BIO~ 20點,,,,快d黎

1)active transport needs energy(ATP),it helps intake some substances against the concentration gradient. For examples, in kidney, active transport is used to reabsorb the minerals; in root of plant, it also helps
to absorb minerals from the soil.

2)phagocytosis is a process of engulfing germ/bacteria. In the
immune system it is a major mechanism used to remove pathogens
and cell debris. Bacteria, dead tissue cells, and small mineral particles are all examples of objects that may be phagocytosed.

3)enzymes work by lowering the activation energy.Substrates bind to the active site of the enzyme or a specificity pocket through hydrogen bonds, hydrophobic interactions, temporary covalent interactions (van der Waals) or a combination of all of these to form the enzyme-substrate complex. Residues of the active site will act as donors or acceptors of protons or other groups on the substrate to facilitate the reaction. In other words, the active site modifies the reaction mechanism in order to decrease the activation energy of the reaction. The product is usually unstable in the active site due to steric hindrances that force it to be released and return the enzyme to its initial unbound state.

4) When a substrate is bind to the active site of the enzyme, the
substrate will be catalyized. Active site is specific because of its 3D
conformation.Enzyme will be affected by temperature, PH. IF
temperature is too high, enzyme will be denatured and loss its
function. enzyme can be reused for many times. each of the enzyme
have its own optimum temperature.

5)Enzyme inhibitors are molecules that bind to enzymes and
decrease their activity.The binding of an inhibitor can stop a substrate from entering the enzyme's active site and/or hinder the enzyme from catalysing its reaction. Inhibitor binding is either reversible or
irreversible. Irreversible inhibitors usually react with the enzyme and change it chemically.

同學: 幫你答都無用，考試時是要你自己寫答案的，我建議你買本天書，讀熟考試重好。想好快找到答案就讀Highlights of A Level Biology，它有index，在index尋找到key point，揭去那頁，立即找到答案，欲買此書，請上官網，在雅虎打書名按搜尋即可，有八折。網址: http://www.rytc.com.hk/bio.htm
還有，前人之答案雖可，但不夠詳盡(到題)，所以你要補充資料。