F3 Food and Humans

The characteristics of life

Food requirements of humans

Why do we need food? Food provides us with :

1. _______________ energy to keep our body warm and support daily activities【支持日常活動】;
2. _______________ raw materials for growth and repair【修復】 of body tissues【身體組織】;
3. _______________ substances that keep us healthy.

The seven major food substances are:

Primary food substances【基本食物物質】 that are essential【必需】 to life

Protective food substances【保護性食物物質】 that keep us healthy and help prevent diseases.

Carbohydrates【碳水化合物】

Carbohydrates are organic substances【有機物質】 which are made of _______________ carbon, _______________ hydrogen and _______________ oxygen.

There are three major types of carbohydrates – _______________ monosaccharides, _______________ disaccharides and _______________ polysaccharides, which differ in their molecular complexity【分子復雜性】.

Monosaccharides

e.g. glucose【葡萄糖】 and fructose【果糖】 in fruits, galactose【半乳糖】

• _______________ small molecules【小分子】 -> properties【特質】
• _______________ soluble【溶於】 in water -> properties
• readily absorbed【吸收】 in the _______________ intestines【腸】
• transported【輸送 】 in the _______________ blood to every part of the body

Disaccharides

e.g. sucrose【蔗糖】 in table sugar, lactose【乳糖】 in milk, maltose【麥芽糖】

• _______________ too large to be absorbed directly【直接地】 in the intestines

Polysaccharides

e.g. _______________ starch【澱粉】 in cereals, taros, maize and potatoes

• made up of _______________ long chains【長鏈】 of _______________ glucose unit【葡萄糖單位】
• size is _______________ too large for absorption【吸收】
• broken down into【分解成】 monosaccharides by _______________ hydrolysis【水解】

Metabolism【代謝】 Of Carbohydrates【碳水化合物】 In The Human Body

Monosaccharides

e.g. glucose

• is broken down during _______________ respiration to release【釋放】 energy.
• provides immediate【即時】 _______________ energy source【能量源】 for body activities.

glucose【葡萄糖】 + oxygen –> (Respiration【呼吸】) –> _______________ energy + _______________ carbon dioxide + _______________ water

Disaccharides

• broken down into【分解成】 _______________ monosaccharides before absorption【吸收】 by hydrolysis【水解】.
• for hydrolysis to happen, _______________ suitable enzyme is required.

maltose【麥芽糖】 + water –> (maltase【麥芽糖酶】) –> _______________ glucose【葡萄糖】 + _______________ glucose【葡萄糖】

sucrose【蔗糖】 + water –> (sucrase【蔗糖酶】) –> _______________ glucose【葡萄糖】 + _______________ fructose【果糖】

lactose【乳糖】 + water –> (lactase【乳糖酶】) –> _______________ glucose【葡萄糖】 + _______________ galactose【半乳糖】

Polysaccharides

• different types of enzymes are required to break down a _______________ starch molecule【澱粉分子】 to form glucose.

_______________ amylase catalyses【催化】 the breakdown of starch to maltose

_______________ maltase【麥芽糖酶】 catalyses【催化】 the breakdown of maltose to glucose

Functions Of Carbohydrates In The Human Body

1.  as main source of _______________ energy (especially glucose) for metabolism【代謝】 in the body
   • 1g of carbohydrates -> 17.1kj of energy
2. as energy storage
   • excess【過多的】 carbohydrates are converted【轉化為】 to _______________ glycogen【糖原】 or _______________ lipids【血脂】
   • glycogen: stored in _______________ liver【肝】 and _______________ skeletal muscles【骨骼肌】
3. as a _______________ building block【組件】 of larger molecules
   • e.g. nucleic acids【核酸】
4. cellulose【纖維素】 as a source of _______________ dietary fibre【膳食纖維】
   • can’t be digested【被消化】 in human body
   • keeps the _______________ digestive system【消化系統】 healthy

Lipids【血脂】

• made up of carbon, hydrogen and oxygen
• _______________ insoluble【不溶於】 in water
• _______________ soluble【溶於】 in organic solvent【有機溶劑】. For example, _______________ ethanol【乙醇／酒精】

Triglycerides【甘油三酸酯】

One main group of lipids is triglycerides.

Saturated fats【飽和脂肪】

• at room temperature -> _______________ solid
• main sources -> animals
• examples -> butter, lard【豬油】, cheese and fatty meat

Unsaturated fats【不飽和脂肪】

• at room temperature -> _______________ oily
• main sources -> plants and fish
• examples -> corn oil, olive oil, and salmon

Metabolism【代謝】 of lipids

A triglyceride molecule is formed from one _______________ glycerol【甘油】 molecule and three _______________ fatty acid【脂肪酸】 molecules by condensation【凝結】. Before absorbed【吸收】 directly in the digestive tract【消化道】, it must first be broken down【分解】 into smaller molecules by _______________ hydrolysis【水解】, in the presence of _______________ water and a suitable _______________ enzyme【酶】.

Function of lipids

• source of energy
  • 1 gram of lipid produces _______________ 38.9 kJ of energy
• excess lipids
  • stored in _______________ adipose tissues【脂肪組織】 in the body as an energy reserve
  • under the skin as _______________ subcutaneous fat【皮下脂肪】 which acts as an insulating layer【絕緣層】 to reduce heat loss
  • around _______________ internal organs【內臟】 to act as shock-absorbers【減震器】.
• transport and storage of _______________ fat-soluble vitamins【脂溶性維他命】
  • e.g. vitamin A & D
• _______________ cholesterol【膽固醇】 is a raw material for producing lipid hormones【脂質荷爾蒙】
  • e.g. sex hormones

Bad fats and good fats

Proteins【蛋白質】

• large _______________ complex【複雜】 molecules
• made up of _______________ carbon, _______________ hydrogen, _______________ oxygen and _______________ nitrogen【氮】.
• some contain _______________ sulphur【硫】
• amino acid【氨基酸】
  • _______________ subunits【亞單位】 of protein
  • human requires _______________ 20 different types of amino acid to _______________ synthesize【合成】 proteins.
    • 11 types are _______________ non-essential【非必須】 amino acids, which can be made using other compounds【化合物】 in our body.
    • 9 types are _______________ essential【必需】 amino acids, which cannot be made in our body and must be included in our _______________ diet.