開學第一課愛德思生物學什麽

如果你看到了這篇推文，很有可能你是“入坑”了。生物作為(wei) 最難的國際課程之一，很多人都是避而遠之的。

一來文字表述多，讀題費時；二來，太多“主觀性”的東(dong) 西，答案不好把握；三來，難拿分，從(cong) 每年的boundary就可以知道。

以October 2022 PDF Grade Boundaries為(wei) 例，大概拿到50%原始分就可以a了。

但其實換句話來說，隻要你夠強，分分鍾拿a*/A*，因為(wei) a*/A*原始分夠低。

那麽(me) alevel生物到底學什麽(me) 呢？根據愛德思考綱，這一節課你要掌握：

考點一：The importance of water

1.1、understand the importance of water as a solvent in transport, including its dipole nature

1.Dipole and Hydrogen bond

The separation of charge is called dipole

There polar covalent bond between Hydrogen and oxygen.

Water is a polar molecule and exhibit dipolarity--— it has a partial negative (δ–) charge on one side and a partial positive (δ+) charge on the other .

2.Properties of water(所有的“properties都來自於(yu) 氫鍵”)

2.1 Water is a polar solvent.

Water can form hydrogen bonds with a variety of different substances(either polar or charged ionic compunds)

2.2 Water is an excellent transport medium

glucose

amino acid

sodium chloride

chloesterol

fat

oxygen

2.3 As water cools to 4 °C, it reaches its maximum density.

--This unusual property enables organisms to live in water, even in countries where it gets cold enough to freeze in winter

2.4 Water is slow to absorb and release heat – it has a high specific heat capacity.

High specific heat(高比熱容)-- water can absorb or give off a great deal of energy without changing temperature a lot.

when water evaporates, large amount of heat energy are used to break hydrogen bonds and allow water molecule to seperate.

2.5 Water is a liquid – it cannot be compressed.

Water molecules are cohesive and adhesive

Cohesive--water attracting to each other by hydrogen bond.

Eg. surface tension; drinking draw; droplet

Adhesive--the attraction between water and other substance.

Eg. capillary action; meniscus; water climbs up paper towel or cloth

2.6 Water has a very high surface tension because the attraction between the water molecules

1.Mass Transport Systems

Single-celled organisms: glucose and oxygen can diffuse directly across the cell membrane because of the short distance

Multicellular organisms: diffusion across the outer membrane would be too slow because of the

large distance

The mass transport systems are used to carry raw materials from specialised exchange organs (e.g. the lungs and the digestive system) to the body cells, and to remove metabolic waste (e.g. carbon dioxide) Eg. circulatory system

資料來自《Edexcel International ALEVEL Biology EXAM GUIDE 》