Enzymes are biological catalysts. They speed up reactions although they are not changed in the reaction. Enzymes are proteins, and therefore are folded chains of amino acids with a specific shape. This shape is determined by the sequence of amino acids held together by bonds, for example Hydrogen bonds. Enzymes speed up reactions by bringing reactants together and reducing the activation energy required to start the reaction (enzymatic reaction).
Enzymes are specific: they have a specific shape, therefore only a certain substrate will fit its active site. There are two theories of enzyme action: Lock and Key and Induced Fit. The lock and key theory states that only a certain substrate will fit a certain active site, just like a key fits a lock. Induced Fit, likewise, states that enzymes wrap around substrates, attracted to each other by opposite charges, forming an enzyme substrate complex.
Answer:
The mechanisms of transport across the cell membrane are as follow: 1- simple diffusion, 2- facilitated diffusion, 3- primary active transport and 4-secondary active transport
Explanation:
The cell membrane is a selectively permeable structure capable of transporting substances by different mechanisms. Simple diffusion is a type of passive transport (i.e. does not require energy) where non-polar molecules (e.g. O2, CO2) pass across the membrane by a process that does not require energy from the cell. Facilitated diffusion is another type of passive transport where larger polar molecules (e.g., glucose and amino acids) pass across the membrane by using specific transmembrane integral proteins. On the other hand, primary active transport is a type of active transport that uses chemical energy (e.g., ATP) to move substances such as metal ions (Na+, K+, Ca2+) across the cell membrane against their concentration gradient. Finally, secondary active transport is another type of active transport where transporter proteins are used to couple the movement of ions (e.g., H+ protons) down their electrochemical gradient to the transport of another ions/solutes against their concentration/ electrochemical gradient.
Nitrogen fixation, N2 --> NH3+, is not something that plants to by themselves but some plants have bacteria that does this. I believe that pea plants have these, but I'm not 100% sure.
<span>Poodle, Boxer, English Bulldog, Yorkshire Terrier, Golden Retriever, Beagle, German Shepherd, and <span>Labrador Retrievers are the most popular breeds of dogs, but there is not a "Most popular breed of dog" but many</span></span>
