deck 4, let's get it! Flashcards
facilitated diffusion
(also known as facilitated transport or passive-mediated transport) is the process of spontaneous passive transport (as opposed to active transport) of molecules or ions across a biological membrane via specific transmembrane integral proteins.
electrogenic pumps
are primary active transporters that hydrolyze ATP and use the energy released from ATP hydrolysis to transport ions across biological membranes leading to the translocation of net charge across the membrane.
competitive inhibition
Blockage of the action of an enzyme on its substrate by replacement of the substrate with a similar but inactive compound that can combine with the active site of the enzyme but that is not acted upon or split by the enzyme. Also called selective inhibition .
non-competitive inhibition
is a type of enzyme inhibition where the inhibitor reduces the activity of the enzyme and binds equally well to the enzyme whether or not it has already bound the substrate.
non vs. competitive comparison, I had trouble with this when I learned it, so here is the best way I can explain it. Take what you can from it.
In a non-competitive inhibitor, the inhibitor binds to the enzyme, but does not compete with the substrate (competitive inhibitor) for the active site. Instead, it will bind to a different site of the enzyme, called an allosteric site, where it will produce changes in the enzyme’s structure and will effectively block enzymatic activity because the substrate cannot bind to the changed active site. In uncompetitive inhibition, an enzyme inhibitor is thought to bind to the E+S structure, or both the enzyme and the substrate together. When this happens, the product is unable to form, thus also inhibiting the product. Think of the lock and key model, where the enzyme is the lock and the substrate is the key. If you were to insert the key into the lock and turn, the lock would open. However, if someone placed a hand on yours and forced it still (the uncompetitive inhibitor) then you would be unable to unlock the lock. There are three kinds of reversible inhibitors: competitive, noncompetitive, and uncompetitive/mixed inhibitors. Competitive inhibitors, as the name suggests, compete with substrates to bind to the enzyme at the same time. The inhibitor has an affinity for the active site of an enzyme where the substrate also binds to. Noncompetitive inhibitor can bind to an enzyme with or without a substrate at different places at the same time. It changes the conformation of an enzyme as well as its active site, which makes the substrate unable to bind to the enzyme effectively so that the efficiency decreases. Simply put: Uncompetitive inhibition takes place when an enzyme inhibitor binds only to the complex formed between the enzyme and the substrate (the E-S complex). Non competitive inhibitor always binds to the enzyme at a site other than the enzyme’s active site (this other site is called an allosteric site). This affects the rate of the reaction catalysed by the enzyme because the presence of the inhibitor causes a change in the structure and shape of the enzyme. This change in shape means the enzyme is no longer able to bind with a substrate correctly.
NAD molecule
In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. The coenzyme is, therefore, found in two forms in cells: NAD+ is an oxidizing agent – it accepts electrons from other molecules and becomes reduced.
Thylakoid Membrane
A thylakoid is a membrane-bound compartment inside chloroplasts and cyanobacteria. They are the site of the light-dependent reactions of photosynthesis. Thylakoids consist of a thylakoid membrane surrounding a thylakoid lumen.
light dependent reactions
These four complexes work together to ultimately create the products ATP and NADPH. The two photosystems absorb light energy through pigments - primarily the chlorophylls, which are responsible for the green color of leaves. The light-dependent reactions begin in photosystem II.
carbon fixing reactions
is a process found in autotrophs (organisms that produce their own food), usually driven by photosynthesis, whereby carbon dioxide is changed into organic materials. Carbon fixation can also be carried out by the process of calcification in marine, calcifying organisms such as Emiliania huxleyi.
Stoma
One of the tiny openings in the epidermis of a plant, through which gases and water vapor pass. Stomata permit the absorption of carbon dioxide necessary for photosynthesis from the air, as well as the removal of excess oxygen. ( I think…)
NADP molecule
NADH, also known as coenzyme 1, is a naturally occurring biological substance. The “H” after NAD stands for hydride, or “high-energy hydrogen”. In metabolism, nicotinamide adenine dinucleotide is involved in redox reactions, carrying electrons from one reaction to another. Redox is fucking impressive, trust me, very cool. In photosynthetic organisms, NADPH is produced by ferredoxin-NADP+ reductase in the last step of the electron chain of the light reactions of photosynthesis. It is used as reducing power for the biosynthetic reactions in the Calvin cycle to assimilate carbon dioxide. Big picture? The overall function of light-dependent reactions, the first stage of photosynthesis, is to convert solar energy into chemical energy in the form of NADPH and ATP, which are used in light-independent reactions and fuel the assembly of sugar molecules.
Calvin cycle
The Calvin cycle (also known as the Calvin–Benson cycle) is the set of chemical reactions that take place in chloroplasts during photosynthesis. The cycle is light-independent because it takes place after the energy has been captured from sunlight.
Calvin-Benson Breakdown read this, but if you need something other than, here is a video and a site that breaks it down pretty well: http://highered.mcgraw-hill.com/sites/98…
Stage 1: Fixation In the stroma, in addition to CO2,two other components are present to initiate the light-independent reactions: an enzyme called ribulose bisphosphate carboxylase (RuBisCO) and three molecules of ribulose bisphosphate (RuBP). RuBP has five atoms of carbon, flanked by two phosphates. RuBisCO catalyzes a reaction between CO2 and RuBP. For each CO2 molecule that reacts with one RuBP, two molecules of 3-phosphoglyceric acid (3-PGA) form. 3-PGA has three carbons and one phosphate. Each turn of the cycle involves only one RuBP and one carbon dioxide and forms two molecules of 3-PGA. The number of carbon atoms remains the same, as the atoms move to form new bonds during the reactions (3 atoms from 3CO2 + 15 atoms from 3RuBP = 18 atoms in 3 atoms of 3-PGA). This process is called carbon fixation because CO2 is “fixed” from an inorganic form into organic molecules Stage 2: Reduction ATP and NADPH are used to convert the six molecules of 3-PGA into six molecules of a chemical called glyceraldehyde 3-phosphate (G3P). This is a reduction reaction because it involves the gain of electrons by 3-PGA. Recall that a reduction is the gain of an electron by an atom or molecule. Six molecules of both ATP and NADPH are used. For ATP, energy is released with the loss of the terminal phosphate atom, converting it to ADP; for NADPH, both energy and a hydrogen atom are lost, converting it into NADP+. Both of these molecules return to the nearby light-dependent reactions to be reused and reenergized. Stage 3: Regeneration At this point, only one of the G3P molecules leaves the Calvin cycle and is sent to the cytoplasm to contribute to the formation of other compounds needed by the plant. Because the G3P exported from the chloroplast has three carbon atoms, it takes three “turns” of the Calvin cycle to fix enough net carbon to export one G3P. But each turn makes two G3Ps, thus three turns make six G3Ps. One is exported while the remaining five G3P molecules remain in the cycle and are used to regenerate RuBP, which enables the system to prepare for more CO2 to be fixed. Three more molecules of ATP are used in these regeneration reactions.
