what I did in C.7.4
C.7.5 Active Site:
-It is a cluster of chemical groupings formed as a part of the enzyme's folding pattern. the properties of the R-gouprs exposed at th active site determine which substrates will bind.
-when enzymes and substrates combine, they change shape: the active site is a flexible pert of the enzyme, which increases the surface area between the substrate and enzyme.
C.7.6 Inhibition:
-COMPETITIVE: compounds that are similar to the substrate, which compete with the substrate by binding to the active site. This decreases the reaction rate because the enzyme cannot bind to the substrate.
-NON-COMPETITIVE:
- The inhibitor binds to a
site other that the active site
- Does not change the active site
-
Increases the actuation energy
- Does not effect Enzyme-Substrate
binding
C.7.7 Effects on Enzyme Activity:
-HEAVY METAL IONS:
- calcium ions are the most commonly found in animals, accounting for
1.5-2% of human body mass of which 99% comes from bones and teeth
- Half a gram phosphorous is
required for attaching each gram of calcium to the bones
- Magnesium, potassium and sodium ions are also present
in biological systems as ions in the fluids in and arouns the cells present in
trace amounts in the human body
Iron
was the first trace metal ion found to be essential in the human diet. The first
row transition metals such as Co, Cr, Cu, Mn and Zn are present in trace amounts
in the human body. These are essential to many enzymes such as Zn (charge 2+) in
carboxypeptidase; Zn is found in almost 100 enzymes and is also present in
insulin. Co (3+) is found in vitamin B12 and iron is present in the hemoglobin
molecule of red blood cells. Magnesium is a secondary element of
bones and
teeth as well as regulating intracellular chemical activity, helping to form
protein and transmitting electrical signals from cell to cell. Mn is essential
for healthy bones and Cr plays a key role in glucose metabolism. On the other
hand, iron deficiency produces anemia and causes fatigue as cells are deprived
of oxygen and Cu deficiency gives rise to bone disease. The nees for trace
amounts of some metal ions such as tin and arsenic has been established in
animals such as rats but not yet in humans.
-TEMPERATURE: when temp rises, molecules move faster, colliding harder and more often, therefore they are more likely to react than at lower temp. When the temp increase is too high (above 60\260C), the enzymes will be denatured permanently, and will no longer function-their 3-D structure will be destroyed. At low temp reactions proceed slowly, and at very low temperatures (below 0\260C) the enzymes are denatured. They normally function at body temperature -37\260C
-pH-enzymes are electrically charged because R-groups may ionize when they dissolve in water. The pH therefore determines the changes in the enzyme. Enzymes will function only at given pH's depending on their electrical charge. Most enzymes function best at neutral pH's.
C.7.8 BIOTECHNOLOGY:
-?????????????
C.8 -- I have nothing on C.8 yet:
C.9 Metal Ions in Biological Systems
C.9.1 Roles in the Body/Chemical Properties:
-Sodium and Potassium are vital the the functioning of nerves and muscles.
-Calcium is necessary for muscular activity
-Calcium and phosphorus are needed for bone formation (see p643 bio book)
C.9.2 Ion Concentration Across Cell Membrane:
-Active transport-moves substances either with or against their electrochemical gradients, and requires energy. A source of energy may be Na+ of H+ concentration on the two sides of the membrane
-Sodium/Potassium Pumps- it uses energy from ATP to transfer sodium ions out of the cell and potassium ions inside. This pump is responsible for the electrical potential across plasma membranes. In the membrane, 3 sodium ions are moved for every two potassium ions that move in. The cell becomes more negative compared with the outside. when the tendency of K+ leaving the cell balances its tendency to enter it, the membrane potential is reached. K+ movement ceases.
-this type of pump controls the water content of the cell. It also drives the transport of sugars and amino acids. This process controls: the ability of nerves to conduct electricity, kidneys to form urine, muscles to contract, absorption of food in digestive tract.
C.9.3 Copper Ions in Electron Transport:
-the electron transport system accepts hydrogen atoms and passes their electrons from one member of the chain to the next.
-cytochromes-electron carrier molecule consisting of a protein and a porphyrin ring, containing a copper ion
Iron Ions in Oxygen Carriers:
-haemoglobin-respiratory pigment that carries oxygen in the blood
-contain a heme group with an iron atom a its center. The iron atom binds to the oxygen. When O binds to Fe, the hemoglobin is oxygenated and appears bright red. Without the iron center, oxygen wouldn't bind to hemoglobin, and oxygen couldn't be carried through the blood stream and to the cells in the body.